ID based ground balance for PI

[Teleno]

I take two successive samples, TargetS and IdS. A level baseline TargetBase is created by low pass filtering (dynamic PI). The ID is the ratio TargetS/IdS. An ID baseline IDBase is created as the ratio of the low pass filtered versions of TargetS and IdS.

A target temporariliy raises TargetS above the baseline TargetBase. The signal level is TargetS - TargetBase and it triggers a target signal, however, it is only accepted if its ID is different from IDBase.

Two coins placed under a magnetically responsive tile:



https://youtube.com/shorts/rbP85u1VJ...EDSCm6-d6b0pEK

[Teleno]

[Altra]

Well done Teleno! Do you have to ground balance the detector or is it taken care of in your filters?

[Teleno]

Well done Teleno! Do you have to ground balance the detector or is it taken care of in your filters?

You just move or hold the detector at normal working distance above ground until the beeping stops, then it's balanced.

It takes some time cause the ID baseline filter updates slowly, so I've added a button that updates faster when you want to balance. For the impatient.

[Altra]

Thanks, if you did the same test as in the video and then put a third coin in the grass, What would happen as you scan from the tile to the coin in the grass?

[Teleno]

Thanks, if you did the same test as in the video and then put a third coin in the grass, What would happen as you scan from the tile to the coin in the grass?

I've just tried it and the coin in the grass is detected normally, then back to the tile and the other 2 coins were detected too.

The behaviour is expected cause the ground ID is memorized, while the coin IDs are different. Only the ground ID is ignored.

[Altra]

[Teleno]

A test with a 0.7g (11 grain) gold nugget slightly above the center of the tile and a 22kt gold chain near the top left corner.

[Teleno]

This GB seems realy stable. After 15 minutes of operation the detector was still balanced.

MCU is Atmega 328P.

[Emersonpaz]

Excellent work congratulations

[Teleno]

Excellent work congratulations

Thank you.

This method stores ground measurements at different heights. Samples are collected by "pumping" the coil.

This allows a much smaller threshold than the traditional PI ground balance of subtracting a later weighted sample, so it's more sensitive. The depth penalty is less and none for targets outside the hot area. The "holes" are smaller and only affect one height value, no target is fully cancelled.

Any commercial PI out there could benefit with a software update. I'm open to business deals