A multimeter refers to a measuring meter that makes multiple types of measurements, such as alternating current (AC) or direct current (DC) voltage, AC or DC current, resistance, temperature, capacitance, and more parameters. A modern digital multimeter uses digital and logic technology to miniaturize and enable many features in its internal system. With digital technology, digital multimeters can have graphical displays, perform data logging and signal digitizing capabilities, programmability, and communicate with external devices.

Most handheld or benchtop digital multimeters have measurement displays in digits. The number of digits on display usually corresponds to the level of resolution the digital multimeter can measure. Resolution is the level of detail that is quantifiable on a digital multimeter. Therefore, the higher the number of digital multimeter display digits, the higher the resolution. It is common to see handheld digital multimeters with display digits of 3.5 and 4.5 digits. Bench digital multimeters tend to have display digits of 5.5 digits, 6.5 digits, 7.5 digits, and even 8.5 digits. It is usually expressed as “N digits of resolution” or “N.5 digits of resolution.” For example, 4.5 digits of resolution mean the half digit is the most significant digit (usually zero or one) followed by N digits (each of which has a range of 0-9).

The accuracy of a digital multimeter is how good its measurements are — for example, how close the measured value is to the true value. Resolution is the level of detail that is measurable or the number of significant digits on a digital multimeter.

Here are a few basic steps on how to use a digital multimeter:

• Plug the leads into the appropriate jacks on the digital multimeter.
• Attach the grabbing ends of the leads to the component or circuit being tested.
• Set the DMM’s range selector knob or button to the parameter and range you want to test.
• Switch on the device or circuit being tested before you make your voltage or current measurements.
• Examine the measurement shown on the digital display or connected computer.

A digital multimeter can measure current (I) and voltage (V). If you have both measurements, calculating the DC power is simply multiplying both the current (I) and voltage (V) measurements. Most digital multimeters have an internal architecture that inhibits their ability to measure both at the same time. However, if you use a few techniques and the right equipment, you can get a good I and V measurement from your benchtop DMM.

A digital clamp multimeter is essentially a digital multimeter with a clamp jaw. Its primary function is to measure an electrical wire’s AC, DC, or AC+DC current flow. Its jaw clamp clamps around the wire and measures the magnetic field emitted from the wire due to the current flow in the wire. It is usually designed for electricians who perform power-quality or troubleshooting work, such as on three-phase AC motors, building power distribution boards, and transformers.

A digital multimeter (DMM) software is a convenient software tool that allows you to remotely control your DMM from a computer via LAN, USB, or GPIB interface. It is especially useful when you need to perform data logging over a long period of time. The data can be stored in the computer for post-data analysis.