Excited for the Zeeweii DSO3D12 Oscilloscope

by David Ashton
Reading time: 7 min

When the opportunity to review the Zeeweii DSO3D12 oscilloscope came up, I was thrilled. The idea of a device that combines a 120-MHz scope, a multimeter, and a signal generator into one compact unit was intriguing. Here’s what I discovered.

Design and build quality

The Zeeweii DSO3D12 is a tidy and compact unit measuring 14.5 × 8.6 × 3.2 cm, with a 3.2-inch screen (just over 8 cm). It includes a fold-out stand on the back for easy bench positioning. On top, there are two BNC sockets for the oscilloscope probes, two small lugs for the signal generator output, a USB-C charging port with an indicator light, and an on-off switch. Below the screen are the multimeter connections: common, one for volts/ohms and capacitance, and two for current—10 A and 600 mA, both unfused, which is a bit concerning. The front panel also includes navigation keys, function keys, and scope setup buttons. (Figure 1).

Figure 1: the Zeewei DSO3D12 — Figure 1. The DSO3D12. (Source: Zeeweii)

Sampling rate concerns

During my review of the Zeeweii DSO3D12 oscilloscope, a particular specification stood out: its sampling rate is 250 Megasamples per second (MSa/s). This rate is just slightly more than twice its maximum signal frequency, which raised some red flags.

To give some context, the Sampling Theorem, developed by Harry Nyquist in 1928 and further expanded by Claude Shannon in 1948/49, is crucial in information theory. This theorem states that to accurately capture and reconstruct a signal, the sampling rate must be at least twice the signal's highest frequency. While the theorem's mathematics are complex, the practical takeaway is that sampling at just twice the signal frequency is often insufficient. More typically, a much higher sampling rate is needed to avoid inaccuracies.

If the sampling rate is too low, the result can be aliasing, where the sampled signal is inaccurately represented. Aliasing causes the signal to appear modulated by the difference between the actual signal frequency and the sampling frequency. To mitigate this issue, systems usually employ an anti-aliasing filter—a low-pass filter that blocks frequencies higher than the desired range from entering the system.

Comparing with Industry Standards

High-quality oscilloscopes typically sample at a rate at least ten times the signal frequency. For instance, my Hantek DSO8060, a dual-channel 60-MHz oscilloscope, also samples at 250 MS/s, and it performs adequately. Therefore, I was keen to see how the DSO3D12 would handle signals around 120 MHz. It's important to note that Zeeweii specifies that the bandwidth drops to 60 MHz when both channels are used simultaneously.

Given these considerations, the performance of the Zeeweii DSO3D12 at its upper frequency limits was a critical aspect of my evaluation. How it manages sampling and potential aliasing at 120 MHz would determine its suitability for precise measurements and complex signal analysis.

Creating Test Signals

To test the Zeeweii DSO3D12 oscilloscope, I needed to generate signals at high frequencies. My collection of crystal oscillator modules, some reaching 120 MHz or more, provided ideal square wave signals rich in harmonics. Using these oscillators, I could thoroughly evaluate the DSO3D12's performance.

For the initial test, I connected a 20 MHz oscillator module. The resulting waveform initially appeared as a mix between a triangular and sine wave. Remembering that oscilloscopes often perform better with a divide-by-10 probe at high frequencies, I adjusted the probes. A 20 MHz square wave includes its fundamental frequency and odd harmonics, such as the third harmonic at 60 MHz and the fifth at 100 MHz (Figure 2).

Comparing the displays on my 60-MHz Hantek and the 120-MHz DSO3D12, I observed the following:

Figure 2 hantek + zeewei screenshots — Figure 2. A 20-MHz square wave from an oscillator module displayed on my 60-MHz Hantek scope (left) and on the 120-MHz DSO3D12 scope (right). Both signals showed some jitter, which was more noticeable on the DSO3D12 trace. Keep in mind, the Hantek screen is about four times larger than the DSO3D12’s.

On the 60-MHz Hantek scope, the 20 MHz signal lacked detail at the peaks but clearly showed the third harmonic. The DSO3D12, with its higher bandwidth, displayed a more accurate square wave, thanks to the inclusion of the fifth harmonic. Despite some jitter, the detail was impressive, marking a win for the DSO3D12

Observing Switch Bounce

Years ago, I had to write articles on switch bounce but struggled to capture the phenomenon with my existing scopes. My Hantek scope excelled in this area, so I tested the DSO3D12 similarly. I set the time base to 50 µs per division, used the 'Single' trigger mode, and connected a switch to a +5 V supply through a 1 kΩ resistor to ground. The DSO3D12 successfully captured the switch bounce, allowing for easy navigation through the captured signal to focus on the bounce detail. Adjusting the trigger level was straightforward, and the performance was impressive. However, I couldn't easily transfer screenshots to a PC (figure 3).

Figure 3 switch bounce — Figure 3. Switch bounce captured on the DSO3D12.

Switch bounce captured on the DSO3D12 showed detailed traces, confirming the scope's capability in handling one-shot events effectively.

User Manual and Documentation

The paper manual that comes with the DSO3D12 is well-written, covering essential information. Trigger adjustments meet quality standards, and the scope includes an X-Y mode if needed. On-screen information is clear and user-friendly, contributing to the scope's high usability.

Signal Generator

Accessing the signal generator is simple: press the GEN button to open a control window on the screen. The generator offers a variety of waveforms, including sine, square, triangle, sawtooth, and noise, with the sine wave reaching up to 5 MHz. The fixed output level is 2.5 V, connected via small lugs near the BNC connectors. While a better output connector and adjustable voltage would be ideal, the generator is versatile and practical for signal tracing.

Digital Multimeter (DMM)

The DMM function includes high-quality probes with standard 4-mm banana connectors, allowing easy use of personal probes. It measures AC/DC voltage and current, resistance, capacitance, diode testing, and continuity. Comparing measurements with my Hantek scope showed less than 1% variance, indicating high accuracy. The DMM is user-friendly, with clear socket indicators on the display. However, the lack of fuses in the current ranges requires caution (figure 4).

Figure 4 dmm range selection — Figure 4. DMM range selection screen.

DMM range selection screen is straightforward, enhancing usability.

Voice Recognition and Additional Features

I tested the DSO3D12’s undocumented voice recognition feature, activated by pressing Shift and CH1 V and saying "Hello Zeeweii". and it will respond with a friendly greeting and wait for your commands. The scope responded to commands, allowing changes in settings and mode switches. There's a good demo video and a longer one showcasing many other features of the unit. Additionally, there are several other undocumented features, such as a quick press of the On/Off switch bringing up a function menu, where you can select an option and then click Auto to display it in full-screen mode. The enclosed manual is decent, but an extensive online manual would be a valuable addition.

Summary

Pros:

Multifunctional and offers excellent value for money.
User-friendly with a variety of features.

Cons:

The sampling rate may limit high-frequency performance.
Initial keyboard layout is not intuitive.
The signal generator has limited output options.
Lack of comprehensive documentation for all features.

Overall, the Zeeweii DSO3D12 is a highly capable oscilloscope, especially considering its multifunctionality and affordability. While some areas could be improved, it performs admirably across various tests and applications.