An experiment for finding the TAU of a target

[Tinkerer]

Can we define the TAU of a target with a PI detector?

If the targets were all nicely laid out flat and there was no hot ground surrounding them, it would definitely be possible. Unfortunately this is not the way the target present themselves in the field.

Can we at least get an idea about the TAU of the buried target?

I think there are a few things we can try to accomplish that.

I will prepare a few screen shots that show targets with different TAU. We will start with non ferrous targets.

Any suggestions? Ideas?

Tinkerer

[Carl-NC]

While it's necessary to look at the "whole response" to get an idea of what's going on, it can also create a false sense of accomplishment. It's easy to look at the whole response and say, "that's obviously iron, that's obviously a silver coin, that's obviously a small nugget." But it's not so easy to get those answers out of a circuit, especially when you have a constantly varying ground signal. We can certainly look at screen shots of target responses, but I'm (so far) not convinced it will help in field use.

[deemon]

Any suggestions? Ideas?

Read attentively my topic about recuperative PI device , and you'll find a very good idea . And it's a working idea , not a "theory"
By the way , it works even with buried targets .

In brief , if we wanna find the target TC - we need to do 2 things :
1. Select the pure target response - it must be a decaying exponent function , without any parasitic signals from our coil ( exponent , ringing , etc ) .
2. Use , for example , Taylor series to approximate the function - http://en.wikipedia.org/wiki/Taylor_series

In my real working device I used only 2 first terms - linear and parabolic , and it's enough to determine a target TC in a relatively wide range ( except an extremely short TC's ) , but if we add the third term ( cubic ) , we can cover all useful range of the real targets . By the way , my new "square wave pulse induction" technology , that I exploring now - being an extension of that principle - can do all these tricks also , and as I think - will do even more .

[Tinkerer]

Read attentively my topic about recuperative PI device , and you'll find a very good idea . And it's a working idea , not a "theory"
By the way , it works even with buried targets .

In brief , if we wanna find the target TC - we need to do 2 things :
1. Select the pure target response - it must be a decaying exponent function , without any parasitic signals from our coil ( exponent , ringing , etc ) .
2. Use , for example , Taylor series to approximate the function - http://en.wikipedia.org/wiki/Taylor_series

In my real working device I used only 2 first terms - linear and parabolic , and it's enough to determine a target TC in a relatively wide range ( except an extremely short TC's ) , but if we add the third term ( cubic ) , we can cover all useful range of the real targets . By the way , my new "square wave pulse induction" technology , that I exploring now - being an extension of that principle - can do all these tricks also , and as I think - will do even more .

deemon, thank you for the feedback.
I think I see what you mean and I looked up the Taylor series, but this is way over my head.

My Tx uses the power recycling with a saw tooth wave form. With this circuit, the target signal decay is not pure, as there is a reverse current (recycling) running in the coil.

The reverse (as seen from the target signal decay) current has the advantage to shorten the decay times.

The shortened decay times make it possible to run a higher PRR.

Tinkerer

[Tinkerer]

While it's necessary to look at the "whole response" to get an idea of what's going on, it can also create a false sense of accomplishment. It's easy to look at the whole response and say, "that's obviously iron, that's obviously a silver coin, that's obviously a small nugget." But it's not so easy to get those answers out of a circuit, especially when you have a constantly varying ground signal. We can certainly look at screen shots of target responses, but I'm (so far) not convinced it will help in field use.

Carl, thanks for the feedback.
Yes, I show the full cycle first, so that people have an idea of what we are talking about, before I show fractions or sample areas of the cycle.
I also want to show the PIVOTS, where the target signal cuts across the reference signal.

With a static ground signal, used as baseline, or reference, using the bi-polar TX, I can show the time it takes for the target signal to decay to the baseline.
The saw tooth TX ramp generates eddy currents. When the current inverts, these eddy currents get killed by the new eddy currents of opposite polarity, generated by the next ramp of the saw tooth.

The eddy current decay is therefore forced and much shorter but still have a relation to the TC of the target.

I hope that if we can glean an indication of target TC, we might be able to separate the ground TC from the target TC.

My hope is to stimulate ideas for extracting target information.

Tinkerer