More on damping..

[porkluvr]

hello , mikebg , diagram correct for what i saw .

porkluver , funny as hell , made me laugh

so it was done that way for saftey , and not for depth and penitration , so not allot of good for us then , all makes sense now , still dont know how they got a useable signal out of the oscillations at the end , a damping resistor would have made all the differance.

unless they were going to look at the slope somehow and ignore the bit at the end.
eitherway , i rekon its easyer metal detecting a captive target with a coil all the way round , they should try a single sided coil and see how difficult that is , the cheats!!!

I appologize for being facetious. This is supposed to be a serious forum.

I was kind of hoping you would come back with a partial scat or maybe a url... or think of something you left out of your description because that sounds like a bizarre contraption.

Then, it occurs to me that if your description was accurate, 7.7% duty cycle with a 10.5 cps signal is almost 4 milliseconds.
That is a tremendously long pulse-width.

Perhaps what is being done is processing the return signal during the ramp-up.
With such a long on-time, they would necessarily be using a coil with very (very) large inductance. Just a guess.

I was looking for some piece of the puzzle to express to you that it is NOT a high voltage that illuminates the target, but instead the current, by producing a changing magnetic field is what illuminates the target. The resultant voltage is relatively consequential.

Case in point, your walk-through detector, or is it just too far off the beaten path?

As an after-thought, safety probably would be an issue for a security scanner, or at least I hope it would be.

[DOOLEY]

HELLO PORKLUVER , the circuit i saw was only what mike bg showed but with the useual mosfet and a 555 atatched to it , on the website is saw , that unfortunatley i didn't make a note of , only had "that scematic" 2 pages of wording on about use in the field , and about 6 pics of scope patterns showing on time and spike and decay.

they were sampling during off time , and showing differing pics of the decay slope held by the diodes and compairing them showing patterns for a hand gun , knife etc..etc...

as i remember , dont think they were to bothered about the oscillation at the end , just the slope , but that ain't going to move much when its held by the zeners , but it was a different way of doing things .

ps , been in my history , but my AV wipes it every night before shutdown so no link there , sorry.

pps , the bit about zapping e'm good was funny. nothing wrong with humour.