I'm trying to measure a potentiometer from an Arduino's ADC. The potentiometer has a maximum value of 100k ohms and is located about 1 meter from the Arduino. The potentiometer's wiper is wired to the ADC pin and the pin to ground. I've enabled the 20k internal pullup on the ADC pin, so the potentiometer creates a logical high and low at the extremes. I have the potentiometer wired using two stranded 24 awg unshielded wires, twisted together.
To filter out noise, I'm using an exponential moving average on the Arduino. However, even with this, I'm still seeing a +/- 10 unit change several times a second, even when the potentiometer is completely still.
The two ways I've read about reducing noise in wires carrying analog signals are:
- Using a shielded cable
Would it make any difference if I instead used a two-conductor shielded audio cable? I have one audio cable that has a red and black wire, as well as metal shielding. If I attach my potentiometer's pin to the two wires, should I also wire the shielding to the ground or leave it unattached?
I see a lot of conflicting opinions over how to leave the shielding, with commenters in this thread suggesting to leave it ungrounded, or grounded at the sensor end, or grounded at the Arduino end, but definitely not grounded at both ends. Which is best for my case?
- Using a capacitor
How much of a difference would it make if I placed a 0.1uF capacitor across the wires, as a low pass filter? Should I place it on the sensor side or the Arduino side? Again, I've seen a lot of conflicting advice about this.