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I'm making a device that will operate in cold environment. The ambient temperature will vary between -50℃ and -20℃. The sensor is supposed to monitor the temperature so that the microcontroller in my device decides, whether a battery heating system in the device runs or not. The temperature could change at a speed of 0.2℃/s.

What would be the best sensor type among a digital temperature sensor (like DS18B20), a RTD, and a thermocouple?

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  • \$\begingroup\$ There are a few thermal conduction and insulation issues, so there is no temperature gradient issues across the battery and from heater to sensor to cell electrodes but any could work as well as several thermistors like TFPT series PTC SMD's with 0.702 R(25'C) @-55C and 0.825R(25C) @-20C in a bridge to drive the heater. But the lag and temp gradient depends on thermal insulation to outside and conduction to cell inside from heater as well as sensors being averaged. But any digital solution can work too. \$\endgroup\$ Sep 11 '17 at 0:21
  • \$\begingroup\$ But for efficiency, good insulation is needed. \$\endgroup\$ Sep 11 '17 at 0:27
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The temperature of the battery will not change by 0.2 degrees per second mostly likely. The ambient isn't all that important, I suspect. Accuracy of a degree C or two is probably fine.

Also, you only need to sense accurately at a single point in the temperature scale, assuming that the sole purpose of the sensor is to make the heat/no heat decision.

So I suspect the best system in your situation is a precision thermistor, an ADC on your microcontroller and a single precision resistor to the ADC reference (might be the supply rail). Even a 10 bit ADC will give you 50 or so counts per degree C at mid-scale, and accuracy can be quite good with a 1% thermistor.

You can use the same kind of thermistor that is used in battery packs to monitor charging, mounted similarly.

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