complete project Circuit diagram

[Tinkerer]

Here are some pictures of my experiments. But it it some time ago. These are with a big (50 cm) IB coil. Center taped RX.

Nulling is not good enough

[Tinkerer]

nice work on the coils.
Which wires do you use for the fine adjustment for nulling?

[mschmahl]

At this days I had use the twisted wire between BU und TX coil to fine adjust the nulling. I had to twist or untwist it a bit more or less.

[Tinkerer]

At this days I had use the twisted wire between BU und TX coil to fine adjust the nulling. I had to twist or untwist it a bit more or less.

that is correct. On the Tinkerer_SB_NM_PSU&TX, I also added a fine adjustment for the Bucking coil current.

With 2 inductances in series, like the TX coil and the Bucking coil in the Tinkerer design, the current is the same in both coils. However, the Bucking coil current adjustment makes it possible to bypass some of the current so that the current in the 2 coils is not the same anymore, thereby adjusting any imbalance caused by magnetic ground.

[Sean_Goddard]

Tinkerer, I was a bit confused to see you had combined all the sample pulses into one point. I, personally, would have kept the 4 channels separate and multiplexed them, via a CD4053, into a single 12bit ADC (like the Eagle Spectrum does ADC804) then processed these signals relatively / comparatively like Minelab do. This would give you much more flexibility as regards the way in which the signals were handled, indeed different software tweaks would allow for real-time optimisation of the machine as a whole. you could also simply do away with the demodulators and use S/H like this http://schematics.dapj.com/2005/01/s...h-standby.html and implement the motion function in softwar