Thermistor reading clamped at -17 deg C

[Neil.Pate]

David,

Thanks for the ideas, they were basically along the same lines as I was thinking.

Unfortunately option 1 is a non-starter as we are forced to interface with the thermistor our client is using (zero chance of them changing it).

Option 2 may be feasible. Do you know if there are any NI modules that can provide excitation currents in the region of 10-->15uA?

There is another option that I can see, and thats to use the parallel resistor you suggested, and then correct for the measurement error in the software. This is certainly the cheapest option, but requires a bit of thought.

Neil

[david.bolt]

Hi Neil

There arent any modules that specifically have a excitation in that range. My advice is to try the parallel resistor, calibrate it correctly and see if this can offer any results. What is your temperature range you are working in for thought?

[Neil.Pate]

David,

I need to be able to measure between -50 and +135 deg C, the thermistor varies between 650k @ -50 and approx 600 ohms at the top end.

Resistor in parallel seems like the way forward for now...

I crunched the numbers in Excel, and have figured out how to apply as precise as necessary a correction, so it should be do-able.

Thanks again for your help.