Old idea and new circuit of discrimination in the PI detector

[sevzirfo]

Old idea - http://www.thunting.com/cgi-bin/geotech/forum/view.cgi?action=message&forum=tech&message=5069

The feature of the new circuit - application the external fast counter, allows good accuracy of measurement





PI-Discr.gif





decay_curve.gif

[jackdetect]

Re: Old idea and new circuit of discrimination in the PI detector

Hi Sevzirfo,
It is a very impressive schematic.
Can you please, help me to understand couple of thing, about such approach in Pi design, because I still learning about it?
First, in Rx phase, coil receiving lot of different and unpredictable noises, and in every next cycle, in defining points, curve can having a different levels, simple because is impossible to filtrate RF, EM etc. Moving coil will change capacitance, and will change curve also.
Second, maybe I misunderstand, but geophysical literature told that last stage of curve (closing to zero), carry information about deep targets, and if you ignore that part of curve, you will get a only shallow detecting. What purpose, then, in using Pi, when Vlf can do such job better, with rather discrimination and with ground balance also.
I can see Pi designs, only like deep searching machine.
Can you give to us some expected performances of it, and about purpose?
Best regards,
Jackdetect.

[sevzirfo]

Re: Old idea and new circuit of discrimination in the PI detector

Hi Jackdetect,
I plan to get rid of handicapes RF, EM etc. by accumulation and averaging of the several received results (program integrator). At frequency TX of pulses 1 KHZ it should work and the speed of movement of the coil will not be a handicap.
The level of operation of the comparator is easy for changing for detection of the deep purposes, the level of operation changes in steps and the steps are possible are to adjusted (for example) on GOLD, IRON, Deep purposes. The number of steps of the comparator is equivalent to number of channels in other circuits.
The purpose of manufacturing it PI of the detector - is easy to make search coils, use of the large coils for deep search (50õ50ñì, 1õ1ì, 2õ2ì), opportunity of work on heavy ground is possible.
Best regards,
sevzirfo

[jackdetect]

Re: Old idea and new circuit of discrimination in the PI detector

Hi Sevzirfo,
Yes, you are right. It can be done by calculation of arithmetic middle of several samples. But maybe is simpler to use capacitor for it. It is true, that serious geophysical TDEM locators are using a similar technique, but also is truth, that they recording about 20 points, and then, they are using the “heavy artillery” like DSP, and PC for analysis. Also, signal close to zero having a much more noise.
But, of course, it is very interesting open Pi design, and you can collect a lot of knowledge in experimenting with it. Good luck!
Best wishes,
Jackdetect.

[abel]

array of comparator lm3914,3915 & 3916

ultra versality
linear or logaritmic (¿more information?)
high impedance
fast?
view of patend


http://www.national.com/whatsnew/index.cgi?v=c&cid=874&p=120