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Thermistor sensor

lucasromeiro

Dec 17, 2022
2
Joined
Dec 17, 2022
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Hello guys.

I'm using an efr32bg22 Bluetooth module and would like to read a thermistor with it!

I've never used a thermistor.

Reading a little about the subject, it seems a little complicated to me.
There are some formulas for obtaining a conversion but apparently the best way is to use a conversion table.

Unfortunately I don't know how to do any of them.

I would like to use the table or a method that helps to have greater precision.

I bought 2 thermistor models and I have them here with me:
NTCSP103JF103FT1S
TX06F103F3435ER

I had a temperature sensor that used a thermistor to measure the temperature inside a refrigerator. I want to do the same thing.

I disassembled the sensor and the circuit I found was as follows:

Captura-de-Tela-2022-12-17-a-s-11-30-01.png



I imagine that I can replicate this circuit, but the part of converting the ADC signal to the temperature accurately I still don't know how to do it.

Can someone help me?

Important: I intend to use the range from 30 to -40 degrees celcius.
Most of the time it will operate in the range of 10 to -20 degrees celcius (inside a fridge or freezer).

Can anyone help me with this?
 

kellys_eye

Jun 25, 2010
5,296
Joined
Jun 25, 2010
Messages
5,296
You will have to do some testing yourself to establish the thermistor value at specific temperature points. The manufacturers datasheet may give all you need to know - have you checked it out?

<edit> the datasheets DO show all the values at the stated temperatures. All datasheets available at the Mouser site you ordered the stuff from.....

When you do eventually make up the correct circuit (the schematic you show is perfectly adequate) then you have to code the processor to read the voltage at that port and then either apply a formula (calculation) to the reading OR use a lookup table.
 

bertus

Moderator
Nov 8, 2019
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FYI, there is also a thread running at AllAboutCircuits:

Bertus
 

lucasromeiro

Dec 17, 2022
2
Joined
Dec 17, 2022
Messages
2

I'm considering using a digital sensor to do this. Seems to make more sense.
I would like a good cost/benefit ratio, but I believe that with a 1% thermistor I will not be able to have an accuracy of 0.5 degrees C. It will certainly be bigger.
There is thermistor error, adc error, other circuit errors...
To improve this I will need a 0.1% thermistor, which is much more expensive...

I looked for a sensor that has a power supply range between 1.7 and 3.3v, with an energy consumption similar to what I mentioned above and with an accuracy of at least 0.5 degrees C. I didn't find good cost/benefit options.... A good one target cost for me is something less than 1 dollar for this sensor.



In my searches I found the following options:

TMP112AIDRLR
TMP126NDCKR
SHTC3
AHT-15
BME-280

I need something cheaper if possible.



Do you know of any CI options that would fit well with this solution?
 
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