Which scale should be selected on an analog meter when checking a circuit of unknown voltage?

Choosing the highest scale on an analog meter when checking a circuit of unknown voltage is often a prudent approach to ensure safety and prevent damage to the meter. In this scenario, selecting the 0-600 volts scale allows for a broader measurement range, accommodating potentially higher voltages without the risk of exceeding the meter's limits.

Analog meters can be susceptible to damage if a voltage higher than what the selected scale can handle is applied. By using the 600 volts scale, you cover a wide range of possible voltages, including household and industrial voltages, while minimizing the risk of meter damage. This approach also allows you to safely observe the measurement, then adjust to a lower scale if needed for more precise readings once the approximate voltage is established.

In contrast, the lower scales could run the risk of not being able to capture the actual voltage present in the circuit, which could lead to inaccuracies or, worse, the potential for damaging the meter.