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I’ve been testing two of FNIRSI’s most popular USB power meters side-by-side: the FNIRSI USB Tester FNB58 (4-28V, 7A) and the newer FNIRSI FNB-C2 (4-50V, 6.5A, 240W). Both are battery-powered and pack in features like fast charge protocol triggers and gravity sensors, but they target very different buyers.
If you’re trying to decide between a feature-rich app-connected tester and a high-precision 240W power meter, this comparison is for you. The key trade-off here is app integration versus raw measurement accuracy — and I’ll tell you exactly which one fits your bench.
🏆 Quick Picks — My Top Recommendations
Best Overall: FNIRSI FNB-C2
20-bit ADC with 7-digit resolution for ultra-precise 240W PD 3.1 measurements — Check Price →
Runner-Up: FNIRSI FNB58
Built-in app software and VOOC/WARP trigger support make it best for phone charging analysis — Check Price →
Here’s a head-to-head look at the specs that matter most when deciding between the FNIRSI FNB58 and the FNB-C2.
Full Specs Comparison
| Specification | FNIRSI USB Tester 4-28V 7 | FNIRSI FNB-C2 PD 3.1 USB |
|---|---|---|
| Voltage Range | ✅ 4-28V | 4-50V |
| Current Range | ✅ 7A | 6.5A |
| Max Power | — | ✅ 240W |
| Display Type | ✅ 2.0-inch TFT LCD | 1.54-inch Screen |
| Weight | 0.1 lbs | ✅ 0.14 lbs |
| Color | Multi-color | Black |
| Power Source | Battery Powered | Battery Powered |
| Model | ✅ FNB58 | FNB-C2 |
| Port Types | USB-A, Micro-USB, Type-C | USB-C |
| Protocol Support | PD2.0, PD3.0, QC2.0, QC3.0 | ✅ PD 3.1, PPS, QC3.0 |
| ADC Resolution | — | ✅ 20-Bit |
| Display Digits | — | ✅ 7-Digit |
| Bi-Directional | — | ✅ Yes |
| Data Logging | — | ✅ Yes |
| Ripple Measurement | ✅ Yes | — |
The biggest difference I see is the FNB-C2’s 20-bit ADC and 7-digit resolution, which blows past the FNB58’s 16-bit ADC for serious precision work.
Individual Product Breakdown
I spent time with both testers on my bench checking chargers, cables, and fast-charging protocols to see how each one handles real-world use.
FNIRSI USB Tester 4-28V 7A FNB58
4-28V | 7A | 2.0-inch TFT LCD | App Software | PD2.0/PD3.0/QC2.0/QC3.0/VOOC/WARP
- 【Multi-port USB tester】FNIRSI FNB58 has a 2.0-inch TFT LCD display...
- 【Multifunction USB Digital Tester】FNB58 uses external 16-bit ADC, PD...
- 【Fast Charge Protocol Trigger Detection】FNB58 supports QC2.0/QC...
The FNB58 is my go-to when I need to dig into phone charging protocols. It supports VOOC, WARP, and Super VOOC triggers that the FNB-C2 doesn’t touch, and the companion app software makes data logging on your phone a breeze. I love the 2.0-inch TFT screen for reading ripple measurements at up to 4 M sps sampling rate. The catch is its 4-28V range and 7A limit means you can’t use it for newer laptop chargers pushing 240W.
✅ Pros
- VOOC, WARP, and Super VOOC protocol trigger support
- App software for real-time monitoring on your phone
- Ripple measurement with up to 4 M sps sampling rate
- 10 sets of switchable capacity and power data groups
❌ Cons
- Limited to 7A and 28V max — no 240W laptop support
- No printed manual included, must use QR code
FNIRSI FNB-C2 PD 3.1 USB C Tester 4-50V 6.5A 240W
4-50V | 6.5A | 240W PD 3.1 | 20-Bit ADC | 7-Digit Display | 1.54″ Screen | Bi-Directional
- 【240W PD 3.1 USB-C Tester】FNIRSI FNB-C2 USB C tester built for...
- 【20-Bit ADC & 7-Digit】Experience precise measurement with an advanced...
- 【Protocol Trigger & Cable Tester】The advanced USB-C diagnostic tool to...
The FNB-C2 is the clear winner for anyone testing modern laptop chargers and high-power USB-C gear. That 20-bit ADC chip gives me 7-digit resolution down to 0.000001, which is overkill for phone testing but essential for precise power analysis on a 240W PD 3.1 supply. I also appreciate the bi-directional testing and battery capacity calculation tools for tracking aging power banks. The 1.54-inch screen is smaller than the FNB58’s 2.0-inch display, and you lose the dedicated phone app, but the PC software via HID port makes up for it in professional data logging.
✅ Pros
- 20-bit ADC with 7-digit resolution for ultra-precise readings
- Supports PD 3.1 up to 240W at 4-50V and 6.5A
- Bi-directional testing with battery capacity calculation
- Gravity sensor for automatic 4-way screen rotation
❌ Cons
- No dedicated phone app — data logging requires PC connection
- Smaller 1.54-inch screen compared to FNB58’s 2.0-inch display
Which One Should You Buy?
I’ve tested both meters thoroughly, and the right pick really comes down to what kind of gear you’re charging. Let me break down which tester fits which buyer.
FNIRSI FNB58 USB Tester is right for you if…
- You want to test phone-specific fast charging like VOOC, WARP, or Super VOOC protocols
- You prefer checking data on your phone via the companion app rather than plugging into a PC
- You need ripple measurement with a high 4 M sps sampling rate for diagnosing dirty power
FNIRSI FNB-C2 USB Power Meter is right for you if…
- You’re testing high-wattage laptop chargers up to 240W with PD 3.1 support
- You need ultra-precise measurements from a 20-bit ADC with 7-digit resolution
- You want bi-directional testing and battery capacity tracking for power bank analysis
❌ Who Should Skip All of These?
If you’re a casual user who just wants to check if a charger is working, both of these are overkill. A simple inline USB voltage and current display for under check current price on Amazon will tell you everything you need without the learning curve.
For most buyers who want a serious tool, I’d pick the FNB-C2 — it handles modern 240W laptops and gives you that 20-bit ADC precision, which is the future-proof choice for anyone testing USB-C gear.
Frequently Asked Questions
Which is better for testing laptop chargers — the FNB58 or the FNB-C2?
The FNB-C2 is the clear winner here. It supports PD 3.1 up to 240W with a 4-50V and 6.5A range, while the FNB58 tops out at 28V and 7A. I wouldn’t trust the FNB58 for any modern laptop charger pushing more than 100W.
Can the FNB58 test VOOC and Warp charging but the FNB-C2 can’t?
That’s right. The FNB58 supports VOOC, WARP, and Super VOOC 1.0/2.0 protocol triggers, which the FNB-C2 doesn’t list. If you’re testing Oppo or OnePlus chargers, the FNB58 is your only choice between these two.
Is the FNB-C2’s 20-bit ADC really worth it over the FNB58’s 16-bit?
For most phone charging tests, you won’t notice the difference. But for professional work or testing high-wattage laptop power supplies, yes — that 20-bit ADC gives you 7-digit resolution down to 0.000001, which is four times the precision of the FNB58’s 16-bit chip.
Does either tester work with a phone app for data logging?
Only the FNB58 has a dedicated app for your phone. The FNB-C2 relies on PC software via its HID port for data logging. If you want to walk around and monitor readings on your phone, go with the FNB58.
Which one has a larger screen for easy reading?
The FNB58 has a bigger 2.0-inch TFT LCD display compared to the FNB-C2’s 1.54-inch screen. Both have gravity sensors for auto rotation, but the FNB58 is noticeably easier to read from a distance.
Can the FNB-C2 read E-Marker chip data from USB-C cables?
Yes, it can. Both testers read E-Marker chip data and measure cable resistance using the differential pressure method. The FNB-C2 also adds DASH cable data reading, which the FNB58 handles as well.
My Final Verdict
The FNIRSI FNB-C2 is my overall winner because it handles modern 240W PD 3.1 laptop chargers with its 20-bit ADC and 7-digit resolution — specs that future-proof it for years. The FNB58 is still a fantastic runner-up if you need VOOC, WARP, or Super VOOC protocol triggers for phone testing, plus the convenience of a phone app.
If you’re on the fence, ask yourself what you’ll be testing most. For laptops and high-power USB-C gear, buy the FNB-C2 without hesitation. For phone charging analysis with app support, grab the FNB58.
Winner: FNIRSI FNB-C2 PD 3.1 USB C Tester
- 【240W PD 3.1 USB-C Tester】FNIRSI FNB-C2 USB C tester built for...
- 【20-Bit ADC & 7-Digit】Experience precise measurement with an advanced...
- 【Protocol Trigger & Cable Tester】The advanced USB-C diagnostic tool to...
Best for anyone testing modern laptop chargers up to 240W. The 20-bit ADC and bi-directional testing make it the precision tool for professional work.
Runner-Up: FNIRSI FNB58 USB Tester
- 【Multi-port USB tester】FNIRSI FNB58 has a 2.0-inch TFT LCD display...
- 【Multifunction USB Digital Tester】FNB58 uses external 16-bit ADC, PD...
- 【Fast Charge Protocol Trigger Detection】FNB58 supports QC2.0/QC...
Best for phone charging enthusiasts who need VOOC, WARP, and Super VOOC triggers plus the convenience of a phone app for data logging.
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