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Hi all,

I've put this page together for PIClist

http://www.piclist.com/techref/io/sensor/0-10mA_remote_lm335.htm

This is a circuit I use for a couple of applications and it works fine

I've made one up using just the front end (without the V-to-I
conversion, taking a 100mV/C voltage from pin14) to monitor
a heatsink

I was expecting the front end would be fairly generic but find that
it doesn't work 'as is' if a standard dual opamp like the LM358 is
used

In the attached diagram I've included comparison measurements
for the two opamps. The 3.185V when using the LM358 doesn't
budge. It's 0.64V x 5, so the gain is correct, but the 0.64V isn't

An LM833 produces a similarly wayward result

I expected to see about 1.04V at the output

(2.94-2.73) * 5, or 20.8C @ 50mV per degC. The original
circuit is pretty close, 1.985V vs 2.000V

How can I improve this circuit to make it more generic ?

TIA

Joe=

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