POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS DC voltage, and if your meter is not self-scaling it should be set to the lowest voltage on the DC volts scale (usually 2 volts). Once the meter is connected, turn the circuit on and take a reading on your meter. The reading is the voltage drop at that point in the circuit. Record the reading. Measure the voltage drop at each wire and connection in the circuit, including the negative return, then add up the results. The total of all these measurements must fall within either the 3 percent or 10 percent limit. Any reading that’s a lot higher than the others in the circuit indicates a point in the circuit with excessive resistance or voltage drop. Correct any problem by cleaning or tightening the connection, or by replacing the connecting wire. Fig. 3-7. In checking source voltage at the back of a switch panel, remember to always verify your power source first when tracing circuits.
testing. Sometimes you’ll be testing directly across switches and relays or from one end of a wire to the other, even though I said earlier that you shouldn’t do this. Figures 3-9, 3-10, 3-11, and 3-12 illustrate the various meter-connection possibilities for this test. Begin with the circuit you’re measuring turned off. The meter should be turned on, set to measure
Measuring Amperage As already discussed there are two methods used to test amperage. One method uses meter leads and requires the disconnection of the DC power lead for the circuit you’re testing (I discuss AC in more detail in chapter 11); the other uses a clamp-type inductive meter.
Using Meter Leads Unlike voltage checks, amperage checks with a basic multimeter require that the meter be connected in
Fig. 3-8 Fig. 3-8. Meter lead connections on a meter and voltage checks for three light-socket types.
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