Sound coming from mono litz coil

[Qiaozhi]

They are the same at 15usec and 20usec apart (delay 2).
Possibly I have the integrator inputs not balanced or gain matched. I will be looking at this.

What is the delay of your secondary (EFE) pulse? Are you saying it's 20us?

The way EFE works is that you take an initial (main) sample after (for example) 15us. Then you take a second (EFE) sample much later (for example) 200us. If there is a signal due to the Earth's magnetic filed, it will have substantially the same amplitude in both samples. However, any target signal will be much stronger in the main sample than it is in the second sample. Therefore, subtracting the second sample from the main sample will leave only the target signal. i.e. the effect of moving the coil in the Earth's magnetic filed will have been eliminated. This method requires both the main and second samples to have the samesample width.

[waltr]

What is the delay of your secondary (EFE) pulse? Are you saying it's 20us?

The way EFE works is that you take an initial (main) sample after (for example) 15us. Then you take a second (EFE) sample much later (for example) 200us. If there is a signal due to the Earth's magnetic filed, it will have substantially the same amplitude in both samples. However, any target signal will be much stronger in the main sample than it is in the second sample. Therefore, subtracting the second sample from the main sample will leave only the target signal. i.e. the effect of moving the coil in the Earth's magnetic filed will have been eliminated. This method requires both the main and second samples to have the samesample width.

Yes, understand but have been trying the 'three sample' GEB method.
Details are in my thread: http://www.geotech1.com/forums/showt...ake-on-the-HH2

I would like more detailed discussion of what I have been trying but this isn't the correct thread for that.

[fo0bar]

I had that wobbling tone and be adjusting the PPS rate was about to eliminate it. Since changing the PPS rate fixed this issue I am sure it is caused by a 'beat' of the PPS and the AC mains frequencies.
In fact when I did the adjustment to wobble was at aabout 1Hz and adjuting the PPS rate change the frequency of the wobble. Adjuting in one direction increased the wobble freq, then adjust the other direction until the wobble went away.

Excellent. I did notice that when I moved away from my workbench the wobble became less apparent however I put that down to my less-than-ideal testing setup where I had the coil cable running close to other noise sources.

One thing that interested me when I first started playing around with PI, is that the signal seemed quite noisy on my home-designed circuit. However I was all stoked to have a working circuit and so tested it with basically every metal object I could lift. One of these things was a little RF choke. When I held the choke against the coil with its turns perpendicular to the detector coil windings, the signal cleaned right up and detection distance increased around 30%. Nothing connected to the choke's legs. I'm not sure what caused this or what it means, but it was just a weird observation that I'm going to investigate further down the line.

Neodymium magnets are detectable. I use ceramic disk or fridge magnets to test for EF.

Thanks for this pointer... I was starting to think my coil was being affected by ground too much! Going to find an old fridge magnet as my 2mm neo's were being detected from a few inches.

[waltr]

Neodymium magnets are detectable. I use ceramic disk or fridge magnets to test for EF.

Thanks for this pointer... I was starting to think my coil was being affected by ground too much! Going to find an old fridge magnet as my 2mm neo's were being detected from a few inches.

Thanks here also. I have been using old black magnets that may be powered iron and it is the iron being detected.
Need to get a frig or ceramic magnet.

[fo0bar]

Are you adding any type of shield or static drain?

I've now removed the coil from the backing, wrapped 0.4mm enamelled copper around it 12 times (wasn't aiming for any number in particular) and the signal is much cleaner, allowing me to bump up the tone and shorten the delay very slightly. It also seems to be less sensitive to the fridge magnet.

I've also tested connecting it to both the pos and neg of the coil and it makes zero difference. I'm going to do further testing with more turns.