Air balancing, soil balancing...

[ivconic]

It is interesting to analyze in details process of balancing at White's machines Eagle II, Spectrum etc..etc..
What is really going on, when such machine is switched ON and balancing message appears on LCD? Air balancing than soil balancing. Ok...for soil balanicng i think i understand what's going on. But Air balancing? What is going on for real there? Any ideas?

(i got idea to start this thread reading Max's and Qiaozhi's correspondence at PD forum)...

[Max]

It is interesting to analyze in details process of balancing at White's machines Eagle II, Spectrum etc..etc..
What is really going on, when such machine is switched ON and balancing message appears on LCD? Air balancing than soil balancing. Ok...for soil balanicng i think i understand what's going on. But Air balancing? What is going on for real there? Any ideas?

(i got idea to start this thread reading Max's and Qiaozhi's correspondence at PD forum)...

Hi,
I'm not sure... but I think that some designs have resonant coils setup, or harmonic setup (e.g. 3rd one is usually preference choice).

In resonant designs it's tricky and hard keep coils balanced (the nulling...and phase change if something mechanical change... e.g. a temperature induced stress to the coil housing/epoxy) so several tricks are employed like ptc/ntc resistors... that will provide compensation required, or even active devices.

I think some designs that have "intelligent" coils (think e.g. at some of these with electronics inside coil housing) use to balance "in air" before other operations, that probably mean an internal software check for offsets at coil rx when "in air" and thus provide compensating control to the coil electronics to suit factory balance on different e.g. temperature environment... changing something at tx or rx path or both...
Or also, the coil could have no internal electronics... but something happens just at control box , same stuff... compensation of startup offset.

Then, just later, the balance "on soil" let device to compensate for ground effect to null it.

As said, I'm not totally sure of that but I will do this way... also think many newer MCU controlled devices perform that "in air" balance before anything else... for reasons explained. It's like auto-checklist of an airplane... before you start engines must check everything is ok... or like BIOS checks at PC startup...


Kind regards,
Max

[ivconic]

I see...
Pretty logical explanation. I had simillar ideas about that.
But would be good to see electrical paths of that air balancing.
For example; how can we make an example of same at some analogue design, without MCU. I have'nt seen air balance feature at analogue detectors so far.
And what should schematic look like with added air balance stage...
Must check some White's schematics i have...
Also wandering; what kind of differences would we expect if there is any chance to skip air balance at mentioned White's detectors (no chance, it is MUST procedure...but let's say it can be skipped)...

[Qiaozhi]

It is interesting to analyze in details process of balancing at White's machines Eagle II, Spectrum etc..etc..
What is really going on, when such machine is switched ON and balancing message appears on LCD? Air balancing than soil balancing. Ok...for soil balanicng i think i understand what's going on. But Air balancing? What is going on for real there? Any ideas?

(i got idea to start this thread reading Max's and Qiaozhi's correspondence at PD forum)...

I think it's because the detector has the ability to display target ID. Different coils have different residual voltages (air test) and the soil causes a different loss in RX amplitude depending where you use it (ground test). These measurements are necessary to obtain an accurate target ID.

[ivconic]

I see. That explains the rest...
Ok...
Thank You (both of You) very much for answers!

Cheers!