[time-nuts] Temperature sensors and bridge amps
lists at rtty.us
Fri Nov 12 12:28:03 UTC 2010
The 100 ohm standard for RTD's dates way back. The assumption was that you had it on a *long* run of cable (2 pair / sense leads of course). The insulation leakage was a bigger issue than anything else in the equation.
On Nov 12, 2010, at 5:36 AM, Poul-Henning Kamp wrote:
> In message <20101112110627.488cbc8f at vz127.worldserver.net>, "Florian E. Teply"
>> In a bridge circuit, you don't measure resistance directly, but use the
>> voltage that appears across the bridge. So for a 100 ohms element,
>> you'd usually have ten times the current flowing in that branch
>> compared to a 1kohm element.
> This was one of the things that I wondered about: How large currents
> are used ?
> Can't be too much because that would lead to self-heating...
> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
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