[time-nuts] Environmental sensor recommendations.

Neil neil at g4dbn.uk
Thu Apr 5 16:06:52 EDT 2018

I've used a few Pt100 RTDs over the years for gas flow temperature 
control in the 200-300C range.  At 0.385 ohms per K, the challenge of 
managing the noise is a lot tougher than a cheapo NTC thermistor, but I 
needed repeatability and stability. 

I use a 4-wire Kelvin connection, with 1 mA current drive. £14 at 10-off


On 05/04/2018 16:27, Dr. David Kirkby wrote:
> Keysights nano volt / micro ohm meter takes
> https://www.keysight.com/en/pd-1000001296%3Aepsg%3Apro-pn-34420A/micro-ohm-meter?cc=ZA&lc=eng
> can do direct SPRT, RTD, Thermistor, and Thermocouple measurements
> SPRT = Standard Platinum Resistance Thermometer
> I don't claim to know much about this, but the uncertainty quoted for the
> SPRT probes with that meter is 0.003 deg C.
> When I Google SPRT probes, I see they are incredibly expensive - many
> thousands of USD each.
> I'm a bit puzzled there seem to be a number of 3-wire platinum resistance
> thermometers. I can understand using 4-wires for a Kelvin connection, but
> can't understand the use of 3-wires.
> Of course, for environmental monitor in a lab, one is most unlikely to need
> very high accuracy.
> Dave
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