Hall effect current probes allowing measurement of direct or alternating currents, without disturbing or breaking the circuit. Multimeter (PAC 20 and 21) or oscilloscope (PAC 22) output. Voltage output. Zero adjustment by means of a thumb wheel (PAC 20) or automatically by simply pressing a pushbutton (PAC 21 and 22). "ON" indicator shows that battery is working satisfactorily and "OL" warns of low battery. Auto-power off, can be disabled, on PAC 21 and PAC 22.