Electrical Safety Tests
High Voltage Testing (High Voltage Test, High Potential/Hipot Test, Dielectric Voltage-withstand Test)
This test ensures the insulation strength of electrical equipment and installations. For the high-voltage test, a voltage is applied that is significantly higher than the operating voltage. The insulation is thus stressed more than under normal operating conditions. The insulation must not be broken during the test for the product to pass the test. The test can be performed with DC or AC voltage.
Insulation Measurement, Insulation Resistance Test
The insulation resistance between each active conductor and the protective conductor/earth is measured. Each individual circuit must maintain a minimum insulation resistance, but the entire system may have a lower value. In many areas, such as for example in house/building technology or in electric vehicles, the proof of the insulation resistance by measurements is required by law and laid down in standards.
Grounding Measurement (Earth Continuity Test, Ground Bond Test)
Grounding measurement is used to test the effectiveness of grounding to ensure the safety of people, animals and technical equipment. Grounding resistance or ground impedance is tested to ensure that protective/operating groundings meet the values required by relevant standards. The possible different measuring methods (e.g. current/voltage measurement according to DIN VDE 0413 part 7, bridge measurement according to DIN VDE 0413 part 5) are performed with alternating current.
Picoampere meters are used when the sensitivity of a multimeter is not sufficient for current measurement. The devices measure very low currents from the lower picoampere to the upper microampere range.
Measurement of Very Small or Very Large Resistances (Milli- and Microohm Meters, Mega- and Teraohm Meters/High-ohm Meters)
Resistance measurement in digital multimeters is performed by measuring the voltage based on a current applied by the multimeter (switchable constant current source). Usually multimeters can measure a resistance range from about 100 mΩ up to the three-digit MΩ range. When measuring very small resistances, contact resistances in the terminals act as measuring errors. This can be compensated by using four-wire connections (Kelvin connection). When measuring very large resistances, on the other hand, the problem is the very small flowing current and thus a necessary increase in the measuring voltage. For the measurement of both types of resistance there are special measuring instruments.