Max's Application #12 - Thermistor?

[max]

Max's Application #12 - Thermistor Example




This is an example of connecting CUBLOC to a dirt cheap thermistor that spits out current temperature to the debug screen.

This is the more "efficient" version than the one on the manual using "formulas" rather than tables.

You will be able to cut processing time and save a bunch of Data Memory by using this code instead.


Oh yeah, this was possible due to help from Mr. Yang from http://www.Wattminder.com.



Source code included here


Download Here:


http://cubloc.com/max/MaxApp12-Thermistor.zip

[David]

Hello Max
I have being using your Application #12 for thermistor conversion but could not get accurate results. I checked through your formulas in excel and as expected they are perfect. But as a result of further checking it seems that the Log function of Cubloc studio returns the result of an Ln function so having changed the code to represent this the results are now pretty accurate I dont know if this is with all versions but I am using version 2.1.F. I hope this is of some help to somebody.

David

[wayhaw]

The following comments are for anyone struggling with thermistor calcs and using the Cubloc manual and Max's notes for primary reference.

I confirm David's comment about the Cubloc Basic function to get the natural log of a number.
All you need is: someVar = Log(X). NOT Log(X) / Log(Exp(1)).

Also highly recommend using the Steinhart-Hart calcs versus loading a table. You'll need the three coefficients though. Omega supplies this information with their thermistors. I used their 44000 series.

Another "gotcha" I discovered that made all the difference in the world was having a matching balance resistor. If the thermistor is rated at 10K then use a 10K standard resistor as the first component in the circuit. Be sure to use the 10000 constant in your calcs for the "R" value leading to the Log statement as well. The manual shows a 1K resistor (and 1000 constant) but doesn't mention the relationship to the thermistor. Had I known this to begin with it would have saved me weeks of hair pulling.

I would be happy to share any knowledge I've gained via email. wayhaw@bellsouth.net.

Wayne