The picture below is my NTC temperature detection circuit.
NTC is 3950 100K.
When I measure the resistance of the NTC separately, it shows that the resistance is 88K
But when I connected the NTC to the circuit, the resistance of the NTC became 10K
This causes my temperature collection to be inaccurate
Is there any good way to solve it?
Jamie postato su September 9, 2020
10K? How much resistance is there between +5V and GND? If the resistance is relatively small, the 10K you measured is the result of NTC connected in parallel with R36, which should not affect the actual voltage divider. The input impedance of the ADC may affect (but not 10K), so the resistance value of R36 and NTC should be reduced as much as possible when the power consumption is acceptable.
Kendall postato su September 9, 2020
This has a certain relationship with the input impedance of your MCU's ADC. It is recommended that you generally do not use such a large voltage divider resistor. It is better to add a same direction follower after the NTC voltage divider and then connect to the ADC. If it is not affected by the ADC impedance and the stability is better.
Quinn postato su September 9, 2020
It is recommended to add a voltage follower to be more accurate.
