I'm developing a data acquisition board for 8 thermistors hooked up through 3 feet wires. The board is gonna be installed inside a package unit air conditioning.
In there, we have compressors, fan motors and contactor generating EMI.
I was wondering how to protect those analog inputs without degradation the thermistor resistance the microcontroller's ADC is measuring.
I saw here and in other forums some alternatives based in 100-ohm resistor and TVS diodes. Also I took a look at the ADG5412xx, but it is for voltages higher than 3.3 v which is the MCU operation voltage.
I would appreciate very much some help with that.
Electronic – How protect analog input connected to thermistor through long wires
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Best Answer
Do this on the inputs. The variable resistor is the remote thermistor.
How concerned are you, about voltage drop across the 10,000 ohm resistors?
Notice we use the 1uF to heavily filter the trash injected.
The assumption is that the injected electric-fields and magnetic-fields have ZERO average current, and thus heavy filtering ---- by a capacitor or in software ---- is all you need to do.
Thus I'm having the 1uF capacitor (3 of them) replace the TVS.
simulate this circuit – Schematic created using CircuitLab