Clamp-on multimeters for AC leakage current measurement - why choose HIOKI?
Let's start a bit broadly, namely what position HIOKI actually has in the field of current measurement. Because regardless of whether the measurement is based on the Hall probe principle or zero-fluxgate technology - the Japanese company HIOKI has been known worldwide for its high-end AC/DC current probes, using both technologies, for many years (although the end user does not always recognize that it is actually the HIOKI brand - many even very reputable manufacturers offer HIOKI products on the OEM principle). Given this long history and experience, it is therefore perhaps not surprising that HIOKI also offers a wide range of hand clamp-on multimeters. In the following article we will introduce one of their special sub-categories, namely a trio of models for AC leakage current measurement.
Before we go into the details of how each variant differs - and what makes them special - let's look at what they all have in common:
- TrueRMS measurement
- measurement range from leakage (differential) to load currents
- Bluetooth can be added to each model in the form of the optional Z3210 adapter, which allows the multimeter to communicate with smartphones and tablets via the free Gennect Cross app
- Not only this trio, but all HIOKI multimeters are both designed and manufactured in Japan, in our own factories in Nagano Prefecture, Japan
So let's take a look at the differences now. The figure above illustrates the practical application of the CM4001. With a height of just 16 cm and jaws that have been designed to be as narrow as possible, you can use it in the tightest conditions and still measure on cables that are up to 24 mm in diameter. You can either take readings directly from the white backlit and highly readable display, or you can use the aforementioned Z3210 adapter. After a quick and easy installation, the multimeter pairs with your smartphone or tablet, where you can display the measured values in real time - and store them directly in memory.
The lowest of the five current ranges is 60 mA, with guaranteed accuracy for values as low as 0.6 mA. The highest current range of CM4001 is 600 A, the frequency range is from 40 Hz to 1 kHz and the measurement category is CAT III 300 V. Despite its very compact size, this multimeter is equipped with features such as automatic hold, min/max/average or inrush current measurement function. In fact, the priority in designing the CM4001 was to achieve the smallest possible footprint while maintaining the greatest possible versatility and usability, especially in small and confined spaces - and the undeniably positive side effect is that it takes up a real minimum of space in your bag or toolbox.
The CM4002 measures 23.3 cm in height, more than 7 cm taller than the CM4001, but wider and thicker. The inevitably chunkier body of this model is linked to the manufacturer's intention to design an instrument that provides the most accurate measurements possible, which can be taken on conductors up to 40 mm in diameter.
As a result, the lowest of the six current ranges is just 6 mA with guaranteed accuracy for values from 0.06 mA, while the highest range is 200 A. The frequency range is also wider than its smaller brother, from 15 Hz to 2 kHz. The CM4002 meets the requirements of IEC/EN 61557-13, which defines the requirements for current clamps for leakage current measurements in electrical installations, such as protection against external magnetic fields (class 2, magnetic fields ≤30 A/m, which the CM4002 meets).
The third and last of the siblings is the CM4003. Putting the CM4002 and CM4003 side by side, it is not easy to find a difference between them. The physical dimensions are the same, as are almost all the technical specifications. But all it takes is a slightly different angle:
On the bottom of the CM4003 we see an extra connector that allows the connection of a special interconnect cable. This cable converts the four-pin output of the CM4003 to the following two connectors:
- The standard USB-C socket found in most smartphones today. It allows external power to be supplied to the CM4003 in case you want to take longer measurements. Power can be provided using the original HIOKI power supply (as an optional accessory), but nothing prevents you from using any power bank you would use to charge your phone.
- Standard BNC (male) connector. Thanks to this connector, the measured current can be converted into a voltage that you can store in, for example, the HIOKI MR8870 memory logger.
However, this connector on the CM4003 affects the measurement category, which is CAT III 300 V. In comparison, the CM4002 without the connector meets the CAT IV 300 V / CAT III 600 V measurement category.
The connection cable is designated as L9097 and is included in every CM4003 multimeter package. An external USB power supply (Z1013) and a USB-A-USB-C cable (L9510) are optional accessories. However, as mentioned above, a standard USB-C connector is used for power.
So whether you are looking for the most compact yet still highly accurate clamp multimeter like the CM4001 for measuring AC leakage - but also load - currents, or on the other hand you require the most accurate measurement possible, possibly supplemented by a voltage output of the measured current values - the CM400x series from the Japanese company HIOKI will meet your requirements.
Kai Scharrmann, HIOKI EUROPE GmbH