PI detector (frequency transmitted)

Someone here with more knowledge than myself,,,,talk about frequency as it relates to pulse detectors.

Is there any advantages to using higher or lower freqs???
Is there such a thing as a multi freq pulse detector (truly) on paper no bs

I would like to be better able to relate how freq affects detection with these types of units.

Firstly, a pulse induction detector doesn't transmit at a 'frequency'...it transmits a pulse, quickly shuts off, receives/'listens', then repeats.
So you could talk about the 'operational frequency' of the pulse train of a PI...but technically not a steady 'frequency transmitted'.

The VLF machines operate in the frequency domain, and the PI machines operate in the time domain.
This makes them so fundamentally different that an argument could be made that a PI detector shares more in common philosophically with SONAR that with a VLF detector.

A transmitted pulse, by it's very nature, is already broadband...therefore there is no need for any multi freq BBS type capabilities.
If you want to increase the detection depth of a PI, just increase the magnitude of the pulse. (Observing the limits of the electronics, of course.)
Thus the popularity of higher voltage aftermarket batteries for the likes of the TDI, etc.

This broadband nature is also the reason PI machines tend to be more sensitive to EMI than VLFs.
The main reason to have adjustable freq on a PI is to avoid that EMI.

I'm sure Carl M would have a whole lot more to say/add...

mike



Edited 3 time(s). Last edit at 02/03/2017 02:16AM by Mike in CO.

Tn..

Do a little digging on the web. Look for answers to your very relevant questions.

There's 10 - 15 years of good and bad data to answer your question/\,

Rick Kempf
Gold Canyon AZ- where there is no gold

You seem to be thinking in VLF terms for P.I. technology..

A PIs sensitivity to types of different metals is basically determined by how powerful and strong the pulse is and also the very important pulse delay/s..


A P.I. is timed gated spikes of energy ...and operates in Time domain...it sends out a square wave at timed intervals..(PPS) and VLF sends out a sine type wave that's constant in frequency..

Usually the frequency adjustment on a P.I. is for shifting the PPS....

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

There he goes again... Keith clearly answering a question ---- when I, lazy as I am, could only suggest that the questioner do a bit of homework.

Nice work Mr. k.

Rick Kempf
Gold Canyon AZ- where there is no gold

Keith Southern Wrote:
-------------------------------------------------------
> You seem to be thinking in VLF terms for P.I. tech
> nology..
>
> A PIs sensitivity to types of different metals is
> basically determined by how powerful and strong
> the pulse is and also the very important pulse d
> elay/s..
>
>
> A P.I. is timed gated spikes of energy ...and ope
> rates in Time domain...it sends out a square wave
> at timed intervals..(PPS) and VLF sends out a sine
> type wave that's constant in frequency..
>
> Usually the frequency adjustment on a P.I. is for
> shifting the PPS....
>
> Keith


Not exactly thinking in those terms.
But have been thinking a lot about how to improve depth with a detector,,,and thinking about the possibilities of a hybrid Vlf PI unit.
Basically trying to brush up some on what has been tried and already done.

http://www.nuggetshooter.com/articles/UnderstandingPIdetector.html

DeepTech Vista X with 3 search coils.
Works for me

Answers so far are correct, the frequency of a PI is its pulse rate in PPS, pulses per second. Some examples: SurfPI and Sandshark run at 600Hz, TDI runs at 3kHz, GoldQuest runs at 10kHz. There are a lot of trade-offs going on here, it's not so simple to say "higher is better" without defining what "better" means.

Yes, there are "multi-frequency" PI's, actually multi-pulse width. The Minelab GPX series ferinstance. And there are hybrid VLF/PI designs. In a past life I did a lot of work in this area. Still am, but in a slightly different direction.

BTW, the old distinction of "VLF" and "PI" are rapidly vanishing. New approaches like the GPZ are neither and both. Same with stuff I (and others) are working on.

Excellent Carl..On the NEW Projects especially..

May I ask if You know

On a BBS or FBS unit's is it in some ways a square wave pulsed technology...

always found that technology UNIQUE!! Yet maybe Overblown in technical jargon and catchy flashy sales brochure diagrams ..

I know you're busy but if you have the Time

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Quote

tnsharpshooter Wrote:
-------------------------------------------------------
Someone here with more knowledge than myself,,,,talk about frequency as it relates to pulse detectors.

Is there any advantages to using higher or lower freqs??? Is there such a thing as a multi freq pulse detect or (truly) on paper no bs. I would like to be better able to relate how freq affects detection with these types of units.

Quote

Keith Southern Wrote:
-------------------------------------------------------
You seem to be thinking in VLF terms for P.I. technology.. A PIs sensitivity to types of different metals is basically determined by how powerful and strong the pulse is and also the very important pulse delay/s.. A P.I. is timed gated spikes of energy ...and operates in Time domain...it sends out a square wave at timed intervals..(PPS) and VLF sends out a sine type wave that's constant in frequency.. Usually the frequency adjustment on a P.I. is for shifting the PPS....

Keith

Quote

tnsharpshooter Wrote:
-------------------------------------------------------

Not exactly thinking in those terms.
But have been thinking a lot about how to improve depth with a detector,,,and thinking about the possibilities of a hybrid Vlf PI unit.
Basically trying to brush up some on what has been tried and already done.

Can't get a better answer than that and it answer the initial question to an exact - so - if not thinking in those "terms" then what exactly are you asking?

Pulse machines work on pulse waves that can be sped up/slowed down (PPS) unless "fixed rate" and VLF work on sine/radio type waves

seems this is what you were asking in a more or less sense as to "how" they work/operate?

Geotech Wrote:
-------------------------------------------------------

>
> BTW, the old distinction of "VLF" and "PI" are rap
> idly vanishing. New approaches like the GPZ are ne
> ither and both. Same with stuff I (and others) are
> working on.

This part of your response,,,interesting.
Sounds like some out of the box thinking has happened and is still happening.

Keith Southern Wrote:
-------------------------------------------------------
> On a BBS or FBS unit's is it in some ways a square
> wave pulsed technology...

That's another "not quite easy to name" type. It's a continuous-time transmitter with discrete-time receiver using time-multiplexed multiple frequencies. Overall more VLF-ish but with a time-domain twist.

Ha, this information is all above my paygrade, but, damned if I don't love to see it on Dankowskis again.

Carl --- Multifaceted appreciation.

Thank you Carl..

I know it does work in certain soils better than anything for I.D. accuracy ..So surely it had to be different tech..

Thank you.

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

on you tube detector mods has a vid of gpx 5000 mod variable gain and frequency. he shows before and after mod tests. it hits small gold like 2300

Here is some good reading on the subject.

[electronics.howstuffworks.com]

Carl..... you ever get one of those combos ready for the water and need a guinea pig to get it wet let me know. About time for something new in the salt water.

Dew

markg Wrote:
-------------------------------------------------------
> Here is some good reading on the subject.
>
> [electronics.howstuffworks.com]
> -gadgets/metal-detector4.htm


Markg, good review of systems--Thanks.