Instruction monocoil for minelab GP series

[porkluvr]

Q?

Q 4.3. This is the Q that I have found works well for a Minelab SD2000/2100/2200 series of detectors.

"Q" is frequency dependent, and is most applicable to a sine waveform, such as in a IB detector.

Without specifying an operating frequency, talking about Q is nonsense.

Sorry, but as an (ex)RF guy, I must chime in.

[Stefan]

"Q" is frequency dependent, and is most applicable to a sine waveform, such as in a IB detector.

Without specifying an operating frequency, talking about Q is nonsense.

Sorry, but as an (ex)RF guy, I must chime in.

You are quite right. However traditionally the measurement frequency was 1Khz. Most LCR meters have the facility to measure Q at 100 Hz and 1Khz.

The Q quoted was measured at 1Khz.

Regards,

Stefan

[gef12]

Hi Rajesh,

I'm sorry but I have only built coils for the Minelab series of PI detectors so can offer no help for the hammerhead coils. If you know the Q of the large coils you have made then use this value for the Tx of the DD. You will have to play around with the Rx coil a bit.

Q 4.3. This is the Q that I have found works well for a Minelab SD2000/2100/2200 series of detectors.

If you construct a low capacitance PI coil and build using the original Minelab Q of 4.5, the ground balance response on highly mineralized
ground is very noisy. I found this out the hard way whilst building low capacitance coils. So that is why I ensure that the
Q is about 4.3 and no greater.


Regards,

Stefan

Hi
Minelab coils work fine on the Hammerhead ..I currently use them.. just make sure you tune it with the correct damper resistor
cheers

[porkluvr]

You are quite right. However traditionally the measurement frequency was 1Khz. Most LCR meters have the facility to measure Q at 100 Hz and 1Khz.

The Q quoted was measured at 1Khz.

Regards,

Stefan

I want to apologize for the tone of my last post. I wanted to be confrontational, but may have been unintentionally nasty.
I should have chosen my words more carefully,
and not been in such a hurry.

I am unfornately without the use of a quality LCR tester;
the idea of a "standard" test frequency had not crossed my mind.
Maybe with the good advice that I have found in this thread
I can be lucky and construct a decent coil on my first attempt.

I have a devised and drawn a fairly complex PI project in Eagle Schematic, but have yet to do the PCB layout. Rather than use an unlicensed copy of Eagle Professional, I am opting to use Eagle freeware - working with three smallish boards.

Then... comes soldering, and building the coil....
and borrowing a test bench complete with scope.

[Stefan]

Hi Porkluvr,

Ok, no problems. Good luck with your design.

I'm also involved in designing a PI using a Micro processor but in the early stages. I've approached the design a little differently in that
I have designed logic consisting of a circular 32 bit shift register in which you can load your pulse sequence via the micro.
( I use two pulse sequences like the Minelab design) The sequence then repeats indefinately without any further input from the micro.
High priority interrupts are set at the correct point in the sequence to allow the micro to generate the sample pulses. This allows the mico
a lot more time to do other things.

I've used Protel to generate a PCB and once I get a board produced will interface with the micro and write some code. This is where I will be pulling
out my little remaining hair.

Regards,

Stefan

[Stefan]

hi stefan can you sent me ddcoil cofiguration for hammerhead?

Hi Rajesh,

gef12 has confirmed that Minelab coils work with the Hammerhead. I have managed to find some info I had for
a 12 inch DD coil which will help you. The coil info is as follows:

Tx 300 micro henries, Q= 4.5 ( Q ok for this application and measured at 1 Khz)

Rx 420 micro henries R= 17 ohms ( DC resistance) damping resistor approx 600 ohms.


The damping resistor of 600 ohms on the Rx side is a starting point. I only had access to 0.15 mm diam
enamelled wire to give me a resistance of about 14 ohms. This worked fine.

For the Tx side you will need to determine the correct damping resistor.

If you want to make a larger size DD then use the same parameters as given above.

Good luck.


Regards,

Stefan

[hargrovebrian]

Hello

I am trying to build a 8 meter coil for a minelab F1A4 Pulse Induction mine/metal detector.

I am new at this sport but am learning fast.

I have tried to get a simple schematic of how to wire a TWO pin coil.

the lead wire has 2 wires that connect to the coil.

but i cannot figure out what to do for the actual coil are thier 2 seperate coils inside
are they endless loops that start and end at the same connection?
or do they just loop and end?

Please Help
Brian

[Carl-NC]

If the connector is 2 pins, and the cable has 2 leads, then the coil will probably be a single multi-turn loop. You need to measure the inductance, then try to maintain that value (+/-) as you make the coil larger. When you say 8 meters, is that diameter or circumference?

[hargrovebrian]

Hi

that is circumferance.

The trouble i have is after i make the coil what wire do i solder to pin A and what wire do i solder to pin B

Thanks Brian

This a P I detector by minelab F1A4

[Carl-NC]

Doesn't matter.

[hargrovebrian]

OK
then i take my coil wire solder to pin A make my loop and then solder the other end to pin B.

Do i have this right that when the transmiter is on the receiver is off so pin B is not working.

and when the receiver is on pin A is not working.

so pin A and Pin B are connected at each end of the coil loop?

Thanks Brian

[Carl-NC]

Yes, pin A and pin B to each end of the coil. One end is usually TX + RX, the other end is usually ground or supply.

[hargrovebrian]

Thank You

Will let you know how it turns out.

Brian

[h9361]

Hello
I have built HH1 Rev. C and tested 11" commander GPX 5000 coil. my best result was 1K damping resistor but my sensitivity is very low than metals.
Is it possible help me? can you tell me your damping value?

[h9361]

Hello Dear Carl
I have built HH1 Rev. C and and tested it with GPX 11" coil. I tested its damping resistor and reached to 10K. But my sensitivity still is very low. Do you think there is any tip to do for reaching high sens like TDI? I opened TDI and see that it also has used 1K for RX coil. Is any one succeed to use GPX coil over HH1 with high sensitivity?!