METERS OF POTENTIAL

QI have just bought a multimeter, but I’m a bit unsure of how to use it. It has four sockets on the front. Can you give me a quick tutorial? Richard Thorley, Sheffield

AThe black probe lives in the black socket market ‘COM’. To measure voltage, put the red probe into the red socket marked V/Ω. Put the black probe to earth and touch the red probe to the point you want to measure at. To measure current, put the red probe into either the 2A or the 10A red socket. Break the circuit you wish to measure and bridge the gap with the probes. Start on 10A and use 2A only when necessary. Remove the red probe immediately after use, as if you absent-mindedly measure a voltage with it in the amps socket, it’ll blow the internal fuse or permanently ruin the meter’s circuitry.

To measure resistance, insert the red probe in the red V/Ω socket. Completely disconnect the component to be measured from its wires and place the probes across its connectors. If the display reads ‘1_’ it means the resistance is higher than the range the meter is set to – or that there’s an open circuit

(ie, no connection).

The multimeter has a number of ‘ranges’ on its dial. The most useful ones will be 20V, 200Ω and 10A. The other helpful feature is the continuity test, usually indicated by a diode symbol (a triangle closed by a line) by a speaker symbol. Use the red V/Ω socket and place the probes at each end of the wire. If the wire’s sound, the multimeter will beep. If the wire’s broken, it’ll remain silent.

Replace the battery promptly when the ‘low battery’ symbol appears or the meter will give inaccurate readings.