Quote:
|
Originally Posted by DeadEye
A few points that may/may not be useful:
You mention accuracy is important, the MAX186's internal reference depending on version can be as bad as +/- 80ppm. If using this chip ensure you get the best version. Much better external references are available.
Incorporating switchable gain instrumentation amplifiers into the design will allow various ranges to be monitored at better resolution.
Linearisation has to be incorporated in the software to handle the thermistor, if working over a shortish range then dependant on accuracy you are trying to achieve a small PRT, could be used which is almost linear over limited ranges.
Consider setting up a small current source (100uA) for powering of sensors, PRT, thermistors or as a resistor measuring device.
Hope this helps.
|
Appreciate the input Deadeye.
I was planning to use a MAX6241 voltage reference via a OP484 type voltage follower buffer to feed both the ADC and the thermistors. Settling on 100K thermistors and 80K 0.1% precision resistors to minimise self heating and lead resistance effects, buffered by said OP484 voltage followers. You sound like you might be able to say if this is a reasonable approach or not.
Linearisation and calibration will be in software (Excel, heh)
Tell me more about these intrumentation amplifiers, I've been looking at the AMP02 but am not sure if I need/can even extract from noise the extra resolution. Plus I want to keep the single rail if possible.
I'm over 15 years beyond studying this stuff.