Question on ground balance

[2wheeldevil]

This is for you high tech guys:

I tested this Phonak hearing aid with a size 13 battery in it.
Used an At Pro, small 5 x 8 coil, with the following settings, pro-zero, full sens and automatic GB at 80. At these settings I got only a blip from the detector and no numbers on the screen.
I just increased the GB to 99 and I got a good grunt sound and a reading of 03 on the screen. I then lowered the GB to 50 and got a good grunt but the numbers jumped from 01 to 03.

I do not really understand ground balance, so could somebody explain to me what is happening here.

 

[John-Edmonton]

You did hold the ground balance button down while pumping the coil up and down until the numbers stabilized? Did you re set the detector with the sniper coil? Each time you switch coils, you must reset the machine, by holding down the on switch until you hear a double beep. My machine ground balances 87 - 90 in my soil.

 

[BLStone68]

If I read that right you first want to understand what ground balance is.
This video below he tries to explain ground balance. I hope this helps

He shows just how much metal particles can be in the ground and I was amazed how much he pulled just off the surface.

[video]https://www.youtube.com/watch?v=r_Ja5ixIm1c[/video]

 

[John-Edmonton]

That's an oldie! On the Garrett ATS, you don't have a switch to reset the audio/threshold, as it is done automatically!

 

[2wheeldevil]

I retried the whole thing over again. Cleaned up the coil and coil cover and put in a new set of batteries in the detector. I automatically GB and manually GR and came up with an 83 for GB.
Basically got the same results.
With the 83 GR I get a blip and one bar showing on the screen and no numbers.
My real question, why am I getting better results on detecting this hearing aid when I increase or decrease the GB from the normal GB for the ground I am working on? I also did a hard reset after each setting on the GB.

 

[BLStone68]

I am guessing the hearing aid has different types of metal in it like Stainless steal, Zinc, and copper.
Now if these metals are the same or close to the same as the metals in the ground, this could be why your results are changing with the GB.
I am new so this is all just a guess on my part.

I would try the same test but use a coin or something that's just one type of metal like nuts, bolts, and washers.

 

[John-Edmonton]

You are testing an object with multiple materials in it ie. battery, probably copper, steel screws, metal frame, and some solder inside along with some gold on the circuitry. And to compliment things further, all the targets are very small compared with coin sized objects, which all metal detectors are tuned to for the most accuracy. When you increased the ground balance to 99, you actually made the detector more sensitive to lower conductors, resulting in the detector picking up some metal components inside and the battery.

When you lowered the ground balance to 50, you made the unit hotter on high conductors such as silver and copper. And.....the amount of copper is very minimum in those hearing aids, and the AT Pro struggled with trying to pick those higher conductors. And, there was probably some masking also going on with all those different materials sharing such a small area.

 

[2wheeldevil]

You guys are correct I think. Just testing the number 13 battery I get readings in 30s, 40s & 50s. Just checking the hearing aid without the battery is just barely a blip.

 

[Grunter]

When GB turn on the machine and before you make any other adjustments pump the coil unit it goes almost silent then make your adjustments.IMHO