Targets frequency response

[mikebg]

Lesson "Target Properties in Frequency Domain"

There is the lesson:

[mikebg]

Wrongful terminology and formulas in the Bruce Candy's Gospel
"Metal Detector Basics and Theory"
http://www.minelab.com/consumer/xstandard/files/ML_08_007WhitePaper8.pdf

[mikebg]

Carl: "I have intended to do these measurements myself, but haven't had time".
Carl, Sean Goddard knows method to measure frenquency response for no time using only one pulse. Please make him to post in the forum! Mike. ***

[mikebg]

Hi Seeker,
Your experiment shows nonlinear properties of conductive object. I,m obtaining nonlinearity by nonconductive meteorites because of its ferromagnetic properties.
To discriminate hot rocks from meteorites, I need information in wide frequency band.
In my city Plovdiv - BG, there is experts on processing targets spectral information , but I dont know them. They have produced a cheap project "Pulsediscriminator PD3200", where spectral information is calculated as "color coefficients" of target. Unfortunately, last year, when I start to design nonmetal detector "meteorite locator", they were disappeared from WEB.
Thanks for information, Mike ***

[Seeker]

Hi guys,
ten years ago I try analyse some characteristics of finds and I found for some multimetal alloys and copper coins with CuO and Cu2O cover semiconductor effect. If that finds are in field of two basic frequencies they produced two different frequencies f1-f2=f' ; f1+f2=f" and can register they on narrowband receiver. I made narrowband filter myself on 32 kHz using clock quartz .

[Carl-NC]

Max, even in phase discriminators, targets can have a "frequency response". That is, their phase response can vary over frequency, and you can plot this as "phase vs frequency."

Mike, to answer your question, no, I've not seen this information anywhere. Might be found in a Geophysics journal somewhere. I have intended to do these measurements myself, but haven't had time.

- Carl

[Max]

Are there published anywhere frequency responses of metal detected targets: different coins, rings, hot rocks, junk etc.? I can,t find in WEB even one frequency characterstic of target in complex (impedance) plane! Mike ***

Hi,
Frequency ?

Usual MDs of today (VLF/IB discriminators) use phase shifts to say which kind of metal and similar stuff, not frequency.

There are characteristic frequencies you can read in e.g. magnetic nuclear resonance but this is another story... and doesn't apply to MDs or other TH devices.

If you see "frequency" identification... you better start having dubts on device (could be a fraud thing) unless you are interested in old BFO stuff where , in some cases, was possible discriminating metals using frequency shifts (so frequency differences) induced by the presence of particular metals etc

Best regards,
Max

[mikebg]

Are there published anywhere frequency responses of metal detected targets: different coins, rings, hot rocks, junk etc.? I can,t find in WEB even one frequency characterstic of target in complex (impedance) plane! Mike ***