FNIRSI FNB58 USB Tester, PD/QC, USB-C E-Marker Reader, 28V 7A, USB-A/C

I've owned this USB tester for several years now, and despite all the newer USB-C equipment that has appeared since then, it remains one of the most useful diagnostic tools on my bench. It's one of those devices that I expected to use occasionally but ended up reaching for regularly. Whether I'm testing USB power supplies, evaluating charging cables, reviewing power banks, checking battery chargers, or troubleshooting charging issues, this tester provides immediate insight into what's actually happening on the USB connection. Being able to see voltage, current, power, capacity, and charging protocol information in real time takes a lot of the guesswork out of USB troubleshooting. Over the years I've used it with everything from basic USB-A chargers to modern USB-C PD devices. The fast-charge protocol detection is particularly useful because it quickly confirms whether a charger and device are negotiating properly. When a phone or tablet isn't charging as expected, this tester often helps identify whether the issue is the charger, cable, or device. One feature I've come to appreciate more over time is capacity measurement. When testing power banks, battery packs, or USB-powered devices, it's nice to be able to monitor actual energy transfer rather than relying on manufacturer claims. The ripple measurement functions are also useful for evaluating power supply quality and identifying potentially noisy chargers. The display is easy to read, the controls are straightforward, and the device has proven surprisingly durable. Mine has been connected to hundreds of devices over the years and continues to work just as well as when I first purchased it. That's saying something considering how often it gets used around my workbench. What really stands out is how relevant it remains. Even with the rapid evolution of USB charging standards, this tester still provides valuable information for modern USB-A and USB-C devices. It has helped me evaluate countless products, diagnose charging problems, and verify manufacturer specifications. If you regularly work with USB-powered devices, power banks, chargers, batteries, or charging cables, this is one of those inexpensive tools that pays for itself many times over. Mine has been in service for years and continues to be one of the most useful pieces of test equipment I own.

It's not perfect.. it has bugs, quirks, and inexplicable interactions, but --- once you figure out how to test the things that matter to you, it's very repeatable and clear. Specifically, it can read the Chip ID in USB-C cables, and show all the available power modes in USB-C PD, on a nice color built-in screen. That's nice. You can see the finer details of PD packet exchange as well, but this was less reliable. For testing batteries and other sources, it has a convenient "Trigger" function that can request any voltage or current from your supply, with a nice physical Switch that engages or disengages the "active" part. Switched off, the device is pass-through only and zero risk. Switched ON, you have a lot of direct control over voltage, and of course, risk. You want to put 20v on a USB-A socket? You can! I find the device is best to use when it's plugged into its own independent Micro-USB power source (5v, low current), because then it's not constantly turning off and on with your devices under test. It's easy to crash the device when messing with USB-PD packets, or even have it just beep nonstop until you pull power. The firmware could use some work. Some functions are duplicated or confusing (how many different trigger menus do you need?) but hey, it's affordable for DIY hobby work and comes in a nice well-made housing with an excellent screen for cheap. Unfortunately, the company web site is terrible, hosted on some Mediaflare thing that runs out of bandwidth, so downloading the firmware updates is way more hassle than it should be. They need to up their game, put up a professional site, and host their own files.

First, this is a very capable little tester. For testing USB-A stuff, no complaints at all. Does what it says on the box and then some. There are even Python libraries that can read the data over the USB port so you don't necessarily have to use an app downloaded from a strange place to access the data. My only complaint - and it may not be the device's fault - is the situation with two USB-C cables. It can be difficult and require some trial and error to actually get a proper USB-C PD connection passing through the device. As I understand it, this is because despite common belief, USB-C cables *aren't* 100% reversible (i.e. flipping the connector 180 degrees doesn't always "just work" because some pins are only connected on one side of the connector) and this is one case. It might take you up to 16 tries (four connection points, two possible orientations) to actually get USB-C PD passing through the device even with the device's own PD negotiation turned off. At best you'll get 0 volts, in the middle you'll get plain 5v/2a power, and in a couple cases I saw the device crash or fully shut down even with external power provided via the PC port. In short, you need two full-function USBC-to-USBC cables to be able to passively measure charging between a USB-C charger and device, and you might have to play with reversing the connectors multiple times before you actually get a successful PD negotiation. I'd love to see a USB-C native version of this, with a USB-C port or cable directly attached to the device so you never have to worry about the two-cable pass-through situation. I do have a TC66 USB-C tester which works well but its UI leaves much to be desired compared to this one!

Pros: 1) Nice metal case with easy to use controls 2) Excellent, bright and clear display, with auto-rotate 3) Loads of technical capabilities 4) Nice storage box to keep the unit protected 5) Companion Windows app (NOT macOS) is nicely done, and turns this into a capable testing and measurement device. The only con is the documentation, which is a bit lacking. I had to go to YouTube to learn how to upgrade the firmware (which was necessary because the unit displayed incorrect temperature readings). All in all though, if you're reasonably technically savvy, there won't be any significant issues. Recommended! The manual and firmware are available at the FNIRSI website.

Very good tester, its nice to use the auto detect though its not 100%. Pd pass thru is amazingly helpful and pd trigger is good when using a USB c charger that requires a load device to provide power. Jitter reading isn't sure useful but the other readout and charts are good for load testing.

My experience with scopes is pretty limited, so take this as the opinion of a FW/SW dev. I love this little guy. Power consumption measurement of MCUs has been elusive until now. The sampling resolution doesn't blow me away, but it is good enough for my needs. Very easy to read and use. I found the menu system on the intuitive side, which surprised me. A like its size as well. At first I was wishing for a bigger screen. After using it for a while, I found that the smallish size is great because now I can leave it connected all the time without hogging up desk space. Excellent. And for the record, I've seen no evidence of interference with MCU D+/D- signals. Wish I'd picked this up a long time ago.

I just got mine so I can't be too specific but I've bought quite a few similar devices over the years and this one is clearly a next-generation above even the one I bought a year or two ago from some other company. Screen is very easy to read, buttons are easy to use, connectors are well labeled and lots of them...this thing is a joy to hold and to have around. My new favorite gizmo!

I am a retired electrical engineer with experience in board design, chip design, and software development. As others have noted, the English documentation is close to being useless. This device is quite complex so without documentation, many functions are unclear. For that matter, even simple things are unclear (or just don't work). It is very buggy and crashes frequently. Updating the firmware is not documented at all, is not intuitive, and requires a physical PC. I could not get it to make even a basic measurement of the voltage and current coming out of an Apple USB C power supply and going into a Mac computer. After spending hours trying to use this device to make various measurements, trying to read the junk documentation, reading web reviews and watching Youtube videos, I am returning it. I just don't want to put in any more time trying to figure out how to use this piece of junk. Furthermore, I am so irritate with this company Fnirsi, that I will make sure to never buy anything form them again.

Produto de excelente qualidade, ótimo acabamento e muito preciso

Excelente , cumple con lo publicado,

Excellent product

I bought the FNB58 as I'm into small electronics and wanted a tester to test cables, chargers, etc. This thing does it all. From simple voltage/current/wattage readings to battery capacity measurement and fast charge protocol control, there's not much else you could possibly need. The feature set is incredible, and the UI is easy to use, although the manual isn't really much help: I looked to YouTube reviews and tutorials to learn how to use it: Pros: Small form factor, large display Physical buttons have great tactile feeling Measures and tests just about everything Cons: Manual is pretty much useless. More expensive than others (but with better features so that's expected) No internal battery (some functions will require a seperate cable and brick to power the device). There is a different variation of the FNB58 with Bluetooth and an app for your phone. The casing on the Bluetooth model is a lighter blue/grey, as opposed to the black casing this one has. I have not tested any PC connection features, as I don't really have the need to. 2 warnings: 1. If you are using any fast charge feature, make sure you know what you're doing, as it is possible to send high voltage to a device and fry it. There is a warning when entering the menu reminding you to unplug anything connected to the output. 2. Flicking the PD COM switch to on will connect the power from all the ports except the PC micro-USB on the top. When using a feature like PD listener, you should power the device with the PC micro USB port, as it's isolated from the rest of the circuitry. One review I saw didn't do this and sent 20v from a laptop charger into a 5V battery pack. Fortunately the battery pack had over voltage protection, but it's not a risk worth taking. Overall, for the hobbyist with the budget, or the professional repair technician, the Fnirsi FNB58 is a great package that you won't be disappointed with.

Lo utilizo para comprobar la calidad de los cables y las prestaciones de los puertos USB. Acoplado a un generador de carga de USB es una herramienta excelente. Inclusive puedes medir la resistencia interna de los cables, o la corriente máxima que puede entregarte un puerto USB. Recomendado.