Quality is crafted into every Major Megger MJ159 Insulation Tester, with excellent test voltage regulation, direct measurement readout and an external guard terminal to eliminate surface leakage current from the measurement. Two models are available for general purpose testing
which include a low-voltage model. Both are portable, self-contained instruments designed to give rapid and accurate measurements.
The instruments feature an analog display having four selectable test voltages of 100, 250, 500 and 1000 Vdc, measuring insulation
resistance up to 2000 MΩ, and an ohm range to 5000 Ω. The only other difference among the two models is the type of power source. Power for model MJ159 is derived from a low-voltage, hand cranked generator which has been designed to be easy to turn even under full load conditions. The low-voltage generator is connected to an electronic inverter to provide a very stable test voltage. Accuracy of measurement is unaffected by variations in the generator cranking speed and the test voltage is maintained at its rated value. Power for model MJ359 is provided by 120 V ac 50/60 Hz or low-voltage generator.
As a safety feature, the ac voltage range becomes effective as soon as the instrument is connected to the circuit under test. Therefore, a
warning is given that the circuit under test is not de-energized before the instrument is operated. Though calibrated for ac voltage, this
range also monitors the automatic discharge feature so that after equipment having capacitance (i.e. a cable), has been tested, an
indication can be given that the voltage has discharged to a level that is safe for removing the test leads. Each instrument has a guard terminal which may be used to prevent the effects of surface leakage from influencing the readings. This is achieved by diverting the leakage current through the guard terminal and away from the instrument’s measuring circuit. The Megger MJ159 is built into a strong ABS plastic case with a fold down carrying handle.