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Science Forum Index » Electronics - Components Forum » Rheostat/Potentiometer...
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 Posted: Mon Jul 28, 2008 7:08 am |
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Guest
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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 |
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| Jamie... |
| Posted: Mon Jul 28, 2008 6:30 pm |
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Guest
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fcache at (no spam) gmail.com wrote:
Quote: 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.
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" |
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| Ross Herbert... |
| Posted: Tue Jul 29, 2008 5:41 am |
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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 at (no spam) 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 at (no spam) 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 |
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| JW... |
| Posted: Tue Jul 29, 2008 8:36 am |
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Guest
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On Tue, 29 Jul 2008 10:41:01 GMT Ross Herbert <rherber1 at (no spam) bigpond.net.au>
wrote in Message id: <4grt84hrknervqgs2b7gr5as943sfeht0v at (no spam) 4ax.com>:
Quote: 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 at (no spam) 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?
Am I missing something here? The OP didn't mention what voltage he would
be working with, where do you get your wattage figures?
Quote: Perhaps you had better start by telling the group what the application is.
On Mon, 28 Jul 2008 10:08:46 -0700 (PDT), fcache at (no spam) 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 |
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| Scott Seidman... |
| Posted: Tue Jul 29, 2008 11:17 am |
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Guest
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JW <none at (no spam) dev.null> wrote in news:347u84d103avl2p4ppoej6404qigf95ius at (no spam)
4ax.com:
Quote: where do you get your wattage figures?
I^2*R would be my guess.
--
Scott
Reverse name to reply |
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| Ross Herbert... |
| Posted: Tue Jul 29, 2008 11:40 pm |
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Guest
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On 29 Jul 2008 16:17:24 GMT, Scott Seidman <namdiesttocs at (no spam) mindspring.com> wrote:
:JW <none at (no spam) dev.null> wrote in news:347u84d103avl2p4ppoej6404qigf95ius at (no spam)
:4ax.com:
:
:> where do you get your wattage figures?
:>
:
:I^2*R would be my guess.
Precisely... |
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| JW... |
| Posted: Wed Jul 30, 2008 8:51 am |
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Guest
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On Wed, 30 Jul 2008 04:40:09 GMT Ross Herbert <rherber1 at (no spam) bigpond.net.au>
wrote in Message id: <s4sv84p3280f4h7eoohdlpklh4mm9bqan6 at (no spam) 4ax.com>:
Quote: On 29 Jul 2008 16:17:24 GMT, Scott Seidman <namdiesttocs at (no spam) mindspring.com> wrote:
:JW <none at (no spam) dev.null> wrote in news:347u84d103avl2p4ppoej6404qigf95ius at (no spam)
:4ax.com:
:
:> where do you get your wattage figures?
:
:
:I^2*R would be my guess.
Precisely...
I guess I *assumed* the OP was looking for a variable load. (I should stop
doing that...) |
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