PI Power Output

[ZED]

Simon,
Yes the purely magnetic effect follows a transmitted waveform instantly so it can’t exist in a period of non-transmission.

Robby you sure about that ? if thats the case then how would you describe the ground signal we see after the transmit ? and dont say resistive.

Zed

[Tinkerer]

Tinkerer lets say there is current regulation and the coil current reaches 2 amps at 100 u/sec and it is held there at 2 amps until 150 u/sec then the transmit is switched off then at a later point we start the same transmit again but this time we switch it of at 350 u/sec [still 2amps coil current] apparently the ground signal will have the same amplitude after each transmit.

Zed

I see now what you mean, but I have no idea how your hot ground behaves.

Tinkerer

[Altra]

Zed,

If the 240uS samples are for the earths field. Why does that demodulator's output run through the two 10t "ground balance" pots and then mixed with the other two demodulators? I could see it also nulling the earth field at the same time. By the way thanks for making those schematics. They are a great study!

I noticed the extra op-amp on Eric's later demodulators and assumed it performed some kind of low pass function. But I will have try some experiments with and without.

Regards
Mark

[ZED]

I see now what you mean, but I have no idea how your hot ground behaves.

Tinkerer

How hot eh....hmmmm.....Well its been said and i have observed the same thing that with a strong magnet if you slide it along the ground you will find a whole stack of gravel sticking to the magnet,not a little bit but lots.
Also if the coil is held 6" of the ground you get the same signal as a steel plate.
One of the things that sets Aussie soil conditions apart from other countrys is the degree of varibility,you balance in one spot,move the coil an inch and you have to ground balance again.

Zed

[ZED]

Zed,

If the 240uS samples are for the earths field. Why does that demodulator's output run through the two 10t "ground balance" pots and then mixed with the other two demodulators? I could see it also nulling the earth field at the same time. By the way thanks for making those schematics. They are a great study!

I noticed the extra op-amp on Eric's later demodulators and assumed it performed some kind of low pass function. But I will have try some experiments with and without.

Regards
Mark

The second sample on each channel performs 2 basic functions,1 it reduces the ground signal in the first sample and 2 it removes the earth field signal in the first sample,also the second sample [gb channel included] serves as a target indicator when targets have long T/C.
In the case of the 2000 the earth field signal in the GB channel is removed before the GB signal is added to the other 2 channels

Zed

[Tinkerer]

Tinkerer,

Your findings in post #59 above are quite interesting. When I get back to it, I will find some of the simulations that I ran and perform some similar tests. I recall some differences in target response by varying the pulse width, but I'll have to dig through my notes, or recreate the tests, to figure out the details.

Hi hobbes,

any luck in finding your test results?

If I can get a team together to make an "Open Source" design, Discriminating IB-PI, I am going to ask Carl to give us a dedicated forum for it.

I would like to invite you to participate in the team.

Tinkerer