2014 Tech study guide: Basic repair and testing

The addition of T7D12 is the only change to this section…Dan

The most common test instrument in an amateur radio shack is the multimeter. Multimeters combine into a single instrument the functions of a voltmeter, ohmmeter, and ammeter. Voltage and resistance are two measurements commonly made using a multimeter. (T7D07)

You use a voltmeter to measure electric potential or electromotive force. (T7D01) The correct way to connect a voltmeter to a circuit is in parallel with the circuit. (T7D02) When measuring high voltages with a voltmeter, one precaution you should take is to ensure that the voltmeter and leads are rated for use at the voltages to be measured. (T7D12)

An ohmmeter is the instrument used to measure resistance. (T7D05) When measuring circuit resistance with an ohmmeter ensure that the circuit is not powered. (T7D11) Attempting to measure voltage when using the resistance setting might damage a multimeter. (T7D06) What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time is that the circuit contains a large capacitor. (T7D10)

An ammeter is the instrument used to measure electric current. (T7D04) An ammeter is usually connected to a circuit in series with the circuit. (T7D03)

In addition to knowing how to make electrical measurements, knowing how to solder is an essential skill for amateur radio operators. Rosin-core solder is best for radio and electronic use. (T7D08) A grainy or dull surface is the characteristic appearance of a “cold” solder joint. (T7D09)

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