Threshold Pot doesn't work

[h9361]

h9361 suggested in reply #96, I used a new PCB rev. D, now i have no noise.
Now i'm working over 4delay ground balancing (suggested by Mr. Carl.). My result is very very nice and i can work in 10us-25us with high stability over mineralization.

Don't know what the problem is. Seems to work one day, not the next.

Dear green
I have built two version HH, one original Rev. D and second include GB.
Version GB is excellent and no problem.
But original HH1 has problem is THD audio, no silent.

[Carl-NC]

Sorry, I lost track of the discussion.
h9361, you have a regular non-GB Hammerhead and then another HH with GB added to it, is that right?
It sounds like the HH+GB works fine, threshold is working and no noise as you move the coil up/down. Is that right?
It sounds like the regular HH had a threshold problem where it would not adjust to silence, but you fixed it. Correct?
Finally, after you fixed the threshold it now responds as you move the coil up & down. Does this mean you are moving the coil up & down over ground? Or motion in the air?

[h9361]

you have a regular non-GB Hammerhead and then another HH with GB added to it, is that right? Yes.
It sounds like the HH+GB works fine, threshold is working and no noise as you move the coil up/down. Is that right? Yes, but i removed your audio part and added Mickstv's Audio.

It sounds like the regular HH had a threshold problem where it would not adjust to silence, but you fixed it. Corrected?
Yes, silence is solved by reducing R30 from 150K t0 100K and 50K. But i have noise in coil up/down.

Finally, after you fixed the threshold it now responds as you move the coil up & down. Does this mean you are moving the coil up & down over ground? Or motion in the air? Over ground.

[Carl-NC]

OK, it is probably because that HH version does not have GB. That is what GB does, it silences the ground response.

[h9361]

Hello
Dear Carl.
I hope you are fine.
I want to add a peak follower to your HH1 for controlling increase/decrease voltage of coil (ferrous/non-ferrous).
I have built your peak follower of Off-Resonance in your book (page- 37-IMD, only top channel-IC1).
Can you guide me which point of your HH1 i should connect to the peak follower as input?
Thanks

[h9361]

Mr. Teleno guide us to use following :

In PI, ferrous/non-ferrous discrimination can be done.

Paramagnetic materials (ferrous) increase the coil's inductance L. Diamagnetic (Copper, Silver, Gold) decrease L.

A simple inductance measurment can produce a discriminating output. For example, you can use a "test period" in which you measure the coil's inductance using a constant voltage source. You measure the time it takes for the coil to reach a test current I. This time is proportional to the inductance. Or you measure the coil's natural frequency making it oscillate. You compare it to the measurements in the absence of a target.

[Carl-NC]

The peak follower is for a different type of design, not for PI.

[h9361]

The peak follower is for a different type of design, not for PI.

Thanks Dear Carl for your guidness.
If possible, please see the link.
Do you think it's OK for PI?

[Carl-NC]

I don't understand. Are you asking if the inductance meter can be used to measure PI coils? If so, it should work.

[Qiaozhi]

I don't understand. Are you asking if the inductance meter can be used to measure PI coils? If so, it should work.

I think he's asking whether a PI could provide ferrous discrimination by periodically switching in an inductance meter to monitor the change in coil inductance.

[h9361]

I think he's asking whether a PI could provide ferrous discrimination by periodically switching in an inductance meter to monitor the change in coil inductance.

Hello
Yes, we can put two leds. When HH1 detected a target, we check inductance of coil, if decrease light up one LED or increase light up other LED

[h9361]

I think we can discriminate between ferrous and non-ferrous.

[Carl-NC]

No, that's not going to work. Inductance shift is very small, in a BFO it is typically a fraction of 1%. Also, it is unlikely you can combine such a circuit with a PI transmitter.

[h9361]

No, that's not going to work. Inductance shift is very small, in a BFO it is typically a fraction of 1%. Also, it is unlikely you can combine such a circuit with a PI transmitter.

Please read the link
Do you have any idea about GPX method for Iron rejection?

[h9361]

Dear Carl
See the attached, it's part of Off-Resonance of your Book.
I want to add the schematic beside of my HH1 but i need your help.
As you see, you mentioned the advantage of the Off-Resonance is its ferrous/non-ferrous discrimination.
Is is possible to guide me how to change the schematic so that it discriminates between ferrous/non-ferrous via two LEDs?


Please consider your off-resonance schematic in p. 37,IMD book. I want to add the two LEDs (attached) in out of IC1b (pin-7). Do you think it works for showing decreasing/increasing inductance coil?


Actually, after detecting a target by HH1, i will turn off it and turn on my Off-Resonance (your schematic) for discriminating ferrous. My main purpose of this is for nail!.