How to improve my Surf PI 1.2 for a mission like this: Underwater search for iron/steel solely

[Loola]

Hi all!

I am hoping to get some advice on how to adjust/improve my Surf PI 1.2 for a mission like this:
Underwater search for iron/steel solely.
I have searched this forum without finding answers to this question.
Many are looking for quite the opposite, reject iron/steel .

I would like the detector to go as deep as possible (our lakes often have very deep silt) and be optimised for Iron/steel.
Small sized items will never be in my interest to find.
Our lakes contain very little or no trasch

I have a search coil with this specification: Diameter 18” / 45 cm. Ohm 0.95. uH 370.
Is this coil a good start, or should I go bigger?
I will use the detector while scuba diving, so there is practical limitations to coil size.

I have an oscilloscope, if that will be needed.

Kind regards,
Leif Lindgren

[waltr]

Tough to do any type of discrimination with that MD and actually with any PI MD.

If you can find a way to reject iron then it can reject all but iron.
Typical PI MDs give a strong response to iron (ferrous) and since iron is much more commonly found I don't think getting an occasional response from non-ferrous is going to be an issue.

[Qiaozhi]

If your mission is to search for "large" iron and steel objects, then simply set your main sample delay above (say) 50us, or maybe even higher. This will reject all smaller targets. A larger coil will also help in that respect, but would be a problem for diving use.

[kt315]

if your mission is to search for large... and with big coil.... so you need...

[green]

If your mission is to search for "large" iron and steel objects, then simply set your main sample delay above (say) 50us, or maybe even higher. This will reject all smaller targets. A larger coil will also help in that respect, but would be a problem for diving use.

Was curious about decay of some ferrous targets. Couldn't think of a large ferrous target that I could chart. Charted three targets and some California ground. Targets have a decay slope very close to the ground, would loose a lot of signal if ground balance was needed. Maybe a different Tx current profile would show something different. Charted two different coils to see if they would chart the same, slopes very close to the same(straight line on log-log chart).

[Loola]

kt315
Nice! Now you got me thinking .................. But no, I will start with a handheld detector.

[Loola]

green

Nice graph. Interesting for sure. A little over my head though. But I guess that your kind of knowledge is what is needed here. Thank you.

[Loola]

Qiaozhi

Okay, I will do adjustment to sample delay to see what changes it makes.
I do not have the opportunity to do it now, but in the near future I will.

Thank you.

[kt315]

I will do adjustment to sample delay
---
you may take a data from deepers. delta pulse has first sample delay width from 40 to 160us.
pulse width from 120 to 500us tuned.

[Loola]

Kt315

How do I adjust pulse width and specially an increase off it, on the Surf PI 1.2?
And what do you mean with ”tuned”?

Thanks for your info

[kt315]

bom bom bom. ITMD? did your read HH article?

'tuned' is if you CAN control the width operatively by a pot on your housing panel. ie not fixed.

[Ferric Toes]

I used to make a diver held detector called Aquatec. The pulse delay was set at 100uS and TX width 350uS. Many of these detectors were sold to the offshore industry to locate tools dropped from drilling platforms; capped off wellheads that were buried under sand waves in the North Sea; lost anchors and anchor chains; iron cannons and cannon balls; lost outboard motors etc etc. It would of course detect large non-ferrous items but nothing small. Also, longer delays make the detector less responsive to the surrounding sea water.
For pure ferrous only detection a diver held magnetometer is best.

Eric.

[kt315]

mine coil 1mx1m was esp-ly projected for seach in winter time and in summer time on boat drilling (you know this small resine fishers pumping boats).
write if you need more winter pics.

[Loola]

I used to make a diver held detector called Aquatec. The pulse delay was set at 100uS and TX width 350uS. Many of these detectors were sold to the offshore industry to locate tools dropped from drilling platforms; capped off wellheads that were buried under sand waves in the North Sea; lost anchors and anchor chains; iron cannons and cannon balls; lost outboard motors etc etc. It would of course detect large non-ferrous items but nothing small. Also, longer delays make the detector less responsive to the surrounding sea water.
For pure ferrous only detection a diver held magnetometer is best.

Eric.

Ferric Toes
This is for sure useful information. To hear it from someone who actually have worked with this. Happy, happy, happy, thank you very much.
As for pulse delay and TX width, I will try those numbers. But at this moment my lack of knowledge on how to adjust TX width on the Surf PI 1.2 keeps me from trying that.
About magnetometers, I have done some fruitless experiments with that. I to, think that this would be the preferred technique to use.
Do you know of any DIY project in this matter? Preferably a soldering kit.

[Loola]

bom bom bom. ITMD? did your read HH article?

'tuned' is if you CAN control the width operatively by a pot on your housing panel. ie not fixed.

Read the ITMD? No!
Can that be managed with the Surf PI 1.2?
If so, where and what to connect to the PCB?