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wingless' Bosch GMS 120 Wall Scanner (Stud Sensor and Much More)


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Bosch GMS 120 Wall Scanner


My decades-old Zircon Stud Sensor still works fine, but the homes I work on now have metal studs. The Zircon electronic stud finder does not locate those new-fangled metal studs, instead looking for REAL studs, made from wood. The Zircon Stud Sensor is an edge finder dielectric constant capacitor detector, using a single sensor. The usage is simple, with a linear LED display.


A Bosch GMS 120 Wall Scanner was selected and purchased to permit detection of metal studs. It does that and more. This is a center finder dielectric constant capacitor detector, using a pair of sensors. When the sensor measurements match, the center of the stud has been located.


In stud detection mode, the Bosch GMS 120 Wall Scanner detects: wood studs; magnetic metal and non-magnetic metal. In metal detection mode the wall scanner locates: nails; rebar or screws. The wall scanner has a live wire detection mode to locate wires carrying 110-220 VAC voltage.


The Bosch GMS 120 Wall Scanner has a red / green illuminated ring around a cylindrical pencil-marking hole. There is a LCD display and tones, with a myriad of symbols that mean success, when properly decoded. 


The tool has a back lighting on / off push button for the display. That was very handy during my last usage.


It is a little complex, but once experience is attained, it is a good / useful tool.


Now I can locate metal studs!


This has a nice pouch for storage / usage protection w/ Velcro flap and Velcro belt loop. It is powered by a single 9V battery. There is an included tether strap.


















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  • 4 months later...

I rarely use an electronic stud finder anymore. C.H.Hanson magnetic ($7-8) rarely misses and is a dream on metal studs. My co-contractor friend has the 200ish dollar Milwaukee stud finder but has since gotten the Hanson as well.

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  • 7 months later...

I am looking for a way to find mortar joints behind plaster.  This is kind of the opposite of a stud finder.  In my 150 year old house the mortar is lime and sand, so the walls are held together by hope and gravity rather than glue.  The plaster is troweled set plaster that sort of sticks to the bricks. Drilling into a joint when trying to hang a picture can result into a variety of unsavoury results.


I want to find either the centre or the edges of the bricks.  Since the mortar was mixed by hand, the mortar lines are sometimes very thin (Right, chaps, we need to get another course done before knock-off time, and Clive is too knackered to mix another batch, so make it last!   I think the real reason is almost the same - the lime mortar was mixed some time in advance to give it time to do what it had to do to become mortar, so if they ran out because someone tipped over a wheelbarrowful, they had to make do with what they had.).  In this case, the tool might find what looks like a very large brick.  No problem - I can drill my hole 1/4 in from the edge to get a brick centre.


Stud finders are tuned to find wood or metal through plaster.  My question is - has anyone successfully used one to find mortar joints through plaster?


Thanks for your help.

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Welcome to the forum.


This is a handy tool w/ a pair of sensors to locate the center of a stud / pipe / wire accurately.


Contact the manufacturer to see if this will provide the required detection.


IMO, an infrared camera is probably a better option, using solar heating, night time cooling, central heating, to create an internal / external temperature differential, so the different thermal conductivity will show up for imaging.



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