The Greenlee PT-500 (52087370) Proof Tester Voltmeter Tester will produce 500VDC at the test leads to confirm proper operation of voltmeters and phasers. The PT-500 tester should be used only with voltmeters/phasers that measure DC voltage. It will not confirm operation of voltmeters/phasers that measure AC voltage only. The PT-500 operates from one 9V lithium or alkaline battery and produces approximately 500VDC at the connecting leads.