Want parts to build your own gaussmeter” Here is an AC magnetic field probe. It generates an AC voltage when exposed to AC magnetic fields. Although we do not know how the output from this unit varies with frequency, we do know that the greater the magnetic field, the higher the voltage generated (at 60 Hz, it produces about 1 mV per 20 mG). It can be connected to a DMM, analog voltmeter, oscilloscope, Audio Amplifier (see below), or recording device. Connect 3 of them in series and create a 3-axis unit. It is quite small: only 0.7″ long x 0.7″ diameter, with a removable rubber suction cup attached. Has 36″ lead and 1/8″ (3.5 mm) mono plug.