SURF PI PROBLEM

[daverave]

what is a whiteboard magnet ??? and where do i buy one ????

[Qiaozhi]

i was out detecting on the beach with my surf pi and a detector friend of mine tried my detector and he said the magnetic field of the earth cancellation was not working correctly and also when i swing my detector i do get a false signal at the end of each sweep..can anyone tell me how to put this right.

If your detector is working correctly, you should be able to wave a whiteboard magnet a few inches away from the coil without detecting it.
Look at the schematic, and you'll see there are two sample gates (CD4066). The lower one (U7A) is the main sample, and the upper one (U7B) is the Earth Field sample. The idea here is that both samples will contain the Earth Field signal, but only the earlier sample will contain any significant target information. Hence, subtracting the late sample from the early sample will leave only the signal information. In other words, the Earth Field gets rejected. If you cannot reject the magnet, then you may have an error in your PCB. There is no adjustment for the Earth Field setting, and no need to include one.

[kt315]

no way. we must work at distance.

br

[daverave]

i was out detecting on the beach with my surf pi and a detector friend of mine tried my detector and he said the magnetic field of the earth cancellation was not working correctly and also when i swing my detector i do get a false signal at the end of each sweep..can anyone tell me how to put this right.