strange effect on PI detectors

[kosacid]

has anyone noticed this i was using my pin pointer its also a PI and my detector was close by, i noticed my detector was also picking up the coin i was using the pointer on also the pointer was picking it up at some distance allot more than usual, it got me thinking is it worth looking into building a duel PI detector basicly 2 coils and 2 pulse circuits, i also tested it on my garret detector it works on that to, alot of chatter but it works you can tell that its detecting it
so has anyone looked into this ?

[Qiaozhi]

has anyone noticed this i was using my pin pointer its also a PI and my detector was close by, i noticed my detector was also picking up the coin i was using the pointer on also the pointer was picking it up at some distance allot more than usual, it got me thinking is it worth looking into building a duel PI detector basicly 2 coils and 2 pulse circuits, i also tested it on my garret detector it works on that to, alot of chatter but it works you can tell that its detecting it
so has anyone looked into this ?

The most likely explanation is this:
A PI generates a pulse that causes eddy currents to flow in the target. The magnetic field created by the eddy currents are then detected by the PI during the TX-off period. However, when you place a pinpointer close to the target, you are also stimulating eddy currents in the target, and it looks like a generator to a nearby PI. Instead of the target signal falling off by a factor it now only drops off by . In other words, an attenuation of 64 versus 8.

[Ferric Toes]

The most likely explanation is this:
A PI generates a pulse that causes eddy currents to flow in the target. The magnetic field created by the eddy currents are then detected by the PI during the TX-off period. However, when you place a pinpointer close to the target, you are also stimulating eddy currents in the target, and it looks like a generator to a nearby PI. Instead of the target signal falling off by a factor it now only drops off by . In other words, an attenuation of 64 versus 8.

I would have thought that this could only work if the two detectors TX pulses were in sych at switch off?

Eric.

[Qiaozhi]

I would have thought that this could only work if the two detectors TX pulses were in sych at switch off?

Eric.

The eddy currents will circulate for some time in the target, and presumably the two PIs will not have exactly the same TX pulse rate. So there's probably enough overlap, plus integration over time, that it makes an improvement in the depth response. Of course, if they were synchronized, then the difference could be significant. Anyway, I don't have an alternative theory to explain what's happening.

[kosacid]

i been testing it i have 2 coils one detecting and pulsing the other just pulsing, i have been delaying the pulse and testing i think tomorrow i will feed both coils into the opamp and look what i see in the scope, but what i have tested so far is delaying the pulse at 300h in the 600h cycle, you can see the pulse coming of the non detecting one and changing when metal is near it might be picking that up, i have not decided what the best setup is yet ill try coils side by side

[Funfinder]

i been testing it i have 2 coils one detecting and pulsing the other just pulsing, i have been delaying the pulse and testing i think tomorrow i will feed both coils into the opamp and look what i see in the scope, but what i have tested so far is delaying the pulse at 300h in the 600h cycle, you can see the pulse coming of the non detecting one and changing when metal is near it might be picking that up, i have not decided what the best setup is yet ill try coils side by side

Good idea, make some tests - place the Pinpointer 25-50cm / 10-20''
behind the coin and next test the PI while the PP is on or off.

Under real search conditions this will not work - perhaps only if
someone works with an 1m PI coil which pulses the ground and some
smaller pickup RX-only coil in the middle.

Maybe some PI "transmitter-receiver" setup could work:
Placing 4 PI-pulse generators at the corners of a 20 x 20m square
and search with the PI as usual. But I doubt this will bring that
much amplification as your direct in air test.

Perhaps you have to bury your PI-Stimulator some meters deep, first,
until it improves the usual PI search-results in the vicinity!