Fisher CZ6 & 1266

[Carl-NC]

CZ TX waveform:



IMO, the CZ is a primitive MF design in that a basic square wave drives the coil and the RX uses the 3rd harmonic to notch out salt water. Other than that, the harmonic really isn't used so the CZ otherwise behaves like a 5kHz single frequency detector. Both Minelab BBS and White's DFX were big steps forward in that they boosted the high frequency and then used both frequencies for target & ground analysis, not just salt notching. Newer MF designs do even more analysis, often with 3 frequencies.

BTW, CZ tech isn't dead, Minelab used it in the X-Terra Pro. The XT-pro is called a SF detector but it can notch salt, in exactly the same way as the CZ.

[ivconic]

Due to the terrible pain in my shoulder and upper arm, I can't devote myself to this for more than a few minutes.
I have never had such serious inflammation (or pinching, not sure) of a nerve.
Ok... I quickly recorded a waveform with the CZ6.

[ivconic]

Carl don't you have a CZ in your collection? I still have the picture from 2004. Have you saved this collection?

[Carl-NC]

Ok... I quickly recorded a waveform with the CZ6.

You need to add a damping resistor.

Carl don't you have a CZ in your collection? I still have the picture from 2004. Have you saved this collection?

There is a CZ-7 on the far left and a CZ-70 about 7 detectors to the right. They are both gone, now I have a CZ-20 and CZ-3d.

[ivconic]

You need to add a damping resistor.
There is a CZ-7 on the far left and a CZ-70 about 7 detectors to the right. They are both gone, now I have a CZ-20 and CZ-3d.

How much will the waveform change when I put a damper resistor?
You intrigued me! I'll try to do that today...
The CZ3D is basically the same detector as the CZ5 and CZ6.
X(X) years ago I had pcbs of both on my desk and compared them, I couldn't tell the difference.

[kt315]

i need full info on the coil. can you do? i have just a block (thank you George again for the help).

[ivconic]

i need full info on the coil. can you do? i have just a block (thank you George again for the help).

Ok KT315, I will measure the CZ coils for You.
...
Here it is:

CZ6 Coils:
20 cm coil:
TX = 3 ohms / 0.99 mH
RX = 32.1 ohms / 11.2 mH

27cm coil:
TX = 2.8 ohms / 0.98 mH
RX = 30.6 ohms / 11.2 mH

1266X Coil:
20 cm coil:
TX = 4.9 ohms / 2.45 mH
RX = 41.1 ohms / 13.1 mH

[kt315]

THANK YOU.

[Carl-NC]

How much will the waveform change when I put a damper resistor?

It will get rid of all the ringing and you will see a nice clean square wave, like this:

[ivconic]

It will get rid of all the ringing and you will see a nice clean square wave, like this:

First case; I used damping jig with minimal resistance = 198R.
Second case; I used fixed resistor = 56R.
I guess the real damping value is somewhere between 56 and 198 ohms.

[ivconic]

But I noticed something else... something "crazy"!
When I took the pictures from post #77;
A "random" 18cm PI coil without damping resistance was placed on top of the CZ coil and served as a "sensor".
Carl, you probably know that the CZ series has an "overload" audio warning; indicating that the signal is too strong?
In the case without damping resistance, that "overload" sound did not appear. The detector was silent.
But now with the damping resistance when the "sensor" is on the top of the CZ coil; "overload" audio appears instantly!?
Let's analyze this situation and what is going on here?

[ivconic]

A rough guess; without damping resistance the "sensor" behaves like "energy theft"
(a common case when you try to detect a coil with many turns of copper wire with any detector, it is easiest to notice with a slow PI detector)
and with damping resistance the "sensor" behaves like a "massive target".
....

P.S.
"...(a common case when you try to detect a coil with many turns of copper wire with any detector, it is easiest to notice with a slow PI detector)..."
I know this from before. This is a dirty trick when you want to diminish the value of a detector in front of the layman onlookers!

[Carl-NC]

The tau of the pickup coil is τ = L/R. With no damping resistor (R = ∞) you have a weak low conductor. When you add the damping resistor, it increases the tau and also the induced current flow, making it a stronger higher conductor. Try R = 1k, 100, 10, and 1Ω and see what happens.

[ivconic]

Kinda interested!



Not for the reasons you can imagine!



I will do that one of these days.
At the moment I am overwhelmed with some trivial obligations.
And it's already midnight!

[ivconic]

Carl, I have an interesting question.
Now when I look at those two oscillograms again, I think that a perfect square will not be obtained even if I change the damping value between 56-198 ohms.
The tendency is clearly visible, the rising slope is always above the falling one.
It cannot be "ironed". I have two assumptions:
- The problem is with the "sensor" and the coupling,
- The problem is with the "lower" capacitor in the TX, the device is quite old, it is possible that the capacity has decreased, so there is no symmetry.
Opinion?
I am not asking this for practical reasons, but it is very interesting as a rhetorical question.
...

I think this is a good opportunity to add this, which I did in 2022. It will also illustrate my question.
This works correctly. It can be called a "jig" for experimenting with various ideas.