PRINCIPLES OF OPERATION: The megohmmeter measures the insulation resistance OF THE ITEM UNDER TEST BY METERING THE CURRENT OUTPUT OF THE HIGHLY REGULATED DC SUPPLY WITH A BALANCED BRIDGE AMPLIFIER. THE 5O/5OO V0LT SUPPLY USES LONG LIFE SILICON RECTIFIERS AND IS REGULATED AGAINST LINE VOLTAGE FLUCTUATION FROM 100 TO 130 VOLTS. A CATHODE FOLLOWER ELECTRONIC REGULATOR HOLDS THE OUTPUT VOLTAGE STEADY UNDER VARYING LOAD CONDITIONS, REDUCES RIPPLE, AND ASSURES MAXIMUM READING STABILITY. THE HIGH GAIN BALANCED BRIDGE AMPLIFIER USED IN THE METERING CIRCUIT IS POWERED FROM AN INDEPENDENT DC SUPPLY WHICH ALSO USES SILICON RECTIFIERS AND IS REGULATED AGAINST LINE VOLTAGE FLUCTUATIONS. Electronic overload circuits protect the constant voltage supply and THE 4-1/2 INCH WIDE VIEW INDICATING METER. Modular construction through the use of latest printed circuit board techniques and internal adjustments to compensate for tube replacement PROVIDE for ease of maintenance and field repair.