Bosch Professional Wall Scanner GMS 120-27 (2xAA Batteries, Marker Pen, max. Detection Depth Non-Magnetic Metal/Magnetic Metal/Live-Wire/Wood: 120/100/50/30 mm, Pouch)

After weeks of use it’s been reliable and very accurate.
I got this model on the recommendation of a professional, so that gave me some confidence. I was told to read the instructions carefully and take some time to familiarise myself with the device, it isn’t hard to use but you should not assume you can work it out without reading the instructions. If not used correctly it will produce wildly inaccurate results like all of these devices.Initially I tested it by scanning around my own home, where I already know much of the layout of pipes and much of the wiring. In some cases I scanned things I built myself from wood, just to see if it picked up the screws hidden inside, and yes, it did so every time. The scanner turned out to be extremely accurate elsewhere too, finding everything I knew was present plus a few things I didn’t know about. Since it was consistent when reporting the extra objects I believe it is trustworthy.The next test was using it in anger, building cupboards and shelf units in other people’s houses. Accuracy in these cases is obviously much more important, and I came to trust the scanner very quickly. If you ever do work in somebody else’s house, professionally or as a DIY favour, you should have something like this to ensure you don’t create any disasters. I found that out the hard way and ended up paying for an electrical cable I drilled into to be repaired by an electrician — I made a loss on that job. This scanner cost me a lot less than the bill for that repair. Lesson learned.After using it for a while I can recommend this scanner with no reservations.

A fairly good detector…
I bought this from Amazon Warehouse, as a “like new” used item for about £9 less than the going discounted rate new on Amazon (£90). Visually it was indeed spotless apart from some sticky tape residue on the original box. However, the battery had been left connected inside the unit and the disposable marker pen was dried out (see photo) and useless. The battery being left fitted, especially, is something Amazon really should check their returns for.It’s easy enough to use but it’s essential to read the manual to get the best out of it. It was mostly satisfactorily detecting studs, extremely good at detecting metals, and hit and miss detecting live cables. It detected a USB cable with just 5 volts in it yet failed to detect 240 volts AC cable buried just 30mm into a plaster wall on a number of tests, whilst finding the same in other locations. It certainly helps to have the cable energised as advised in the manual. It seemed to have a better success rate with live cables when held tilted towards the wall. Go figure that! I also noted in the manual that it said it only detects twisted wires, not solid. Scanning can initially be done fairly quickly but once a potential target has been identified you need to slow down and scan back and forth across the target 2-3 times in order to activate the fine adjustment scan and get an accurate centering. This is especially relevant detecting studwork & metal more than live cables.Out of curiosity I scanned my cats for their implanted ID chips using the metal mode and it found it on one cat but not the other. Not it’s intended use but an interesting revelation nonetheless. What I didn’t expect was it to tell me it was detecting electricity in the other cat despite me grounding him to discharge any static electricity. 🙀The supplied canvas holster is a tad too large for the detector and the velcro keeping it closed has been sewn on wonky and only partially aligns (see photo). Bosch quality isn’t what it once was! The belt loop on the rear is very sturdy and also has velcro, so you can open it to put around a belt or strap.Overall it’s a cautious thumbs up for this detector so far. It still needs putting through some more real life scenarios before it’s a qualified recommendation though. Just a pity Amazon overlooked the pen and battery issues…

Typical problems of inexpensive detectors
Before buying I read the negative reviews but decided to give this whirl as it sounded as though if you carefully follow the instructions this was a product which would do the job. However, the one delivered to me does not work in any coherent fashion. I removed my shoes, phone, watch. I used one hand flat on the wall etc as per the detailed instructions. The detector went nuts on every wall I tried it on while in drywall mode with near constant beeping and flashing lights. I have had recent building work in my house so I know the location of the studs one wall in particular but the detector was unable to indicate where they were. I tried detecting live electrical wires and the only circumstance in which it was able to detect anything was when I literally ran it down the wire of a vacuum cleaner. Sadly the detector simply did not do it’s job so I shall be returning it.

My project was to install shelf brackets on a gyp- board wall.I first bought a magnetic stud finder, which located nails, but not the studs. After missing a stud, I bought the Bosch Pro GMS 120. The magnetic stud finder was quicker to locate the general area of the studs. I used it to find and mark (wirh masking tape) all magnetic nails or screws. This help me avoid drilling into a nail head when attaching the shelf brackets (which have very precise requirements, and must all line up). Then it was a simple matter to locate the studs with the Bosch device. I marked them with a different color tape. Then made sure all the brackets lined up and avoided nails. The rest was easy.

J’ai pu tester cette accessoire, et effectivement force est de constater que cet appareil repère bien les endroits où il ne faut pas percer. Un appareil un peu cher, mais très utile.