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Sensor type
Posted: Wed Mar 15, 2023 6:58 pm
by Countrypaul
Does anyone know what sort of sensor is used in these cheap and cheerful LCD thermometers?
https://www.amazon.co.uk/dp/B0BK8SVW1P
Partially for curiosity, but also I have a number that don't work so am looking a letting my 10yo play with them and an Rpi so would be best that I know what they are first. They could be an 10K NTC thermistor for example.
Re: Sensor type
Posted: Wed Mar 15, 2023 7:28 pm
by Caesium
I've actually got one of these so cracked it open for a look. It's only marked RT on the board.
Put a multimeter across it and it was 12.5k ohm at 20c, rising to about 24k ohm in a glass of ice water if that helps any?
Re: Sensor type
Posted: Wed Mar 15, 2023 7:30 pm
by Tinbum
I remember having some of them as a child myself, from maplin I would think. No Internet shopping then. I will have a look as I'm certain I still have one in a box of old childhood toys.
Re: Sensor type
Posted: Wed Mar 15, 2023 7:43 pm
by marshman
Pretty sure you are correct, the "sensor" is a 10k (ish) NTC. I bought a load a few years back and have a couple of defunct ones and the sensors measure just over 10kOhm at around 20 deg C & drops to around 1kOhm at approaching 100 deg C. Should be pretty easy to check/calculate the B value and then plumb some numbers in the code to make a working Thermometer on a RPi.