How to Identify the interference of the instrumnets

There is a problem with the instruments that have a interfernece, in order to solve the problem, I try to change the sensor, I found that the interference is disappear. so that is the best way to distiguise where is the source of the interference. it is come from the sensor or the instrumets, sometimes in the sensor there is an amplifier with battery, that will be very easy to be interference.