This review examines the Fnirsi DPOS350P 4-in-1 multi-function instrument, which combines an oscilloscope, function generator, spectrum analyzer, and frequency response analyzer. While praising its core oscilloscope functionality, display quality, and fast startup, the reviewer highlights significant criticisms regarding its software implementation for the more advanced features. Key issues include a surprisingly loud cooling fan, a reflective screen, lack of multi-touch, a proprietary charging system, and inaccuracies in claimed sampling rates. The spectrum analyzer and frequency response modes are noted as "unfinished," suffering from coarse resolution, display issues, and suboptimal signal generation, despite their inherent coolness and potential utility. The reviewer ultimately finds the device trustworthy as a basic oscilloscope but expresses a strong desire for firmware improvements to unlock its full potential.
Reviewing the Fnirsi DPOS350P: A Promising Multi-Function Instrument with Unfinished Software
0:00 Initial Impressions & Startup: The Fnirsi DPOS350P is a 4-in-1 touchscreen-based oscilloscope, function generator, spectrum analyzer, and frequency response analyzer. It boasts a rapid 3-second startup time, significantly faster than Rigol and other comparable devices.
0:45 Design & Noise Issues: A major drawback is the loud, tiny cooling fan, which is necessary due to the device's 12-watt power consumption. The screen is also noted as being quite reflective.
1:44 User Interface & Ergonomics: The touchscreen interface is intuitive for dragging traces and cursors, but it lacks multi-touch functionality (e.g., pinch-to-zoom). The reviewer also finds the trigger level adjustment cumbersome, often leading to accidental "auto" button presses.
2:14 Power & Portability: The device can run on battery for about 2 hours and requires a beefy 12V adapter (drawing up to 20 watts when charging). Running off the adapter can introduce noise, which significantly reduces when on battery or when the ground is connected.
3:40 Display Quality: The 7-inch display features 1024 pixels across, offering a noticeably crisper image than the 800-pixel Rigol display of the same size.
3:55 Oscilloscope Mode Features: While offering roll mode and a 60,000-sample trace buffer (better than some cheaper alternatives), it falls short of scopes with much deeper buffers for extensive post-capture zoom. The automatic interpolation of samples is disliked as it can hide true sample points.
5:55 Advanced ADC & Signal Integrity: The DPOS350P features a 16-bit Analog-to-Digital Converter (ADC) compared to common 8-bit ADCs, resulting in cleaner signal capture with less quantization noise and better handling of small signals, especially when running on battery power.
9:50 Function Generator Performance: The built-in function generator supports various waveforms up to 50 MHz (for sine waves) and uniquely offers a DC offset control, though its maximum output is limited to 3 volts.
10:09 Sampling Rate Discrepancies: The device sometimes reports a sampling rate (e.g., 50 MS/s or 1 GS/s) that is higher than its actual effective sampling rate, leading to aliasing or reduced resolution.
12:21 Spectrum Analyzer Mode (Unfinished): While able to pick up strong signals like FM radio with a simple wire antenna, the spectrum analyzer mode has coarse frequency resolution (approx. 29 kHz with 32k FFT), useless amplitude scaling, and poor performance in lower bands like AM due to a fixed high sampling rate. The software is considered "unfinished" and not comparable to a dedicated spectrum analyzer.
16:16 Frequency Response Analyzer (Unfinished): This mode is a "cool" feature, utilizing the internal function generator and scope channels to plot Bode plots. However, it suffers from automatic and problematic phase autoscaling, and an inaccurate logarithmic frequency scale that doesn't adapt correctly to arbitrary start/stop frequencies. The reviewer also notes an inefficient, stepping signal generation process with unexplained DC periods.
20:51 Overall Conclusion: The reviewer generally trusts and likes the Fnirsi DPOS350P as an oscilloscope, praising its core functionality, display, and fast startup. However, the advanced features (spectrum analyzer, frequency response analyzer) are considered "unfinished" due to software limitations and bugs, hindering their full potential. The loud fan and proprietary charger/cable are notable annoyances.