Cylinder Coils?

[Detectorist#1]

Hi Tinkerer,
If you uses only one Rx coil, you loose the possibility to make simple Fe discrimination by connecting of the two Rx coils as planar gradiometer.

[Tinkerer]

Hi Tinkerer,
If you uses only one Rx coil, you loose the possibility to make simple Fe discrimination by connecting of the two Rx coils as planar gradiometer.

I am not sure what you mean by "planar gradiometer"?
With a single coil you can use differential signal processing. Is that different?

[Detectorist#1]

Hi Tinkerer,
Attached is the picture of some possible planar gradiometer configurations. Output signals of two RX coils are processing from differential amplifier. In "Fe" mode no TX pulses. This guarantee that if a target is recognized, this target is 100% sure from Fe. I think that differential signal processing of the signal from single coil reduces the overall sensitivity of MD and not guarantee 100% Fe recognition for small targets - or I'm not right? Planar Gradiometer Used in PI MD.pdf

[hykj888]

Sorry, I rarely go to the forum, regarding the DOD coil, my TX coil inductance is 300uh, RX are each 350uh, regarding bipolar transmission, I have tested many ways, these two are more satisfactory, it's just that the control is more. Please refer to the picture.

[Detectorist#1]

Also, have in mind, the schematic of the bipolar transmitter in attached document - sch2 at page 4

[hykj888]

I have also tested the PMOS and NMOS combination to achieve bipolarity. However, due to their different characteristics, a single damping resistor meet the needs of two different types of Mosfets, resulting in one side having a perfect waveform while the other side is very poor. The picture I showed is a simplified circuit diagram. In practice, I also added a constant current circuit, using an instrumentation amplifier, which can achieve a perfect output from the preamifier.

[Detectorist#1]

What is the schematic of constant current bipolar transmitter used from you?