Ground Balance

[Danno]

Hi,
I am trying to get my head around ground balance on a VLF. Do most detectors just balance (or set the null) to a specific ground phase VDI or is it more of a notch setting where a group of VDI are nulled out? Reading some material on Whites detectors it says that the ground balance null can wrap around to the high positive VDI loosing sensitivity in this area, this makes me think it's a notch of several VDI?

Taking the Whites scale for an example if the ground was say -87 does it just null -87 or is it a notch between -90 to -87 or say -90 to -84 as a rough guide?

Am I also right in saying that if you put a positive offset onto the ground balance it will make the balance point essentially more negative so that it doesn't null on a positive ID near the actual ground balance point, making sensitivity to small targets better? I am thinking detectors that run with a positive offset will run a little "sparkier" rather than silent?

I am also assuming the nulling of the threshold to read ground conditions only really works in non motion modes, the threshold in motion mode is something else?

Thanks and hope that makes sense?

[kt315]

i had noticed if i answer then George and Carl begin answer after me. why not BEFORE me??
do your comments and do not wait my comments.

[Danno]

i had noticed if i answer then George and Carl begin answer after me. why not BEFORE me??
do your comments and do not wait my comments.

I don't understand your reply, nobody has replied yet?

[kt315]

yes. initialization.

[Qiaozhi]

Have you read "Inside the METAL DETECTOR"?
It will answer a lot of your basic questions ->
https://www.amazon.co.uk/Inside-Meta...s%2C144&sr=8-3

[dbanner]

i had noticed if i answer then George and Carl begin answer after me. why not BEFORE me??
do your comments and do not wait my comments.

And true to form, Qiaozhi has replied....after you. You have become the peanut butter between a good question and a good answer. The whole thing, when taken in totality, makes for a very sumptuous sandwich.
Danno, here is an article attributed to George Payne:

[Carl-NC]

You have a lot of questions that have very involved answers. I don't have time for the details but will start with this...

Hi,
I am trying to get my head around ground balance on a VLF. Do most detectors just balance (or set the null) to a specific ground phase VDI or is it more of a notch setting where a group of VDI are nulled out? Reading some material on Whites detectors it says that the ground balance null can wrap around to the high positive VDI loosing sensitivity in this area, this makes me think it's a notch of several VDI?

Ground balance works by adjusting the phase of the demods until the resistive demod has a null response to ground (ferrite). It is a notch response so if the GB point is mis-adjusted you will hear ground but will notch out something else. Since ferrite is at the extreme end of the range, it is possible to push it past "absolute zero" and cause a wrap-around effect on high silver.

Taking the Whites scale for an example if the ground was say -87 does it just null -87 or is it a notch between -90 to -87 or say -90 to -84 as a rough guide?

You would get an exact null at -87 and progressively worse as soon as you move away from -87.

Am I also right in saying that if you put a positive offset onto the ground balance it will make the balance point essentially more negative so that it doesn't null on a positive ID near the actual ground balance point, making sensitivity to small targets better? I am thinking detectors that run with a positive offset will run a little "sparkier" rather than silent?

Yes, you can offset the GB slightly so that ground gives a slightly positive signal (as you lower the coil), this will help reduce masking. There are really no target IDs near the GB point, but deep targets that are right at the threshold of detectability don't have enough signal to generate an ID, and those can get masked if the GB isn't perfect. A slightly positive GB will prevent this.

I am also assuming the nulling of the threshold to read ground conditions only really works in non motion modes, the threshold in motion mode is something else?

Depends on the machine. Some motion mode designs are threshold-based where you can easily hear the ground. Some motion modes are silent search where you can't.