I have a pressure sensor that outputs 0.5V with a +/- 20 mV noise. I am trying to identify the root cause of the noise using an oscilloscope. The noise occurs in waves of twice the mains frequency, and each noise wave pulse is made of smaller pulses of much higher fequency.
The noise used to be much higher when I was using a "wall wart" 12V power supply to the sensor than when I used the bench top power supply or a proper 12 V dedicated power supply.
Weird clue 1) although the noise was partially related to the power supply used, the power output of the wall wart supply didnt show any noise.EDIT: the noise is there, but catching a 50mV noise on a 12V signal was just difficult on my oscilloscope.
Weird clue 2) when I touch with my finger the conductive probes (either positive or negative) of the oscilloscope, while measuring the sensor signal, the noise decreases
I got minor improvement in the noise by putting capacitors between the signal and the ground, but I have a feeling my main issue is elsewhere. Can you please clarify the root cause of the noise ?