The Chinese manufacturer Fnirsi is constantly introducing new measuring instruments. The 4-in-1 oscilloscope DPOS350P, which we tested a few months ago, has now been joined by a more modest version that offers somewhat lower specifications at a lower price, but does offer some features we haven't seen from Fnirsi before: a number of physical push buttons and rotary knobs for operation, along with a touchscreen. Sounds like a winning combination, doesn't it? We tried it out!

The combination of touchscreen and physical control buttons has been around for some time in professional oscilloscopes, and it generally works very well. While this Fnirsi 2D15P isn't particularly large, its design does resemble a "large" oscilloscope. Measuring approximately 19.5 x 12.5 x 5 cm, the device is quite thick, making it resemble a miniature version of a benchtop oscilloscope.

Complete package

With the 2D15P, Fnirsi has once again combined several instruments into a single case. This time, these are a 2-channel oscilloscope, a signal generator, and a multimeter. Several test cables are also included: two 100 MHz probes for the oscilloscope, a BNC cable with alligator clips for the signal generator, a set of test leads for the multimeter, and finally, a USB cable for charging the internal battery and for PC communication. A carrying case is unfortunately not included this time. The bilingual manual (Chinese and English) is concise but definitely worth reading carefully.

The 2D15P features a 4.3-inch IPS touchscreen with a good viewing angle. Below the display are three BNC connectors: two for the scope and one for the generator. Furthermore, below and next to the display are several rotary and push buttons for operation. On the side is a large on/off button, and on the top are two large pushbuttons for single-shot and auto-triggering. The multimeter inputs are also located on the top. On the back, besides the fan slots, there's only a USB-C connector. The case looks well-finished and sturdy, and thanks to two large, fold-out legs on the back, you can tilt the device slightly back on your lab bench.

The 2D15P's specifications are quite decent. The oscilloscope has an input bandwidth of 100 MHz and a maximum sample rate of 500 Msamples/s (50 MHz and 250 Msamples/s in dual-channel operation). The signal generator offers nine waveforms with a frequency up to 2 MHz (10 for sine wave) at a maximum output voltage of 3 Vpp. The multimeter has a resolution of 4.5 digits and can measure DC and AC voltages and currents, as well as resistance, capacitance, and diodes.


Like most Fnirsi devices, the 2D15P comes with the necessary accessories.

Using the 2D15P

After pressing the power button, the DPOS350P boots up in about 5 seconds. The oscilloscope function always appears then. Two things are immediately noticeable during use. The small fan on the back is clearly audible, but I wouldn't call it annoying (my own benchtop oscilloscope and generator are noisier). And every operation triggers a terribly loud beep. Fortunately, you can reduce the volume in the menu or turn it off completely!

The display provides a wealth of information, such as sample rate, trigger setting, and signal frequency. To the right of the signal section are two boxes that show the settings for the two channels. Touching a box selects that input, but you can also do this using the two CH buttons next to it. Below that are two more boxes that show the settings for the DDS signal generator and the multimeter, respectively. To access these two functions, you can touch either of these boxes. The signal generator can also be selected with a physical pushbutton (DDS), but the multimeter is only accessible by touching that box.

Below the display are two rotary knobs for setting the time base and sensitivity. The other rotary knobs allow you to adjust the trigger level, the horizontal and vertical offset of the signal, and cursor lines, among other things. Some functions can also be controlled using the touchscreen, but for the time base and sensitivity, you must always use the rotary knobs.

As I mentioned earlier, the 2D15P offers a combination of a touchscreen and real buttons. Most functions are therefore accessible via one of the keys on the right side of the front panel. Pressing the large Menu key also displays all these functions together on the screen. After touching or pressing a function, a submenu with several options appears, and then you're forced to configure the settings via the touchscreen. This isn't entirely consistent; it would have been nice if you could also navigate through the menu items using a rotary knob. But you get used to it after a while.


At the back there are two sturdy fold-out supports to tilt the device slightly backwards.

Oscilloscope

The oscilloscope works very well and responds quickly to signal changes. The bandwidth will be more than sufficient for most applications. I tested the bandwidth up to 60 MHz (my function generator doesn't go any further), and the signal remained virtually constant up to that frequency. The auto-trigger function (Auto Measurement) is activated with one of the large buttons on the top, and it works very good; it finds a usable setting within seconds. The other large button at the top can be used for manual triggering. At first glance, it seems a bit odd to place such large buttons on top of the box for these two functions, but in practice, it works quite well.

The oscilloscope offers a fair number of measurement options. You can choose from 13 different measured values that are continuously displayed on the screen. The Math functions are limited to standard options like A+B, A-B, etc. You can also place horizontal or vertical cursor lines on the screen and have values calculated between them. For calibrating the oscilloscope probes, a separate probe tip on the left side delivers a 1 kHz square wave. Screenshots can be taken with the Save button, which can also be transferred to a PC.


The multimeter inputs are located on the top of the case.

DDS Function Generator

The function generator in the 2D15P builds on the design already used in other Fnirsi devices. In this case, you can choose from 9 waveforms, including sine, triangle, square, and staircase. The output voltage can be adjusted between 0 and 3 Vpp, but the signal is always positive (not symmetrical). The controls are clear, and there's also a button to mute the signal, something that was sometimes missing in predecessors. The waveforms are good, with no visible distortion, but for audiophile applications you'd be better off looking elsewhere. The frequency for most waveforms extends up to 2 MHz. According to Fnirsi, the sine waveform goes up to 10 MHz, but above a few MHz, the number of steps per period seems to decrease rapidly, and the generator produces an unusable signal. Conclusion: use the generator up to 2 MHz and it will do its job well!

Multimeter

The multimeter screen displays not only the measured value but also a graph showing the measurement history over time. At the bottom, you can choose from various functions. In Auto mode, the meter automatically detects DC or AC voltage or resistance values, but this doesn't work with voltages below 800 millivolts. You can also manually select a specific measurement, but the meter always uses auto-ranging. The voltage and current measurements, as well as the resistance measurements, proved to be very accurate, with a deviation of less than 0.05% for the values I tested (strange that Fnirsi itself doesn't mention accuracy in its specifications). The capacitance measurement also worked reasonably well, on par with that function on more expensive multimeters. However, in the capacitance and mA ranges, the resolution is limited to 4 digits instead of 4½ digits in the other ranges. The continuity beeper works quite slowly and displays nothing on the screen; it only beeps.


On the left is the display of the DDS generator, on the right the display of the multimeter.

Conclusion

The Fnirsi 2D15P is a handy 3-in-1 measuring device that is reasonably priced and delivers good measurement results. All three functions in this device work properly and are ideal for general electronics work. The presence of several physical push buttons and rotary knobs makes it much more user-friendly than a touchscreen-only model, in my opinion. The fact that the operating philosophy isn't entirely consistent is something I can live with. In any case, I would definitely choose the 2D15P over a "buttonless" version. Highly recommended!