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It was stated that the first link shows up on Protection software as a Trojan but I can't find anything wrong with it. I think his software is flagging on the JavaScript it's made up of. Use at your own risk.
Tell us why you gave up. It was an interesting experiment.
I don't understand comment that increasing TX would decrease phase difference between targets. I would think its the opposite. Can someone explain?
You would need to examine all the phases of the sync pulses etc. to make sure the discrimination and GB are working as expected or whether you need some mods (probably).
Probably harder to tune everything at higher freq, but I say keep trying, let us know. We can try to help troubleshoot.
I'm sure a bit of search engine use will tell you the details, but I recall a skin depth of 0.5mm is common at MD frequencies, so you're probably OK with a single conductor, especially as the Q factor doesn't need to be very high. But I'm sure some Geotech-ers will have more practical experience.
There is something called "proximity effect" which is similar to skin effect only for a bundle of wires. Our coils may be subject to proximity effect. I think it would mainly raise the effective resistance of the coils.
Tell us why you gave up. It was an interesting experiment.
I don't understand comment that increasing TX would decrease phase difference between targets. I would think its the opposite. Can someone explain?
You would need to examine all the phases of the sync pulses etc. to make sure the discrimination and GB are working as expected or whether you need some mods (probably).
Probably harder to tune everything at higher freq, but I say keep trying, let us know. We can try to help troubleshoot.
Regards,
-SB
Simon, the attached diagrams show what happens when we increase TX frequency. The diagrams are valid for soils and for targets.
Simon, the attached diagrams show what happens when we increase TX frequency. The diagrams are valid for soils and for targets.
I guess it depends on how you model the target.
Using the simple "coil and resistor" target model that the PI boys use in their simulations, an AC analysis seems to indicate that the phase difference between targets typically increases with frequency over a range, then decreases with frequency. So it does both!
Attached is the simulation. Maybe I'm not doing the right sim, or maybe its not true to life. But interesting. I'm still not clear why the phase difference gets smaller with really high frequencies; need to dig into the sim.
Using the simple "coil and resistor" target model that the PI boys use in their simulations, an AC analysis seems to indicate that the phase difference between targets typically increases with frequency over a range, then decreases with frequency. So it does both!
Attached is the simulation. Maybe I'm not doing the right sim, or maybe its not true to life. But interesting. I'm still not clear why the phase difference gets smaller with really high frequencies; need to dig into the sim.
Cheers,
-SB
P.S. I guess on thinking about it, there is only so much phase shift a simple first order circuit (inductor-resistor or capacitor-resistor) can do, so they eventually converge to the same maximum value.
Hi,
I've been thinking about increasing the frequency for prospecting also, but I thought I'd try decreasing the inductance of the coils by half. That would increase the resonant frequencies by a factor of 2.
I suspect I'd need to use a slightly smaller gauge wire to satisfy other circuit parameters.
I need to build my circuit yet, but was wondering if anyone else has experimented with alternate inductance values and what circuit mods may've been required.
Seems that sensitivity to small targets such as nuggets is not just a function of frequency, but also ratios of inductance between Tx and Rx coils, this is one reason why the Lobo and Diablo etc., have such large Rx coil inductance in relation to the Tx, it is a transformer boosting effect magnifying sensitivities.
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