TDI Ground Balance On Versus Ground Balance Off

[Steve Herschbach]

On 5/10/2019 at 2:53 AM, auminesweeper said:

3 For some reason my SL saw things deeper in Air Tests with the GB On, which I decided was a good thing if a person was operating it in bad ground

I have never experienced this on any version of the TDI. The “ground balance off” mode should be the pure unfiltered signal. Engaging the ground balance engages a filter which reduces the air test results in a properly functioning TDI. The only reason the TDI has the ability to turn off the ground balance is to get this extra depth back, as has been highlighted in numerous online posts and videos. The manual says air test depth increases with the ground balance shut off. What you are saying simply makes no sense from a pure electronics standpoint and how the ground balance functions. If a TDI loses depth in air tests when the ground balance is shut off then in my opinion it is not working properly.

 

[auminesweeper]

Well Steve I did wonder if it was working properly because I never got the results others got out of their SL's, and not once did I ever get it to see bits weighing 0.17grams or less which diggerbobs SL clearly did, So I don't have the answers as to what or why because mine could not do those things, On big Items it was extremely deep but for what I wanted it for a VLF was the better option,

I wish I had sent it back for a tune up but life took over time slipped by so I gave up and forgot about it as my health declined, Still they are a very good machine and for certain tasks and they are a great all rounder.

 

[Jim in Idaho]

The "deeper with GB on" is true with the SL, but apparently not the others. Auminesweeper is right, and my tests also bore it out. Regardless of the GB setting, as long as it's "on" the air tests show a definite improvement. Reg S. and I discussed this at length, and didn't come to any conclusions as to why, though Reg mentioned the GB circuit on the SL is different than the other TDI's.

Jim

[auminesweeper]

Well Jim It just about drove me nutz, because every thing people said did not happen the way they said, And I found it to be better with the GB On,  It worked like a charm but just opposite the my TDI Pro, Must admit I do love being able to select low or high conductors, Not quite discrimination but it sure cuts down in the junk, Great machines they just need hotter coils is all.

[Jim in Idaho]

John, I couldn't agree more. I'd be happy with a TDI SL that ran from a 21v 5-cell Li-ion battery pack.

Maybe with Reg Sniff's filter capacitor modification to ice the cake! Combine that with a Nugget Finder

12" round, spiral wound coil and you'd have a lightweight, really capable PI.

Jim

[Mark Gillespie]

I have a couple videos on SL air test and hope to do some other comparative videos soon.

 

[Mark Gillespie]

White's TDI SL, manufactured 2014, pulse delay 10
Air Test	Freshly Charged Battery Pack
			GB OFF		GB OFF		GB ON MINIMUM		GB ON MAXIMUM
			GAIN MAX		GAIN 8		GAIN MAX		GAIN 8
7 1/2" Dual Field Coil			11"		11"		11"		11"
Super Pulse 350			11 1/2"		11 1/2"		11 1/2"		11 1/2"
12" Dual Field Coil			13"		13"		13"		13"
To be honest I'm kind of disappointed
Very smooth threshold In ground performance may be different

[auminesweeper]

4 minutes ago, Mark Gillespie said:

White's TDI SL, manufactured 2014, pulse delay 10
Air Test	Freshly Charged Battery Pack
			GB OFF		GB OFF		GB ON MINIMUM		GB ON MAXIMUM
			GAIN MAX		GAIN 8		GAIN MAX		GAIN 8
7 1/2" Dual Field Coil			7 1/2"		7 1/2"		7 1/2"		7 1/2"
Super Pulse 350			11 1/2"		11 1/2"		11 1/2"		11 1/2"
12" Dual Field Coil			13"		13"		13"		13"
To be honest I'm kind of disappointed
Very smooth threshold In ground performance may be different

When you air test a PI you can listen to it's maximum distance where it goes woo woo or just listen for a slight break in the threshold, In quiet non junky sites you can use the break in threshold way of detecting to gain maximum depth out of the machine, I also use this method when using my VLF because it can change depth from inches to Feet,  IE where a coin might bleep at 14/15 inches with some coins using just the threshold can add between 4 to 10" depending on the coil being used, of coarse in ground depths would be as little as 20 to 25% of those figures but it is just another way of detecting and requires a massive load of concentration.

[Mark Gillespie]

These test were with a nickel approaching the coil, not simulating an actual sweep, right to left.

I was listening for a slight increase in threshold.

Still, I thought it did better than this.

An 18 volt battery pack my help.

[auminesweeper]

Well Air testing a PI although it's fun and informative, Many believe that PI's actually do better when a target is in the ground because when a target is in the ground a PI sort of electrifies the Ground/Target combo and it measures the response time hence the name TDI and depending on the moisture/ ground makeup can add to the depth although a PI does not like soaked ground it does do well is the ground is slightly damp, Where as a VLF is good in very damp ground but not soaking and they start to loose depth in very dry ground,.

The depth of a machine can only be seen on genuine target recovery, I had a 3500 that air tested quite well yet in mild ground in 2 spots at the same location I found a VLF seemed to be just as deep.

This is not a dig at anyone because I made this very mistake. "But".

The trouble is many folks see a PI as a magic stick like some Super deep  all seeing eye but the truth is they are not, All they do is give normal good detection depths in difficult ground conditions where a VLF Suffers, In normal conditions a Sovereign GT with a 10" coil and a GP3500 with an 11" DD have fairly even depths, and in the same soils the MXT with the 12" Concentric coil will match or even beat a TDI when it comes to all out depth, I actually saw someone do that with one of the first MXT's when I gave them a 12" coil to try out and he only had the Gain up around 6 to 7, The only honest to God reason to buy a PI machine is if you have bad ground to detect, Again this is not directed at anyone but these are a couple of examples of what I found by owning and buying the above machines,

Take a PI and a VLF in to hot prospecting gold baring land and a PI will whoop the VLF all day long.

Don't be down about your air test results because in bad ground or at the beach a PI will do those depths all day long where as a VLF will be lucky to get 50% of those depths but on a good day or the right soil conditions a VLF will surprize a person,  As to which is better or deeper is more of a case of matching the machine to the soil conditions.

 

J.