Multimeters are valuable measuring instruments that are capable of measuring several different types of electrical parameters within one device.
Multimeters are one of the most popular tools used by technicians, electricians and hobbyists for measuring and troubleshooting electronic circuits and other electrical systems across nearly every industry where critical measurements need to be made.
Multimeters are typically hand-held, portable, units used for quick, general-purpose measurements. They are also available in bench mounted instruments that have very high accuracies and resolutions and are frequently used as reference standards in testing and calibration laboratories.
Nearly all multimeters are capable of measuring resistance and both AC and DC voltages and currents. Most digital multimeters can also measure capacitance, frequencies, continuity and diode/transistor functions. More advanced multimeters may also have capabilities to measure temperature, conductance, decibels and duty cycles.
Various accessories or sensors can be added to increase the capabilities to include high currents with clamp-on adapters and higher voltages with high voltage probes.
The safe use of multimeters is very important. Most multimeters can measure up to 1000 Volts and 10 Amps of current so damage to the unit or physical harm could occur when using the multimeter in an unsafe way. The proper leads and appropriate connectors should always be used when making measurements on live circuits or measurements near the limits of the multimeter’s capabilities.
Users should always consult the manufacturer’s operating manual for the proper connection methods, operating instructions, safety precautions, and maximum ratings of the multimeter’s measurement functions.
Multimeters are available in both analog and digital types, although digital multimeters are by far the most popular type of multimeter available today.
Analog multimeters have been around for many years and are still used for specific applications in the electronics industry. Analog multimeters create a magnetic field that moves a pointer over a graduated scale with values for various ranges. The meter movement requires a certain amount of current to deflect the pointer at full scale and the internal circuitry is built around that value. It can be somewhat confusing to read the various scales and trying to determine intermediate values between scale divisions if more accurate measurements are required. They must also be handled carefully as the delicate meter movement can be easily damaged if the unit is dropped.
Digital multimeters have an easy to read numerical LCD display instead of the needle and scale in analog meters. Digital multimeters are able to measure with higher accuracy, reliability and readability. The digital processing available on digital multimeters enables them to check many functions not available on analog meters such as frequency, capacitance, duty cycle, temperature and more. Many digital multimeters have an ‘Auto Range’ feature where the measurement range is automatically set by the meter depending on the measurement value.
Like all measurement equipment, regular calibration is extremely important to ensure that the multimeter’s measurement values are within the stated manufacturer’s specifications. Multimeters should be calibrated annually unless specific industry regulations require more frequent calibrations.
The accuracy specifications of multimeters are usually based on a percentage of the range of the parameter being measured. Digital multimeters also add a number of least significant digits of the display resolution to the specification. Each range will typically have a different display resolution.
The calibration of multimeters is usually accomplished by using a Multifunction Calibrator. These calibrators provide highly accurate outputs for nearly all of the parameters to be calibrated on a multimeter. Some multimeter parameters may require other equipment to fully test specific ranges, such as a Function Generator to test frequencies over 1 Mhz.
For most calibrations, one measurement is taken for each function and range of the multimeter at a near full-scale value (90%) of the range. Calibrating the range at the near full-scale value versus a full-scale value will ensure that the measurement will not be off-scale or over range if the measurement is reading high. The full range of AC frequency measurement capabilities are also checked during the AC measurement functions.
For additional information on the use of multimeters or their calibration requirements, contact e2b calibration.
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