In electrical engineering, an electrical isolation test is a

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or eve ...

(DC) or

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

(AC) resistance test that is performed on sub-systems of an

electronic system Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...

to verify that a specified level of isolation resistance is met. Isolation testing may also be conducted between one or more electrical circuits of the same subsystem. The test often reveals problems that occurred during assembly, such as defective components, improper component placement, and insulator defects that may cause inadvertent

shorting In finance, being short in an asset means investing in such a way that the investor will profit if the value of the asset falls. This is the opposite of a more conventional " long" position, where the investor will profit if the value of t ...

or grounding to chassis, in turn, compromising electrical circuit quality and product safety. Isolation resistance measurements may be achieved using a high input impedance

ohmmeter An analog ohmmeter An ohmmeter is an electrical instrument that measures electrical resistance (the opposition offered by a circuit or component to the flow of electric current). Multimeters also function as ohmmeters when in resistance-measu ...

, digital

multimeter A multimeter is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, resistance, and current, in which case it is also known as a volt-ohm-milliammeter (VOM), as the unit is equipped w ...

(DMM) or current-limited

Hipot A dielectric withstand test (or pressure test, high potential or hipot test) is an electrical test performed on a component or product to determine the effectiveness of its insulation. The test may be between mutually insulated sections of a part ...

test instrument. The selected equipment should not over-stress sensitive electronic components comprising the subsystem. The test limits should also consider semiconductor components within the subsystem that may be activated by the potentials imposed by each type of test instrumentation. A minimum acceptable resistance value is usually specified (typically in the mega ohm (MΩ) range per circuit tested). Multiple circuits having a common return may be tested simultaneously, provided the minimum allowable resistance value is based on the number of circuits in parallel. Five basic isolation test configurations exist:''Electrical Isolation Verification (DC) Practice No. PT-TE1417'', Preferred Reliability Practices, NASA # Single Un-referenced End-Circuit – isolation between one input signal and circuit chassis/common ground. # Multiple Un-referenced End-Circuits with a single return – isolation between several input signals and circuit chassis/common ground. # Subsystem with Isolated Common – isolation between signal input and common ground. # Common Chassis Ground – isolation between circuit common and chassis (chassis grounded). # Isolated Circuit Common – isolation between circuit common and chassis (chassis floating). Isolation measurements are made with the assembly or subsystem unpowered and disconnected from any support equipment.

References

{{reflist Electrical tests

See also

References