Which range should you select when checking for unknown voltage supply with an analogue meter?

When checking for an unknown voltage supply using an analogue meter, selecting the highest range is advisable. This is because the highest range will prevent the risk of damage to the meter from a potential over-voltage situation, allowing it to measure without the danger of exceeding its capacity.

Using this approach, if the voltage present is indeed high, the meter can accurately read it without any risk of pegging the needle or causing permanent damage. The highest range will also give a more reliable indication of the voltage present without the interference that might occur in lower ranges, where the meter may not provide a proper reading if the voltage exceeds the measured range.

In practical terms, once you identify the voltage on the highest setting, you can then switch to a lower range if a more precise reading is required.