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My USB-TEMP is not reading my thermistor(s) correctly.

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My USB-TEMP is not reading my thermistor(s) correctly.

Measurement Computing’s USB-TEMP and USB-TEMP-AI utilizes the standard Steinhart-Hart equation below to calculate temperature values.
 1/T = A + Bln(R) + C(ln(R))3

    T is temperature
    R is resistance @ T (25C)
    A,B,&C are the Steinhart-Hart coefficients



These coefficients values are necessary for calculating the proper temperature and are provided by the supplier of the thermistor. However, we have come across a few thermistor manufacturer’s that supply the resistance in a ratio (Rt/R25) versus the raw resistance value; this creates an error when the coefficients are used in our InstaCal utility resulting in erroneous data.


To remedy this you must turn the given ratio values back to resistance by multiplying the ratio value by the thermistor’s resistance value at 25 . Then you will need to calculate the Steinhart-Hart coefficient for A, B, & C using a Steinhart-Hart coefficient caculator which can be easily found via Google search. You can then take these values and use them when configuring your USB-TEMP or USB-TEMP-AI under InstaCal. 

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Article ID: 50326

Last Modified:2/21/2012 2:54:15 PM

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