A+ Hardware Service Technician: Upgrades, Troubleshooting and Preventative Maintenance

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The Ammeter

An Ammeter measures current through a circuit. Since it measures the current, the ammeter should not interfere with the circuit, therefore it requires low resistance. In order to measure the current, the ammeter must be part of the circuit, therefore you must "break" the circuit so the ammeter can run in series with the circuit.

The Voltmeter

A Voltmeter is used to measure voltage, or potential difference in a circuit. A voltmeter runs in parallel with the circuit, the circuit does not need to be broken for a voltmeter. The voltmeter requires high resistance. The voltmeter is providing a parallel pathway, this is why a high resistance is required.

The Ohmmeter

An Ohmmeter measures resistance. In order to measure resistance, the circuit must not have a power supply connected. The ohmmeter functions by passing a small amount of current through the circuit and measuring the voltage.

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