Ground Balance

[Carl-NC]

Carl, I forgot to ask, the EF sample is that short for Earth Field ?

Yup

[Mick-GD]

Carl, I forgot to ask, the EF sample is that short for Earth Field ?



Thanks

[Mick-GD]

Hi Carl, thanks for the reply, i'll see if I can implement something similar and see what happens. When I have it finished I'll post some results and info about how i've set it up.



Thanks
Mick-GD

[Carl-NC]

Just the opposite... mineralization decays rather quickly. Here is how the TDI does it (this is all public knowledge, so NBD):

Turn TX on for 100us
Shut off, enter flyback
Wait 10us, take the Target sample
After the end of the Target sample, wait a short delay, take the GB sample
After the end of the GB sample, wait a long delay, take the two EF samples
Use a diff integrator to subtract Target-EF1
Use another diff integrator to subtract GB-EF2
Subtract A1*(Target-EF1) - A2*(GB-EF2)
Adjust A2 for ground balance

In TDI, all the samples have identical widths. I could tell you what to use, but you would learn more trying a range of settings, say 5us up to 25us. The delay between Target and GB samples as well; try 5us to 25us. Technically, this same delay should be used to space the two EF samples. The spacing between GB and EF1 samples should be 50us or more.

There are other ways to do GB, even simpler, but this one has particular advantages that TDI uses to produce distinct audio responses.

- Carl

[Mick-GD]

Hi all, I've been building a version of the hammerhead PI with some changes including a second amp in the frontend and a Atmega8 to run the timing of the TX and both sample channels. This section is working correctly.

What I want to do is add another sample channel for ground balance because the ground where I want to use it is highly mineralized the problem is I can't seem to find much information on ways to implement this type of mod.


My first idea was to set the Atmega8 up to transmit 3 TX pulses at about 100us each with 100us receive with between each and sample two times for each receive time one for target and one for earth field cancel. Then have a receive period after the third TX pulse of say 300us and sample once during this time for ground balance, then amplify and invert and feed back into the main channel output.

Would this idea work and does the ground mineralization take a long time to decay ?


Thanks
Mick_GD