The insulation resistance test is intended to detect very small breaks in the cable's insulation before, during and after installation. These breaks are often not detected during the continuity test because they do not necessarily constitute short circuits between the conductor and the ground braid. Even though they are small, these breaks can cause a current leak to ground. Such a leak is generally detected by the mandatory ground-fault circuit interrupter (a thermostat with a built-in ground-fault circuit interrupter or a panel-mounted ground-fault circuit interrupter). When a current leak is detected, the ground-fault circuit interrupter cuts off the circuit, thereby deactivating the floor heating system. A megohmmeter (sometimes called a « megger ») is a special type of ohmmeter that supplies a high voltage to measure the electrical resistance of insulators. An ordinary ohmmeter or multimeter is not capable of producing the required voltage and therefore cannot be used to perform this test.
The Model 6527 is a true portable multi-range megohmmeter® capable of measuring the resistance of an insulator from 1kΩ to 4000MΩ. It has three user-selectable test voltages: 250V, 500V and 1000V. The Model 6527 is also a multimeter featuring an AC/DC voltmeter function capable of measuring up to 600VAC and 1000VDC, a continuity test function with an audible signal for resistances below 35Ω, and 600Vrms overload protection. In addition, it can measure resistance up to 400kΩ. The TEST button is paired with a lock function for continuous testing up to 15 minutes, thereby eliminating the risk of overload.
