Ground resistance testers are devices that are used to measure and test electrical grounding systems. Grounding enables optimum electrical continuity between conducting objects and earth. Effectively grounded equipment is permanently connected to earth through a ground connection with a sufficiently low impedance and sufficient current- carrying capacity that a ground fault current cannot cause dangerous voltage buildups.
Ground resistance testers can be to take several different measurements, including grounding system resistance, insulation resistance, earth continuity, current leakage, and ground bond. Grounding system resistance and insulation resistance are common measurements made with ground resistance testers. Grounding system resistance testers are used to measure grounding systems for construction projects and roads, telecommunications projects, and other applications. Insulation resistance testers measure the resistance of insulators or insulation.
Ground resistance testers can be used to measure earth continuity, current leakage, and ground bond. Earth continuity devices are used to test electronic instruments and appliances. Current leakage testers measure the amount of current that leaks into the ground. These devices are important for maintaining the safety of instruments that come into contact with people. Ground-bond ground resistance testers are used in ground bond or high-current continuity testing. These tests are performed to confirm the electrical integrity of an instrument. Other types of ground resistance testers are also available.
Most ground resistance testers have an analog or digital display, or an LED indicator. Analog meters display values on a dial, typically with a needle that moves when a signal is applied. Digital meters provide a numeric reading. Light emitting diode (LED) and liquid crystal display (LCD) are common types of digital displays. LED indicators use a light to indicate that a test is occurring. In some models, the LED light blinks on and off throughout the test.
Ground resistance testers come with several different interfaces. Choices include GPIB, RS232, printer port, scanner port, and print out. General-purpose interface bus (GPIB) is designed to connect computers, peripherals, and laboratory equipment. RS232 interfaces for ground resistance testers are used for serial communications between instruments and computers. Printer port devices have a connector or port that is designed to interface with a printer. Scanner ports are similar to printer ports, but are designed to interface with a scanner. Another common interface for ground resistance testers is a print out. Print outs are hardcopies of formatted data collected during testing. Other interface types for ground resistance testers are also available.
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