Zoyi ZT-703S Oscilloscope, Multimeter and Function Generator (Review)

In recent years, an increasing number of multifunctional measuring devices have emerged, almost all manufactured in China. These devices typically combine the functions of a multimeter, oscilloscope, and function generator in a compact case about the size of a large multimeter. Often, these meters can be purchased for less than 100 euros – an amount for which you couldn’t even buy a standard multimeter from a renowned brand. Some time ago, I reviewed the Fnirsi 2C23T, and now it’s time for the Zoyi ZT-703S, which promises even better specifications for just a few euros more. Naturally, this makes the choice difficult, so we’ll explore whether the Zoyi ZT-703S offers enough additional value for the higher price.
 

The Zoyi ZT-703S looks exactly like a regular multimeter. Fnirsi often tries to give its devices a modern appearance, but that’s certainly not the case with Zoyi. When I place the ZT-703S next to my everyday multimeter (both powered off), only the different button layouts suggest that they don’t have the same functions. The dimensions of the ZT-703S—approximately 18 × 9 × 4 cm – are also similar to a typical multimeter. The large 3.5-inch color display indicates that this meter can do more than just measure voltages and currents. There are 13 buttons, including four function keys and a keypad. The slightly rubberized casing feels sturdy, and the buttons all have a clear tactile response. Power is supplied by an internal 18650 lithium battery, which should last several hours (though Zoyi does not specify usage time).
 

At the bottom of the front panel, we find the familiar four sockets for voltage and current measurements, just like on a regular multimeter. At the top, there are two recessed BNC sockets for the two-channel oscilloscope, with enough space around them to connect standard probes and BNC cables. On the right side, there is a cover that hides a USB-C connector and two pins, which serve as the generator output and for probe calibration. The battery can be charged via the USB port, and the device can be connected to a PC for firmware updates and uploading screenshots.
The ZT-703S comes in a carrying case, including two oscilloscope probes and accessories, a set of test leads, a USB-C cable, and a small English manual.

Capabilities of the Zoyi ZT-703S

The specifications of the Zoyi ZT-703S are impressive. The two-channel oscilloscope has a sample rate of either 200 MSPS or 280 MSPS (manually adjustable) and an input bandwidth of 50 MHz. It includes an X-Y mode to display Lissajous figures. Various cursor measurements are available, and the signal’s key parameters (such as frequency and peak value) can be displayed. Additionally, screenshots can be taken and stored in internal memory. These can be viewed later on the device or transferred to a PC via USB.
 

The true-RMS multimeter features 25,000 counts, a basic accuracy of 0.05%, and performs all the standard functions of a regular multimeter, including capacitance and diode measurements. The meter is autoranging, but users can also manually select a range. An additional 250 mV range is accessible via one of the function buttons. Above the numerical display, there is an analog scale, useful for monitoring variations in the measured signal. It’s worth noting that the power inputs are internally fused, and the fuses can be easily replaced by loosening four screws – a feature sometimes missing in cheaper multifunctional Chinese measuring devices.
 

Function Generator and Waveforms

There isn’t much to say about the function generator. It has a standard frequency range of 1 Hz to 1 kHz (as per the specs) and can generate various waveforms (sine, square, pulse, triangle). An additional setup window offers access to more waveforms (single and double rectified sine waves, plus sawtooth), and there is an on/off switch for the output. I will cover this additional settings window in more detail later.

Getting Started With the Zoyi ZT-703S

Upon powering on, the Zoyi displays the last selected function on its easy-to-read IPS screen. When using the oscilloscope function, the screen appears crowded with information, which is unavoidable given the screen’s small size. The oscilloscope responds smoothly to input signals, and the cursor keys allow for easy adjustment of the time base and input sensitivity. Trigger options are limited to rising or falling edges, but this should suffice for most cases. The buffer memory is displayed at the top, and it can be scrolled through when the signal is paused. The generator’s output signal is shown at the bottom right of the screen.
 

Switching between options and settings is done using the four function keys and the keypad. This can be confusing at first because, in addition to the main menu, there are six function menus, and their labels are not always clear. It’s worth reading the (very small) manual to understand what everything means. For example, you can set separate auto-off times for the display and the entire meter, clear the internal memory, and more. One notable setting is ‘Run Mode,’ which controls the maximum sampling frequency. By default, it’s set to ‘Normal’ at 200 MSPS. Switching to ‘High’ increases it to 280 MSPS, but this also increases power consumption. In Normal mode, the oscilloscope is usable up to around 30 MHz. Beyond that, the signal becomes unstable, with the amplitude constantly fluctuating. In High mode, I reached around 50 MHz, though the signal wasn’t completely stable above 40 MHz. Still, 30 MHz is a solid value for a device in this price range. Firmware version 1.42 even added an FFT function, though it’s not very useful in its current form.
 

With three readings per second, the multimeter isn’t the fastest, but it performs well. The basic accuracy of 0.05% is indeed achieved, and in the higher voltage and current ranges (which are specified at 0.5%), the meter is usually accurate within 0.2%, which is impressive for this price point. Resistance measurements are similarly within 0.2%. The ZT-703S also handles capacitor measurements quite well, performing comparably to my other multimeters. However, for larger electrolytic capacitors, the readings may vary slightly – though as is often recommended, large capacitors are best measured with a dedicated LCR meter with frequency settings.

Function Generator Issues

The function generator is, frankly, not great. While the number of available waveforms is acceptable, the process for adjusting settings is confusing. Through the ‘Output Setting’ option (found on the sixth menu page), you can set the waveform, frequency, duty cycle, and output voltage. For sine, triangle, and pulse waveforms, frequencies up to 5 kHz are selectable, but the output voltage is limited to either 1 Vpp or 2.5 Vpp. For square waves, there are no adjustable parameters, and the output is fixed at 1 kHz/2.5 V, likely for probe calibration. The set output voltage is constantly present, so you can switch to the oscilloscope to measure the generator voltage, for example.
 

There’s a second settings menu for the generator, which includes rectified sine waves and a sawtooth waveform (found under ‘MoreAPPs’). However, any settings made here only remain active while you stay in this menu. Once you exit (using ‘Mode’), the output reverts to the values set in the first menu. I managed to generate sine waves up to 344 kHz and square waves up to 500 kHz, while the other waveforms extended to a respectable 100 kHz. Although this menu also displays the output voltage, you can’t adjust it here – only the frequency and duty cycle can be modified. You can disable the output, but as soon as you exit this menu, the output automatically turns back on. I suspect higher frequencies can be set in this menu because the oscilloscope function is disabled, allowing more processing power for the generator. However, the setup is confusing, and Zoyi definitely needs to improve the software.
 

Conclusion

Despite the confusing operation of the function generator, I found the Zoyi ZT-703S to be a sturdy and versatile device with a good, relatively large display. While the operation takes some getting used to due to the many submenus, the variety of options it offers is worth the effort. The oscilloscope function is excellent, with responsive performance and decent bandwidth for its price range. The multimeter is also impressive, proving to be more accurate than the specifications suggest. However, the function generator is mediocre, particularly in terms of ease of use. Firmware updates may improve this in the future. Overall, if you’re aware of the limitations of the generator, the Zoyi ZT-703S is a solid multipurpose measurement tool at a reasonable price.