Introduction to Voltage Measurements

Voltage measurements are very easy to make with a DMM. On meters with manual range selection, start with a value one setting higher than expected. An auto range DMM will automatically select the range based on the voltage present. Figure 1 shows the process.

Figure 1 – Using a Digital Multimeter to Measure Voltage

Follow these steps to measure voltage:

1. Wearing the appropriate PPE: safety glasses, voltage rated rubber gloves with leather protectors and nonflammable clothing, etc.
2. Select the appropriate voltage setting, A/C or D/C.
3. Plug the test probes into the appropriate probe jacks, Common and V.
4. Connect the tips of the probes across the source or load.
5. View the reading on the display unit. Be sure to note the unit of measurement. If you are testing DC voltage and a negative sign appears in the display, the polarity of your probes is incorrect and needs to be reversed.
6. Turn the meter off when testing is complete. This will prolong battery life.

Auto ranging units display the unit of measurement in the top right corner. In manual ranging units, the meter will use the range selected. Auto range will determine the highest setting and automatically display that unit.