The insulation resistance test is intended to detect very small breaks throughout the cable insulation before, during, and after installation. These breaks often remain undetected during the continuity test since they are not necessarily short circuits between the conductor and the ground braid. Even though they are small, these breaks can cause a current leakage to ground. Such a leakage is usually detected by the mandatory ground-fault circuit interrupter "GFCI" (thermostat with integrated GFCI or panel mount GFCI). When a current leakage is detected, the GFCI trips the circuit, thus disabling the floor heating system. A megohmmeter (sometimes referred to as a "megger") is a special type of ohmmeter, which supplies high voltage to measure the electrical resistance of insulators. An ordinary ohmmeter or multi-meter is not capable of producing the required voltage and therefore cannot be used to perform this test. The Model 6527 is a portable multi-range True Megohmmeter® capable of measuring insulation resistance from 1kΩ to 4000MΩ. It has three user selectable test voltages of 250V, 500V and 1000V. The Model 6527 is also a multimeter that features an AC/DC voltmeter function capable of measuring up to 600VAC and 1000VDC, continuity test function with audible beeper for resistances under 35Ω, and an overload protection of 600Vrms. In addition, it can measure resistance up to 400kΩ. The TEST button has an associated locking feature for continuous tests up to 15 minutes, eliminating the need to manually hold down the button. This lightweight, easy-to-use megohmmeter can be used for most commonly performed insulation tests, such as on cables, switch gears, motors, DC generators, power tools and small appliances.