Final answer:
To test the integrity of a transformer, the multimeter should be set to ohmmeter mode, where it will measure the resistance of the windings by sending a small current through them. The transformer must be isolated from its circuit during this test. A voltmeter mode is used in parallel to measure voltage and should not significantly alter the circuit.
Step-by-step explanation:
The multi-meter must be set to ohmmeter mode to test the integrity of a transformer. To effectively measure the transformer's winding resistance, the multimeter will send a small current through the transformer's windings and measure the resulting voltage drop, which allows it to calculate the resistance. This type of testing necessitates that the transformer be isolated from the circuit. It's important to remember that an ohmmeter should only be connected to a de-energized circuit since it contains its own power source for testing purposes. When using a multimeter for various measurements, always ensure proper settings are applied, such as the correct mode and range based on the expected values to prevent damage to the device and ensure accurate readings. When measuring voltage with a multimeter set as a voltmeter, the tool is placed in parallel with the circuit component to record the voltage across it without significantly altering the circuit.