Current leakage testers measure the amount of current that flows through a ground conductor. They include a measuring device or probe that connects to a conductive point, a voltmeter that displays root mean square (RMS) values, and a circuit with specific resistance and frequency characteristics. Current leakage testers are used during both normal and single-fault conditions in order to determine whether electrical devices pose a shock hazard. For medical devices and other specialized equipment, additional single-fault conditions may be required. Organizations such as the International Engineering Consortium (IEC) establish and maintain standards for acceptable levels of current leakage from different classes of devices.
Manual, automatic, and semi-automatic current leakage testers are available. Manual devices require operators to set and change test parameters. Automatic devices are programmable, fully automated, and can often perform an entire series of electrical safety tests in succession. Semi-automatic current leakage testers combine features from both manual and automatic devices. Some current leakage testers include a general-purpose interface bus (GPIB) and are designed to connect to computers, peripherals, and laboratory instruments. Other devices include an RS232 serial bus or a parallel port that is designed to connect to a printer.
Current leakage testers differ in terms of current leakage range, resistance range, communications, and special features. Analog devices display current levels on a dial, usually with a moving pointer or needle. Digital devices display information numerically, typically with a light emitting diode (LED) readout or liquid crystal display (LCD). In terms of special features, some current leakage testers include remote controls, built-in calibration, and warning indicator lights. Other devices allow users to select an output frequency, usually 50 or 60 Hz, and include audible buzzers that sound when test conditions fail. To protect testers from high voltage or current, current leakage testers may include a rapid cutoff. Front panel lockouts prevent tampering with instruments during testing.
Current leakage testers meet the requirements of various national and international standards organizations. Examples include Underwriters Laboratories (UL), the IEC, and IPC, formerly known as the Institute of Interconnecting and Packaging Electronic Circuits. Various certifying marks are also available. For example, the CSA Mark is used in Canada and the CE Mark is used in Europe. The VDE Cable Mark denotes certification for cables, insulated cords, installation conduits and ducts. TÜV Rheinland / Berlin-Brandenburg also provides international approvals services for product safety.
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