High Voltage MD !!!

[Funfinder]

As it is physical well know, higher voltage has more power and reaches far more distances.

The main problem in MD development was (and still is) the needed powerful battery supply. Li-ion has changed this issues within the last years but still not good enough.

Low voltage (5-30) is for children, if we really want to develop really deep seeking detectors wie need much more juice.

I bought already 2 tesla coil driven plasma-balls for special experiments. Those are functional with 9V batteries or Li-Ion accus too. The initial experiments will concern the distraction and what it's better, magnetical pulses or transceiver.

[homefire]

Your going to find Current is the requirement , Not Voltage.

[goldfinder]

Problem w/ High Voltage

High voltage if you don't get too high (i.e. <1000 volts) you can use HV mosfets. Anything higher and you'll be shocking the crap out of the user. HV is very tricky to handle and keep from affecting the operator. Things like x-rays start cropping up w/ HV. Also, the problems w/ blowing out ICs most of which can't handle HV at all. I've blown entire circuits of ICs w/ stray HV that didn't get shunted away from them.

Goldfinder

[mikebg]

Your going to find Current is the requirement , Not Voltage.

Funfinder, the change of TX current creates eddy currents in target. The change of eddy currents induces signal in RX coil.
No need of high voltages. Note that AIR & GND signal in input of RX preamp is a useless relative high voltage which forces us to reduce its gain.
We have too high TX voltage at pulse induction metal detectors. It saturates the preamp when we use monocoil. We need induction balanced RX coil to suppress this voltage.
The AIR & GND signal is only milivolts, but it is high voltage relative to TGT signal, which is microvolts. You have in input of RX a useless voltage which is tausend times more strong than target signal.
The attached diagram is part of TX circuit with center taped TX coil. Such coil increases voltage of tank circuit only twice, but increases battery current 4 times. The AIR & GND signal increases twice and you should reduce the gain of preamp twice to avoid its saturation.

[Geo]

I saw a modified MD who work the oscillator at 50V.
Depth is twice and more compare to other normal MDs.

[Funfinder]

Thanx for your answers!

MikeBG (btw. a week ago I recorded Raina at the Planeta Derby 2010 @ Plovdiv - there are nice party people ) - thank you for your good information.

I'm shure this is correct, but those problems we have just are because the transmitter and receiver coils are so close together and the circuit is on the same PCB.

Usually the EM-field can't reach more depth than the coil diameter for four times (10'' coil, 40'' max. depth).

This is because the transmission - receiving ratio is not good enough. TR detector receivers have to deal with both - the powerful transmission signal and the very weak eddy currents.

And PI most of the time use the same coil and part of the same circuit for TX and RX.

This can't lead to high sensitivity or highest depths.

I think TX and RX coils and circuits really need to be seperated and shielded for really good results!


@ Geo
This is very cool information, thx!
I knew it!

High-End P.I. detectors also use around 30V that are giving around 1000V flyback for good depths.

And with higher voltage we can user higher frequencies for still penetrating the ground more powerful and more directional.

At the moment without reflector half of the coils energy is wasted by radiating upwards into the air.

Perhaps I also better start with doubling the usual voltage experiments...