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Electronics Forum / Components / July 2008Rheostat/Potentiometer
Hi, I'm working as a Biomedical Engineering Technician intern in a local hospital and I need help finding a rheostat or potentiometer that can meet my needs. I'm looking for a linearly variable resistance device that goes from 0 to 150 ohms, can handle between 1.5 to 2 amps of current, and that has a very smooth (granular) change of resistance as the wiper is rotated. Resistance changes of %4 or more would not be acceptable? I have spent hours looking for such a device. Any pointers? Thanx, Ed > Hi, > [quoted text clipped - 9 lines] > Thanx, > Ed. As you have noted, it maybe hard to find what you're looking for with in a reasonable physical size. What kind of signal are you passing through it? DC,AC HV etc...? http://webpages.charter.net/jamie_5" You gotta be kidding.... Did the technician give you this as a task? It sounds like it could be the typical trickery played on newby tech assistants who know next to nothing. In my day we had to find left handed screwdrivers or a skyjack to lift heavy equipment racks into awkward places. For starters, at the maximum resistance of 150 ohms @ 1.5A power dissipation would be 337.5W. If it were carrying 2A then dissipation would be 600W. You would also need some safety margin, so a 700W rating might be sufficient. I haven't seen a pot rated higher than 300W and this was around 5" in diameter and that would need some pretty good ventilation to keep it cool when carrying maximum current. Now what would a biomed tech need this sort of a beast for I wonder? Perhaps you had better start by telling the group what the application is. :Hi, : [quoted text clipped - 9 lines] :Thanx, :Ed >You gotta be kidding.... Did the technician give you this as a task? It sounds >like it could be the typical trickery played on newby tech assistants who know [quoted text clipped - 8 lines] >maximum current. Now what would a biomed tech need this sort of a beast for I >wonder? Am I missing something here? The OP didn't mention what voltage he would be working with, where do you get your wattage figures? >Perhaps you had better start by telling the group what the application is. > [quoted text clipped - 11 lines] >:Thanx, >:Ed JW <none@dev.null> wrote in news:347u84d103avl2p4ppoej6404qigf95ius@ 4ax.com: > where do you get your wattage figures? I^2*R would be my guess.  SignatureScott Reverse name to reply :JW <none@dev.null> wrote in news:347u84d103avl2p4ppoej6404qigf95ius@ :4ax.com: : :> where do you get your wattage figures? : :I^2*R would be my guess. Precisely... >:JW <none@dev.null> wrote in news:347u84d103avl2p4ppoej6404qigf95ius@ >:4ax.com: [quoted text clipped - 4 lines] > >Precisely... I guess I *assumed* the OP was looking for a variable load. (I should stop doing that...) |
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