Fnirsi has built a reputation for creating affordable, feature-packed test equipment for hobbyists, makers, and budget-conscious professionals. The DPOS350P is their latest 4-in-1 tablet oscilloscope, combining a dual-channel 350MHz scope, 50MHz function generator, frequency response analyzer (Bode plotter), and spectrum analyzer – all in a compact 7-inch touchscreen device priced around €270. This review covers real-world performance, build quality, and where this device excels versus where software limitations hold it back.
Fnirsi DPOS350P: Complete Package And Build Quality
As expected from Fnirsi, the DPOS350P arrives in a sturdy carrying case with a generous set of accessories.
What is in the box
- DPOS350P oscilloscope unit
- Two oscilloscope probes
- Test lead with alligator clips
- Power adapter
- USB charging cable
- Bilingual manual (PDF download recommended)
Build quality and dimensions
The oscilloscope case measures approximately 19 x 13 x 4 cm and is neatly finished with aluminum side panels. The front features a 7-inch touch display with 1024 x 600 resolution. Controls are minimal: on/off button and USB-C port on the side, three BNC connectors on top (two for scope inputs, one for generator output). A foldout bracket on the back and a small cooling fan are included – though the fan runs continuously at full power and is noticeably noisy.
Display and touchscreen
The 7-inch touchscreen is bright, high-contrast, and easy to read even at an angle. The touch response is accurate and responsive. According to Fnirsi, the screen is coated with tempered glass for scratch resistance. Boot time is impressively fast at just 2-3 seconds.
Oscilloscope Performance: The Main Attraction
The oscilloscope section is where the DPOS350P truly shines, delivering performance that punches above its price point.
Key specifications
- Bandwidth: 350MHz
- Sampling rate: 1 GSamples/s
- Dual-channel operation
- 8-bit ADC (up to 16-bit via software averaging)
Real-world performance
The sampling rate of 1 GSamples/s with 350MHz bandwidth is quite high for a device in this price range. The scope responds quickly to all kinds of input signals and produces a very sharp image. The auto-setup function almost always finds the correct settings quickly, requiring minimal manual adjustment.
In dual-channel operation, input channels are automatically limited to 150MHz, suggesting the A/D converter operates at 500 MSamples/s when both channels are active – still respectable at this price point.
User interface and controls
- Main display area shows measured signals
- Controls located on three sides of the screen
- Bottom panel: input channels, time base, sampling rate, triggering, generator
- Right side: auto-setup, sensitivity, start/stop buttons
- Top panel: System and Function menus, measurement parameters
Zoom function
A handy zoom option (top right of the screen) displays the measured signal at the top, allowing you to select a portion for enlarged display below. This works for one or two channels simultaneously.
Limitations
The trigger function is somewhat limited – only rising or falling edge options are available, which could be expanded in future firmware updates. The FFT display for each input lacks a proper scale, providing limited measurement information.
Signal Generator: Significant Improvement
The built-in function generator in the DPOS350P is a substantial upgrade over previous Fnirsi models.
Generator specifications
- Maximum frequency: 50MHz
- Output: Clean, high-resolution signals
- 14 pre-programmed waveforms
- Signal perfectly symmetrical (max ±2.5V)
- Separately adjustable offset
- Save-wave function (up to 500 waveforms)
The generator delivers clean, high-resolution signals with excellent symmetry. The ability to save and recall waveforms is a valuable feature for repeatable testing.
Frequency Response Analyzer (Bode Plotter)
The DPOS350P includes a Bode plot function for determining frequency and phase characteristics of filters and networks up to 50MHz.
How it works
Connect generator output to first scope input and to circuit input. Connect circuit output to second scope input. The device plots the response automatically.
Limitations
- Lowest frequency is 100Hz (disappointing for audio enthusiasts)
- Frequency range always divided over logarithmic scale of three decades
- Vertical scales (dB/degree) are auto-ranging, producing strange results
- No user-adjustable scales
- Very fast scanning with no averaging, causing inconsistent results between scans
Verdict: A good start, but the software still needs fine-tuning. Not yet useful for professional measurements.
Spectrum Analyzer
The built-in spectrum analyzer has a range of 200kHz to 350MHz (display shows up to 500MHz).
Adjustable parameters
- Vertical scale (reference value and attenuation per division)
- Start and stop frequencies
- Center frequency and frequency width
Critical limitation
Maximum FFT length is 32k. The analyzer always uses this length for the entire band. When you select a narrow band (e.g., 10-16MHz), there are so few samples in that range that only broad lobes are visible. The lower the frequency range, the worse the resolution.
Verdict: The spectrum analyzer is only suitable for roughly scanning the entire frequency band up to 500MHz. For detailed analysis, this feature is not yet useful. Significant room for software improvement.
Fnirsi DPOS350P Vs Previous Models
Compared to earlier Fnirsi oscilloscopes, the DPOS350P offers meaningful upgrades.
| Feature | DPOS350P | Previous Fnirsi Models |
|---|---|---|
| Bandwidth | 350MHz | Lower (typically 100-200MHz) |
| Function Generator | 50MHz, clean signals | Less capable, noisier output |
| Display | 7-inch touch, 1024×600 | Smaller or lower resolution |
| Bode Plotter | Yes (limited) | Rarely included |
| Spectrum Analyzer | Yes (limited) | Rarely included |
| Fan Noise | Continuous, noticeable | Similar or quieter |
The generator is the most significant improvement – delivering clean, high-resolution signals that outperform previous integrated generators.
Pros And Cons Of The Fnirsi DPOS350P
| Pros | Cons |
|---|---|
| Excellent 350MHz scope for the price | Fan runs continuously at full power (noisy) |
| Very fast boot time (2-3 seconds) | Trigger options limited to rising/falling edge |
| Sharp, responsive 7-inch touchscreen | Bode plotter software needs refinement |
| Great function generator with 14 waveforms | Spectrum analyzer lacks narrow-band resolution |
| USB-C charging and PC connection | Manual is too small (PDF recommended) |
| Save-wave function for up to 500 waveforms | FFT display lacks proper scale |
| Good auto-setup function | No user-adjustable scales for analyzers |
Frequently Asked Questions (FAQs)
Is the Fnirsi DPOS350P worth €270?
Yes, for the oscilloscope and function generator alone. The 350MHz bandwidth, fast sampling rate, and clean generator output deliver excellent value at this price point. The additional analyzers are nice extras but not fully developed.
What is the real bandwidth in dual-channel mode?
In dual-channel operation, input channels are automatically limited to 150MHz because the A/D converter operates at 500 MSamples/s when both channels are active.
Can the spectrum analyzer be used for serious RF work?
No. The 32k FFT length applied across the entire band means narrow-band resolution is poor. It is suitable for rough scanning of the full 500MHz band but not for detailed analysis.
Does the DPOS350P require a subscription?
No. All features are included with the device. No ongoing fees.
What is the battery life?
The device includes a rechargeable battery charged via USB-C. Exact battery life is not specified, but typical use ranges from 3-5 hours depending on screen brightness and fan operation.
Who is the DPOS350P for?
Hobbyists, electronics students, makers, and budget-conscious professionals who need a capable oscilloscope and function generator. The extra analyzers are fun to explore but not reliable for professional measurements.
