TESORO GOLDEN SABRE

[Qiaozhi]

Now I have to set the rx to the lowest possible amplitude where the waveform changes I did this but the sense of metals was poor
Why does the shift not happen? Why is the tx waveform static when nulling and not moving left or right?

Setting the RX null to the lowest possible amplitude is not the correct way to balance the coil.
Turn the DISC pot to minimum and the GB pot to the middle, and then adjust the null until ferrite is rejected.
For Tesoro designs the RX signal will be offset by approximately 20 degrees.
If you don't understand what you're doing, then I suggest reading ITMD -> Inside the METAL DETECTOR - Second Edition - Published 2015

[mostafalesnar91]

Setting the RX null to the lowest possible amplitude is not the correct way to balance the coil.
Turn the DISC pot to minimum and the GB pot to the middle, and then adjust the null until ferrite is rejected.
For Tesoro designs the RX signal will be offset by approximately 20 degrees.
If you don't understand what you're doing, then I suggest reading ITMD -> Inside the METAL DETECTOR - Second Edition - Published 2015

If the coil nulling by removing the ferrite, what is the need for a scope? What is the use of a scope?

[Qiaozhi]

If the coil nulling by removing the ferrite, what is the need for a scope? What is the use of a scope?

A scope is useful for many other things. Without one it's like trying to work with one hand tied behind your back.

[kt315]

For Tesoro designs the RX signal will be offset by approximately 20 degrees.

meant 20 degrees measured before op amp or after? preamp gives itself some phase shift?

[Qiaozhi]

For Tesoro designs the RX signal will be offset by approximately 20 degrees.

meant 20 degrees measured before op amp or after? preamp gives itself some phase shift?

Output of the preamp. See pages 140 and 141 of ITMD.

[mostafalesnar91]

A scope is useful for many other things. Without one it's like trying to work with one hand tied behind your back.

I will test this method of removing the ferrite today. When I do this, the coin should be sensed above 30 cm. If it doesn't, it means that all this time has been wasted, because on the first day when I joined this site, you said that it should be for The nulling must be scoped so that you can adjust the phase difference, but now I see that all my coils are automatically adjusted to 20 degrees and there was no need for a scope.

[mostafalesnar91]

See the photo in the best condition for the coil!!!! This coin your country should sense in a few centimeters????[ATTACH]58119[/ATTACH]
[ATTACH]58120[/ATTACH]

this coin

[mostafalesnar91]

I completed this project without using oscilloscope!!
just with a simple multimeter!!
very very easy!!!!!!!!!!https://m.youtube.com/watch?v=eEQmZNyUJo4

So I already went the right way with the multimeter

[dbanner]

Set the gb trim in mid position.
Null coil with rx lead tx by 20 degrees.
Then adjust the gb trim so that ferrite is just barely rejected.

Without oscilloscope I have observed that using good wideband AC milli voltmeter(or any ac milli voltmeter for that matter regardless of bandwidth limitations, because we are not concerned with absolute values, but with minimum value) null for minimum output of preamp and gb trim adjust to edge of reject ferrite( checking also for good detection range in so doing), everything seems to work and fall into place. A little back and forth is necessary to optimize detection distance.
If the gb trim cannot reject ferrite within its adjustable range then you will know that your null is far away from the 20 degrees.

This 20 degrees is measured on oscilloscope from factory tesoro search head connected to original tesoro metal detector.

[Qiaozhi]

I will test this method of removing the ferrite today. When I do this, the coin should be sensed above 30 cm. If it doesn't, it means that all this time has been wasted, because on the first day when I joined this site, you said that it should be for The nulling must be scoped so that you can adjust the phase difference, but now I see that all my coils are automatically adjusted to 20 degrees and there was no need for a scope.

You still need the scope to "see" what's going on. Yes, it's possible to build a metal detector without one as long as everything works as expected, you don't make any mistakes, and none of the components are faulty. But Murphy is always present and waiting to screw things up. On the rare occasions, when I decide to build a balanced coil, I always use the scope to initially do the nulling. After that I use a ferrite target to set the GB with the pot in its middle position. This is not rocket science. It just takes a patience and a lot of fiddling around.

[kt315]

Output of the preamp. See pages 140 and 141 of ITMD.

my thread. no offset, nothing of offset. nulling in nule. i write that because there is NO phase shift. not exist.
just as en example.

[mostafalesnar91]

You still need the scope to "see" what's going on. Yes, it's possible to build a metal detector without one as long as everything works as expected, you don't make any mistakes, and none of the components are faulty. But Murphy is always present and waiting to screw things up. On the rare occasions, when I decide to build a balanced coil, I always use the scope to initially do the nulling. After that I use a ferrite target to set the GB with the pot in its middle position. This is not rocket science. It just takes a patience and a lot of fiddling around.

Well, now tell me what is your method for nulling the loop with the scope

[waltr]

Commens on the RX coil resonance and phase shift.

The RX coil along with the Cap, C6, on the RX coil need to resonate at ~16kHz for all the functions, GB & Disc, to work correctly.
There is NO GOOD way to determine is this is correct.
If C6 and/or coil inductance is off then the TGSL will not work properly.

I have added another cap across C6 to increase the capacitance and reduce the resonant frequency to try tuning the RX circuit. I have had luck with this to get it working.
Simply adding a cap will work if C6's value is too low but not if too high (caps in parallel add).
If adding say a 1nF cap makes it worse then C6 needs to be replaced with a smaller value. Then add caps to obtain correct phase, nul, GB and Disc.

The first build of the TGSL and coil took me months to get it to work properly. Once I had the proper values in the TX & RX Circuits the second and third coils (DD & Concentric) builds were not hard and worked well.

[mostafalesnar91]

Commens on the RX coil resonance and phase shift.

The RX coil along with the Cap, C6, on the RX coil need to resonate at ~16kHz for all the functions, GB & Disc, to work correctly.
There is NO GOOD way to determine is this is correct.
If C6 and/or coil inductance is off then the TGSL will not work properly.

I have added another cap across C6 to increase the capacitance and reduce the resonant frequency to try tuning the RX circuit. I have had luck with this to get it working.
Simply adding a cap will work if C6's value is too low but not if too high (caps in parallel add).
If adding say a 1nF cap makes it worse then C6 needs to be replaced with a smaller value. Then add caps to obtain correct phase, nul, GB and Disc.

The first build of the TGSL and coil took me months to get it to work properly. Once I had the proper values in the TX & RX Circuits the second and third coils (DD & Concentric) builds were not hard and worked well.

Disk mode doesn't work and I can't remove the ferrite by moving the rx on the tx, I can only remove the ferrite by turning the gb

[mostafalesnar91]

What number should I set the rx amplitude to for disc mode to work properly 1.2 or 2.2 or 3.2 or any other number or it's not a fixed value at all and it's different for each loop My scope settings are 20us_5V_100mV .