Hammerhead with Ironchannel?

[Ganesh]

I build the Hammerhead PI. It works quite nice but in order to find out if my target is iron or something else I've to change the delay with the pot or flip a switch to use a preconfigured resistorvalue.
Is there a way to create something similar like a mixed mode on a VLF machine? Would be left channel everything and right channel only Iron.

Thanks for your input
Ganesh

[Qiaozhi]

I build the Hammerhead PI. It works quite nice but in order to find out if my target is iron or something else I've to change the delay with the pot or flip a switch to use a preconfigured resistorvalue.
Is there a way to create something similar like a mixed mode on a VLF machine? Would be left channel everything and right channel only Iron.

Thanks for your input
Ganesh

If you're wanting to eliminate iron, then a PI detector is not for you.
To get the HH to ignore small iron nails (for example) you would need to modify the design by adding a GB sample, which could then be adjusted to reject small nails. With some extra circuitry, you could provide a two-tone audio response for target TCs on either side of the GB notch. This is how the TDI works. However, this would not be reliable for all iron targets, as the discrimination is based solely on conductivity. It would also be difficult to realise on the HH without adding a PIC.

[Ganesh]

Seems there is no easy way. I mused about setting the pulse delay to 90 and adding the first and second sample in another opamp or create a circuit which signals only if both samples give a signal. In theory that should work doesn't it?

[Carl-NC]

Your idea will work for large iron targets which have a long eddy-based time constant, and will be equally effective at eliminating e.g. silver coins which also have a long eddy-based time constant.

[kt315]

Ganesh, leave this dreaming to make PI with the disc... look at a VLF design side... a time to make New Project...

[Ganesh]

Thank you KT315 for your advice. Already Qiaozhi pointed in that direction. I've owned several VLF machines and I still own a DFX. I've never owned a PI. Now it is snow outside here -10 C and I like to sit at home and tinker. I build the HH. I want to make a bigger coil and have a little idea what the target may be before digging deep holes. May be that is illusory. That is why I ask here. I can't make a big coil for the DFX. Making coils for VLF machines is to difficult for me and in the end I've to run preamp gain very low because of EMI. For the HH I can make a big coil for a few Euros. It seems as if I can trim it just to find aluminium/copper buckles . May be it doesn't work well enough and I'll resort to a bulgarian pic controlled ready made PI. May be that also doesn't work so well as advertised on Youtube. So in the end I better dig eveything until it is in reach of my trusty DXF. At least I had fun soldering the Hammerhead and playing a bit with it.
Greetings Ganesh