How to use the current probe

Want to know how to use the current probe? Please understand the following basic usage of current probes and precautions for use first.

Since electricity is not visible, it is not possible to immediately determine whether a fault has occurred. In some cases, current measurements are required on a daily basis to prevent malfunctions, as well as to identify the cause of a malfunction if it occurs. Current can be measured using a variety of tools such as digital multimeters, clamp meters and current probes.

This article will provide an easy-to-understand introduction to the basic use of current probes and the precautions to be taken when using them.

■ Basics of current measurement

Current measurement is one of the basics in electronic equipment measurement and is required in many situations. It is used not only for quality checks during product development, but also for maintenance work to check the operation of electronic equipment and for checking whether the current is normal in the event of a malfunction of electronic equipment.

Because of the wide variety of uses, there are a variety of instruments that measure current. The main types of instruments that can measure current are as follows.

Digital multimeter

Clamp Meter

・Current probe (monitor the output voltage of the current probe with an oscilloscope/recorder)

Digital multimeters can easily measure not only current, but also voltage and resistance. For example, they come in a variety of types, from large benchtop digital multimeters to card-type digital multimeters designed to be carried around.

Many people are familiar with digital multimeters and their use. However, in many cases, there is a lack of understanding of other tools for measuring current, such as current probes.

■ Current probe that enables measurement without disconnecting the circuit

The current probe is one of the optional measurement features of the oscilloscope/recorder. The best feature of the current probe is that it can measure current without disconnecting the circuit. When using an ordinary multimeter, you must disconnect the circuit and connect the multimeter and the circuit in series in order to make measurements.

However, the use of current probes without having to disconnect the circuit means that, compared to digital multimeters, current probes allow more accurate current measurements to be made with as little disruption to the circuit as possible. However, "Why is it possible to measure just by clamping the wire?" Some may wonder.

This is because current probes sense the magnetic field generated around the measured current in various ways. There are various types of current probes, such as those that specialize in AC measurements, and those that measure both AC and DC, which will not be repeated here. There are also highly sensitive probes that can be connected to an oscilloscope/recorder to observe waveforms.

■ How to use the current probe

Actually, it is not difficult to use the current probe. Measurements can be made by connecting the current probe to an oscilloscope/recorder. For example, HIOKI HIOKI's memory recorders use a BNC connector that can be removed with a simple push of a button, making disassembly very easy. In addition, some models have automatic zeroing and demagnetization functions, which are efficiently accomplished with a long push of a button.

Current probes for oscilloscopes/recorders include, for example, AC/DC zero-flux current sensors (Hall-element method), which can measure DC current by combining a current sensor with a Hall element.

This current probe not only allows DC and AC measurements, but also has excellent linearity and is not affected by the B-H magnetism of the core. Furthermore, a wide frequency bandwidth and a high signal-to-noise ratio can be realized. In addition, since there is no excitation current interference, the overall interference effect during the measurement tends to be very low.

■ Precautions for using the current probe

There are many types of current probes, including current probes for measuring large currents and high-precision current probes for measuring very small currents. In general, if the current is too small, the waveform tends to be masked due to the influence of interfering factors. In this case, try winding the cable of the circuit to the core of the measurement. The waveform can be displayed in proportion to the number of windings for correct measurement.

In addition to current probes, HIOKI offers a range of current sensors and other products.

For example, clamp-on sensors for measuring current can be categorized into clamp-on current probes for observing waveforms, current probes, and clamp-on sensors for level observation, AC/DC current sensors.

Clamped current probes for waveform observation are characterized by a wide frequency band.

In addition, probes and transducers specify amplitude accuracy and phase accuracy for each frequency band, so it is important to be clear about which measurements you want to make before selecting probes and transducers.

■ Confirm the use of the current probe and the precautions before making current measurements.

Measurement instruments such as digital multimeters, clamp meters and current probes are available as options for measuring current. Current probes are an option for oscilloscopes/recorders and can measure DC and AC currents.

In addition, current can be measured without disconnecting the circuit, so accurate measurements can be made with as little interference with the circuit as possible. Please refer to the current probe usage and precautions described in this article, and make sure that you select the appropriate current probe for your measurement needs before proceeding with current measurement.