COMMUNICATION CABLE MEASUREMENT Converting Megohmmeter 3921 Measures the insulation resistance of the cable and converts it into the normalized value (M.km) DESCRIPTION The megohmmeter 3921 was specially designed to measure the insulation resistance of telecommunication, signalling, coaxial, LV and MV cables. It factors in the cable length during the test. This provides a direct reading in Mkm on an analog galvanometer. Over a rotary switch, which also allows the selection of the measuring range, the device is turned on. The actual time needed for measuring is only a function of the polarisation characteristics of the cable dielectric. The analog galvanometer allows following the evolution of the measurement. The output voltage is fixed at 500VDC. The stability of the displayed value is ensured thanks to the triaxial measuring cable, which acts as a guard ring up to the connection of the cable under test. At the end of the test session the cable is automatically discharged. On discharge position, a relay shorts the cable on a resistance of low value for 30 seconds. A position of the switch allows checking the batteries. The position “1000 meters” allows its use as a conventional megohmmeter (without conversion). Direct normalized value reading (in MΩ.km) Analog display for better reading (value evolution) Portable test device for laboratory and shop floor Automatic cable discharge at the end of the test session Powered from battery or main

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