Importance of Proper Volt Range Selection When Using a VOM

What is the significance of setting the selector dial to the correct voltage range when using a VOM?

When reading voltages using a VOM, where should you set the selector dial?

Answer:

When reading voltages using a VOM, select the appropriate voltage range that corresponds to the voltage being measured. Choose a range that provides sufficient meter deflection for readability without exceeding the meter's capacity.

When using a Volt-Ohm-Milliammeter (VOM) to measure voltage, you should set the selector dial to the voltage measurement area and select the appropriate voltage range for the voltage you are testing. For instance, if you expect a voltage close to 300 volts, you would set the dial to the 300-V full-scale reading. Conversely, if you are measuring a smaller voltage, such as one close to 0.300 volts, you would choose the 0.300-V full-scale reading.

Since VOMs can have multiple voltage scales, ensure that you are using the correct scale that would provide an accurate and readable deflection of the galvanometer for the expected voltage. For instance, a very low voltage below 0.5 volts may require a different meter or a suitable range that allows for an accurate reading, as the meter deflection would be too small otherwise.

As with any electrical measurement, accurate range selection protects the device and provides the most accurate reading. For higher voltages, such as a 3000-V full-scale reading, the VOM must be specifically designed to handle such ranges and would typically require additional series resistances for safe operation.