These Major Megger Extended Range Insulation Resistance Testers are the ideal instruments when high ranges are needed for measuring insulation resistance. Both provide excellent test voltage regulation and an external guard terminal to eliminate surface leakage current from the measurement. The instruments are all electronic; they generate a regulated dc high voltage and use low-zero-drift, high-accuracy circuits, with high current sensitivity. Designed for portability, each is enclosed in a molded, impact-resistance, flame-retardant case.

Both instruments are protected for connection to power distribution systems up to 300 V Line-Ground and 500 V Line-Line for Installation Category III. This relates to transient overvoltage likely to be found in fixed installation wiring.

This unit provides high-resistance readings up to 20,000 MΩ. It features an analog meter movement calibrated directly in megohms, ohms and ac volts. Test voltages of 100, 250, 500 and 1000 volts dc are selected by a rotary switch. Insulation resistance measurements up to 20 GΩ can be made on all voltage ranges. The unit is also equipped with a 0- to 5000-ohm continuity range and a 0- to 600-volt ac or presence of dc voltage measuring range. Power is supplied by an ac generator, driven by a hand crank, through a gear train.

• Guard terminal to eliminate surface leakage current from the measurement
• High-resistance readings up to 20,000 MΩ (analog model)
• Digital autoranging with readings up to 1999 MΩ (digital model)
• Multiple test voltages