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Ohmmeter vs. Multimeter vs. Voltmeter vs. Ammeter: What's the Difference?

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Digital multimeter with test leads - ohmmeter vs voltmeter vs ammeter: What's the difference?

Whether it's troubleshooting or repairs, there are multiple types of electrical meters that measure different units of electricity. You might hear people refer to these meters interchangeably, but each of them has unique traits and benefits. Want to know the difference for diagnostic purposes? The guide below quickly outlines an ohmmeter vs. multimeter vs. voltmeter vs. ammeter.

What is an Ohmmeter?

An ohmmeter measures electrical resistance. Ohms are the official unit of measurement for electrical resistance, which is the opposition to current flow in an electrical circuit. The meter can be connected either in parallel or in series. If in parallel, it draws higher amounts of current while resistance increases. If in series, current decreases while resistance rises. There are three variations of an ohmmeter:

  • Micro-ohmmeter – Measures low amounts of resistance
  • Milli-ohmmeter – Measures low amounts of resistance with extremely high accuracy
  • Megohmmeter – Measures large amounts of resistance.

A voltmeter is used to measure the difference between two points of an electrical circuit. The meter is connected in parallel with the circuit, so the same decrease in voltage occurs across it. It also has a high internal resistance that takes small current from the circuit, allowing it to measure potential difference as accurately as possible. With low resistance, current would pass completely through, and the meter would provide an incorrect reading.

What is an Ammeter?

An ammeter measures the current in an electrical circuit. Amps are the official unit of measurement for current, which is the stream of electric charge or charged particles that flow through an electrical space or conductor. The meter has a low internal resistance and must be connected in series, so it doesn't affect the circuit and provides an accurate reading.

What is a Multimeter?

A multimeter is used to measure multiple electrical properties, including resistance, voltage and current. Also referred to as a Volt-Ohm-Milliammeter (VOM), it essentially combines the functions of an ohmmeter, voltmeter and ammeter into one convenient tool. An advanced multimeter can measure other properties like continuity, capacitance and duty cycle.