How do I measure the frequency?

How to measure frequency? Measurable Devices, Measurement Methods, and Precautions

In everyday life, many people say they are not aware of the frequencies of their appliances. However, some appliances have specific compatible frequencies, and using electricity on a frequency that is not compatible with the product can lead to malfunctions, fires and other risks.

In addition, in industrial equipment, there are electrical devices designed to operate at fixed or variable frequencies. Here, we present the basics of frequency measurement methods in electrical measurements in an easy-to-understand manner.

▪ Knowledge of frequencies and proper use of electrical equipment

Frequency (Hz) is the number of times an alternating current alternates between positive and negative signals in one second. For example, there are 30 waves per second at 30 Hz and 60 waves per second at 60 Hz, so it can be said that the alternation between positive ↔ negative waves is stronger at 60 Hz.

The frequency of the power system is fixed, but there are concerns about degradation of power quality due to the increasing complexity of the power system, such as the proliferation of power electronic application equipment (mainly inverters) and the increasing coordination of distributed power sources, which can cause product failures due to voltage anomalies and frequency fluctuations.

In addition, "inverters", a typical technology for the efficient utilization of electrical energy, can also be used as equipment for controlling the speed of motors by means of variable frequency. Depending on the circumstances, the variable frequency can control the number of revolutions, thus realizing efficient operation.

■ Equipment that can check the frequency

There are several devices that can measure frequency.

・Digital multimeter

This is a measuring instrument that displays the measured frequency numerically on a digital screen. Since the display is digital, it also has the advantage of being less susceptible to misinterpretation. In addition to frequency measurement, there are also digital multimeters that can measure current and voltage.

・Power quality analyzer

Power quality analyzers measure values and waveforms of frequency, voltage, current, and power to determine where faults in receiving and transforming equipment and faults in electrical control equipment are occurring.

・Power analyzer

Power analyzers are used to measure voltage, current and power in harmonic bands such as carrier frequency components, in addition to the fundamental frequency components that dominate the output of inverters, with high accuracy.

-Oscilloscope

An oscilloscope is a measuring instrument that allows you to observe the frequency waveform itself. It can measure not only frequency but also voltage.

In addition to frequency measurements, many people tend to say that it is possible to measure current or voltage, or that they have never measured the frequency of an inverter. Therefore, in the next section, we will describe how to measure frequency using a digital multimeter.

■ How to use a digital multimeter to measure frequency

If you want to measure frequency using a digital multimeter, use a digital multimeter with a frequency measurement function. When using the digital multimeter, first adjust it to a state where it can measure frequency. Set the measurement item to "Hz" by selecting a function switch or the like, and if "Hz" appears on the digital display, the selection is complete.

Plug the red and black test leads into the frequency measurement terminals and you are ready to start measuring frequency. In most cases, the red meter pointer is the terminal with the Hz symbol and the black meter pointer is the terminal with the COM symbol. Some models can measure voltage and frequency at the same time, and there are cases where the red pointer is inserted at the V terminal. Please refer to the instruction manual of each digital multimeter before inserting.

After that, you can measure the frequency of the circuit by touching the test lead to the circuit you want to measure. The digital display will show the frequency at the time of measurement, and the measurement will be completed after confirmation.

■ Precautions when measuring frequency

A digital multimeter makes it easy to measure frequency, but there are some considerations to keep in mind when performing the operation. First, make sure that the measurement function is frequency measurement (Hz), and then lap the meter pen. Touching the measured object with the meter pen in a different function may result in malfunction.

In addition, an electric current will flow when measuring frequency. Even household power outlets have a 220V voltage, so be sure not to get electrocuted. In addition, since the measurement circuit is switched by a rotary switch, if the wrong voltage is input into the resistance range, a large current will flow into the measuring instrument, resulting in accidents such as false tripping of the earth leakage circuit breaker or arcing.

▪ Summary

You may want to measure frequencies for various reasons, such as "equipment maintenance" or "moving to an area that uses a different frequency". In this case, a measuring instrument such as a digital multimeter is necessary for frequency measurement.

A digital multimeter is an easy-to-use meter even for beginners, and it is recommended that you try using it to test frequencies according to your needs.