Review: Fnirsi 2C23T Oscilloscope, Multimeter and Signal Generator

The Chinese company Fnirsi has released quite a few electronics measuring devices recently, ranging from a component tester to a Geiger counter. They are all very affordable and often offer features or combinations of options that you don’t easily find with other brands or for which you pay much more. This time we take a look at the Fnirsi 2C23T, a handy device that combines an oscilloscope, a multimeter, and a signal generator in a compact case. And all this for a price that is well under €100. Is the 2C23T worth the money, and can you really do something with it as an electronics engineer? That’s what we’re going to explore in this review.

The Fnirsi 2C23T Is Solid with Few Buttons

With dimensions of approximately 17 cm × 9 cm × 3.5 cm, you can easily hold the meter with one hand. The 2.8-inch color LCD delivers a reasonably bright and high-contrast image, especially when looking straight at it. The case has a rubber-like material at the corners and seems quite strong. The power supply is a lithium battery with a capacity of 3 Ah, which, according to the manufacturer, is sufficient for about 6 hours of operation.

Oscilloscope, Multimeter & Signal Generator in One

There are separate connections for the three functions. At the front there are 4 banana sockets for the multimeter, and at the top of the device there are 3 BNC sockets: two for the (two-channel) oscilloscope and one for the DDS signal generator. Everything is controlled using 15 pushbuttons under the screen. Finally, there’s a USB-C connector on the side for charging the battery and updating the instrument’s firmware. The device comes with a set of test leads, an oscilloscope probe, a BNC cable with alligator clips, a USB-C cable, and a separate Elektor manual in four languages.
 

The specifications of the 2C23T are nice but not spectacular, but then again, you don’t expect that from a 3-in-1 measuring device in this price range. The oscilloscope has two channels, a bandwidth of 10 MHz and a sample rate of 50 MSPS.

Multimeter

The 4-digit multimeter has an accuracy of 0.5% and can measure DC and AC voltages and currents, plus resistance, capacitance and temperature. There is also a continuity and diode tester, and you can determine the phase of the mains voltage with one probe. The meter automatically detects whether a DC voltage, an AC voltage or resistance is connected to the inputs, but you can also manually switch to a certain function.

The built-in DDS generator has one output channel that can deliver a signal up to 3.3 V (peak-to-peak) with a frequency from 1 Hz to 1 MHz. The user can choose from 6 preprogrammed waveforms.

Possibilities

First, let’s take a look at the oscilloscope feature. A lot of information is available on the screen, there even is an icon at the top that indicates which kind of signal the generator is currently outputting. The number of settings is limited. For example, you can only set the probe attenuation and AC/DC coupling per channel. For triggering, there is an Auto feature that works really nice, but there are only a few manual trigger options: the channel and rising or falling edge. The PRM button allows you to show a few automatically measured values in the scope window. There is a choice of 8 values. The Save button is for taking screenshots, which are stored in memory. The user interface of the scope is quite logical in structure, but it does take some time getting used to.
 

 

A Fnirsi S1 with Current Measurement

The multimeter is very similar in terms of possibilities to the Fnirsi S1 that I tested some time ago but with a current measurement function (which the S1 unfortunately lacked). On the display the measured value appears in the center, on the left and right there is an analog scale which shows the voltage in a range from 0 to 100.

By default, the multimeter is in Auto mode. Depending on the voltage or resistance being measured, it shows the value of the alternating current, direct current or resistance. For resistance values below 50 Ω, the (continuity) beeper also sounds. As with the S1, the auto-measurement doesn’t work for voltages below 0.7 V, but once you know that, it functions well.

With the four upper pushbuttons, the various measurement functions can be selected manually. It’s a pity that the corresponding indications above the buttons are not clearly readable due to the gray color.

Simple Function Generator

The function generator is kept pretty simple. You can choose from 6 waveforms (sine, square wave, triangular wave, half and fully rectified sine, noise and DC). For each waveform, the frequency, the duty cycle (only for square wave and triangular wave) and the output voltage can be set. Operation is also simple; just remember to validate with the central cursor key after changing a value. Enabling and disabling the output is possible with the central cursor when you are in the waveforms list.

Using the Fnirsi 2C23T

The first thing you’ll notice is that the device switches on fast: after pressing the On/Off button it takes about 1 second for the function overview to appear. Here you choose which instrument you want to use. In the Config menu, it is possible to select a default instrument after power-on.
 

The screen is on the small side for oscilloscope mode. It is a bit crowded, especially if multiple automatic measurements are being displayed. Often, one channel is sufficient, and then I like to turn off the unused channel to unclutter the display.

Good Response

The scope responds quickly to changes in the input signal and button presses also have immediate results. The auto function works quite well too. Occasionally, it is necessary to adjust the trigger level manually, but that also happens with a ‘normal’ oscilloscope.

The BNC sockets on the top are recessed into the housing and quite close together. As a result, it is not possible to connect probes with a plastic covering around the bus. I couldn’t use the probes of my own oscilloscope here. Pay attention to this if you want to buy an additional probe.

Fnirsi 2C23T Is Almost Always Autoranging

The multimeter works well if you know that the auto-detection does not work properly below a value of 0.7 V. If the voltage is lower, you have to choose a function yourself. This is done by pressing the four top buttons once or several times. Keep in mind that a function can be selected, but not the range. The meter always does this automatically. Only current measurement mode lets you choose between a low and a high range.

I tested the accuracy of the multimeter at a number of values for voltage, current, resistance and capacitance, and it turned out to at least a factor of 2 better than the specifications given by Fnirsi. There is certainly nothing to complain about for this price!

For the two current ranges, the meter has two fuses that you can replace, but you must open the instrument to access them.

Socket Spacing of Fnirsi 2C23T Is Not Standard

The distance between the four banana sockets is a little less than the usual 19 mm. If you buy a thermocouple for this meter, make sure it has two separate banana plugs; otherwise, it won’t fit.
 

 

The Signal Generator in Practice

Finally, we have the built-in signal generator. It is useful for occasional use, but the quality of the signals could be a bit better. The number of steps per period is limited and there are also small glitches in some steps. This applies only to the sine wave and triangular wave, rectangular wave, noise and DC do not suffer from those problems. Maybe something for a future firmware update?

Operating the generator is easy, although entering a frequency value requires some care due to the number of digits (7). The maximum output voltage is 3.3 V, which is top-top and without load. The output impedance of the generator is not the usual 50 Ω but 100 Ω; when terminating with a standard 50 Ω load, you only have 1/3 of the voltage left. Also keep in mind that the output signal is always positive with respect to ground (meaning that it has a DC component), no output capacitor or symmetrical power supply has been used.

The frequency range of the generator goes beyond the specified 1 MHz, I was able to get 2 MHz out of it (albeit with a bit more distortion).

Conclusion

For less than €100, the Fnirsi 2C23T is a handy 3-in-1 device that can be very useful, especially when used on location. All three features work well, although, of course, you shouldn’t expect top-notch performance from them. There are some minor shortcomings, but if you take those into account, the 2C23T is a great instrument with which you can tackle most electronics measurements without having to carry around half a laboratory of equipment. Definitely recommended, especially for this price!