The Yokogawa 2406E Series (240641) Analog Insulation Testers have two and three ratings available. The 2406E has a max AC voltage measuring range of 0 to 600V. The tester automatically begins discharge when you turn off the MEAS switch. The pointer swings if there is any residual voltage in the circuit under test. You can make sure discharge is complete by checking that the pointer swings back to the infinite (∞) scale value. Under this condition, the tester is ready to enter voltage measurement mode.