Chart for pulse delay settings in saltwater????

[Anonymous]

On a previous post Mr. Bill stated, "Diving PI detectors are around 30uS. as a starting point. Of course this does not make them very sensitive to small items." My question is, has anyone ever put together a chart showing an acceptable MINIMUM pulse delay for a range of saltwater depth? For example, from 0-10 feet of saltwater 20uS would work without much interference, at 10-15 feet of seawater 25uS, etc... How hard would it be to develope such a chart?
I am a shipwreck salvor here in Florida and one day I may be diving in 30 feet of water (usually not any deeper)and the next day be in just 8 feet of water. I would like to be able to find thin gold rings and chains. Are there submersible PI units with adjustable pulse delay that would cover a whole range of saltwater depths?
Thanks in advance for your responses,
Scallywag

 

[Anonymous]

Thats an interesting thought. I have no experience with PI in saltwater but I always assumed that the pulse delay would be adjusted as to whether it was in saltwater or not. Your thinking is that how deep the water is affects the minimum pulse delay you could use. I hope someone experienced will answer your question.
Fred

 

[Anonymous]

I am working on a circuit that tracks the end of the damped pulse and hopefully will minimize delay down to a few micro seconds. Will post on this board when I get it working. Karl

 

[Anonymous]

Any PI with a pulse delay that is adjustable within the ranges you mentioned will work.
The Aquastar has a minimum delay at 10uS. As one goes into deeper water, slight adjustments will be needed, but it won't be much ???
30 foot depth should not present any problem.
The Headhunter PI's minimum is at 15uS., and I haven't heard of the need of much adjusting with it at normal shallow SCUBA ranges.
Mr. Bill