pi preamp

[Gwil]

Try Google.

[kt315]

i'm living in russian segment of the net. i have not sure understand what in english one are going on this matter.
so i can give just books in russian http://depositfiles.com/files/nafeackgo

[liudengyuan]

Can't download, don't know what

[kt315]

click on right side of page, wait a time.

[Ferric Toes]

Can anyone provide a solution to the impossibility of using pulse detectors under high-voltage lines? How to eliminate the interference of high voltage wires, thank you

A very effective way of eliminating overhead power line noise is to use a differential coil arrangement as in the picture. Lower coil is mono TX and RX. Upper coil is identical, damped the same, and is for noise pickup. It is fed into the opposing input on the preamp and cancels the noise picked up by the lower coil. The other method is a figure of 8 type coil, but the response is more complicated.

Eric.

[Vadim18]

Thanks for advise mister Eric.
As i see from the picture main requirement is to keep both coils on the same position to avoid phase dismatching. I think what if keep just a small and lightweight coil fixed anywere on the shaft instead of standard big one, but i guess this simplification may do circuit more complicated.

[Carl-NC]

Can anyone provide a solution to the impossibility of using pulse detectors under high-voltage lines? How to eliminate the interference of high voltage wires, thank you

Assuming monopolar pulsing, and also assuming you have a late subtractive Earth field sample, the normal sample and the late subtractive sample form a comb filter with a null at DC and a subsequent null at 1/tsp, where tsp is the spacing between the samples. The comb filter effect will attenuate 50/60 Hz interference, but it does a better job as tsp is reduced. Every time you halve tsp, you get a 6dB improvement in rejection. But tsp also determines target attenuation, and a lower tsp causes higher tau targets to get attenuated. If you are hunting small gold nuggets, then I would suggest reducing tsp to 50us or maybe even less. Targets with a tau equal to or less than tsp/5 will come through with practically no attenuation.

[liudengyuan]

Since the single-chip microcomputer cannot detect negative pressure, but the op amp is powered by positive and negative power supply, is there any way to implement a single-chip microcomputer to detect negative pressure?

[waltr]

Since the single-chip microcomputer cannot detect negative pressure, but the op amp is powered by positive and negative power supply, is there any way to implement a single-chip microcomputer to detect negative pressure?

Either AC couple to an Op-amp with single supply or offset op-amp Or reference the microprocessor to the Negative Voltage rail and scale the op-amp's output to the microprocessor's Vdd/Vss.

[liudengyuan]

Either AC couple to an Op-amp with single supply or offset op-amp Or reference the microprocessor to the Negative Voltage rail and scale the op-amp's output to the microprocessor's Vdd/Vss.

Can you draw me a schematic, thank you

[waltr]

Can you draw me a schematic, thank you

Many schematics here on Geotech using those ideas.
Check the MPP, Barracua, Surf PI, etc. Also my Hammerhead II project where I put the processor on the Negative rail.

[liudengyuan]

Help again, who has a circuit and method of making fish, thank you

[WM6]

who has method of making fish,

What you mean by method of making fish?

[Orbit]

Hi liudengyuan I think you mean to hunt for fish bait electronic ? Am I right ?

[Orbit]

Otherwise it depends on the processor some work from zero to 5v create the condition that the voltage at the input is say 2.5v so you can work in the negative voltage and positive voltage!