Rheostat/Potentiometer

Guest
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
 
fcache@gmail.com wrote:
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.
Click to expand...
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.

On Mon, 28 Jul 2008 10:08:46 -0700 (PDT), fcache@gmail.com wrote:

: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
 
On Tue, 29 Jul 2008 10:41:01 GMT Ross Herbert <rherber1@bigpond.net.au>
wrote in Message id: <4grt84hrknervqgs2b7gr5as943sfeht0v@4ax.com>:

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?
Click to expand...
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.

On Mon, 28 Jul 2008 10:08:46 -0700 (PDT), fcache@gmail.com wrote:

: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
Click to expand...
 
On 29 Jul 2008 16:17:24 GMT, Scott Seidman <namdiesttocs@mindspring.com> wrote:

: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...
 
On Wed, 30 Jul 2008 04:40:09 GMT Ross Herbert <rherber1@bigpond.net.au>
wrote in Message id: <s4sv84p3280f4h7eoohdlpklh4mm9bqan6@4ax.com>:

On 29 Jul 2008 16:17:24 GMT, Scott Seidman <namdiesttocs@mindspring.com> wrote:

: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...
Click to expand...
I guess I *assumed* the OP was looking for a variable load. (I should stop
doing that...)
 
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