All models in the range are water and dust resistant, with an IP54 ingress protection rating. The low-cost entry-level RCDT310 model is suitable for use on supplies between 100V and 280V, and offers 0.5I, I and 5I tests, with provision for tests starting at 0?/180? of the supply waveform, as well as for DC tests. It also has facilities for testing standard and selective RCDs, and covers current ranges from 30mA to 500mA. When connected to a live supply, it defaults to voltmeter mode. The mid-range RCDT320 covers a wider supply voltage range of 50V to 290V, allowing use with centre-tapped 110V supplies. It incorporates ramp testing testing, for RCD tripping current measurement, and the unique Megger auto sequence test feature, which saves time by allowing the tester to conduct all the RCD tests, and to store the results while the operator stands by the RCD, resetting it as appropriate.The operating current range of the RCDT320 is extended to cover 10mA to 1,000mA devices, and the ability to measure AC supply voltage and frequency is added. The large liquid crystal display for test results is backlit in this model, making it easier to use in locations with low ambient light levels. All models in the range comply fully with the requirements of IEC61010-1 for Category III 300V applications, and are supplied complete with appropriate test leads and a calibration certificate.