Depth Read.

[Geo]

Hi to All.
Last time i study how works and how to construct a depth reader. I believe that it is time to design and construct a general purpose depth reader, so we to have the ability to connect it at the most detectors. So i need your opinion. A good place to see how it work is the schematic of Whites 6000D-2 and newer. Or everyone that knows any patent about it.... he may attach it here.

[Geo]

For start i attach the shematic from 6000D-2 with the depth read. It take 2 signals, one from oscilator and one from the out of GEB. The out of the depth read is going directly to a mooving coil instrument.
Now how does it work ???? Does it measure the time delay between Tx and Rx signal .....Or..........

[Max]

For start i attach the shematic from 6000D-2 with the depth read. It take 2 signals, one from oscilator and one from the out of GEB. The out of the depth read is going directly to a mooving coil instrument.
Now how does it work ???? Does it measure the time delay between Tx and Rx signal .....Or..........

Hi Geo,
I don't know well this white's model... or its feature of depth meter...
and also circuit of it... so my are about guesses and advices.

If the coil is a normal TX-RX with just one RX coil like in schematic then the depth estimation must be done by using some tricks... I think this is a case.

Have you to push the button for having the depth reading ?

If so... ok... maybe something happens when you push that button... I mean some analog gate could be in conduction or not... then "something" happens: actually I think that there you have investigate... if e.g. some stage change its gain and the like.

That way you'll find the solution.

Another thing... have you tested it very widely ? Gives sometimes errors like indicating a little mass at few cm and then you found a large thing depeer ??? If so... you can be confident that the "trick" is around gain setting for RX stages.

Best regards,
Max

[JC1]

Depth

Hi Geo,

Here is one patent, where Garrett is doing it for real.

Most depth on detectors is made up guess based on

signal strength. This is more real. there are other patents

where there are a bunch of coils, sometimes at odd angles,

but I suspect they may or may not even work but are

certainly not very practical.

http://www.google.com/patents?id=ikk...BAJ&dq=5786696

[Geo]

I will read a little more and i will come back soon
red and read and read and......... when we will stop

[Geo]

"True depth, which can only be found on Garrett's GTI and GTP detectors, is made possible with additional receivers in a metal detector that offer added depth perception much like having two eyes open".
Garrett at GTI and GTP uses 2 Rx coils, the normal Rx and one else small in the center of the coil house. So it takes 2 signals..... convert and analyze them at Fourier type and then compare them and takes a signal that is analog to the depth of the coins.
Very good method but needs 2 Rx coils........ so it is not good for a general purpose depth reader construction.

Anything else..??????????

[Max]

"True depth, which can only be found on Garrett's GTI and GTP detectors, is made possible with additional receivers in a metal detector that offer added depth perception much like having two eyes open".
Garrett at GTI and GTP uses 2 Rx coils, the normal Rx and one else small in the center of the coil house. So it takes 2 signals..... convert and analyze them at Fourier type and then compare them and takes a signal that is analog to the depth of the coins.
Very good method but needs 2 Rx coils........ so it is not good for a general purpose depth reader construction.

Anything else..??????????

Hi Geo,
is complicated having two different sized RX coils but is a really good method to do what you are looking for: using two RX coils is possible making an better estimation of depth cause you can also estimate the surface dimensions involved in detection ...so you can understand if it is from a large or small objects... that's cause you know the flux densisty and geometry of the system (TX and RX coils) and so the magnitude information coming from two different RX coils can give you that "ratio" between the two lectures... then an MCU of something similar could run a program for the depth estimation of a such sized object.

The way this approach could fail is more restricted than the method explained before (changing gain of RX stages...) cause in the previous method you haven't any information about active area estimation.

The most common fail could be found in the orientation in soil of object ... if maximum area is not normal to coils plane... but tilted somehow at arbitrary angle and maximum error is when a flat object (like a coin) is tilted near 90° from coils plane.

Anyway... though complicated... I think this is one right way for getting some useful information from such a device... and , at the end, require just one more RX coil and some MCU programming... not so much.

Best regards,
Max

[Geo]

On weekend i program to check the XLT and the GTI2500 for the accurary of the depth meter. I am sure that firms as Whites or Fisher use some tricks to measure the depth. I believe that i will find it. JC1 wrote that "Most depth on detectors is made up guess based on signal strength". Yes ....but. A coin at 5 cm gives the same signal with a larger target at 15.....30cm. So maybe they use a trick to find the target and after it to read the depth. But don't seem to me as a good solution. I am sure that they found a clever solution but who????
Does have anyone any schematic for Fisher with depth meter??
Regards

[ivconic]

Garrett GTI 2500 works with 70% accuracy. I already checked it so many times. This percentage falls down fast on highly mineralized terrains...
GTI2500 has 2xOP37 opamps at front end. Usually one is coupled to gnd when "single RX" coil is used. This function is useable at medium shallow depths, let's say up to 40cm... It makes sence only when detected item is very small. Otherwise, larger item is usually easy to pinpoint and dig.
Now...this function would be very usefull on some deep PI, when we talk about greater depths; 2meters and more. It is not same for you to dig hole 1.2m or 2.3m for example!?

But down to 30-40cm in the ground doesnt play a role at all..It is easy to dig some extra 10cm....Not a big deal.

[Qiaozhi]

On weekend i program to check the XLT and the GTI2500 for the accurary of the depth meter. I am sure that firms as Whites or Fisher use some tricks to measure the depth. I believe that i will find it. JC1 wrote that "Most depth on detectors is made up guess based on signal strength". Yes ....but. A coin at 5 cm gives the same signal with a larger target at 15.....30cm. So maybe they use a trick to find the target and after it to read the depth. But don't seem to me as a good solution. I am sure that they found a clever solution but who????
Does have anyone any schematic for Fisher with depth meter??
Regards

You don't need to guess how Garrett do their depth measurement. Their patent has all the details.

[Geo]

As i wrote before Garrett patent is very good but needs coil with 2 Rx inductions. I want to make a depth meter able to can puting in any detector .....Anker....TGS..... etc with any coil.
At PI detectors this is more easy because i can measure the time between Tx and Rx (VERY LOW FREQUENCY)

[ivconic]

As i wrote before Garrett patent is very good but needs coil with 2 Rx inductions. I want to make a depth meter able to can puting in any detector .....Anker....TGS..... etc with any coil.

At PI detectors this is more easy because i can measure the time between Tx and Rx (VERY LOW FREQUENCY)

How accurate? If accurate enough, i suggest you to do that for PI! I'll be first to implement it in Delta Pulse...

Regards!

[Max]

As i wrote before Garrett patent is very good but needs coil with 2 Rx inductions. I want to make a depth meter able to can puting in any detector .....Anker....TGS..... etc with any coil.
At PI detectors this is more easy because i can measure the time between Tx and Rx (VERY LOW FREQUENCY)

Hi Geo,
you can do easy on PI using just having standard monocoil + another smaller receive coil and receive amplifier channel... just compare the two signals to get a good estimate of flux difference at the two respect what you expect cause of geometry of the system....you can then calculate using that difference if object is great or small and which is the depth... all can be done using an ADC/MCU or also some non-linear analog function differential meter.

But on VLFs the story is different... you need one TX and 2 RX or 2TX and one RX to make it work like in the patent ... I mean... with good accurancy.

If you use just one RX coil , in both cases, you cannot say if effect is due to a great object deeper or a smaller object at less depth... cause signal could be about the same for different sized objects at different depth due to the exponential decay due to distance from coil.

Also I don't understand your reference to TX-RX latency ? EM signal find its way in the ground at much more speed you can evaluate by the timing section of an e.g. PI detector. If you wanna implement something like in radars you have to use an ultrastable timing circuit (maybe cesium driven) to evaluate such differences on so short distances.

Kind regards,
Max

[JC1]

Nice Pic

Hi Geo,

Nice picture of the insides of the 2500 coil/s. neat.

You may need two eyes to see depth.

and two speakers to hear stereo.

Or maybe not, but if you figure it out let us know.

[Geo]

Hi Geo,

Nice picture of the insides of the 2500 coil/s. neat.

You may need two eyes to see depth.

and two speakers to hear stereo.

Or maybe not, but if you figure it out let us know.

Hi JC1.
The photo is not mine. I don't remember good but maybe Ivconic post it here before 3 years
Regards