Martindale vt25 voltage tester and pd690 proving device martindale vt25 the martindale vt25 is a tough compact two pole tester for measuring acdc voltages from 12 to 690v additional capabilities include continuity and phase rotation testing plus single pole voltage detectionthe acdc voltage detection continuity and phase rotation functions all have bright led indication auto power off ensures a long battery lifetime the voltage indicator conforms to all the latest safety standards and