ground balance capability

[mohalothman]

hi
i did some measurements to compare the soil response with some other targets which are a bag of soil a thin aluminum foil and an iron screw
i plotted the preamp output for the three targets when they were laid on the coil and i got this charts:




we could see that the aluminum foil as expected has a short TC, practically i could reject it totally with sample delay less than 40us
the iron screw has a longer TC as well the soil which TC seems to be very long (i forget to plot the soil response with a longer time sorry for that maybe i ll do later)
i think that clarify a lot and explains why i was sensing the soil even with long sample time delay
here the sampling data for who is interested https://drive.google.com/open?id=0B1...W5iWDctTEw3Wlk

[mohalothman]

here the extended time chart for display the response of the bag of soil
i notice that the soil has very long time effect on the decay of preamp output
any one can explain what i got here?

[kt315]

can you decreese TX power (pulse width) and do new charts?

[mohalothman]

can you decreese TX power (pulse width) and do new charts?

sure i can
do you want to be confirmed about the result?

[Qiaozhi]

here the extended time chart for display the response of the bag of soil
i notice that the soil has very long time effect on the decay of preamp output
any one can explain what i got here?
[ATTACH]40801[/ATTACH]

Is the soil attracted to a magnet?

[mohalothman]

Is the soil attracted to a magnet?

no the soil is not attracted to a magnet

[eclipse]

I dont think you can modify the MPP board for GB. The soil sample you got there is quite difficult. You can refer to SD2000 schematic which is the only schematic available here capable of providing ground cancellation.

[mohalothman]

I dont think you can modify the MPP board for GB. The soil sample you got there is quite difficult. You can refer to SD2000 schematic which is the only schematic available here capable of providing ground cancellation.

the technique which SD2000 use to achieve a ground balance is a bit complicated and the first sample of ground balance channel is 90us delayed!! do this mean the soil has a long TC?

[eclipse]

You can test different timings for example:

EF Sample (40-60uS)
TX (100-200uS)
Delay (10uS)
Target Sample (+)30us
GB Sample (-) 100-150uS
GB Delay (10-20us)
GB Sample (+) 100-150uS

[Davor]

the technique which SD2000 use to achieve a ground balance is a bit complicated and the first sample of ground balance channel is 90us delayed!! do this mean the soil has a long TC?

It has separate Tx pulses, short and long, with corresponding Rx samples. That is also a way to do it. The reasoning behind these schemes is to achieve sum of samples is zero for a viscous soil that responds in 1/t fashion.

[kt315]

sure i can
do you want to be confirmed about the result?

yes. what pulse width you have now?

[mohalothman]

eclipse, davor thanks for your notes and guidance
kt315
the MPP work now with PW=60us
what do u like me to experiment PW=30us for example?

[kt315]

40 and 20us. be enough.

[mohalothman]

40 and 20us. be enough.

coming soon

[Orbit]

Who did something in your practice from those theories what you write ?