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A Note On Saltwater Detector Performance


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Great read Steve......all PI and potential PI users must understand this concept.

Also, moving saltwater in shallow depths can be much more of a challenge than calm water in deeper depths. Eric Foster has mentioned somewhere in an old post that generally the deeper the saltwater then the bigger the signal will be generated and that is why diving PI detectors such as the Aquapulse AQ1B have a 40uS starting delay but after about 20 to 30 feet of salt water the salt signal levels off...that is to say, it is no worse deeper than that.

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50 minutes ago, phrunt said:

It is interesting and different parts of the world have different salinity levels too, cooler water tends to be less salty.  The polar regions are unable to be salt mapped as they can't see the salt through the ice so they're just white.  So detectors should in theory work slightly better in different parts of the world. 

mappingsalty.thumb.jpg.fe59becb142cc95745bfbd0ab8ff0818.jpg

The numbers to the right are the salinity, 32 grams per kilogram being the lowest, and 38 the highest.  The deep ocean has a lot less salt than the surface, warmer climates have more partly due to evaporation.

Thanks for the post Steve, I now have a much better understanding of the issue with salt and detectors.

Thanks to this map I confirmed my doubts!

Regardless of a reduced gain, of a turned off GB and really slow coil movements, there's no way for me to keep my Tdi usable without 17uS delay minimum.

I'm in the more higher salt concentration area!

In this way, (underwater), forget tiny thin stuff, forget depth and forget to be effective, spending time in over digging activity.

I'm also convinced that a smaller coil will change almost nothing to this machine reactions, unless a lower magnetic field impact.

This is where I hope the AQ can make a difference. If I only will be able with it to keep 60 to 70% sensitivity and 11.5uS delay should be fine enough.

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Thanks Steve, 

That has to be one of the clearest layman explanations I've seen on PI's!  

   So what do you think is going to be the "Special Sauce" for the AQ to be deeper than your previous PI experiences?? If any?? Other than what you've stated previously!👍👍

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I read this article a couple of times and it really helped my understanding of the effects of salt water on detector performance- thanks! It also made me think about all the targets that I've missed over the years when the Dual Field with its 15us pulse delay was my primary beach detector. 😞

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1 hour ago, Joe D. said:

Thanks Steve, 

That has to be one of the clearest layman explanations I've seen on PI's!  

   So what do you think is going to be the "Special Sauce" for the AQ to be deeper than your previous PI experiences?? If any?? Other than what you've stated previously!👍👍

“Deeper“ is a one dimensional way of looking at metal detecting. My goal is to be more efficient and to locate more “good” targets per hour of metal detecting. The Fisher Impulse AQ offers great ergonomics, superb audio, an advanced discrimination system (for a PI), allowing focus on ring type targets, and as much power as the hunting environment will allow. It’s not just “more depth”, though the AQ has as much as is possible, but the total package that matters to me. When it comes to the total package, including depth, the Impulse AQ delivers. 👍🏼

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Sorry Steve,

I ment "depth" in a more generic term than i may have stated! I get that the AQ is a more "focused  detector" than other PI's before it! I understand that there is more to detecting than "raw depth" onto itself!  Hence the intent to split into several specific models! You've done the "dig everything" routine, and are acutely aware of where you would like to focus!

I, myself have never used a PI, and am considering weather my beach detecting would warrant the expense to purchase the AQ, or another more generic "dig it all" PI!  I still love finding coins, as well as jewelry, and other metal targets; especially on the Treasure Coast! The AQ is shaping up to be an awesome addition to a stable of PI's, but I'll probably only be able to make that "one" purchase into that realm, for a long time forward! So i am just a student, for the time being!👍👍

 

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2 hours ago, Compass said:

I read this article a couple of times and it really helped my understanding of the effects of salt water on detector performance- thanks! It also made me think about all the targets that I've missed over the years when the Dual Field with its 15us pulse delay was my primary beach detector. 😞

Actually, if You're able to keep 15uS and to hear a stable noisefree treshold with the 12'' dual field, You're doing pretty good.

I mean, I (air) tested with higher delay rings of various shape and weight, whithout big signal difference till 25uS!..

In saltwater however You'll find Yourself to do a detuning, to use in the right way the machine unless You want to fight with boring noise.

So the trade is between stability and sensitivity / depth on small stuff...I've seen gold chains captured underwater with Your machine, but the clasp was the reason!

There's a point few people think about...Depth means also blind machines to environment's created noise and this thing almost doesn't exist unluckily...

I'm a vlf user prevalently, and when I need depth, I go back on the same place with the PI to double check for less relevant things in terms of urgency...

When a time window is open and I need to be fast, there's no way my Tdi can be the first weapon of choice...I ended up to quit with the idea to use the GB turned on, to obtain sound discrimination..The only way to use it efficiently is like a straight PI with GB off, otherwise loosing half of depth I can do the same with a CTX and leaving (not so much) deep stuff in a lot less time too. 

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Basically I wanted to call it AQUAMANTA and not IMPULSE, but I had no choice.
There is as much commonalities between a potato and a ford raptor V8, as between a 1985 IMPULSE and an AQUAMANTA ... Smiley Main sur la bouche U+1F92D

I wanted us to forget all notion of PI, because metal masking is very powerful on AQ.
It is so advanced that in the years to come masking will seem to be confused with the discrimination of a multi-frequency detector....

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Thanks Goldskulldiver,  I used to think that the Dual Field had a somewhat stable, noise-free threshold. It is pretty stable but compared with the threshold of the Beachhunter it is a bit noisy which probably prevented me from hearing some weaker signals.

 

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