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Electrical testers designed to measure the impedance in a section of the grounding system, usually by measuring the ratio of the voltage between the point under test and a reference point to the current applied to the point under test. These testers consist of a direct-current source (e.g., a battery) and/or an alternating-current line power supply (e.g., through a step-down transformer); a measuring instrument; a display that shows the results, typically in ohms; and long-wire (e.g., 3 m [10 ft]) test leads appropriate for connection to both the test point and the ground reference point. Grounding system testers are used to measure the integrity and electrical characteristics of hospital grounding systems; some testers may be used to apply a resistance of known value between the phase and ground conductors to simulate a fault, measuring the ground-fault loop impedance.
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