What is a Multimeter?

2023-07-10 | By Maker.io Staff

What is a Multimeter? Image Source: https://www.digikey.com/en/products/detail/digilent-inc/480-001/4090113

When starting out with electronics projects, a precise and reliable multimeter is one of the must-‎have tools that every maker should keep in their toolbox. This article explores what exactly a ‎multimeter is, what functions they typically support, and what these handy measuring devices ‎can be used for in the context of electronics projects and other tasks, such as household ‎maintenance work.

What Is a Multimeter, and What Can It Be Used For?

A multimeter is a tool that combines multiple measuring instruments into a single device, allowing ‎its users to measure an array of different electrical properties, typically in various supported ‎ranges. Most multimeters support gauging electrical current, voltage, and resistance of circuits ‎and components, eliminating the need to keep different measuring instruments for each task. ‎Multimeters are not only practical because they combine multiple measuring tools in one handy ‎device, but they are often more cost-effective than buying separate, dedicated measuring ‎instruments, which becomes especially important when you begin to regularly work with ‎electronics. Additionally, these tools are typically straightforward in their operation. You can ‎generally choose between mobile devices that operate on batteries and don't need a fixed power ‎supply or a lab multimeter that permanently resides on your bench.

While some more cost-effective models may only support measuring a circuit's voltage, AC and ‎DC current, and resistance, more elaborate instruments can gauge additional properties such as ‎capacitance, temperature, duty cycle, and inductance. Oftentimes, even the simplest of devices ‎allows measuring continuity, which lets its users detect problems in a circuit, such as an open ‎circuit or shorts.

Comparing Multimeters Based on Their Characteristics

As with choosing any tool, newcomers can quickly find themselves overwhelmed by a plethora ‎of terms associated with various features and characteristics used when comparing multimeters. ‎The most commonly used terms are easy to explain, and it's good to know how they impact a ‎multimeter's operation and performance.

A multimeter's resolution refers to the smallest part of the scale a device can show. ‎Manufacturers typically define this characteristic in dependence on the range used, as digital ‎multimeters might support multiple measuring ranges such as up to 10 V or up to 100 V. For ‎example, a device with a resolution of 1 mV on its 10 V scale can detect voltage differences in 1 ‎mV increments. While some devices allow configuring of the resolution, higher resolutions ‎typically take longer to calculate.

A multimeter's accuracy describes the device's overall accuracy in taking measurements. ‎Typical consumer-grade digital multimeters have an accuracy of around 0.5%, meaning the ‎value they measure may deviate from the actual value by 0.5% in either direction. However, you ‎should remember that the accuracy drifts over time as the device moves out of calibration.

When used for measuring voltage, a multimeter's input impedance must be very high compared ‎to the circuit under test. This prevents the gauging process from affecting the circuit and, thus, ‎yields incorrect measurement results. The input impedance of most consumer digital ‎multimeters is either one or ten megaohms.

When using a multimeter to measure current, the instrument's ideal resistance would be zero so ‎as not to interfere with the circuit or the measuring results. However, in real-world situations, ‎there will always be a slight resistance present caused by the circuit used to measure the current. ‎Most digital multimeters, in addition, will use a shunt resistor and measure the voltage drop ‎across that resistor to calculate the current. The combined voltage drop of that resistor and the ‎rest of the circuit is referred to as the burden voltage.

Summary

A multimeter is any measuring instrument that can gauge various physical characteristics of a ‎circuit. These devices can come in multiple shapes and sizes, ranging from cost-effective ‎handheld beginner devices with acceptable accuracy to lab-grade bench-top instruments with ‎superior accuracy that can easily cost thousands of dollars.

What is a Multimeter? Multimeters come in a large variety of different shapes and sizes. Some are small and portable, ‎while others are more substantial and accurate. Image source: https://www.digikey.com/en/products/detail/b-k-precision/2831E/2280305

Most multimeters can at least determine voltage, current, and resistance in circuits. Even the ‎cheapest devices can measure continuity, letting users detect open and short circuits. More ‎advanced models may include features such as impedance, capacitance, and temperature ‎measuring, as well as logic detection, duty cycle, and frequency calculations.

It’s essential to keep a few fundamental characteristics in mind when choosing between ‎multimeters, the key points being the device’s resolution, accuracy, input impedance, and ‎burden voltage.