rebar finder

huangyhg

rebar finder
does anyone have any experience with devices used to locate rebar in concrete?  good, bad, ugly?  i hear hilti makes a device called a ferroscan (or similar), and runs abut $15,000.  zircon makes a hand held device like a stud finder that goes for $199.  anyone use anything like these?  easy to use?  good results?
why not use a standard metal detector?
i've had a lot of experience several years ago and cannot recall the names of the equipment.  i could go back through the files....but that's not likely!
anyway, my experience would have me suggest that if original drawings are available your best bet is to use those with words of caution and a provision for redrilling another hole when rebar is encountered in the original.
most detectors are only good for the surfaces and penetrate only a few inches into the concrete.  and that is assuming good solid concrete.  any material with delaminations will throw off the results since that represents a void through which detection cannot pass.  
usually there are many elements in a concrete element that are worth worrying about besides detecting the outer most stirrups which are closest to the surface.
really sophisticated equipment will take an experienced reader to interpret the results.  thus its better to hire a company rather than buy a peice of equipment.  you'd be surprised how fast the salesman backsdown on his claim of definite rebar to a measly "well here is an anomly in our reading that may represent something similar to rebar".  that's usually what happens when you ask them if they were hired to tell the contractor where rebar is.
good luck.
regards,
qshake
eng-tips forums:real solutions for real problems really quick.
if you are just trying to avoid rebar (probably for dowels), then the cheaper models usually get the job done.  the high-end models are necessary if you want to determine the size and/or depth of the bars.  
i'd hire a company if you need to size the rebar, and i'd buy a cheapo if you're just trying to locate it.  consider renting the equipment if its available.