- 1). Put on a pair of rubberized gloves to prevent receiving an accidental electric shock. High voltage DC power is dangerous.
- 2). Check the label on the power source to ascertain the DC voltage it produces. Make a mental note of this figure.
- 3). Turn on your multimeter. Select "DC" by turning the dial or pressing the appropriate button. Select a voltage range that's about 20 percent lower and 20 percent higher than the voltage noted earlier. For example, if the label on the power source indicates 120 volts, then set the lower range on the meter to 100 volts and the upper range to 140 volts.
- 4). Locate the terminals on the DC power source. One is labeled "+" and the other "-." It's also likely that the "+" terminal has a red wire connected to it and the "-" terminal has a black wire connected to it.
- 5). Place the metal sensor on the end of the black wire from the meter firmly onto the "-" terminal of the power source. If the meter wire has alligator clips, then open the jaws by pressing the handles together and placing the jaws over the terminal and releasing the pressure.
- 6). Place the sensor on the end of the red wire from the meter firmly onto the "+" terminal of the power source. Expect to see a few sparks; the firmer you place the sensor, the fewer sparks you will see. If the wire from the meter has an alligator clip, then place the open jaws over the terminal and release the pressure as before but expect a few sparks.
- 7). Read the display on the meter. It tells you the exact voltage your DC power source is producing. The reading is the same as you noted from the label earlier if the power source is operating correctly; five percent either way is usually acceptable, but if the reading is more than 10 percent lower or higher, then it's sensible to get the power source professionally checked.
- 8). Remove the sensors or alligator clips from the power-source terminals. Turn off the multimeter.
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