Cars Simplified: Everything Automotive Explained

Digital Multimeters/DVOMs

A digital multimeter, also called a DVOM (Digital Volt/Ohm Meter), is a tool used to measure various properties of electrical circuits and components, typically voltage, resistance, amperage, and continuity. Some multimeters are also equipped with ways to test diodes and transistors, but it is quite rare to encounter an automotive repair that requires testing those components.

A multimeter differs from an ohmmeter or voltmeter in that it can do what both of those tools do in one unit. A multimeter can also test amperage, but an ammeter can typically test higher amperage by measuring the magnetic field signature it leaves around a wire.

Analog multimeters also exist, but have been the less common option for a long time.

How to Use a Multimeter for Beginners by

In this video, explains and shows the basic functions of a multimeter, showing how to use the voltage, amperage, resistance, and continuity settings found on most DVOMs. This video was published on June 24th, 2023.

    Multimeter Categories

    Multimeter categories were designed with residential/commercial power distribution service in mind, so there are some requirements for each category that aren't listed because they generally don't apply to automotive applications. This page does not provide enough information to safely use multimeters on residential, commercial, industrial, military, or power plant applications. These are the current 4 categories of DVOMs available:

  1. Category I
  2. Category one multimeters are the first rating and have the lowest level of protection within them from the four total categories.

  3. Category II
  4. For single-phase AC receptacle connected loads.

  5. Category III
  6. For three-phase AC distribution, including single-phase commercial lighting systems.

  7. Category IV
  8. Three-phase AC at utility connection, outdoor conductors. Typically the most expensive classification of the four.

    Note that these categories are not a guarentee that the multimeter you own or buy will perform as described. One factor to consider is the condition of the meter; casing damage and damaged leads will reduce the safety of using the multimeter, regardless of the category rating.

Bosch FIX7677/Actron CP7677

Actron CP7677 AutoTroubleShooter Multimeter Review

This multimeter, as its name suggests, is particularly tailored for automotive use. On top of the usual voltage, resistance, and amperage settings, there are also settings for dwell angle and RPM. These new settings have their limits, like how they are limited to 4, 6, and 8 cylinder engines.

- , June 25th, 2023

An interesting thing to note is that this product, CP7677, is nearly identical to the . It makes sense, because Bosch currently owns the Actron automotive tools brand, but the Bosch version now seems to be more readily available.