Owon VDS1022I 25-MHz USB-Oscilloscope: Precise, Robust ... - Elektor

The Owon VDS1022I 2-channel USB oscilloscope (25 MHz) is designed for use with a computer, laptop or tablet. It comes with many useful features, such as math functions and an integrated spectrum analyzer. It measures 170 mm × 120 mm × 18 mm and has a weight of only 260 g; therefore, it is highly portable and suits every lab bench. Its isolated USB connection provides complete electrical separation of the device from the connected PC or laptop while reducing interference. It also protects the computer against overvoltage. A "multiple port" provides external triggering, trigger or pass/fail output. Figure 1 shows a typical set-up of the device, using a compact tablet PC.
 

Figure 1: The Owon VDS1022I connected to a Windows tablet PC.

Short Specifications of the Owon VDS1022I

• Bandwidth: 25 MHz
• Channels: 2
• Sample rate: 100 Megasamples/second (MSa/s)
• Horizontal scale (s/div): 5 ns/div to 100 s/div
• Vertical resolution (A/D): 8 bits (2 channels simultaneously)
• Vertical sensitivity: 5 mV/div to 5 V/div
• Communication interface: isolated USB 2.0
• Record length: 5k samples

All Inclusive

The oscilloscope comes with all the necessary accessories, so you can start measuring immediately:

• Owon VDS1022I oscilloscope in a robust metal housing
• 2x 60 MHz oscilloscope probes including clips
• USB cable
• Silicone case protectors

 
The two high-quality 60 MHz probes are sufficient for all typical applications. Some manufacturers charge the same price for a single probe as they do for the entire Owon device.

Owon VDS1022I Performance

One prominent advantage that jumps out is the quick and easy setup of the software. The initial installation is complete within a few minutes. When completed, unlike conventional bench-top oscilloscopes, the device is ready for use after a few seconds.
 
After connecting the 60 MHz probes, the first measurements can begin. As a first step, you should calibrate the probes using the 1 kHz signal that the device provides (Figure 2). This task takes only a few seconds using the included adjustment tools. When done, the probes will deliver clean signals without requiring any further calibration. As the figure 2 shows, the signal is reproduced with excellent accuracy after calibration.
 

Figure 2: Calibration with the internal 1 kHz signal. Top/red: uncalibrated; bottom/yellow: calibration completed.

Next, a 10 MHz / 5 V signal from a 60 MHz function generator (JDS6600) was examined. The screenshot (Figure 3) shows that the sine wave signal is displayed with the expected amplitude. With the square wave signal, the reduced rise time of 10 ns produced by the 25 MHz bandwidth becomes visible, as expected.
 
A frequency sweep with the same set-up showed an effective 3-dB bandwidth of 35 MHz on both channels, which is well above the advertised value of 25 MHz. Of course, due to manufacturing tolerances, this value may be slightly different for other devices.
 

Figure 3: 10 MHz test signals (sine &  square waves)

Ease of Use

The provided software offers a clear virtual oscilloscope interface. It does not have virtual knobs, which are often difficult to use and provide no technical advantages. The screen layout is user-friendly, and the numerous useful shortcuts make operating the device easy and quick to learn.
 
The shortcuts (Figure 4) allow for a fast and comfortable workflow. With a few keystrokes, the settings for the signals are quickly and efficiently optimized.

 

Figure 4: Shortcuts simplify the operation considerably.

The AutoSet function, activated by a green 'A' in the upper-right corner, operates reliably and provided a satisfactory display for all tested signals.
 

Figure 5: Math functions: multiplication of a low-frequency and a high-frequency signal.

Math traces (Figure 5) and FFT (Figure 6) functions can be selected to appear in the same or on a separate grid from the main traces, allowing the scope to also be used as a spectrum analyzer. The split screen is a highly useful feature, that even many much pricier devices do not have.
 

Figure 6: Spectrum analyzer functionality.

 
Persistence can be adjusted from zero to infinity. On the other hand, it should be noted that the sample interpolation method is fixed. You cannot modify the trace colors, which correspond to the probes and input connectors, either.
 
Other features include versatile triggering options (edge, variable slope and pulse, TV and with variable hold-off). Alternate triggering is also possible, providing the ability to trigger on two unrelated signals at the same time (Figure 7, lower traces). The display of Lissajous figures in XY mode is also no problem (Figure 7, upper left). This makes it possible to precisely capture signal phases or frequency ratios with the Owon VDS1022I.
 

Figure 7: XY mode for two separate signals.

Connectivity and Isolated USB

The oscilloscope features an isolated USB port, offering several advantages. This enhances greatly the electrical safety since the isolation provides a barrier between the computer and the device. This protects against electrical hazards such as shocks, surges. It also avoids ground loops, which occur when there are multiple paths to ground.
 
Moreover, the isolation helps to reduce electrical noise, such as electromagnetic (EMI) and radio frequency interference (RFI), which can affect the accuracy of measurements or cause errors in data transfer. Therefore, using the isolated port, the signals under test can be analyzed with minimal distortion.
 
The Owon almost completely excludes parasitic current flow and noise problems. Overall, the isolated USB port provides a safer and more reliable connection for data transfer and control between a computer and the device.

Multifunction Connector

Finally, a dedicated connector can be used as Trigger In, Trigger Out, and Pass/Fail out, using internally set rules. This allows for automatic test procedures or triggering of external devices, etc. Therefore, the VDS1022I can also find applications in service and production.

Pros and Cons

On the pro side, the following points are worth mentioning:

• Complete package
• Installation (Windows 10) without problems, completed within 3 minutes.
• Fast power-up
• Small footprint on the bench
• Isolated USB connection
• Robust design

 
However, there are also some downsides:

• No extensive user manual included
• Sample memory limited to 5k
• Menu wording needs getting used to
• Occasional hang-up or crash

 
The one real downside is the 5k sample memory depth, which may limit the versatility of the device to some extent. A small memory in a digital storage oscilloscope can have several disadvantages. For instance, the device cannot be used as a long-term transient recorder. Also, analyzing signals with low repetition rates or the limited ability to capture signal waveforms at high sampling rates may be inconvenient in some special use cases.

Tips and Tricks for the Owon VDS1022I

While working with the oscilloscope, the user interface occasionally hangs on the PC side, especially when the window is active in the background. Stopping the recording when idle avoids this issue. Also, for low-frequency signals, the "auto set trigger level" should be turned off to avoid trigger issues.

Conclusion

The Owon VDS1022I offers excellent functionality, especially considering its price. Its applications are not limited to entry-level or educational use. Experienced technicians can also benefit from using the device in many situations. Together with a tablet computer or laptop, it is a very useful measuring instrument that can be easily used in a mobile setup.