AEMC AC/DC Clamp-on Current Probe Model MD500. The AEMC AC/DC current probe is a battery powered clamp on current probe that is used with a volt meter to measure AC or DC current up to 500 amps. The jaws clamp aaround a conductor allowing current measurements without breaking the circuit. A Hall sensor mounted in a gap in the core senses the magnetic field produced by the current being measured. An amplifier circuit generates an output signal of 1 mV per amp. Demagnetizing (degaussing) is accomplished by means of a thumbwheel. Package shows shelf wear. Don't forget to check out my other auctions. Please feel free to ask questions prior to buying. I DO NOT TAKE RETURNS SO ASK QUESTIONS PRIOR TO BUYING. Feedback will be left when feedback is received. Thank You.