Troubleshooting Motor Bearings 159

terminal. If the leads are connected to opposite terminals, the needle will move in the reverse direction.

AC Circuits Since voltage constantly reverses polarity in an AC circuit, there is no need to observe polarity when measuring voltage on ac circuits (Figure 1-4). Voltage Ranges Many analog voltmeters have two or more voltage ranges that can be read on a common scale, such as 0 to 150 V, 0 to 300 V, and 0 to 600 V (Figure 1-5). When using a multirange voltmeter, always select a higher range than needed to assure that the meter won’t be damaged. Then, if the initial reading indicates that a lower scale is needed to obtain a more accurate reading, switch the voltmeter to the next lowest range.

1-4 Checking voltage at a 125-VAC duplex receptacle. 7