Stud Detector - operation.

[McGuinn]

I understand that pipe and metal detectors use electromagnetic pulses to locate metalic objects within range, but how does such an object also detect a beam or stud which has no iron within it?

Does it use ultra-sonic?

 

[laroche73]

Stud detector

Years ago, I had the same question, so I took apart my Sears studfinder to see how it worked. It used a simple oscillator based on some CD4000 gates, and the back side of the circuit board as a split-plane capacitive sensor (ingenious & extremely simple). The circuit responds to changes in the capacitors' dielectric material, which in this case is the drywall and any studs behind it.

 

[McGuinn]

Oh, Ok, thanks for that.