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Question for Eric

A

Anonymous

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Hello Eric.
The Aquastar a PI detector that has a 10usec pulse, which translates to 100Khz and does a outstanding job on small Gold items. Why can't a discriminator be designed to run at 100Khz to get the same result a 10usec pulse? The closes machine I know is the Fisher GB-2 but it is a all metal machine. The Gold Bug two operates at 71KHz which is a 14usec pulse or frequecy-not to bad. Lee
 
Eric can do a better job of answering but I think you are confused. I don't think that the Aquastar has a 10uS pulse but has a 10uS minimum pulse delay that is adjustable from 10uS to 40uS I believe. Just going by memory I think the detector has a 3000pps.
Here is a post Eric made a while back regarding pulse frequency.
http://www.findmall.com/metal/school1/config.pl?read=613
Good Luck,
Charles
 
Charles you are right I got side tracked by the 10Usec. Thanks for setting me straight. Lee
 
Hi Lee,
It is difficult to compare sensitivities of induction balance detectors and P.I. detectors in terms of the working frequency. I.B. types usually work at one discrete frequency, i.e the 71kHz you mentioned for the Goldbug 2, while P.I. detectors transmit a wide spectrum of frequencies with most of the energy at the lower end. For I.B., the presence of metal disturbs the electrical balance of the search coil arrangement, giving both amplitude and phase changes. In P.I. the receiver coil (which often doubles as a transmitter) senses the decaying eddy currents in the metal object.It turns out that a P.I. detector using a 5uS transmitter pulse and a sample delay of 1uS is similar in sensitivity to the Goldbug. High sensitivity detectors for the food and pharmaceutical industries are invariably I.B. running at frequencies of up to 250kHz. At the present state of the art, a P.I. comes nowhere close to matching them for small object performance.
Eric.
 
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