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What Are Timings?


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16 minutes ago, Valens Legacy said:

drink after digging for an hour to reach that buried aluminum can

Hmmmm, I know that story well . 😁

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  • The title was changed to What Are Timings?

When you say that "different targets decay at different rates" I assume this is based on the size of the target more than what metal the target is made of? If not, it seems to me that with some creative electronics and programming , you could come up with a discriminating PI. You also stated that Minelab came up with the dual channel PI. I always thought that White's did that. Interesting.

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Just to clarify for people who don't know what dual channel and single channel PI is all about. Early PI did not ground balance per se, they relied on the pulse delay to take out the ground and saltwater. This was insufficient however for real bad ground commonly encountered by gold prospectors. I think it was Eric Foster who came up with the first widely sold PI with an actual ground balance. A simple knob as seen on the TDI which was originated in Erics Goldscan models.

Unfortunately a PI ground balance setting creates a huge "hole" where certain targets get eliminated at common ground balance settings. Like 1/4 oz nuggets and certain gold rings for example. Bruce Candy came up with the idea of having two ground balances, each one creating a "hole" at different locations on the scale. The two "channels" as he called them were compared, and if one channel lost an item in the hole the other found it, and by comparing the two channels properly targets missed by single channel systems were revealed. This is all explained by Brent Weaver in the first link I gave in the last post.

Single channel single ground balance PI creates two classes of targets based on the ground balance setting. Dual channel can create three classes.

The early Minelabs actually has two separate ground balance controls that separates them from machines like the TDI. Then Minelab and Garrett learned to manipulate both channels simultaneously for better results. Yet the ability to manipulate the dual channels separately was lost, and I may have to pick up an old SD2100 to be able to play more directly with this stuff.

Again, this is all explained in much greater detail at the second link I provided above.

From the SD2100 manual:

minelab-sd2100-dual-channel-ground-balance.jpg

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