Fnirsi DMC-100 600A Current Clamp/Multimeter (Review)

A current clamp is a measuring device that not every electronics technician owns, but it is especially useful for measuring large currents. The fact that you can measure current without interrupting the cable is a big advantage. This time, I’m reviewing the Fnirsi DMC-100, the first clamp meter launched by the now well-known Chinese manufacturer. Like most Fnirsi devices, this current clamp is competitively priced (less than 50 euros), has a modern design, and features a beautiful color screen—something rarely seen in current clamps. Except for a model from Owon, I don’t know of any current clamp with a color display.
 

Many Features

A current clamp is an instrument that measures current that flows through a wire by passing it through a transformer core, designed as a “jaw” that opens to allow the wire to pass through. In this case, it has a relatively small jaw that accommodates cables up to approximately 2.5 cm in diameter, which should be sufficient for most home, garden, and automotive applications. The meter can measure currents up to 600 A, and in addition to AC, the Fnirsi DMC-100 can also measure DC.

Many current clamps combine contactless current measurement with multimeter functions, and this device is no exception. The DMC-100 performs almost all the functions of a typical multimeter: DC and AC voltage and current, resistance, capacitance, temperature, frequency, diode testing, and continuity testing. Additionally, the DMC-100 offers some extra features, which I’ll discuss later.

The Fnirsi DMC-100

The relatively thin current clamp measures approximately 19.5 × 7.5 cm and is powered by an internal 1500 mAh lithium battery, providing about ten hours of use. The device feels sturdy, the clamp closes precisely, and it has a strong spring. On the front, there’s a 2-inch color display that provides a high-contrast image with extensive information. Operation is handled via five buttons below the display. On the side, there is a sixth button that turns on the built-in flashlight.

A USB-C port is located under a cover for charging the battery and communicating with a PC. The two terminals for the multimeter are at the bottom. A current terminal is not present because the current clamp already provides that function.
 

The Fnirsi DMC-100 comes with a brief Chinese/English manual, a set of test leads for the multimeter, a temperature probe, and a USB-C charging cable. Unfortunately, a carrying case is not included this time (I had gotten used to that with Fnirsi products recently—they are very handy).

Powering On and Measuring

Using the DMC-100 is very simple. However, since each key has a dual function, you need to be mindful of what you press and for how long. For example, the power button not only turns the meter on and off when held but also activates the zero setting for DC measurements with a short press.

The display shows a wealth of information. At the top, you see the unit and the measured value (three digits for current measurements, four digits for the multimeter). Below that, the minimum and maximum measured values are displayed, and at the bottom, symbols indicate all the multimeter’s measuring options. The arrow keys are used to select one of these symbols. Pressing the center key briefly selects the second (or third) function in the symbol (e.g., switching from DC to AC, or from frequency to temperature measurement).

Pressing the Save button for an extended period accesses a settings menu where you can adjust the language, display brightness, temperature unit, and auto power-off time, among other options.
 

Useful Extra Features

In addition to all the basic functions, the DMC-100 offers various extra features. You can use a single probe to determine the phase connection in an outlet. Additionally, there is a sensor on the front of the jaw that detects live wires without contact.

However, what I like most is the graphical representation of current measurements over time. The Save button allows you to store the current measured value in memory. The last eight saved values appear next to the graph, and the memory can hold up to 30 values. You can review these stored values through the settings menu.

The meter can also measure voltage and current simultaneously and calculate power. I assume this doesn’t account for the phase relationship between the two, but it’s still a useful feature.

There is also a built-in flashlight, though it doesn’t provide much illumination—at best, it helps light up the clamp in dark spaces.

The Fnirsi DMC-100 in Practice

Using the DMC-100 is truly enjoyable. The device powers up in less than a second and provides a wealth of information on the clear display. I had to get used to the dual functions of the buttons—early on, I often pressed the wrong one, such as switching to another function when I actually wanted to activate the Hold function. But after some practice, it became more intuitive.

I tested the accuracy of the various multimeter and current clamp functions, and all results were well within Fnirsi’s listed specifications—often more than twice as accurate. With the clamp meter, I could only test up to about 15 A, but I assume accuracy remains acceptable at higher currents.
 

Measuring DC with the Fnirsi DMC-100

With AC, you can measure immediately, but for DC, you must first reset the meter to zero by briefly pressing the power button. As far as I know, this is necessary for all current clamps to compensate for environmental influences. The transformer in the clamp reacts to surrounding metal objects, causing the meter to display a non-zero reading. Moving the meter around on a lab bench even slightly affects the zero setting.

Thus, it’s important to zero the meter just before taking a DC measurement and then perform the measurement immediately. The cable’s position in the jaw also influences accuracy when measuring thin wires. This is why current clamps generally have a precision of about ±2.5%. However, for higher currents, the goal is more about obtaining a general measurement rather than an exact value.

What About Small Currents?

Many electronics engineers want to measure small currents with a current clamp, but most clamps aren’t well-suited for this. In this case, the resolution for both AC and DC is 10 mA, but a reasonably reliable measurement requires a multiple of that—let’s say at least 100 mA. You can work around this using the old trick of winding a cable through the jaw multiple times. With five turns through the jaw, the meter displays five times the actual current through the cable.
 

Final Thoughts

I find the graphical time display very useful, along with the ability to store multiple values. Moreover, this feature works not only with the current clamp but also with the multimeter. Stored values are presented in a neat overview, clearly labeled with their respective units (current, voltage, capacitance, etc.).

The non-contact voltage detector also performs well, unlike previous Fnirsi devices I’ve tested. The only disappointing aspect was the temperature measurement—it was significantly off with the included sensor. However, I don’t consider that a major issue, as I wouldn’t buy a current clamp for that purpose.

Conclusion

I don’t have many uses for a current clamp, but this versatile instrument offers so many great extras that I’m considering getting one anyway. For less than 50 euros, you get a well-designed device with a high-quality display and a wide range of features. That’s well worth the money!