PI Target Identification

[Tinkerer]

Target identification

Marc, thanks for the feedback. I added the ferrite and the moving nail targets to the list for the next experiments.
It would be very helpful if I could get some comparative numbers of signal amplitude at the output of the front-end. I believe that I get very high signal amplitude, relative to the pulse power, however, unless I get some numbers to compare with, I might be deluding myself.

Could anybody supply some signal amplitude values?

Tinkerer

[hobbes_lives]

Tinkerer, is the target signal taken from a separate receive coil? In other words, it's not a mono-coil setup, right?

[Tinkerer]

PI target identification

Tinkerer, is the target signal taken from a separate receive coil? In other words, it's not a mono-coil setup, right?

You are right, the coil is composed of a Tx winding of 300uH and 280mm diameter a bucking winding and a RX winding of 300uH and 140mm diameter.
Tinkerer

[okantex]

can you arrange scopes of mono coil.
also give information about timing values
regards

[Tinkerer]

PI Target Identification

can you arrange scopes of mono coil.
also give information about timing values
regards

sorry, I have no suitable mono coil available. Maybe in a few days.
For timing I use a PIC more info look at my posts EDDY CURRENTS and TARGET TIME CONSTANTS

Tinkerer

[1843]

Thank you Tinkerer for the pictures.
I wonder why the signal goes in opposite polarity for the ferrous target. Can you rationalize that?

[Tinkerer]

PI Target discrimination

Thank you Tinkerer for the pictures.
I wonder why the signal goes in opposite polarity for the ferrous target. Can you rationalize that?

Non magnetic targets give a resistive (R) response.
Magnetic targets give a reactive (X) response.
The setup shown in the pictures above show a method of separating the resistive and the reactive responses of targets.

Some targets, like a thin steel disk or washer, let you see the separation of the X and R responses very easily.

Make the following experiment:

Take a thin steel washer and present it to the coil the flat way.
Take a brass or copper washer and do the same.

The response is nearly the same.

Now present both targets on edge.

The brass or copper washer gives a very faint signal.
The steel washer gives nearly the same signal in the flat position as in the vertical position.

The vertical position shows mostly the X response.

Tinkerer

[Tinkerer]

http://www.falstad.com/vector3dm/

At the url above there is a very nice open source Java applet for download.
Somebody who knows Java, could add to it to include magnetic targets, non magnetic targets, spheres, disks, ground and seawater, so that we could all visualize what is happening when the TX pulse expands and collapses.

Tinkerer

[1843]

That's very interesting! That's more interesting to me that why some targets show (X) response and some others (R)...

Anyway thanks.

[ciuccacci]

To Tinkerer

Thank you for sharing the wonderful photos from your scope, through these photos and your comments teh PI technology is now more understandable for an amateur like me.


Just a little query: how the effects of soil mineralization or salt combine with the targets response present in the Target Identification table.


can you consider the possibility of creating a custom table, in which to store the signals response at the time of the findings? after a few days of searches we can have a range of responses, from different area, we can refer to.

Ciao
Massimo

[Tinkerer]

Thank you for sharing the wonderful photos from your scope, through these photos and your comments teh PI technology is now more understandable for an amateur like me.


Just a little query: how the effects of soil mineralization or salt combine with the targets response present in the Target Identification table.


can you consider the possibility of creating a custom table, in which to store the signals response at the time of the findings? after a few days of searches we can have a range of responses, from different area, we can refer to.

Ciao
Massimo

Massimo,

Salt and minerals:

First the detector is "ground balanced", that means the output of the front end is adjusted to give a "no target" signature.
For salt this adjustment is of opposite polarity than for magnetic minerals.

Look-up table of target identification:
This is very well possible. A certain amount of specific signatures could be stored in EEPROM and be "looked up" by the mcu.

However, the general idea is to give the detector the capability to indicate to the operator several means to recognize the targets. The human brain is still the best computer that can be carried out in the field. We just need to supply it with information that it can compute.

I have a detector that can supply this information in analog form. I need help to convert this design into digital form. Specifically, I need help in writing the firmware.
I am using a PIC mcu to do the timing and I wrote the timing schedule and programmed the mcu. It took me a long time. It will take me a much longer time to write the code for the mcu to do the ground balance adjustment, and the conversion of some analog signals into an output that the operator can easily assimilate.

So, if anybody out there wants to help with the software, we could have a new generation detector ready in a short time.

Tinkerer

[Tinkerer]

That's very interesting! That's more interesting to me that why some targets show (X) response and some others (R)...

Anyway thanks.

With VLF detectors the same phenomena can be observed in the form of phase shift to the right or to the left.

With a PI, there are several methods.
One method is to feed the signal into a resonant tank and then observe the same phase shifting.

Tinkerer