Threshold Pot doesn't work

[Carl-NC]

About decreasing delay, i changed R42.a from 1.5K to 1K. For reaching 6us, do you think i should decrease it to 560R?

I don't know, you'll have to figure that out.

According to your information, so GPX is using low TX width, is it true? I remember that the gpx frequency is 5kHz.

GPX has 1 long pulse and 3 short pulses. I don't know the exact timings.

[h9361]

About decreasing delay, i changed R42.a from 1.5K to 1K. For reaching 6us, do you think i should decrease it to 560R?

I don't know, you'll have to figure that out.

According to your information, so GPX is using low TX width, is it true? I remember that the gpx frequency is 5kHz.

GPX has 1 long pulse and 3 short pulses. I don't know the exact timings.

Thank you dear Carl
Today, i adjust frequency to 4.7kHz. The other settings is as following:
TX Pulse width = 26uS
Delay = 6-7 uS
All sample width = 20uS
I figure out timing diagram and adjusted EFEs and GB delay.
Now, my PI works very nice but i unfortunately have too much noise at home. I will test outside and report back here.
Dear Carl, i have a question about TDI. As you know, TDI frequency is high near 3kHz. Do you think its TX pulse width is low?
Generally, Do you think TX pulse width can effect on depth detection?

[Carl-NC]

The TDI has a pulse width of 100us but it also burns 6 watts of power and has heat sinks. A wider pulse width helps more with high-tau targets than low-tau targets.

[h9361]

The TDI has a pulse width of 100us but it also burns 6 watts of power and has heat sinks. A wider pulse width helps more with high-tau targets than low-tau targets.

Thank you dear Carl.
Today, i read user manual of the Axiom (new PI machine) from Garret company.
What caught my attention is the frequency of 1500 Hz!
The detector can detect low tau target with the frequency.

[h9361]

The TDI has a pulse width of 100us but it also burns 6 watts of power and has heat sinks. A wider pulse width helps more with high-tau targets than low-tau targets.

Dear Carl
Thank you for your guiding.
Today i tested my HDD, now it detects foil of smoke box 60cm.
My settings is as follows,
Freq. = 2.6 kHz
Sample width = 25 uS
TX pulse = 100 uS
Delay = 6-7 uS

[h9361]

The TDI has a pulse width of 100us but it also burns 6 watts of power and has heat sinks. A wider pulse width helps more with high-tau targets than low-tau targets.

Hello
Dear Carl
Please forgive me for my more questions, i hope you forgive me.
Time that the question has engaged my mind. Please first see attached, it's my two channels for GB processing. In fact, we use the GB pot (in ch2) for reaching zero volt at final output.
The my question is here! I don't connect any coil to my PI, so we must have a static dc voltage at output. But i have a voltage fluctuation output in without using coil!. For example, 2.741-2.750 V.
This fluctuation will show at audio sound and unfortunately i have not a stable audio in basic mode. Do you have any suggestion for solving such problem (for stabilizing audio)?
Thanks for your kindness.

[Carl-NC]

This most likely due to thermal noise generated within the circuitry. Probably CH2 is worse because it typically runs at a higher gain. You can't get rid of all the thermal noise but you may be able to improve it. That requires knowledge of noise analysis. Search the forum, there have been discussions on this.

[h9361]

This most likely due to thermal noise generated within the circuitry. Probably CH2 is worse because it typically runs at a higher gain. You can't get rid of all the thermal noise but you may be able to improve it. That requires knowledge of noise analysis. Search the forum, there have been discussions on this.

Hello
dear Carl
Please forgive me for my questions.
As you know, i added GB (based on 4 sampling) to HHD (attached). Now, my HHD works as non-motion mode so that it produces a constant audio (noisy audio) if i keep a target near the coil.
Do you have any suggestion for changing my HHD to motion mode? I also added its SAT part but it had no result.

[h9361]

I already added SAT at final out, no result.
Do you think i should add two SAT at CH1 and CH2, before subtracting and gain ?

[Carl-NC]

I already added SAT at final out, no result.
Do you think i should add two SAT at CH1 and CH2, before subtracting and gain ?

Yes, that's the way I would do it. Here is a (very) simplified diagram:



It is important to closely match the delays through the integrators and the SAT stages.

[h9361]

Yes, that's the way I would do it. Here is a (very) simplified diagram:



It is important to closely match the delays through the integrators and the SAT stages.

Thank you dear Carl for your helping.
See attached, is the position true (red points)?

[Carl-NC]

Yes.

[h9361]

Yes.

Thank you.

[h9361]

Yes.

Hello dear Carl
Before everything, thank you for your guiding (changing non-motion to motion).
According to your advise, i added your suggestion part to my PCB and it works motion.
But i have still a problem and i can not solve it.
For better understanding, first see attached pic.
I connected my O-scope to last opamp output (final subtraction, red point ) and captured a short video over O-scop from ( link attached).
As you see in video (o-scop), i have not a clear DC output and it fluctuates. So, my audio also will show the fluctuation voltage as shaky voice.
(my audio schematic is at #339)
What is interesting is that i have still such fluctuation output even without connecting coil! I also screw GB pot but still it is not clear dc (without connecting coil).

you can download my video from the link
https://www.mediafire.com/file/k2dy9...04509.mp4/file

Do you have any idea to solve the problem?

[Carl-NC]

If you probe the signals at CH1 and CH2 are they noisy? Be sure to increase the oscope sensitivity to compensate for the gain of IC10.

Circuits generate their own noise and I have no idea where your noise might be coming from. You will need to probe the circuitry, including the power supplies, to figure it out. Noise is more sensitive in the preamp because it sees the most gain through the whole signal path. Also, it would help if you posted a real schematic instead of a block diagram.