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GI-40 < BASIC INSPECTION > SERVICE INFORMATION FOR ELECTRICAL INCIDENT • For detailed ground distribution information, refer to “Ground Distribution” in PG section. VOLTAGE DROP TESTS • Voltage drop tests are often used to find components or circuits which have excessive resistance. A voltage drop in a circuit is caused by a resistance when the circuit is in operation. • Check the wire in the illustration. When measuring resistance with DMM, contact by a single strand of wire will give reading of 0 ohms. This would indicate a good circuit. When the circuit operates, this single strand • Unwanted resistance can be caused by many situations as follows: Measuring Voltage Drop — Accumulated Method • Connect the DMM across the connector or part of the circuit you want to check. The positive lead of the DMM should be closer to power and the negative lead closer to ground. • Operate the circuit. Measuring Voltage Drop — Steb-by-Step • The step-by-step method is most useful for isolating excessive drops in low voltage systems (such as those in “Computer Controlled Systems”). • Circuits in the “Computer Controlled System” operate on very low amperage. SGI853 SGI974 |