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NTC thermistor gain calculation for Board Manager

DMeie.2
Senior

Can anyone explain to me how to calculate the "gain" property for a "NTCThermistor" hardware variant?
The NTCs we use (NTCS0805E3103FMT) are not linear, so a "Thermistor gain in mV/°C" as mentioned in the wiki doesn't apply.

As a side note: The wiki says the property should be named "ntcThermistorGain" but inside the board configuration json this name is invalid and it is simply named "gain" instead.

4 REPLIES 4
raptorhal2
Lead

The gain is a logrithmic equation, as explained in this TI application note:

https://www.ti.com/lit/an/slua621.pdf

The B25/85 factor to apply is in the Thermister data sheet.

I used a non-linear function generation table to relate thermister resistance to temperature.

Calculating a conversion table is not the issue, the NTC manufacturer provides a tool for that. However, the MCSDK doesn't seem to be using a converstion table.

What I don't understand is how to get the "gain" value, as its description ("mV/°C") implies a linear correlation.

Its description implies a "smart sensor" with a built-in conversion table.

Using your NTC in a resister network of ref to NTC to fixed resister (or ref to fixed to NTC resister) to ground would provide a voltage tap between NTC and fixed. The mid-temperature gain in your application may be adequate.

Is the Board Manager software modifiable to include a function table?

 

The function to calculate and read out the value is define as weak, so it should be possible to implement an alternative method for calculation.

Guess that's what I'll have to do then.