Do you set a higher number or lower number to get a negative ground balance on the Equinox and X-Terra detectors? I have read with the X-Terra if it balances at a higher number it means the ground is more neutral.
'graybeard', please pardon my tardy reply, but Jeff, 'jmaclen', gave you the correct answer.
I don't know about how MInelab messes around with Ground Balance on other models, but I do know I wish I had GB capability on my two Vanquish 540's.
You asked specifically about the X-Terra series, and my handling of them goes back to their earliest introduction when they contacted me and provided an X-Terra 30
(factory preset) and X-Terra 50 which offered Ground Balance. I was then sent an X-Terra 70 when they were about ready and I preferred the X-Terra 70 over the X-Terra 50 for a few reasons, mainly because I could better fine-tune the GB compared with the X-T 50. The newer 505 and 705 are just some slightly changed models from their earlier siblings, and when I helped a Dealer friend of mine, who is a big Minelab Dealer, I did a lot of explaining and demonstrations for people to help them learn the 'backwards' Ground Balance of the X-Terra series.
With most detectors on the market, be it a Fisher F75 or F-19, Garrett AT Gold or AT Max, Makro Racer 2, Nokta FORS CoRe or Relic, Nokta / Makro Impact or Anfibio Multi, Teknetics T2 or Omega 8000, White's MXT Pro or MX-7, XP Deus or ORX, and the list could go on and on .... they produce a numeric Ground Phase read-out to reference the level of challenging ground mineralization. The higher the mineralization, the larger or greater the numeric read-out.
Most of the brands have a 'default' GB setting that is for higher mineralized environment, but the operator can use Automated GB or Manual GB and fine tune it for their search site. XP Deus and ORX have a high-mineralized default setting of '88' or '90.' The Nokta / Makro models, Teknetics T2 and some other also use a default GB of '90, while models like White's MXT Pro uses a default GB of '83.'
\Most of the places I hunt in Oregon, Nevada, Utah and a few other western states are rather mineralized and tha functional GB setting might run anywhere from '78', which is in he upper-end of the moderate ground mineral rang, up to '85' to '88' which is a higher-mineralized setting. So you'll note the higher mineralized ground is close to or just very slightly less than their default GB setting.
I also do some Coin Hunting in some urban environment s that have a moderate level of mineralization and the non-Minelab models will then reflect a GB read-out in the '40s' to maybe the mid-to-upper '60s'.
Thus, with MOST makes and models of metal detectors that use a numeric read-out, the lower the number, adjusting to the smaller numeric reading, signifies a lower mineralization level. If the GB number is a much larger number, the bigger or higher reading number, that's an indication the mineralization level is also a greater amount you are dealing with.
The X-Terra series, and perhaps the Equinox which I haven't manually tinkered with, are just the opposite. When I got my Minelab X0-Terra 50, I noticed right away it was goofy because I was living in one of the very mineralized areas, and the majority of my detectors feature manual GB control, although some also have an Automated
(bob the search coil technique) Ground Balance.
When it arrived I did some quick indoor evaluations with some test samples and playing with the Manual GB I set it at about '20'if I recall. Then I headed over to a renovation site and local park and checked the detector's response and using Pinpoint and just analyzing, it nulled out as I lowered the search coils from about 4" down to an inch of the ground. What does that suggest? That the GB was too negative and I needed to increase the GB setting.
With a 'normal' detector what would you do? Increase the control clockwise or to a higher
(numbered) setting to increase the GB to make it more positive. I did that, by increasing the GB to a larger number, but the result was a more negative GB setting! I then recued the numeric read-out for the GB, adjusting to a smaller or lower numerical number and checked as I worked my way down. The GB for that mineralized site was '12.'
So I learned right then the day I got the X-Terra 50, and later the '70' and later used the '705,' that Minelab has a backwards way of doing some things. The smaller the number, the more positive or more mineralized the ground, and the larger then number, the less mineralized the ground.
Both the Equinox 800 and X-Terra 705 Owner Manuals do a very poor job of describing Ground Balance or make a correct reference to what is positive or negative.
Sorry for the long reply, but if you're using an X-Terra and GB close to 'spot-on' but want to manually adjust to a slightly Negative setting, then select a larger or increased number. Example: If you have an Automated GB setting of let's say '18' and you want to adjust for a slightly Negative GB, just increase the GB number to '19' or '20' but do not over-compensate.
Monte