Target ID Meter for older detectors

[Ganesh]

Hello tinkerer community,
I think a target ID Meter would be a useful add-on for some (older) detectors.
Since the the differerent conductivity values cause phaseshifts in the RX coil signal it should be possible to feed this amplified signal into a phaseshift/voltage converter.

A single IC solution:



May be this could be used in the various Tesoro detectors?
What I don't know is if the disc setting circuit might interfere with the phaseshift detector in some detector desings.

Ganesh

[mikebg]

ATTENTION! The circuit is designed to operate at frequencies above 100KHz. Several resistances and capacitances should be increased in order to operate at metal detecting frequencies.

[Ganesh]

You are right. The capacitors and resistors at the input might need to be bigger. In the datasheet they are 1 nF. The data sheet of the circuit says that it can operate from "very low frequencies" it says from >0 up 2100Mhz.

I havn´t tested this scheme myself so far. I just found it and thought it would be a simple choice to detect a phase change and convert it into a voltage change.

Ganesh

[Vladimir]

Is this better .....
Some opinion?

[Ganesh]

Hallo Vladimir,
at least somebody pondered about my suggestion. MikeBG was referring to the input capacitor/resistor dimension. The electronics mag I pulled the sketch from used 10nF capacitors and added 100Khz up to 2,7 MHz. In our field we deal with 6 - 20 Khz. So Mike pointed that out. The capicitors should be bigger if such low frequency is used. I would just try out the value. I think also the 50 OHm resistors should get a higher value or some sort of decoupling unit in order not to weaken the tapped signal from the receiver unit.
....................
Thanks for adding this response delay module. That will store the measured value for a moment depending on the dimensioning of the capacitor and the discharge resistor I guess. Very good.
.....................

Now Phase 2 of this idea has to come into play:
where to pick up the signals and connect the unit in such a way that the signals of the receiver circuit do not suffer and the disc still works. May be it could even be used in all metal mode??? I remember some Garrett machines who have this function.

To start with may be somebody from the experts here could suggest some way to connect this to the Tesoro Bandido (if that is a suitable machine for this concept) in order to understand the way of doing it.

I myself have a Nautilus DMCIIBa and I would take some snapshots of the PCB to send to somebody willing to give suggestions.

In general many expert diggers and Tesoro fans don't give much on meters because some goldrings look anyway like certain pulltabs or foilfragments to the meter. You've to dig it because you never know. But if you search in an area with many hunting or war activity and you dig bullet casing after bullett casing you would want a meter in order not to dig them.
Ganesh

[Vladimir]

I think we should use the output of the first gain in the Rx and the output of the oscillator.