Stanley 100 stud sensor at Wally World - calibration problems

PhotonWrangler

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We picked up one of these stud sensors the other night and for eight bucks it seemed to be a good deal fomr something that can detect wood as well as metal studs. However when we got it home we found that it wouldn't calibrate - it just kept beeping constantly. Looking at some reviews of the unit online this appears to be a problem for others also.

So I opened it up and found the fix. This unit operates with a capacitive sensor, not an inductor, which is why it's able to detect changes in wood density. The sensor head is a PCB capacitor plate, and it measures somewhere around 24nf on my meter. Moving it across various objects, the capacitance seemed to change only by a nanofarad or so. This is a REALLY tiny change that it has to sense. There was a little bit of excess silicone sealant across the capacitor plates so I carefully removed it just in case this was affecting the circuit.

And I discovered that there is a 20-turn pot on the board that is a factory calibration setting. It is hidden under the left side black cushioned grip, which has to be pried off for access. This adjustment was off by a couple of turns. Setting the unit on a wooden surface and slowly turning the screw, I eventually found the sweet spot where it would calibrate and start functioning properly. This sweet spot is only about 180 degrees wide in terms of pot rotation, so it's a pretty narrow window and it probably drifted after being set at the factory, maybe from changes in humidity or vibration during shipping. Or they don't calibrate them carefully, I don't know. Anyway it's working now and I thought I'd pass this tip along for anyone else who might've bought this stud sensor at Wally World and had this problem.

And of course this will void your warranty if you open it up, but you only have to pry off the left-side black cushion grip to get to the hidden calibration pot. And for eight bucks, so what if I void the warranty?
 

BobBrian

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Joined
Feb 27, 2018
Messages
6
I have been using Zircon for years. Very basic but works well. It uses a very small radar system to detect the stud. If you want more info on stud finders, just check out this informative resource https://studfinderexpert.com/
 
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