BOSCH GMS120-27 Professional Wall Scanner, Multi-Function Stud Finder, and Live Wire Detector for Electricians, Plumbers & Contractors

This easy-to-use stud/metal/wire finder is great
I use it for the thick drywall/plaster or wood floors in my house and works much better than the cheaper electronic ones I have used in the past. Most of my 1950s home’s walls have drywall coated in plaster and are about 1″ thick is most spots so non-electronic and electronic stud finders never worked too well. Remodeled areas of my home also have the standard 5/8″ or 1/2″ thick drywall and 3/4″ thick wood paneling which I use this mostly successfully on. I also used this successfully to detect flood joists beneath wood flooring, copper and galvanized pipes behind cement board/tile and to find rebar in cement. It can detect steel as deep as 4.75″ in the wall, wood up to 1.5″ and wires up to 2″.Using it around the house, I find it works better in the thick walls and wood paneling, especially for finding live wires. In the standard thickness drywalled walls, it does not find electrical wires well but it does find studs and plumbing well. The only downside to this detector is I cannot get it to consistently find electric wires behind 1/2″ or 5/8″ drywall which is standard on most homes. In most cases, it will not detect them at all but does give a reading sometimes. This is probably due to the finder only being able to detect wires up to 2″ deep in the wall. Sometimes wires are not within 2″ of the drywall surface. It also cannot detect studs well behind wood paneling which is not surprising.I find it pretty user-friendly, just turn it on, set your mode (wood, metal, electrical) then place it on the wall and give it a second to calibrate. Afterwards, start searching. It will alert you to whatever mode you have it set on with a bar gauge. When you have it on wood mode, it will also alert you to metal and wires which is convenient. It makes noises as you get closer (you can turn the sound off, it is a bit irritating). When you find the center of a stud, pipe or wire, the finder has a convenient holes you can stick a pencil through the mark it. It seems to find wood with the assistance of finding screws/nails and overall, I find its best to scan up and down to find the exact position of the stud, pipe or wire. You probably wont get the exact location on the first bullseye. The finder also has a backlight for the screen when using in dark areas.The finder comes with a 9v battery, carrying case and directions as well. The directions take a little reading. Overall, this is great for finding studs and pipes but 4/5 stars for the general inability to find electrical behind standard thickness drywall. 5 stars for versatility and ease of use. I thought about knocking it down a star for general failure to detect wiring but its scan range for wiring is limited as stated.

Works on plasterd walls!
This is the only stud finder that has worked with our plastered walls. So grateful to have it.

Bosch Really disappointed me!
Wow! I pity the poor fool trying to make a living using this thing. I own 3 other stud finders and decided to go for, what I perceived to be, the best. I have purchased plenty of fine Bosch tools so I arrived at the conclusion that all of the individuals rating this stud finder so low just didn’t know how to use it. Later I would reveal to myself that this was indeed a pompous conclusion.Then I bought one. My background is in Electrical Engineering so I do know a thing or two about how these devices work. I decided to put the Bosch Scanner to the test. First, I scanned a section of wall with three studs on 16 inch centers sheeted with standard 1/2 inch dry wall.This was a relatively simple task as the bays were clear of any pipes, wire or insulation. I used a $15 Zircon, a $25 Zircon and a $20 Stanley to map the area. As expected, all three found the studs accurately. I had been using these 3 units for years and trusted all for this type of scan. I marked the studs on a strip of painters tape about 6 feet long to document the results.Then I attempted to settle the Bosch unit down and let it self calibrate over a known empty bay. The Green Ring lit up and I thought this is sweet! That was it for the excitement. As I moved the unit across the tape the blasted thing beeped and showed center about every 3-4 inches. I tried everything above and below the tape marked with the other stud finder’s results.Other Notes:The readability of the LCD display is ridiculous! This one had to be held about 20 degrees above eye level to see anything. Ah, but I thought, If I turn it upside down I will not have to squat to get readings below neck high. I could see it alright, but it was still incorrect and really cumbersome to use upside down.I cannot imagine how Bosch let this thing get on the market. Maybe this was a LEMON but if it was: There are most assuredly too many lemons produced with this model.By the way, the electrical wire sensor never did work even with a loaded circuit of 100 Watts. The metal finder did find the drywall nails, but so can my $1.25 swivel magnet nail finder. I have no embedded ferrous or nonferrous metal pipes in my walls, so to be fair; I could not test this function.

Very accurate and robust.

Great quality item from Bosch.