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Electronics Forum / Electronics / July 2009An unusual Oscilloscope phenomenon
Check out a rather unusual phenomenon you can see on your oscilloscope in my latest blog (#14): http://www.alternatezone.com/eevblog/ See if you can get it to happen on your scope! I'll offer a free subscription to my blog for the best screen shot posted :-> Oh, and the probe doesn't have to be shorted either. Have fun. Dave.  Signature================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14): [quoted text clipped - 7 lines] > Have fun. > Dave. Got it immediately, because I once worked in lab that had cheap plastic chairs that generated 1cm sparks when you stood up! SignatureDirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff >> Check out a rather unusual phenomenon you can see on your oscilloscope in my >> latest blog (#14): [quoted text clipped - 10 lines] >Got it immediately, because I once worked in lab that had cheap plastic >chairs that generated 1cm sparks when you stood up! Back in the old days, they used to generate 1/2" sparks. >>> Check out a rather unusual phenomenon you can see on your oscilloscope >>> in my [quoted text clipped - 14 lines] > > Back in the old days, they used to generate 1/2" sparks. Nasty stuff that Bakelite. >>>> Check out a rather unusual phenomenon you can see on your oscilloscope >>>> in my [quoted text clipped - 16 lines] > >Nasty stuff that Bakelite. Goes nicely with wood cases: http://ip.co.za/shop/images/wheatstone.jpg http://www.surplussales.com/Images/Equipment/TestEquipment/Leeds-Northrup/eqp-wb m-119828/eqp-wbm-119828_lg.jpg >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope >>>>> in my [quoted text clipped - 21 lines] > http://ip.co.za/shop/images/wheatstone.jpg > http://www.surplussales.com/Images/Equipment/TestEquipment/Leeds-Northrup/eqp-wb m-119828/eqp-wbm-119828_lg.jpg When I started out with a government run telco and some of the gear was still in nice wooden cases. Over the years I saw pallet loads of test gear consigned to scrap. Loads of bridges, wood cased multimeters and bakelite AVO meters. These things sell for quite a few dollars nowadays - aint hindsight nice! >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope >>>>> in my [quoted text clipped - 19 lines] > http://ip.co.za/shop/images/wheatstone.jpg > http://www.surplussales.com/Images/Equipment/TestEquipment/Leeds-Northrup/eqp-wb m-119828/eqp-wbm-119828_lg.jpg Bad focus but shows the concept, when I was a teenager I made almost everything in wood, nicely polished, several layers of laquer, some more polishing: http://www.analogconsultants.com/ng/images/oak2.jpg I usually spent a lot more time on the enclosures than on the electronics but the stuff is still working. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > I usually spent a lot more time on the enclosures than on the electronics > but the stuff is still working. Didn't anyone tell you that dovetail joints were optional? :-) Just kidding. I can't imagine even you would have chiseled out dovetail joints (since I'm thinking those dovetail jigs you use with a router didn't exist for the casual home woodworker back then)... I built a small table (~2'x2'x1') for test equipment to live on not quite a month ago. I thoroughly enjoyed using a dado blade to cut a bunch of lap joints, and verified the table could hold 300lbs. Old boat anchors, here I come! >> I usually spent a lot more time on the enclosures than on the electronics >> but the stuff is still working. [quoted text clipped - 4 lines] > joints (since I'm thinking those dovetail jigs you use with a router didn't > exist for the casual home woodworker back then)... I didn't go that far but I polished and stained the corners until you couldn't really see where things butted up anymore. Saw a contractor commercial lately about the Fein Multimaster. Drooling all over the place. Fein is "the" electric tool company in Germany, only the good stuff. You had to call a 1-800 number to find out the price and that should have been a dead give-away. Well, found it on the Internet, saw the prices of spare inserts and decided that I do not need it this urgently. http://www.amazon.com/Fein-MultiMaster-FMM-250Q-Top/dp/B000U8S3QA > I built a small table (~2'x2'x1') for test equipment to live on not quite a > month ago. I thoroughly enjoyed using a dado blade to cut a bunch of lap > joints, and verified the table could hold 300lbs. Old boat anchors, here I > come! That's the other thing I built, or partially had built when I was around 15, size 6ft by 4ft and extremely sturdy (boat anchor proof). I made a drawing of the frame and asked my parents whether it was ok to get some metal stock, borrow a welding transformer and weld it in the garage. Oh no, no dice. So I went to the local HW store, a larger kind of mom and pop place. My classmates said they'd laugh at me there. The foreman took a look, "Yep, will be ready in two days, then we'll drive up there and chuck the frame over the hedge and you come down here to pay us the 70 Deutschmarks". They didn't even want up front cash. Oh, now my chest swelled and I felt like an engineer. Until I glued the formica onto a panel that would become the top and I had it slightly skewed ... SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > swelled and I felt like an engineer. Until I glued the formica onto a > panel that would become the top and I had it slightly skewed ... I guess nobody told you about the shims. ;-) Cheers! Rich >> swelled and I felt like an engineer. Until I glued the formica onto a >> panel that would become the top and I had it slightly skewed ... > > I guess nobody told you about the shims. ;-) No shims. The trick is to lay the Formica upside down onto the floor, butter it up with glue, then lay the wood piece on top. While doing the latter it slipped my hand and ... thud, landed on the Formica. Almost perfectly line up. With the emphasis on "almost". There was no way to get this off because it was the Henkel Pattex type glue which never lets go of anything. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >> swelled and I felt like an engineer. Until I glued the formica onto a >> panel that would become the top and I had it slightly skewed ... > >I guess nobody told you about the shims. ;-) How do shims fix a skewed veneer? > On Fri, 26 Jun 2009 00:23:28 GMT, Rich Grise <richgrise@example.net> >> [quoted text clipped - 4 lines] > > How do shims fix a skewed veneer? You put the glue on the surface and let it dry, and lay thin pieces of wood across it. Put the glue on the formica, let it dry, and lay it on top of the shims. The shims have no glue, so don't stick. Line the formica up, on top of the shims, and one by one take the shims out and let the formica stick to the surface. I've seen it done on those "home improvement"-type TV shows. :-) Cheers! Rich >> On Fri, 26 Jun 2009 00:23:28 GMT, Rich Grise <richgrise@example.net> >>> [quoted text clipped - 10 lines] > > I've seen it done on those "home improvement"-type TV shows. :-) With a fresh can of Henkel Pattex glue the shims may never come out again. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>> On Fri, 26 Jun 2009 00:23:28 GMT, Rich Grise <richgrise@example.net> >>>> [quoted text clipped - 12 lines] > > With a fresh can of Henkel Pattex glue the shims may never come out again. Well, then I guess using Henkel Pattex glue isn't all that great an idea. ;-) Use just plain ol' ordinary common off-the-shelf "contact cement", and let it DRY before you start placing the shims. Come to think of it, when I was a video game tech, the shipping guy used to do it to the sides of video games when they'd convert a cabinet from one game to another. Cheers! Rich >>>swelled and I felt like an engineer. Until I glued the formica onto a >>>panel that would become the top and I had it slightly skewed ... >> >>I guess nobody told you about the shims. ;-) > > How do shims fix a skewed veneer? They don't fix it - they prevent it. You contact cement the veneer & the top and let the cement dry. Lay shims on the top, lay the veneer on top of the shims. Line the veneer up properly, then withdraw the shims one at a time, pressing the veneer down onto the top as you go. You cut the formica before you start, such that it will hang over the top by about 1/4" on all edges. After sticking the formica to the top, you use a router to trim the formica to be exactly even with the top on all edges, with a bit of a bevel on the dege of the formica. Ed > Saw a contractor commercial lately about the Fein Multimaster. Drooling all > over the place. I first saw the Fein Multimaster at the Portland Woodworking Show not that long ago. They were having a grand time demoing it -- and letting anyone who cared to try it out themselves -- and it was *very* tempting. > Well, found it on the Internet, saw the prices of spare inserts and decided > that I do not need it this urgently. There's been a lot of competition with it lately (apparently Fein's patent expired?): Rockwell: http://www.amazon.com/Rockwell-RK5100K-Sonicrafter-20-Piece-Kit/dp/B001EYUGM8 (looks really good) Dremel: http://www.amazon.com/Dremel-6300-01-120-Volt-Multi-Max-Oscillating/dp/B001FORC9C (dunno) Habor Freight (!): http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=65700 (you're lucky if you get what you pay for?) ...and there's always eBay for knock-off Fein inserts... (quality level... who knows?) Nice story about getting your workbench frame built. I suspect that just couldn't be done today, unfortunately. :-( ---Joel >> Saw a contractor commercial lately about the Fein Multimaster. Drooling all >> over the place. [quoted text clipped - 21 lines] > ...and there's always eBay for knock-off Fein inserts... (quality level... who > knows?) Alright! Thanks. I guess I do have to check out Harborfreight. > Nice story about getting your workbench frame built. I suspect that just > couldn't be done today, unfortunately. :-( No, the HW store closed. The usual, the 3rd generation drove it into the ground :-( SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >> Saw a contractor commercial lately about the Fein Multimaster. Drooling all >> over the place. [quoted text clipped - 26 lines] > > ---Joel Interesting. I was intrigued by this just last month and meant to look into it: Fein: www.4multimaster.com SignatureCheers, James Arthur Almost forgot... Bosch has a rechargeable version, but the reviews are mixed: http://www.amazon.com/Bosch-PS50-2A-12-Volt-Multi-X-Cutting/dp/B001E281DG (which is really too bad... you might recall the discussion about the little Bosh impact drivers -- http://www.amazon.com/PS40-2A-12-Volt-Lithium-Ion-Impact-Driver/dp/B001C4AQVG -- and how they're a very, very good tool...) >>> I usually spent a lot more time on the enclosures than on the electronics >>> but the stuff is still working. [quoted text clipped - 14 lines] >saw the prices of spare inserts and decided that I do not need it this >urgently. Fein is simply crazy expensive. I looked at their routers over the weekend. I wasn't impressed, for 4X what a Bosch or PC costs. Bosch has a "Multi-Master type tool ("Multi-X", I think) that's a lot cheaper and looks just as good (Li-Ion battery, though). A little lower down the line, Dremmel has a copy for $100ish. If you want to go cheap, HarborFreight has one for $40. The reports are decent, acknowledging that it's a $40 tool. The only real complaint is that the blades loosen. >http://www.amazon.com/Fein-MultiMaster-FMM-250Q-Top/dp/B000U8S3QA > [quoted text clipped - 14 lines] >swelled and I felt like an engineer. Until I glued the formica onto a >panel that would become the top and I had it slightly skewed ... >>>> I usually spent a lot more time on the enclosures than on the electronics >>>> but the stuff is still working. [quoted text clipped - 22 lines] > acknowledging that it's a $40 tool. The only real complaint is that > the blades loosen. The $40 version will be good enough for me. I've used Fein drills, they are really top notch. I think grampa's drill in the garage is a Fein. About 100 years old, works like a champ. [...] SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>> I usually spent a lot more time on the enclosures than on the electronics >>>>> but the stuff is still working. [quoted text clipped - 24 lines] > >The $40 version will be good enough for me. But it's ugly orange. ;-) I think I'll spring for the Bosch. I want to rip up some bamboo flooring and inlay a hearth in front of our fireplace. I can't figure out another way to make the cuts against the wall. > I've used Fein drills, they >are really top notch. I think grampa's drill in the garage is a Fein. >About 100 years old, works like a champ. I now have seven cordless drills (will likely give one to my son). I just bought a little Bosch 12V Li-Ion to match the impact driver. 100 years ago a cordless drill was a brace and bit. ;-) >>>>>> I usually spent a lot more time on the enclosures than on the electronics >>>>>> but the stuff is still working. [quoted text clipped - 28 lines] > fireplace. I can't figure out another way to make the cuts against > the wall. Look at the bright side: It could be worse. My Chinese meters here are bonbon-purple. Channel 3 on my DSO is bonbon-pink. >> I've used Fein drills, they >> are really top notch. I think grampa's drill in the garage is a Fein. [quoted text clipped - 3 lines] > just bought a little Bosch 12V Li-Ion to match the impact driver. 100 > years ago a cordless drill was a brace and bit. ;-) I am very impressed with the little Durafix single Li-Ion pistol-style electric screwdriver. $15. We had to build a large step box for our Rottie because he has trouble getting in and out of the car. The long deck screws were hard to turn but it muscled them in. Sure saved me a blister. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>>>> I usually spent a lot more time on the enclosures than on the electronics >>>>>>> but the stuff is still working. [quoted text clipped - 31 lines] >Look at the bright side: It could be worse. My Chinese meters here are >bonbon-purple. Channel 3 on my DSO is bonbon-pink. It seems it costs a lot of money to get a decent color. The Tek scopes at work have gawd-awful trace colors. Not only are they "fruity", they're hard to see. >>> I've used Fein drills, they >>> are really top notch. I think grampa's drill in the garage is a Fein. [quoted text clipped - 9 lines] >deck screws were hard to turn but it muscled them in. Sure saved me a >blister. We talked about that before. I *love* the Bosch "Impactor" as a screwdriver. I can even drive large Phillips screws without chewing up the heads. It's the neatest tool I've bought in a long time. [...] >>> But it's ugly orange. ;-) I think I'll spring for the Bosch. I want >>> to rip up some bamboo flooring and inlay a hearth in front of our [quoted text clipped - 8 lines] > "fruity", they're hard to see. > Oh, they aren't engineered in China, are they? >>>> I've used Fein drills, they >>>> are really top notch. I think grampa's drill in the garage is a Fein. [quoted text clipped - 12 lines] > screwdriver. I can even drive large Phillips screws without chewing > up the heads. It's the neatest tool I've bought in a long time. That's what impressed me, getting the really long Phillips-head deck screws almost all the way into a 4 by 4 without chewing up the head is something I thought wasn't possible with one of those little things. The screws let of a loud squeal as they went in. There is one tool from Bosch I really love: My Bosch Bulldog rotary hammer. When I use it as a jackhammer it sure sends the stuff flying. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > That's what impressed me, getting the really long Phillips-head deck > screws almost all the way into a 4 by 4 without chewing up the head is > something I thought wasn't possible with one of those little things. The > screws let of a loud squeal as they went in. Use parafin (AKA Canning Wax) on the threads and they will go in easier. Then the hot sun melts the wax so that it soaks into the wood, and doesn't affect the holding power of the deck screws. Also, it doesn't hurt to drill a small pilot hole through the top piece of wood. SignatureYou can't have a sense of humor, if you have no sense! >> That's what impressed me, getting the really long Phillips-head deck >> screws almost all the way into a 4 by 4 without chewing up the head is [quoted text clipped - 4 lines] > easier. Then the hot sun melts the wax so that it soaks into the wood, > and doesn't affect the holding power of the deck screws. Thanks, that sound like a great trick. > ... Also, it > doesn't hurt to drill a small pilot hole through the top piece of wood. I always do that :-) Otherwise the top piece will ride up if there is some thread on the shaft inside of it. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>> That's what impressed me, getting the really long Phillips-head deck >>> screws almost all the way into a 4 by 4 without chewing up the head is [quoted text clipped - 6 lines] > >Thanks, that sound like a great trick. Depending on the screws and use, liquid soap works better. Parafin can keep stain from penetrating. Soap washes away, though some can damage cheap screws. >> ... Also, it >> doesn't hurt to drill a small pilot hole through the top piece of wood. [quoted text clipped - 3 lines] >Otherwise the top piece will ride up if there is some thread on the >shaft inside of it. If that's the concern, the top piece should be drilled to the same size as the screw shank (perhaps a *little* smaller). The pilot hole should go the length of the screw, though in the bottom piece it should be the size of the thread bottoms. Pilot drills do this, with a countersink, to the right size all in one swell foop. >> That's what impressed me, getting the really long Phillips-head deck >> screws almost all the way into a 4 by 4 without chewing up the head is [quoted text clipped - 5 lines] > and doesn't affect the holding power of the deck screws. Also, it > doesn't hurt to drill a small pilot hole through the top piece of wood. a cake of hand sop works very well , stick the screw point in and they slip in like c... ahem :) > >> That's what impressed me, getting the really long Phillips-head deck > >> screws almost all the way into a 4 by 4 without chewing up the head is [quoted text clipped - 8 lines] > a cake of hand sop works very well , stick the screw point in and they > slip in like c... ahem :) Soap works, but the wax is better. SignatureYou can't have a sense of humor, if you have no sense! [....] >> a cake of hand sop works very well , stick the screw point in and they >> slip in like c... ahem :) > > Soap works, but the wax is better. I bet you say that to all the boys/gals :) > [....] > [quoted text clipped - 4 lines] > > I bet you say that to all the boys/gals :) I do. When teaching woodworking. SignatureYou can't have a sense of humor, if you have no sense! >[...] > [quoted text clipped - 12 lines] > >Oh, they aren't engineered in China, are they? I think some of ours are. The UI is more Greek, maybe Japaneese-VCRese. >>>>> I've used Fein drills, they >>>>> are really top notch. I think grampa's drill in the garage is a Fein. [quoted text clipped - 17 lines] >something I thought wasn't possible with one of those little things. The >screws let of a loud squeal as they went in. I generally use pilot holes, but even then heads get stripped out. Stainless screws are really bad that way. I don't hear the squeak, though. The Impactor bangs 'em home and is rather noisy, itself. >There is one tool from Bosch I really love: My Bosch Bulldog rotary >hammer. When I use it as a jackhammer it sure sends the stuff flying. I have a Bosch hammer drill too, but have never used it. ;-) About half my new tools are Bosch (most of the rest are Dewalt or Delta/PC). I think I'll replace my Harbor Freight SLCS with a Bosch too. > Look at the bright side: It could be worse. My Chinese meters here are > bonbon-purple. Channel 3 on my DSO is bonbon-pink. When I was a lad, we called that color "Nipple Pink" ;-) Signature"Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock) >> Look at the bright side: It could be worse. My Chinese meters here are >> bonbon-purple. Channel 3 on my DSO is bonbon-pink. > > When I was a lad, we called that color "Nipple Pink" > > ;-) Thats not very PC Fred. These days we don't have nipples we have pediatric sustenance dispensers. >> Look at the bright side: It could be worse. My Chinese meters here are >> bonbon-purple. Channel 3 on my DSO is bonbon-pink. > > When I was a lad, we called that color "Nipple Pink" > > ;-) Well, I got meeself a lass and married her so I can't say that never no more :-) SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>> Look at the bright side: It could be worse. My Chinese meters here are >>> bonbon-purple. Channel 3 on my DSO is bonbon-pink. [quoted text clipped - 5 lines] >Well, I got meeself a lass and married her so I can't say that never no >more :-) There's an enormous pink triangle on the side of Twin Peaks today. Mo calls it "the thong." It's Gay Freedom Day, ground zero about 3 blocks away. John > But it's ugly orange. ;-) I think I'll spring for the Bosch. The cordless one? Or do they have a plug-in one now? > I > just bought a little Bosch 12V Li-Ion to match the impact driver. 100 > years ago a cordless drill was a brace and bit. ;-) We still used those back in industrial arts class in the mid-'80s since they didn't have enough electric drills to go around. (I imagine they'd had them for decades!) We had pretty good instructors... of the many demos they gave, I remember one where the guy said, "You want to know the difference between this cheap Black & Decker power drill here and this much-more-expensive Milwaukee? Watch this?" -- Guy wraps his hand around the chuck on the B&D, hits the trigger with his other hand and... chuck doesn't turn, the drill just sitting them humming a bit. "Don't try this with the Milwaukee!" ---Joel >> But it's ugly orange. ;-) I think I'll spring for the Bosch. > >The cordless one? Or do they have a plug-in one now? Cordless. 12V Li-Ion, that matches three of my drivers and drills. ;-) >> I >> just bought a little Bosch 12V Li-Ion to match the impact driver. 100 [quoted text clipped - 3 lines] >didn't have enough electric drills to go around. (I imagine they'd had them >for decades!) We didn't have electric drills in shop. I *hated* shop. >We had pretty good instructors... of the many demos they gave, I remember one >where the guy said, "You want to know the difference between this cheap Black >& Decker power drill here and this much-more-expensive Milwaukee? Watch >this?" -- Guy wraps his hand around the chuck on the B&D, hits the trigger >with his other hand and... chuck doesn't turn, the drill just sitting them >humming a bit. "Don't try this with the Milwaukee!" I've sprained a wrist driving screws. A good driver has a *lot* of torque. OTOH, I have a 3/8" air wrench that I think I could stop. I bought a 1/2" impact wrench that I could stop by hand with a 1" socket installed. It went back. <snip> > Fein is simply crazy expensive. I looked at their routers over the > weekend. I wasn't impressed, for 4X what a Bosch or PC costs. Bosch [quoted text clipped - 4 lines] > acknowledging that it's a $40 tool. The only real complaint is that > the blades loosen. Where do you get reports on the Harbor Freight stuff? I'd like to be able to see what others think about what I might buy - like their 12' sliding compound miter saw. Sometimes they're good for power tools that will be used infrequently. The stuff I've bought from them for light use has never disappointed - but I haven't used it either under harsh conditions or extensively. Ed > Where do you get reports on the Harbor Freight stuff? http://www.google.com/search?hl=en&q=%22harbor+freight%22+reviews Hope This Helps! Rich >>Where do you get reports on the Harbor Freight stuff? > > http://www.google.com/search?hl=en&q=%22harbor+freight%22+reviews > > Hope This Helps! > Rich Thanks! It did help. Mine's now on order, 39.99 and it includes a set of 6 screwdrivers for free. http://ww2.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=66653 Don't know what I'll use the screwdrivers for. :-) Ed >>> Where do you get reports on the Harbor Freight stuff? >> [quoted text clipped - 6 lines] > includes a set of 6 screwdrivers for free. > http://ww2.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=66653 Let us know how it performs, will ya? > Don't know what I'll use the screwdrivers for. :-) Opening beer bottles etc. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>> Where do you get reports on the Harbor Freight stuff? >>> [quoted text clipped - 12 lines] > >Opening beer bottles etc. I was going to say opening paint cans, but beer tastes better. ;-) > >>>> Where do you get reports on the Harbor Freight stuff? > >>> [quoted text clipped - 14 lines] > > I was going to say opening paint cans, but beer tastes better. ;-) Why did you drink the paint? SignatureYou can't have a sense of humor, if you have no sense! >> >>>> Where do you get reports on the Harbor Freight stuff? >> >>> [quoted text clipped - 16 lines] > > Why did you drink the paint? Because the doctor said I couldn't drink beer anymore? > >> >>>> Where do you get reports on the Harbor Freight stuff? > >> >>> [quoted text clipped - 18 lines] > > Because the doctor said I couldn't drink beer anymore? Must have been a long time ago, before they switched to latex based paint;-) SignatureYou can't have a sense of humor, if you have no sense! ><snip> > [quoted text clipped - 10 lines] >I'd like to be able to see what others think about what >I might buy - like their 12' sliding compound miter saw. I have their 10" SLCS. For $100 it's not bad at all. I just bought it to cut 2x4s and it does that very well. I did some molding with it in my last house, too. I'll likely replace it with a better saw in the next year or so, though. As far as discussions of these things, rec.woodworking is likely the best place. There are a lot of tool snobs there too, but also a lot of information. >Sometimes they're good for power tools that will be used >infrequently. The stuff I've bought from them for light >use has never disappointed - but I haven't used it either >under harsh conditions or extensively. I don't have too many HF power tools, but a few. You really have to be careful. The above SLCS is fairly good (it's weak on compound miters). I've looked at their wet saw and would have bought it if I knew about it before I bought mine. OTOH, I have a couple of cordless drills that are just so bad that I don't even count them. >><snip> >> [quoted text clipped - 30 lines] > knew about it before I bought mine. OTOH, I have a couple of cordless > drills that are just so bad that I don't even count them. Thanks for the info on the saw. My use would be like yours, primarily rough carpentry. I have a bunch of decorative "garden ties" to replace, and the 12" saw will handle them. I have a $24 1/2" hammer drill from them - flawless for the few times I've used it. The cordless 9.6V is pretty much useless, except for maybe drilling a couple of holes in a project box. I love their cheap $2.99 meters for monitoring stuff, and as a source of LCD displays for projects. Haven't seen that price for a while though. It's kinda fun to watch them mis-measure noisy DC. :-) Ed >>> <snip> >>> [quoted text clipped - 40 lines] > a project box. I love their cheap $2.99 meters for monitoring > stuff, and as a source of LCD displays for projects. ... How do you wire up the LCD? Just the bare glass or did you find a trick to get into their blob chip? [...] SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>> <snip> >>>> [quoted text clipped - 45 lines] > > [...] I wish I could get into the blob, just as a matter of interest. I doubt it would be work the effort, though. Displays don't cost that much to make it worthwhile. The simple hack is to just use the thing on the meter PC board - you can saw away what you don't need. The last one I hacked used the whole meter, minus the switching, just to monitor a supply voltage. There was plenty of room inside the supply cabinet so I just soldered leads to the input and did a little surgery on the front panel so yo could see the LCD. I had a little DC-DC converter that provided the 9V for the meter. The supply ramps the voltage up slowly between set points over time, and the built in meter provides a way to watch the progress without needing to connect an external meter each time. Ed >>><snip> >>> [quoted text clipped - 34 lines] >primarily rough carpentry. I have a bunch of decorative >"garden ties" to replace, and the 12" saw will handle them. The only thing I'd recommend is to buy it in one of their brick and mortar stores, where it can be easily returned. A couple of friends also bought one, after I recommended it, and one apparently had damaged slider bearings. >I have a $24 1/2" hammer drill from them - flawless for the >few times I've used it. The cordless 9.6V is pretty much [quoted text clipped - 3 lines] >seen that price for a while though. It's kinda fun to watch >them mis-measure noisy DC. :-) I put their meters in my tool box (and hide the Flukes) in case someone decides to borrow one. I lost a Fluke-77 that way. [...] >> ... I love their cheap $2.99 meters for monitoring >> stuff, and as a source of LCD displays for projects. Haven't [quoted text clipped - 3 lines] > I put their meters in my tool box (and hide the Flukes) in case > someone decides to borrow one. I lost a Fluke-77 that way. Which loss method? It grew legs and walked away or pop ... *BAM* ... "Whoops, sorry, guess I must've left it on amps"? SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >[...] > [quoted text clipped - 8 lines] >Which loss method? It grew legs and walked away or pop ... *BAM* ... >"Whoops, sorry, guess I must've left it on amps"? Legs. > <snip> > [quoted text clipped - 17 lines] > > Ed I use their cheap arse IR thermometer for eyeballing hot spots. Item 96451, $29 on sale. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96451 If you find a price on their website, they honor it in the store if you bring the print out. I can't tell you how many of those $3 DVMs I have. Why use a Fluke or HP when doing cheap and dirty testing? I was checking a gel cell voltage in the boonies, but the meter was on current. It died. Maybe it was fuzed internally. I didn't bother checking. I pulled out a spare and went on with the testing. Later I gave away the meter to someone who wanted to retrieve the battery. ;-0 > >> I usually spent a lot more time on the enclosures than on the electronics > >> but the stuff is still working. [quoted text clipped - 16 lines] > > http://www.amazon.com/Fein-MultiMaster-FMM-250Q-Top/dp/B000U8S3QA http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=67097 > > I built a small table (~2'x2'x1') for test equipment to live on not quite a > > month ago. I thoroughly enjoyed using a dado blade to cut a bunch of lap [quoted text clipped - 20 lines] > "gmail" domain blocked because of excessive spam. > Use another domain or send PM. SignatureYou can't have a sense of humor, if you have no sense! >>> Check out a rather unusual phenomenon you can see on your oscilloscope >>> in my latest blog (#14): [quoted text clipped - 13 lines] > > Back in the old days, they used to generate 1/2" sparks. Oh yeah? You young punks have it easy. Back in my time, we didn't have plastic chairs. If we wanted to make sparks, we had to rub two cats together. SignaturePaul Hovnanian paul@hovnanian.com ---------------------------------------------------------------------- Have gnu, will travel. >>> Check out a rather unusual phenomenon you can see on your oscilloscope in my >>> latest blog (#14): [quoted text clipped - 11 lines] > > Back in the old days, they used to generate 1/2" sparks. They had more volts in them as well SignatureDirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff > Check out a rather unusual phenomenon you can see on your oscilloscope in > my latest blog (#14): [quoted text clipped - 7 lines] > Have fun. > Dave. When I worked a Century Data we had a problem with our new reel to reel vaccuum column tape drive when ever someone would walk by the drive when it was reading it would get data errors. The problem was that the shield on the cable from the heads to the preamp was grounded on both ends. Bob >> Check out a rather unusual phenomenon you can see on your oscilloscope in >> my latest blog (#14): [quoted text clipped - 14 lines] > >Bob That's usually the best way to ground shields. John >>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>> my latest blog (#14): [quoted text clipped - 17 lines] > > John IIRC head signals mostly went via twisted pair. If they had a shield as well we would certainly not ground them on both sides. Tony >>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>> my latest blog (#14): [quoted text clipped - 20 lines] >IIRC head signals mostly went via twisted pair. If they had a shield as well we >would certainly not ground them on both sides. You *want* large amounts of high-frequency common-mode noise? John John Larkin a écrit : >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>> my latest blog (#14): [quoted text clipped - 22 lines] > > You *want* large amounts of high-frequency common-mode noise? Probably. Lots of people don't understand this and I've seen this kind of mistake (opened shield) recommended in lots of highly regarded EMC books. But that's really nice for us. (Joerg?) SignatureThanks, Fred. > John Larkin a écrit : >> [quoted text clipped - 30 lines] > > But that's really nice for us. (Joerg?) Yeah! But shhht, don't spill the beans here, at least not until I am retired :-)) SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. Joerg a écrit : >> John Larkin a écrit : >>> [quoted text clipped - 33 lines] > Yeah! But shhht, don't spill the beans here, at least not until I am > retired :-)) I think I'll retired after you, but this kind of misconception is sufficiently widely spread that we don't have to worry :-) SignatureThanks, Fred. > Joerg a écrit : >>> John Larkin a écrit : [quoted text clipped - 37 lines] > I think I'll retired after you, but this kind of misconception is > sufficiently widely spread that we don't have to worry :-) Oh, I am not worried at all :-) But I am concerned about what happens when guys like you and I are in their 90's, the hands are shaky, the mind ain't what it used to be and the senior living place doesn't allow a Tektronix mainframe in the rooms. The next generation doesn't have anough analog engineers. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >> Joerg a écrit : [snip] >>>> Probably. Lots of people don't understand this and I've seen this >>>> kind of mistake (opened shield) recommended in lots of highly [quoted text clipped - 14 lines] >the senior living place doesn't allow a Tektronix mainframe in the >rooms. The next generation doesn't have anough analog engineers. Won't matter. We'll all be deep into communal despair :-( ...Jim Thompson | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Think things are bad now? Wait until Obama "takes care" of you. > But I am concerned about what happens when guys like you and I are in > their 90's, the hands are shaky, the mind ain't what it used to be and the > senior living place doesn't allow a Tektronix mainframe in the rooms. The > next generation doesn't have anough analog engineers. All the more money for me. ;-) Tim SignatureDeep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms >Joerg a écrit : >>> John Larkin a écrit : [quoted text clipped - 37 lines] >I think I'll retired after you, but this kind of misconception is >sufficiently widely spread that we don't have to worry :-) Yup. Once people get fixated on "ground loops" they are forever lost to reason. Ditto high-speed "return currents." John >>Joerg a écrit : >>>> John Larkin a écrit : [quoted text clipped - 44 lines] > >John Two coaxial shields with one end of each grounded at opposite ends is pretty nice. Best regards, Spehro Pefhany Signature"it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com > Yup. Once people get fixated on "ground loops" they are forever lost > to reason. > > Ditto high-speed "return currents." > > John OK, how about "image charge" then? Jeroen Belleman > Yup. Once people get fixated on "ground loops" they are forever lost > to reason. There is a fairly mindless thread about ground loops on news:sci.electronics.repair right now. SignatureYou can't have a sense of humor, if you have no sense! > John Larkin a écrit : > [quoted text clipped - 38 lines] > Thanks, > Fred. Is that open end shield rather than opened shield, or am I missing something here. Grounding one side is pretty common knowledge, though you get arguments over which side to ground. > On Thu, 25 Jun 2009 16:31:09 +0800, TonyS <scarborofun@gmail.nspm.com> >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in [quoted text clipped - 17 lines] > > You *want* large amounts of high-frequency common-mode noise? No, which is precisely the reason to ground only one end of the shield. Cheers! Rich >>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>> my latest blog (#14): [quoted text clipped - 17 lines] > > John Depends. With floating transducers and shielded twisted pair, it's best to ground the shield only at the transducer end. That way any capacitive imbalance doesn't produce any currents, because the shield is at the transducer's idea of ground. Cheers Phil Hobbs SignatureDr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net >>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>> my latest blog (#14): [quoted text clipped - 22 lines] >capacitive imbalance doesn't produce any currents, because the shield is >at the transducer's idea of ground. At the receive (instrument) end, the ungrounded end of the coax shield becomes the hot side of a resonant "vertical" antenna. Any voltage there becomes 100% common-mode signal on the inner twisted pair. What's wrong with a little current in the shield? The signal pair isn't affected. But volts, or tens of volts, of common-mode RF can be nasty. John >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>> my latest blog (#14): [quoted text clipped - 30 lines] > isn't affected. But volts, or tens of volts, of common-mode RF can be > nasty. It could become really, really nasty if the cable length happens to be close to 1/4, 3/4 and so on wavelength of the offending RF signal. If the shield current is of concern it can be broken by a wee ferrite. Probably the litmus test for RF stuff like this is when people schlepp it to Otis Street and see if it can survive Sutro Tower. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>>> my latest blog (#14): [quoted text clipped - 33 lines] >It could become really, really nasty if the cable length happens to be >close to 1/4, 3/4 and so on wavelength of the offending RF signal. Or a nice wideband ESD spark. Then the receive-end differential signal might see a kilovolt p-p common-mode ring. If >the shield current is of concern it can be broken by a wee ferrite. Right. That's easy to add as needed. >Probably the litmus test for RF stuff like this is when people schlepp >it to Otis Street and see if it can survive Sutro Tower. It's terrible here. Scope traces are gross fuzz, and all sorts of opamp front-ends like to rectify stuff. You should see the spectrum of a 10" clip lead. http://www.jimprice.com/sutro/tower1.jpg We did do a useful simulation of a system that has a superconductive magnet/front end on one side of a room and some ADCs on the other side. We convinced ourselves that we need to go differential. John [...] >> Probably the litmus test for RF stuff like this is when people schlepp >> it to Otis Street and see if it can survive Sutro Tower. [quoted text clipped - 5 lines] > > http://www.jimprice.com/sutro/tower1.jpg Once I took off on a Europe flight out of SFO and the antenna top stuck out of the clouds while the rest of the tower was in the white. Picture perfect, and I had my camera in the overhead <aargh>. I could still bite myself, that opportunity never came again. > We did do a useful simulation of a system that has a superconductive > magnet/front end on one side of a room and some ADCs on the other > side. We convinced ourselves that we need to go differential. Yesterday I had my comeuppance WRT to the Instek GDS-2204 scope that I thought is so much better than Tektronix. In many ways it is, and also doesn't have the nasty conducted emissions on the probe cables. But when debugging 74MHz gear I could not figure out where a weird buzz was coming from. Until I turned off the scope ... SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >[...] > [quoted text clipped - 12 lines] >perfect, and I had my camera in the overhead <aargh>. I could still bite >myself, that opportunity never came again. A couple of times I've been up on Twin Peaks and there was a sharply defined fog layer below. Only a couple of big buildings poke through, and a few plumes from power plants and such. Sometimes the sun gets under the fog at sunrise/sunset. Cool. ftp://jjlarkin.lmi.net/Kit1.JPG >> We did do a useful simulation of a system that has a superconductive >> magnet/front end on one side of a room and some ADCs on the other [quoted text clipped - 5 lines] >debugging 74MHz gear I could not figure out where a weird buzz was >coming from. Until I turned off the scope ... CPU clock maybe? John >> [...] >> [quoted text clipped - 19 lines] > > ftp://jjlarkin.lmi.net/Kit1.JPG Nice. Would be even nicer without the attached city :-) >>> We did do a useful simulation of a system that has a superconductive >>> magnet/front end on one side of a room and some ADCs on the other [quoted text clipped - 7 lines] > > CPU clock maybe? Possibly. It even happens in standby power so maybe it's the SMPS in there. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. <snip> > A couple of times I've been up on Twin Peaks and there was a sharply > defined fog layer below. Only a couple of big buildings poke through, [quoted text clipped - 3 lines] > > ftp://jjlarkin.lmi.net/Kit1.JPG Wow. You're making me drool. ><snip> > [quoted text clipped - 7 lines] > >Wow. You're making me drool. But a lot of the time we look out the kitchen window and see a wall of fog. John >> <snip> >> [quoted text clipped - 9 lines] > But a lot of the time we look out the kitchen window and see a wall of > fog. Or a shoot-out ... Well, not in your neighborhood but we had first-time visitors from Germany a few years ago, our former neighbors. After two week of west coast sightseeing they stayed in a ritzy S.F. hotel to see the town before heading out to us. Shooting right in the lobby there, IIRC a fatal one. They were quite shaken when they got here. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >> But a lot of the time we look out the kitchen window and see a wall of >> fog. > >Or a shoot-out ... Glen Park is a quiet, bucoloc village on the rim of an actual canyon with an actual stream. Seven restaurants, one sports bar, one dry cleaner, fresh-baked bread and pastries, one book store, one public library. We hear the distant, muffled gunshots from Visitacion Valley and the gentle roar of Interstate 280; we pretend it's a waterfall. >Well, not in your neighborhood but we had first-time visitors from >Germany a few years ago, our former neighbors. After two week of west >coast sightseeing they stayed in a ritzy S.F. hotel to see the town >before heading out to us. Shooting right in the lobby there, IIRC a >fatal one. They were quite shaken when they got here. Well, didn't they buy a ticket to The Wild West? They can get a lot of mileage out of the story back at home. I've never been that close to a human shooting. My sister did shoot her husband, but he deserved it. John >>> But a lot of the time we look out the kitchen window and see a wall of >>> fog. [quoted text clipped - 6 lines] > library. We hear the distant, muffled gunshots from Visitacion Valley > and the gentle roar of Interstate 280; we pretend it's a waterfall. Luckily we don't hear shootings, except the occasional rifle shots into the air out of trucks when the drivers had too much booze on Friday nights. They don't seem to realize that what goes up also comes down. >> Well, not in your neighborhood but we had first-time visitors from >> Germany a few years ago, our former neighbors. After two week of west [quoted text clipped - 4 lines] > Well, didn't they buy a ticket to The Wild West? They can get a lot of > mileage out of the story back at home. They didn't think it would be this wild. But it can. When I did EMC runs at CKC near Mariposa a saloon fight broke out. A real one, guys flying across tables, glass crashing, beer everywhere. All the tourists ran as fast as they could. And the music kept playing. > I've never been that close to a human shooting. My sister did shoot > her husband, but he deserved it. Wow! SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>> But a lot of the time we look out the kitchen window and see a wall of >>>> fog. [quoted text clipped - 29 lines] > >Wow! Really. The local cops showed up and said "don't worry lady, we'll take care of it." And they did. John [...] >>> I've never been that close to a human shooting. My sister did shoot >>> her husband, but he deserved it. [quoted text clipped - 3 lines] > Really. The local cops showed up and said "don't worry lady, we'll > take care of it." And they did. Yikes. He must have been a character, and probably not unknown to them. With some marriages I wonder how they could hold on that long. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. On Jun 26, 4:15 pm, John Larkin <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > ><snip> > [quoted text clipped - 12 lines] > > John I got this brilliant idea a few decades ago to watch the 4th of July fireworks from Twin Peaks. Bad idea. The place is full of yahoos shooting off their own fireworks. Should a fire break out, you are screwed. I did watch the Oakland Hill fire from Twin Peaks. I kid you not, there was a group singing the Grateful Dead's "Fire on the Mountain", over and over.... >On Jun 26, 4:15 pm, John Larkin ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: [quoted text clipped - 20 lines] >shooting off their own fireworks. Should a fire break out, you are >screwed. Fireworks are usually silly here. Fizz, boom, a dull flash of color in the fog. >I did watch the Oakland Hill fire from Twin Peaks. I kid you not, >there was a group singing the Grateful Dead's "Fire on the Mountain", >over and over.... The fire was awesome. From Diamond Heights, looking across the bay, it looked like the whole east side was on fire. Above the Clairemont Hotel was a huge ball of fire with a black center... it looked like the Gates of Hell. John >I got this brilliant idea a few decades ago to watch the 4th of July >fireworks from Twin Peaks. Bad idea. The place is full of yahoos >shooting off their own fireworks. Should a fire break out, you are >screwed. Oh come on, there's a huge reservoir up there. I am amazed by the DIY fireworks at Dolores Park. Much more fun than the official shows. >> I got this brilliant idea a few decades ago to watch the 4th of July >> fireworks from Twin Peaks. Bad idea. The place is full of yahoos [quoted text clipped - 5 lines] > I am amazed by the DIY fireworks at Dolores Park. Much more fun than the > official shows. We had this here, yesterday (photo is from last year though), top view from a friend's deck: http://goldcountryimages.static.adqic.com/uploads/inline/1213875563_8746.jpg SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>I got this brilliant idea a few decades ago to watch the 4th of July >>fireworks from Twin Peaks. Bad idea. The place is full of yahoos [quoted text clipped - 5 lines] >I am amazed by the DIY fireworks at Dolores Park. Much more fun than the >official shows. I used to live on 16th street, across from the mission, when the area was still a real dump, and cheap... a 3 room flat for $315. Now the whole area has gotten trendy and expensive, and Dolores Park is a weekend flesh market. Cool. Been to The Monk's Kettle? That have 20 exotic beers on tap and make a different pot pie every day. But Joseph Schmitt will be shut down soon. Boycott Hershey's! John > In article <7716bb9f-f71a-43a4-bcb0-9847e42f5...@i6g2000yqj.googlegroups.com>, > [quoted text clipped - 8 lines] > I am amazed by the DIY fireworks at Dolores Park. Much more fun than the > official shows. The road can't handle much traffic unles things have changed. I haven't brought a car to SF in a few years. Too much hassle. I do recall the official fireworks being more like an "impressionistic" painting. One of the better 4th of July displays I saw was in Las Vegas. I was at the Paradise Hilton. From the parking garage, you could see their fireworks and displays all around town. The top level was packed with people, so I guess this is a common way to watch the events. I'm sure the Stratosphere is packed for the 4th. >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>> my latest blog (#14): [quoted text clipped - 32 lines] > > John It depends on the shield resistance. Putting a 1-ohm resistor between the shield and ground on the Rx end is as good as an open circuit for ground loop purposes, and should get rid of the antenna problem. Cheers Phil Hobbs SignatureDr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net > At the receive (instrument) end, the ungrounded end of the coax shield > becomes the hot side of a resonant "vertical" antenna. Any voltage [quoted text clipped - 3 lines] > isn't affected. But volts, or tens of volts, of common-mode RF can be > nasty. That's the reason you see lots of six inch wide copper bonding straps in radio studios. They use one and a half inch straps to connect between the equipment, and the bonding straps. SignatureYou can't have a sense of humor, if you have no sense! >> At the receive (instrument) end, the ungrounded end of the coax shield >> becomes the hot side of a resonant "vertical" antenna. Any voltage [quoted text clipped - 7 lines] > in radio studios. They use one and a half inch straps to connect between > the equipment, and the bonding straps. Same in this here lab :-) SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>> ... was reading it would get data errors. The problem was that the >>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 13 lines] > What's wrong with a little current in the shield? The signal pair isn't > affected. But volts, or tens of volts, of common-mode RF can be nasty. I think half of us are talking about low-noise audio frequencies, and half of us are talking about RF. The way I heard it, you leave one end unshielded for audio preamps and stuff, but ground both ends for RF; I think it has to do with wavelength and, well, propagation characteristics. Of course, the thing that was drummed into me while they were teaching me this was "GROUND LOOPS!". :-) Cheers! Rich >>>>> ... was reading it would get data errors. The problem was that the >>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 23 lines] >Cheers! >Rich Audio: if one end of a shield is disconnected, the delta-voltage (60 Hz, RF, esd spikes) between chassis is greater. If the signal is single-ended, that increases noise directly. If differential, it increases common-mode noise. Why would you want to do that? A 60-Hz (and RF, and ESD) "ground loop" can result from different boxes being plugged into different outlets which have some 60 Hz difference voltage (or form a relative antenna for RF.) Connecting the shield on both ends shorts out some or most of this difference voltage and REDUCES the effect of the "ground loop" on the signal. Whoever did the drumming was passing on folklore. John >>>>>> ... was reading it would get data errors. The problem was that the >>>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 35 lines] > shield on both ends shorts out some or most of this difference voltage > and REDUCES the effect of the "ground loop" on the signal. Unless the shield slowly commences a faint red glow, followed by some "amperage scent" wafting through the room ... Seriously, I've seen that happen. > Whoever did the drumming was passing on folklore. Yup. OTOH that provides a good business opportunity 8-D SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>>>> ... was reading it would get data errors. The problem was that the >>>>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 40 lines] > >Seriously, I've seen that happen. Yup. I've seen some ghastly wiring, some done by licensed electricians. The most 60 Hz I've experienced (between outlet ground pins, in an office building) was a few volts RMS, and plenty stiff. Messed up some printer signals pretty good. The real way to pipe signals around is fiberoptics. A kilovolts of common-mode is no problem. Hey, time for our engineering meeting; Japanese food today! John >>>>>>>> ... was reading it would get data errors. The problem was that the >>>>>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 50 lines] >The real way to pipe signals around is fiberoptics. A kilovolts of >common-mode is no problem. I wish... I'm working on interfacing a current sensing coil from a welding transformer. During welding there is a couple of hundred volts everywhere. This project starts to give me a headache :-) SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- >>>>>>>>> ... was reading it would get data errors. The problem was that the >>>>>>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 52 lines] > welding transformer. During welding there is a couple of hundred volts > everywhere. This project starts to give me a headache :-) Try differential transfer, shielded twisted pair or Twinax soldered to the burden resistor, from there to your measurement box, place a 2nd signal transformer there. Make sure the twisted pair is source- and/or end-terminated properly, usually 100-120ohms. And never, never use this connection as the burden resistor even if there is a fire extinguisher at hand ... SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>>>>>>> ... was reading it would get data errors. The problem was that the >>>>>>>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 56 lines] >the burden resistor, from there to your measurement box, place a 2nd >signal transformer there. Make sure the twisted pair is source- and/or I already went for a differential input. Solves most of the problems, but not all but I'm pretty sure the inputs where overdriven as well. I fixed that, but didn't field-test it. A 2nd signal transformer won't fly because the pulses may be quite long (up to 100ms). The problem is that nobody seems to know what the pulses look like exactly. The transformer is pulsed by a 1000Hz PWM signal. This makes me assume the current sensor sees pulses as well. But the shape probably depends on the induction in the welding circuit while carrying many kA... >end-terminated properly, usually 100-120ohms. And never, never use this >connection as the burden resistor even if there is a fire extinguisher >at hand ... That might be worth something to explore. The burden resistor (1k is specified) is now on the measurement board itself. I'd like to keep it there though to keep the installation procedure easy. The wiring in the test setup is pretty short (2 meters) but bad (not twisted, unshielded). I'll order some shielded twisted pair tomorow. I already figured this must be part of the problem. SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- [...] >>> I wish... I'm working on interfacing a current sensing coil from a >>> welding transformer. During welding there is a couple of hundred volts >>> everywhere. This project starts to give me a headache :-) Recipe against headache in cases like this: Proper matching of literally everything, shielding, a glass or two of Beerenburger. >> Try differential transfer, shielded twisted pair or Twinax soldered to >> the burden resistor, from there to your measurement box, place a 2nd [quoted text clipped - 4 lines] > fixed that, but didn't field-test it. A 2nd signal transformer won't > fly because the pulses may be quite long (up to 100ms). 100msec? Is it a DC welder? Anyhow, 100msec is feasible if you use a small doorbell transformer, the kind with two compartments where you can scrap one of them out with wire cutters and without having to disassemble the core. Calculate it so it's well under the saturation limits at 10Hz. Commercial current transformers can also go that low if you use one that's totally oversized for your current. Unless the input diff-amp has a huge common mode range even for fast stuff such as spikes I am not sure you can do it without another transformer at the receiving end. Or rather, I've seen cases where it didn't work. > The problem is that nobody seems to know what the pulses look like > exactly. The transformer is pulsed by a 1000Hz PWM signal. This makes > me assume the current sensor sees pulses as well. But the shape > probably depends on the induction in the welding circuit while > carrying many kA... If it's fed 1kHz then 1kHz should come out. >> end-terminated properly, usually 100-120ohms. And never, never use this >> connection as the burden resistor even if there is a fire extinguisher [quoted text clipped - 3 lines] > specified) is now on the measurement board itself. I'd like to keep it > there though to keep the installation procedure easy. ... Not good. Increases noise, big time, because the cable is mismatched because even regular cord won't have a Z of 1000ohms. And if the cable ever comes off ... tungggg ... phssssss ... *PHUT* > ... The wiring in > the test setup is pretty short (2 meters) but bad (not twisted, > unshielded). I'll order some shielded twisted pair tomorow. I already > figured this must be part of the problem. Ook niet zo goed. In an environment like this you can't work without shielded twisted pair, definitely not across two meters. That's like trying to listen to a Mozart concerto on a Harley-Davidson. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >[...] > [quoted text clipped - 4 lines] >Recipe against headache in cases like this: Proper matching of literally >everything, shielding, a glass or two of Beerenburger. Shielding sounds doable. The Beerenburger is out of the question though :-) >>> Try differential transfer, shielded twisted pair or Twinax soldered to >>> the burden resistor, from there to your measurement box, place a 2nd [quoted text clipped - 8 lines] >small doorbell transformer, the kind with two compartments where you can >scrap one of them out with wire cutters and without having to Yup. It's a DC welder. I already tried a small mains transformer but that doesn't work out very well in a test. Besides that would exceed budget and space constraints. >Unless the input diff-amp has a huge common mode range even for fast >stuff such as spikes I am not sure you can do it without another >transformer at the receiving end. Or rather, I've seen cases where it >didn't work. I think I have a pretty decent diff-amp. It can handle about 800V p-p common mode. >> That might be worth something to explore. The burden resistor (1k is >> specified) is now on the measurement board itself. I'd like to keep it [quoted text clipped - 3 lines] >because even regular cord won't have a Z of 1000ohms. And if the cable >ever comes off ... tungggg ... phssssss ... *PHUT* The cord coming off doesn't seem to be a problem. All similar systems I've seen so far have the burden resistor on the measurement board, not on the welding transformer. But I'll try it anyways. The old ways are not necessarely the best ways :-) SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- > The cord coming off doesn't seem to be a problem. All similar systems > I've seen so far have the burden resistor on the measurement board, > not on the welding transformer. But I'll try it anyways. The old ways > are not necessarely the best ways :-) Every CT I've built has had the resistor as close to the transformer (i.e., on it) as possible. I've had quite awful results putting the resistor on any kind of length. Come to think of it, that may be more due to the resistor itself having length, which would be a problem. Still, better safe than sorry... 'Course, I wind my own, encapsulated in masking tape, so embedding a burden resistor is no big deal. ;o) Tim SignatureDeep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms > > The cord coming off doesn't seem to be a problem. All similar systems > > I've seen so far have the burden resistor on the measurement board, [quoted text clipped - 11 lines] > > Tim 'Course, I wind my own, encapsulated in masking tape, so embedding a burden > resistor is no burden. ;o) SignatureYou can't have a sense of humor, if you have no sense! >> [...] >> [quoted text clipped - 7 lines] > Shielding sounds doable. The Beerenburger is out of the question > though :-) I liked this stuff ;-) >>>> Try differential transfer, shielded twisted pair or Twinax soldered to >>>> the burden resistor, from there to your measurement box, place a 2nd [quoted text clipped - 11 lines] > that doesn't work out very well in a test. Besides that would exceed > budget and space constraints. A doorbell transformer blows the budget on a welder? Man, and here I thought I was uncle Scrooge. >> Unless the input diff-amp has a huge common mode range even for fast >> stuff such as spikes I am not sure you can do it without another [quoted text clipped - 3 lines] > I think I have a pretty decent diff-amp. It can handle about 800V p-p > common mode. In a welding environment 800V may not be good enough. Plus you'd have to check the CMRR for fast pulses, like when the arc starts and stops. >>> That might be worth something to explore. The burden resistor (1k is >>> specified) is now on the measurement board itself. I'd like to keep it [quoted text clipped - 8 lines] > not on the welding transformer. But I'll try it anyways. The old ways > are not necessarely the best ways :-) Often they sure aren't. A burden resistor at the other end of a cable is usually a bad idea. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > In a welding environment 800V may not be good enough. Which "welding" environments did you have in mind? SignatureGreat advances in Debian Linux; post a bug report and get spam in three days. > >> In a welding environment 800V may not be good enough. > > Which "welding" environments did you have in mind? The usual. >100 amps, electrodes touching, arcing, getting stuck once in a while, thick cables floating around the room, ground potential of equipment bouncing, and so on. I once told someone to get his ham radio gear out before we start welding a broken gate. "Nah, this stuff is tough" ... "Better get it outta here" ... "No, really, it's ok, just get cracking on the gate" ... "Ok then" ... bzzt, bzzt, bzzzzzzzzzzt ... beep ... *PHUT* SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>> In a welding environment 800V may not be good enough. >> [quoted text clipped - 7 lines] > cracking on the gate" ... "Ok then" ... bzzt, bzzt, bzzzzzzzzzzt ... > beep ... *PHUT* Umm, have you ever put a volt meter across the cables? I was under the impression that that stuff matched the telephone and was in the vicinity of 40volts. I politely suggest that if it was around 800volts, then black and crispy would be a welder who made the wrong circuit. Hint, it is the current that causes the field. SignatureGreat advances in Debian Linux; post a bug report and get spam in three days. -- Great advances in Debian Linux; post a bug report and get spam in three days. > >>> In a welding environment 800V may not be good enough. > >> [quoted text clipped - 16 lines] > > Hint, it is the current that causes the field. Its the collapsing field that generates the HV spikes that can, and does knock careless welders on their a.ses. SignatureYou can't have a sense of humor, if you have no sense! >>>>> In a welding environment 800V may not be good enough. >>>> Which "welding" environments did you have in mind? [quoted text clipped - 14 lines] >> >> Hint, it is the current that causes the field. Hint: There's lots of inductances involved, wanted ones as well as undesired ones. Inductance -> current -> current suddenly stops -> inductance says "I don't think so!" -> tsssk ... *PHUT* > Its the collapsing field that generates the HV spikes that can, and > does knock careless welders on their a.ses. And mains connected power supplies. That's what croaked in the radio. The spikes on a mains circuit of sufficient length (and thus impedance) look rather terrifying. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > And mains connected power supplies. That's what croaked in the radio. > The spikes on a mains circuit of sufficient length (and thus impedance) > look rather terrifying. If you live anywhere near high voltage power lines, be very afraid if they ever collapse. The induced voltages in length of cable are interesting. SignatureGreat advances in Debian Linux; post a bug report and get spam in three days. >> And mains connected power supplies. That's what croaked in the radio. >> The spikes on a mains circuit of sufficient length (and thus impedance) [quoted text clipped - 3 lines] > they ever collapse. The induced voltages in length of cable are > interesting. I remember a report and a photo where some guy installed a cable TV hookup at a house near power lines. It cinged the whole side of the house. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>> [...] > [quoted text clipped - 16 lines] >A doorbell transformer blows the budget on a welder? Man, and here I >thought I was uncle Scrooge. The problem is that there is an existing board. The new board must be more or less budget neutral. I blew most of the budget on 0.1% resistors and instrumentation amplifiers. >>> Unless the input diff-amp has a huge common mode range even for fast >>> stuff such as spikes I am not sure you can do it without another [quoted text clipped - 6 lines] >In a welding environment 800V may not be good enough. Plus you'd have to >check the CMRR for fast pulses, like when the arc starts and stops. Its for a resistive spot welder. There is no arc. Just tens of kiloamperes! An arc would be very bad for the particular application. >>>> That might be worth something to explore. The burden resistor (1k is >>>> specified) is now on the measurement board itself. I'd like to keep it [quoted text clipped - 11 lines] >Often they sure aren't. A burden resistor at the other end of a cable is >usually a bad idea. I hope I can get some testing on a real rig this week. SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- >>>> [...] >>>>>> Try differential transfer, shielded twisted pair or Twinax soldered to [quoted text clipped - 18 lines] > more or less budget neutral. I blew most of the budget on 0.1% > resistors and instrumentation amplifiers. Then there's cost reduction potential :-) No way to clamp anything so you don't need all these precision parts? >>>> Unless the input diff-amp has a huge common mode range even for fast >>>> stuff such as spikes I am not sure you can do it without another [quoted text clipped - 8 lines] > Its for a resistive spot welder. There is no arc. Just tens of > kiloamperes! An arc would be very bad for the particular application. Until the spot contact lets go at a not so good moment, or one of the panels to be welded had a bad spot there, or a cable breaks, and so on. Never assume things to remain as perfect as they are on paper or in the engineering lab. >>>>> That might be worth something to explore. The burden resistor (1k is >>>>> specified) is now on the measurement board itself. I'd like to keep it [quoted text clipped - 11 lines] > > I hope I can get some testing on a real rig this week. Good! I'd test for faulty conditions as well, like the ones above. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > Hey, time for our engineering meeting; Japanese food today! Can you get decent yakisoba in SFO? I also like plain ol' ordinary fried rice, but I can make that at home; I wish I had the recipe that the Java Curry Shop in Shinjuku used - best curry I've ever had! :-) Yes, Japanese curry. :-) Thanks! Rich > Audio: if one end of a shield is disconnected, the delta-voltage (60 > Hz, RF, esd spikes) between chassis is greater. If the signal is > single-ended, that increases noise directly. If differential, it > increases common-mode noise. > > Why would you want to do that? Because that's what it said to do in the instructions that came with the kit. Cheers! Rich >>>>> ... was reading it would get data errors. The problem was that the >>>>> shield on the cable from the heads to the preamp was grounded on both [quoted text clipped - 19 lines] > characteristics. Of course, the thing that was drummed into me while > they were teaching me this was "GROUND LOOPS!". :-) Trouble is, since we moved from Alexander Graham Bell's wall phone (with crank) to cell phones RF frequently turns into audio after getting into such single-end shielded cables. All it takes is an opamp with bipolar input structure. Of course, with a good old tube amp you'll continue to be fine :-) SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>> my latest blog (#14): [quoted text clipped - 11 lines] > > That's usually the best way to ground shields. When I was a kid, my brother built a Heathkit TOOB amp; in the low level circuits, they only ever grounded one end of the shields. Cheers! Rich >>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>> my latest blog (#14): [quoted text clipped - 14 lines] >When I was a kid, my brother built a Heathkit TOOB amp; in the low level >circuits, they only ever grounded one end of the shields. Inside a steel chassis pan, it wouldn't matter. But then Heathkit was hardly an authority on signal management. John >>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>> my latest blog (#14): [quoted text clipped - 14 lines] > Inside a steel chassis pan, it wouldn't matter. But then Heathkit was > hardly an authority on signal management. Now wait a minute, they engineered darn good stuff. The old HW100/101 transceivers were among the best ever made back in the tube days. Still got one. No noises or buzzes whatsoever and its performance in the vicinity of strong signals is stellar. The only not so good thing was the two rubber pulleys because they cooked out too fast, but you could keep a stash of them in the drawer. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>>> my latest blog (#14): [quoted text clipped - 21 lines] >the two rubber pulleys because they cooked out too fast, but you could >keep a stash of them in the drawer. Toob amps didn't rectify RF as well as silicon does. John >>>>>>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>>>>>> my latest blog (#14): [quoted text clipped - 23 lines] > > Toob amps didn't rectify RF as well as silicon does. But: We used such transceivers in multi/multi type ham radio contests and field days. There you had to deal with another 100W transmitter blasting into an antenna maybe 100ft away. You could make a light bulb glow on the other antenna. Many transceivers fell off the rocker there, the only ones that always performed were the super-expensive Collins line and the Heathkit at the budget end of the price scale. If their signal management wasn't up to snuff this would never have worked. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. >>>>>> Check out a rather unusual phenomenon you can see on your >>>>>> oscilloscope in my latest blog (#14): [quoted text clipped - 25 lines] > the two rubber pulleys because they cooked out too fast, but you could > keep a stash of them in the drawer. Brings back pleasant memories. I donated my HW101 to the Boy Scouts radio club many years ago. I wish I still had my HW 16 - lots of wee hours CW with that (my first) rig. Ed >>>>>>> Check out a rather unusual phenomenon you can see on your >>>>>>> oscilloscope in my latest blog (#14): [quoted text clipped - 30 lines] > radio club many years ago. I wish I still had my HW 16 - lots of wee > hours CW with that (my first) rig. At least you've got the memories, that's all that really counts. I donated my HW101 to a ham in former East Germany after the wall fell. Back then they didn't have the funds to buy western quality gear. I kept the older HW100 because that has a white-knuckle supply, direct rectification and Cockroft-Walton cascade from 230VAC mains. Plug it in the wrong way ... *BAM*. He got the good set, with original power supply and the whole thing looked hardly used, almost like new. He was really happy. SignatureRegards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. > When I was a kid, my brother built a Heathkit TOOB amp; in the low level > circuits, they only ever grounded one end of the shields. My Heathkit IO-103 scope is the same way. Tim SignatureDeep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14):http://www.alternatezone.com/eevblog/ [quoted text clipped - 9 lines] > ================================================ > Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/ Hey, is that Chinese take-out I spy? >> Check out a rather unusual phenomenon you can see on your >> oscilloscope in my [quoted text clipped - 13 lines] > > Hey, is that Chinese take-out I spy? No. Where? Dave. Signature================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ > m...@sushi.com wrote: > >> Check out a rather unusual phenomenon you can see on your [quoted text clipped - 21 lines] > ================================================ > Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/ On the right. Eh, probably an open box. >> m...@sushi.com wrote: >>>> Check out a rather unusual phenomenon you can see on your [quoted text clipped - 20 lines] > > On the right. Eh, probably an open box. Yep, an open Altronics box! Curiously though the contents were made in Australia and not China - how novel! Dave. Signature================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14): [quoted text clipped - 7 lines] > Have fun. > Dave. Look at a piece of blank paper and you will see what i see on that site. Therefore the mashed and flattened tree wins. >> Check out a rather unusual phenomenon you can see on your oscilloscope in >> my latest blog (#14): [quoted text clipped - 9 lines] > Look at a piece of blank paper and you will see what i see on that site. > Therefore the mashed and flattened tree wins. If you set the time base correctly and crunch down on a carrot you will see a complex waveform on the scope. Very difficult to store on a digital scope though. :-) Mike >> Look at a piece of blank paper and you will see what i see on that >> site. Therefore the mashed and flattened tree wins. > > If you set the time base correctly and crunch down on a carrot Lunch pictures? > If you set the time base correctly and crunch down on a carrot > you will see a complex waveform on the scope. > Very difficult to store on a digital scope though. :-) > Mike I wonder if you take a picture with a longish shutter speed while eating Doritos if you could capture that. >> If you set the time base correctly and crunch down on a carrot >> you will see a complex waveform on the scope. [quoted text clipped - 3 lines] > I wonder if you take a picture with a longish shutter speed while > eating Doritos if you could capture that. only if you bolted the camera to your head... >>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>> my latest blog (#14): [quoted text clipped - 14 lines] >Very difficult to store on a digital scope though. :-) > Mike Just hit the top of your head with your fist. You'll see the typically underdamped transient response of your visual tracking system. John > Oh, and the probe doesn't have to be shorted either. I always call a probe shorted as in the video an "inductive pickup loop" :-). Of course, even when a probe isn't shorted it's an inductive pickup loop too. Tim. >Check out a rather unusual phenomenon you can see on your oscilloscope in my >latest blog (#14): >http://www.alternatezone.com/eevblog/ >See if you can get it to happen on your scope! >I'll offer a free subscription to my blog for the best screen shot posted >:-> I'm afraid someone already got a patent on electrostatic discharge. SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14):http://www.alternatezone.com/eevblog/ [quoted text clipped - 9 lines] > ================================================ > Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/ Nice, love your accent. If it were winter here, I'd fire up my Tek 547 (since my Rigol is at a friend's). But in summer, the 547 cancels the A/C so I don't use the 547... > Check out a rather unusual phenomenon you can see on your oscilloscope in > my latest blog (#14): > http://www.alternatezone.com/eevblog/ > See if you can get it to happen on your scope! Hello: Since you're into it, why don't you compare the refresh rate of digital vs analog scopes? Also known as the waveforms-per-second capability? It's something i'm very curious about in practice, and also, do the digitals behave as the analogs (like a low-pass filter) when you increase the freq of a wave-form or suddenly start aliasing? Thank you. I really enjoy your blog Best Regards Steve Sousa "Steve Sousa" > "David L. Jones" > Since you're into it, why don't you compare the refresh rate of digital vs > analog scopes? ** Be like comparing chalk with cheese. > Also known as the waveforms-per-second capability? ** Pretty meaningles with analogue scopes that show the input signal continuously. > It's something i'm very curious about in practice, ** Digital scopes SAMPLE the signal, both in amplitude and time - then show you one screen's worth of SAMPLEs. Bit later they show you another one. Bit like tasing a pot of stew with your little finger. > and also, do the digitals behave as the analogs (like a low-pass filter) > when you increase the freq of a wave-form or suddenly start aliasing? ** The topic of " aliens " with DSOs is verboten among makers and fanatics alike. Plain fact is that you do not get to see what is actually coming down the probe cable and you may well see stuff that is not there at all. Bit of a worry, really. ..... Phil >> Check out a rather unusual phenomenon you can see on your >> oscilloscope in my latest blog (#14): [quoted text clipped - 15 lines] > Best Regards > Steve Sousa It's not only about waveforms-per-second, it's also about the capture and display engine as well. The manufactuers have various technologies (e.g. Tek Digital Phosphor) to make their digital scopes have an "analog type" display and response, and they work superbly. In fact they can be better than analog in many respects. But that performance costs money, so you have to start paying around say the $5K mark before you get a digital scope that really performs like an analog one in terms of variable display intensity, response time, and capture dead-time. See here for more info: http://www.tek.com/products/oscilloscopes/dpo_technology/ http://www.tek.com/Measurement/App_Notes/Technical_Briefs/55-13757/eng/55w-13757 -0.pdf Lower end scopes don't have these "analog like" display technologies, so then "waveforms-per-second" is pretty much the basic benchmark. Modern scopes are pretty darn good though, and even the low end cheap ones are streets ahead of previous generation DSO's. Those who haven't used a modern high end digital scope don't know how superb they can really be. With modern fast real-time deep memory scopes, aliasing is pretty much a thing of the past. Might make an interesting future blog... Dave. Signature================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ >It's not only about waveforms-per-second, it's also about the capture and >display engine as well. [quoted text clipped - 18 lines] >With modern fast real-time deep memory scopes, aliasing is pretty much a >thing of the past. Is that an Agilent 6000 series scope I see in front of you? >Might make an interesting future blog... > >Dave. >> It's not only about waveforms-per-second, it's also about the >> capture and display engine as well. [quoted text clipped - 21 lines] > > Is that an Agilent 6000 series scope I see in front of you? It is indeed. In fact, it's that exact same setup where I first found this issue, debugging that actual design as you see there, probably only days before or after that photo was taken. Dave. Signature--------------------------------------------- Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ >> Check out a rather unusual phenomenon you can see on your oscilloscope in >> my latest blog (#14): [quoted text clipped - 7 lines] >Also known as the waveforms-per-second capability? It's something i'm very >curious about in practice, and also, do the digitals behave as the analogs The waveforms-per-second depends on the sample rate, the length of the acquisition memory and the throughput of the display system. Another thing that limits the refreshrate is the refreshrate of the display. The latter can be circumvented by adding several swaps into one signal. >(like a low-pass filter) when you increase the freq of a wave-form or >suddenly start aliasing? That depends on the samplerate and the bandwidth. If the samplerate is lower then the maximum bandwidth expect aliasing effects unless it is a sampling oscilloscope. SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- >>> Check out a rather unusual phenomenon you can see on your oscilloscope in >>> my latest blog (#14): [quoted text clipped - 12 lines] >thing that limits the refreshrate is the refreshrate of the display. >The latter can be circumvented by adding several swaps into one ^^^^^ sweeps >signal. > [quoted text clipped - 4 lines] >lower then the maximum bandwidth expect aliasing effects unless it is >a sampling oscilloscope. SignatureFailure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" -------------------------------------------------------------- > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14):http://www.alternatezone.com/eevblog/ [quoted text clipped - 9 lines] > ================================================ > Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/ After watching your video, for some reason I was reminded of Starbuck Flying and his computer adventures. Aren't you glad he doesn't have a scope? :D Michael > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14):http://www.alternatezone.com/eevblog/ [quoted text clipped - 9 lines] > ================================================ > Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/ His schematic of the scope probe and scope input are oversimplified to the point of incorrectness. Also, he ignored the low-pass nature of the oscilloscope input, which might contribute to the clean "sinusoidal" waveform. >> Check out a rather unusual phenomenon you can see on your oscilloscope in my >> latest blog (#14):http://www.alternatezone.com/eevblog/ [quoted text clipped - 14 lines] >the oscilloscope input, which might contribute to the clean >"sinusoidal" waveform. Scope vertical amps don't ring. John On Jun 28, 6:03 pm, John Larkin <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > On Sun, 28 Jun 2009 12:45:41 -0700 (PDT), Richard Henry > [quoted text clipped - 19 lines] > > Scope vertical amps don't ring. That was not my point. The limited low-pass band of the input amplifier and sampling circuit will either completely filter out higher-frequency components, or will alias them down. If you are seeing a nice sinusoidal waveform on an oscillioscope whose fundamental frequency is close to the frequency limit of the scope, chck it with a higher-frequency device. > On Jun 28, 6:03 pm, John Larkin > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: [quoted text clipped - 29 lines] > fundamental frequency is close to the frequency limit of the scope, > chck it with a higher-frequency device. I've seen the same (or similar) result with a higher bandwidth (300MHz) scope, so the vertical bandwidth limit has nothing to do with it. The TDS-220 is just the one I happened to have available at the time. I filmed some comment on this extra stuff but it didn't make the cut. Dave. Signature================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ > Check out a rather unusual phenomenon you can see on your oscilloscope in my > latest blog (#14):http://www.alternatezone.com/eevblog/ [quoted text clipped - 9 lines] > ================================================ > Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/ Do you still get the ringing if the nose of the probe is shorted to the tip? I thought it was the inductance of the ground lead which contributed mostly to the ringing. >> Check out a rather unusual phenomenon you can see on your >> oscilloscope in my [quoted text clipped - 14 lines] > Do you still get the ringing if the nose of the probe is shorted to > the tip? Yes. >I thought it was the inductance of the ground lead which > contributed mostly to the ringing. Nope. As I've said, it works without the groud lead even attched, or even on a bit of coax. Dave. Signature================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/ |
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