ground balance capability

[mohalothman]

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

here the soil response for pulse width=60us and pulse width=20us
what do you think kt315?

[kt315]

perfect result! wow! that i waited ))))

thank you

[mohalothman]

welcome kt315
so you still think the problem is not mineralized soil or not?

[Wahyu]

that soil very mineralized, what IC preamp do you use? and gain?

GB Tepco work for me
http://www.geotech1.com/forums/showt...096#post184096

Video test GB
https://youtu.be/UnILRf9Udws

[mohalothman]

that soil very mineralized, what IC preamp do you use? and gain?

GB Tepco work for me
http://www.geotech1.com/forums/showt...096#post184096

Video test GB
https://youtu.be/UnILRf9Udws

thanks Wahyu
i use for preamp the ne5532 op-amp, the preamp is two stage with totally gain 1000 (gain 33 for each stage)

[Wahyu]

maybe lower gain would help you, my gain 200 - 400 NE5532 Philips

[mohalothman]

how the lower gain would help?
if i decrease the gain i will decrease the device sensitivity

[Wahyu]

yes sure its decrease sensitivty, but you can tune coil for that, if you see SD2000 and QED, preamp gain its lower

[mohalothman]

yes sure its decrease sensitivty, but you can tune coil for that, if you see SD2000 and QED, preamp gain its lower

yes that is true but the totally gain with the next stages is the same range with the MPP which i use
i mean the decrease the preamp gain and increase the next stages (the integrator , final gain...ex) with totally gain is the same would not change the result

[Wahyu]

more gain at preamp, more detect soil (cmiiw)
https://www.youtube.com/watch?v=VFHIBczslgI
at 7:20 sensitive to extra, soil detect

[eclipse]

Goldscan IV also has sort of ground ballance, it's complete, it's tested and built by many, so you can also check it out.

[mohalothman]

more gain at preamp, more detect soil (cmiiw)
https://www.youtube.com/watch?v=VFHIBczslgI
at 7:20 sensitive to extra, soil detect

dude that was normal he got a higher sound because he increased the sensitivity, with high sensitivity the ground balance become more difficult but the target response become stronger however the ground target signal ratio will be the same
Q: you experimented the GB with high conductivity (long time constant) target, according to the GB timing you used you would lose sensible sensitivity for the long time constant target for example large target

[Wahyu]

yes your correct, i test silver ring, result poor,
but nickle, lead and gold still good sensitive

[mohalothman]

yes your correct, i test silver ring, result poor,
but nickle, lead and gold still good sensitive

i expect that , unfortunately i m care about the long time constant targets not the short. you would say you can modify the GB sample timing but this also would not work in my case because the targets i care about have almost the same soil decay form so i must think in a different way
i m thinking in something like compare the final output (not necessary the final) with absolute threshold this threshold equal to the offset in the output due to the soil response
of course this technique has its difficulties because the final output is unstable with long time (battery voltage drop, non homogeneous soil,input offset voltage drift with temperature for op-amp,...ex ) especially i can not directly use AC coupling for the final output (using high pass filter) but this technique will not affect the sensitivity at all

[eclipse]

mohalothman what you describe is perhaps something like this (by Eric Foster), would love to hear more!

http://www.geotech1.com/forums/showt...880#post224880