Possible reson for depth discrepancies with the Teknetics ETP..

I decided this week to test the GB setting on my ETP. I pushed in the pinpoint button and while lowering my coil to the ground, the detector strted sounding off at 6" above the ground!! This is way too positive !

Another indication of too positive GB is that a Half Dollar doesn't respond as strongly as a quarter.

I'd like to get the GB down to 3" or less above the ground. I understand there is a pot inside for B that is adjustable.

You didn't tell us at what height you held the coil when you pressed the pinpoint button. The height at which 'sounding off' occurs depends on the ground phase, ground strength, and how much ground pickup you had when pressing the pinpoint button. So it's not a particularly useful / informative test.
I guess one test you might perform is the machine's response to a ferrite rod. This has 'zero phase angle', and should match the detectors setting. Bringing a ferrite rod end-on towards the centre of the coil whilst in pinpoint mode should give no significant response. Bring the rod to within 6 inches of the coil, this gives a pickup level similar to moderate ground.

Pimento Wrote:
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> You didn't tell us at what height you held the
> coil when you pressed the pinpoint button. The
> height at which 'sounding off' occurs depends on
> the ground phase, ground strength, and how much
> ground pickup you had when pressing the pinpoint
> button. So it's not a particularly useful /
> informative test.
> I guess one test you might perform is the
> machine's response to a ferrite rod. This has
> 'zero phase angle', and should match the detectors
> setting. Bringing a ferrite rod end-on towards the
> centre of the coil whilst in pinpoint mode should
> give no significant response. Bring the rod to
> within 6 inches of the coil, this gives a pickup
> level similar to moderate ground.

Started about 2 feet above ground. Unless you have invented a new way to ground balance, that's the standard height I've always used. Positive is positive. the only question is how much the GB trimmer affects the disc mode. I'll find out soon enough.

I've had folks tell me that the GB on various units vary wildly.

I had a Delta 4000, that worked supper on the beach. Got rid it it and later got a differnt one and could not hunt the sand. The first one worked good in the wet sand and edge of water. Wish i had the first one back.

Quote:"Unless you have invented a new way to ground balance"
I haven't invented anything, it's simply that several modern machines, (The T2 / F75 as an example) will perform a computerised ground-grab. This requires the operator to bob the coil from 1" to 8" up and down. This might lead you to think that at 8 inches above the ground, the coils ground pickup is minimal. But it's not - go to 18+ inches and you're in the 'very low' pickup zone.
Regardless, doing what you've done doesn't sound out of the ordinary. Without sophisticated measurements, there's no easy way to determine if you've got ground with a sigificant phase lag, or ground with a strong pickup, or some combination of the two. If you had a machine like an F75, you could get some ideas about your ground, based on Ground Balance value and Fe3O4 meter readings. But it probably wouldn't help much...
On this forum (and Geotech1 too) there's an "adjustable GB" mod project, I'll try and find it.

Pimento Wrote:
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> Quote:"Unless you have invented a new way to
> ground balance"
> I haven't invented anything, it's simply that
> several modern machines, (The T2 / F75 as an
> example) will perform a computerised ground-grab.
> This requires the operator to bob the coil from 1"
> to 8" up and down. This might lead you to think
> that at 8 inches above the ground, the coils
> ground pickup is minimal. But it's not - go to 18+
> inches and you're in the 'very low' pickup zone.
> Regardless, doing what you've done doesn't sound
> out of the ordinary. Without sophisticated
> measurements, there's no easy way to determine if
> you've got ground with a sigificant phase lag, or
> ground with a strong pickup, or some combination
> of the two. If you had a machine like an F75, you
> could get some ideas about your ground, based on
> Ground Balance value and Fe3O4 meter readings. But
> it probably wouldn't help much...
> On this forum (and Geotech1 too) there's an
> "adjustable GB" mod project, I'll try and find it.

I understand. However, I've tested other detectors with no GB or 'fixed' GB and they were much closer..maybe positive starting 2 inches above the ground. Ground here is avg to milder than avg.

Here's some links to Paul's (California) mods :
[compass-metal-detector-forum.548136.n2.nabble.com]
[www.dankowskidetectors.com]

Pimento Wrote:
-------------------------------------------------------
> Here's some links to Paul's (California) mods :
> [compass-metal-detector-forum.548136.n2.nabb]
> le.com/Recently-picked-up-a-EuroTek-Pro-td7589834.
> html
> [www.dankowskidetectors.com]
> .php?2,46548,46593

Thanks. I'll just try to adjust the pot for a better GB.

Got the GB to sound off to only 3" above the ground. Much better than before. Appears to give me at least an inch or more added depth on my buried targets. May do some detecting tomorrow.

you can do a ground mod on the machine or just open it up and set it for your dirt if your dirt does not change alot.....Yet your target i.d.s will move to new readings so keep that in mind...

Keith Southern Wrote:
-------------------------------------------------------
> you can do a ground mod on the machine or just
> open it up and set it for your dirt if your dirt
> does not change alot.....Yet your target i.d.s
> will move to new readings so keep that in mind...

Yea, I adjusted it to where it starts sounding off 2"-3" above the ground instead of 6" Appears to have a bit better depth. The trimmer pot is very touchy. Didn't want to mess with it too much.