The Sand Shark's Pulse Delay

[midas]

So, other than insulting me and questioning my knowlrdge base and experience, I noticed that not one of you actually disputed my original post. Is that because it is factual and you can't?

Surely that is the reason.

Just out of curiosity, how many of you think this whole metal detecting thing is rocket science?

I think it's too easy.

Seriously, It takes about 50-hours for the average person to feel comfortable on most machines, although I would say the Minelab GPX probably requires more like 200-hours.

Reading a beach took me about 5-minutes to get down, just like it would anybody else that had a good teacher (in my case a Navy SEAL).

Reading the mountains and learning the geology of gold prospecting is many times more difficult

That is for sure! I actually apply some of the rules of gold prospecting to detecting. Gold moves in water. Figure out where it moves to and...

I do get a chuckle out of the "Core-Four" here that can't stand me because I won't bend to their "superior experience and knowledge."

The core four have experience and knowledge? They are more like comedians!

...

 

[Dig-on]

I have no knowledge on PI, but get a kick out of canslaw with his copy and paste message to Terry

 

[Jason in Enid]

So, other than insulting me and questioning my knowlrdge base and experience, I noticed that not one of you actually disputed my original post. Is that because it is factual and you can't?

Dude, what the hell is your problem? You really are just trying to create useless drama. I am starting to lose respect for anything you write.

 

[CanSlaw]

I have no knowledge on PI, but get a kick out of canslaw with his copy and paste message to Terry

Maybe he'll get the message...I hope

 

[imalookin2]

Whoever made a claim that shorter pulse delays lead to more depth lacks an understanding of physics, geophysics and electronics.

Having said that, a detector capable of stably operating at shorter pulse delays will, everything else being equal, be more sensitive to small gold items and other so called "low conductors". Target signals are spread in time from the transmit pulse shut off. The signals will reach a peak sometime after the transmit pulse is turned off and this time is given by the geometric shape of the target, its mass and its admittance (a vector quantity combining its conductance and reactance). The signals from low conductors (including ground mineralization) are the first ones to decay after the transmit pulse is turned off. High conductors --such as silver-- peak later and will hang around a lot longer because their high conductivity do a better job of supporting Eddy currents. Ideally, for maximum pickup, we would like the detector's sampling delay to not happen after the target's signal has totally decayed. One could envision the delay time acting as a sort of discriminator, progressively discriminating out lower conductors as we increase the delay time.

Now, we can't start sampling immediately after removing the transmit pulse. Inductors (which is what the coil is) resist an instantaneous change in current flowing through them and will respond with a very large transient voltage spike, trying to keep the current through them flowing. During this voltage spike the detector can't sample a think, it is blinded by said transient.

We may ask what determines the length of time this transient condition exists. Although there are things an engineer can do to minimize the length of time the transient takes e.g. clamping diodes, damping resistors, etc., the coil's inductance and parasitic capacitance play a large role. For depth and reception sensitivity, we want a large inductance, but how large is limited by things like coil wiring resistance, power source, target pulse repetition rate, etc. Parasitic capacitance is something we can do without. Certainly the coil's self resonant frequency needs to be dealt with, but in general, a larger than necessary capacitance is undesirable and may lengthen the time at which the detector is able to sample. In this regard it should be noted that --for the same inductance value-- a coil made from a spiral PCB trace will have a significantly larger parasitic capacitance than a well designed wire coil. This is plain physics and it's due to the much higher dielectric constant µr of the PCB substrate (usually an FR4 type copper clad material), compared to enameled wire and air as the dielectric. A detector with a PCB coil can not in general be used at lower sampling delay values as one made with a well engineered wire coil. It does however have a cost advantage as PCB spiral coils can be manufactured in a batch process and each unit has a near identical behavior, cutting down on manual tuning.

Wether a particular ground/gain combination allows the delay to be set at 10µs is immaterial. It could well allow a delay of 15µs and pick up a small gold item that may not be "seen" by a detector with a longer delay, simply because the signal has peaked and has practically decayed to nothing before the longer delay machine gets to sample the signal. Perhaps this is the reason why you may have heard some people say the shorter delay machines go deeper?

As you said, pulse delay is but one parameter of a machine's performance. Filtering, good low noise amplifiers on the receive side, coil power are also important, as are others not even mentioned.

This is the best description of pulse delay and after reading it carefully I DO understand what you wrote. Thanks!!!!

I now see why certain delay times are important so the machine can read the target before the pulse decays completely and no longer returnable. Knowing the decay rate of a specific target (gold) then being able to tune the delay for the best effect on that conductor is what pulse delay is all about. (right?) Terry, please take a vacation out to your "business" prospecting for gold and leave the laptop in NJ. Drink water.

 

[Crumble]

Terry,

Look at my video, about halfway through where I turn the pulse delay up from 10uS (minimum), to 25uS (setting of 3). Then tell me it doesn't effect depth/sensitivity.

I run minimum pulse delay everywhere, on my super hot southern california ground, in the water also.

You're so full of sh%$, just stop, just making yourself look stupid.

 

[Rudy]

Great post Rudy. So, did you see a factual problem with my original post in this thread?

I was trying to be impartial and non controversial in my explanation. Apparently I should have been blunter?

Yes, you kind of ignored the 12µs interval between your"unstable" 10µs delay and the 22µs minimum delay of the SandShark. A lot of gold goodies can be found in the 12 to 18µs or so delay interval that is forbidden to the SandShark.

I also should also have said that if the sampling doesn't start before the target signal has fully collapsed into the noise floor, no amount of fancy filtering or special amplifiers are going to bring the signal back. You need good filters and good, low noise amplifiers, but you need to have a pulse delay small enough to let you sample the signal while it's still there.

Hope this doesn't change your opinion of my original post.

 

[imalookin2]

I was trying to be impartial and non controversial in my explanation. Apparently I should have been blunter?

Yes, you kind of ignored the 12µs interval between your"unstable" 10µs delay and the 22µs minimum delay of the SandShark. A lot of gold goodies can be found in the 12 to 18µs or so delay interval that is forbidden to the SandShark.

I also should also have said that if the sampling doesn't start before the target signal has fully collapsed into the noise floor, no amount of fancy filtering or special amplifiers are going to bring the signal back. You need good filters and good, low noise amplifiers, but you need to have a pulse delay small enough to let you sample the signal while it's still there.

Hope this doesn't change your opinion of my original post.

You did say this. That is what turned on the light bulb in my head. I understand now. Thank you Rudy!

 

[Rudy]

You did say this. That is what turned on the light bulb in my head. I understand now. Thank you Rudy!

You are very welcome.

 

[Crumble]

Rudy, I love your in depth explanations of the technical side of how metal detectors work! I take it you are an electrical engineer by trade?

I'm in college at the moment studying electrical engineering, but still haven't gotten to the high level engineering classes. I hope to have the vast amount of knowledge you have one day...

 

[Rudy]

Rudy, I love your in depth explanations of the technical side of how metal detectors work! I take it you are an electrical engineer by trade?

I'm in college at the moment studying electrical engineering, but still haven't gotten to the high level engineering classes. I hope to have the vast amount of knowledge you have one day...

Thanks. Was an engineer is the operative word. I was a EE design engineer, rose to management position, in the end running a department of 22 engineers (hardware and software) and 7 technicians. I couldn't take it. Spent most of my time in meetings and arguing with the finance department over how much money we spent or didn't as the case might be. So, I moved to marketing, where I could define the products we needed to design and build without the headaches or directly running a large group. I got to do more engineering in marketing than I did while I was an engineering manager.

Now I am retired.

 

[OBN]

Was an engineer is the operative word. I was a EE design engineer, rose to management position, in the end running a department of 22 engineers (hardware and software) and 7 technicians. I couldn't take it. Spent most of my time in meetings and arguing with the finance department over how much money we spent or didn't as the case might be.

. That's funny..I get the same line from Greg Diablo about his engineer mgr position...Long days, most weekends to stay on schedule, or try.... all those places must be the same. Good you are retired!!

 

[Rudy]

. That's funny..I get the same line from Greg Diablo about his engineer mgr position...Long days, most weekends to stay on schedule, or try.... all those places must be the same. Good you are retired!!

 

[trsrseeker]

Great posts Rudy and Crumble - thank you!

 

[Cfmct]

So, other than insulting me and questioning my knowlrdge base and experience, I noticed that not one of you actually disputed my original post. Is that because it is factual and you can't?

Just out of curiosity, how many of you think this whole metal detecting thing is rocket science? Seriously, It takes about 50-hours for the average person to feel comfortable on most machines, although I would say the Minelab GPX probably requires more like 200-hours.

Reading a beach took me about 5-minutes to get down, just like it would anybody else that had a good teacher (in my case a Navy SEAL). Reading the mountains and learning the geology of gold prospecting is many times more difficult

I now have about 150-hours on the Dual Field; 70-hours on the Garrett Seahunter; and well over 300-hours on the Infinium. I never stated any of these machines were bad or not capable. I have repeatedly said that the Sand Shark is just as good as any of them, easier to learn, and has a better warranty for less money.

So, do ANY of you have ANYTHING intelligent to add to my original post? Anyone disagree with my assertions on pulse delay? I do get a chuckle out of the "Core-Four" here that can't stand me because I won't bend to their "superior experience and knowledge."

While the Core-Four are busy bashing my experience and knowlrdge, I would ask what articles they have written and where they are published. My very first article on Beach Detecting was publshed by Lost Treasure Magazine just this year. I guess Carla Banning decided I DID know what I was talking about.

OK. I have had a lot of fun, but unless someone really has something intelligent to add, I have more than made my point about this silly pulse delay argument. - Discuss..

I didn't respond last night because honestly I am tired of the same old, same old...


With all those hours on those machines you would think you would have alot more goodies to show... you can write all the articles you want but the bottom line is finding the good stuff... I don't write articles although articles have been written about me... I think my finds do the best talking for me...

You can believe whatever you want about a detectors pulse delay ... at this point I don't care anymore what you write...the Sandsharks 22uS pulse delay is better in deeper water (diving) as you mention but not 5 feet ...

The bottom line is the Sandshark is a capable machine and many enjoy using it and thats fine but there are better machines out there to find the good stuff...

When I buy a machine I research it to death, I talk to actual users, I don't buy a machine based on warranty or price that is irrelevant for me... I swing the Dual Field and a Sovereign GT...my finds do my talking... end of story.

 

[Hotrod Tom]

Am I one of the core four? I hope so. Make a shirt of the core four and sell it on your website. Here we go. Check out the two top posts. More free publicity for you.
https://mobile.twitter.com/#!/terryrsoloman

You are waiting for your new Sand Shark,and your righting a beach hunting article at the same time. You posted elsewhere your first water gold ring find on 5-11-11 A month before you even found a gold ring.And now your going to teach water PI hunting? Like they say those who can't, teach. I am still learning to read the beach after all these years. I bow to your superior intelligence and Navy Seal beach reading training. You endlessly babble EVERYWHERE and anyone that takes two seconds out of their life to see who it is giving them advice will understand that they should not believe anything you type. You put on a good show,you would make a good Carnival Barker but as far as your credibility?

I correct myself.I was wrong when I said two seconds,it's more like two days to go through all the nonsense you spew online. You should just teach a class on how to shamelessly promote oneself with total disregard for factual information. You do excel at that.I'll give credit where it's due.

 

[Crumble]

Thanks. Was an engineer is the operative word. I was a EE design engineer, rose to management position, in the end running a department of 22 engineers (hardware and software) and 7 technicians. I couldn't take it. Spent most of my time in meetings and arguing with the finance department over how much money we spent or didn't as the case might be. So, I moved to marketing, where I could define the products we needed to design and build without the headaches or directly running a large group. I got to do more engineering in marketing than I did while I was an engineering manager.

Now I am retired.

Nice, I had a feeling you were an EE. My step father had the same experience in management, he was an aerospace engineer, turned project manager, and said he hated it, for the same reasons you gave.

 

[roob47]

I'm still learning my dual field but the learning is coming fast. It is very informative to read these types of post after all that's why they call it a "forum" thanks to all for your input.

 

[BEACH-HUNTER]

This says it all!! Craig!!

This is where the truth lies!! show me the loot!! "When I buy a machine I research it to death, I talk to actual users, I don't buy a machine based on warranty or price that is irrelevant for me... I swing the Dual Field and a Sovereign GT...my finds do my talking... end of story!!! " Well put Craig !!

 

[Hotrod Tom]

Okay comparing Terry to Midas is just down right dirty! I have taken advice from many members on the forum here. I have never felt that anyone has tried to mislead me or cost me money. I am smart enough to make my own decisions based on the opinions and advice this site generates. We are a competitive bunch. The power struggles playing out on this site can be entertaining from time to time. However they are becoming more frequent and personal. The site will lose some of what makes it so great if it persists. Just my crusty 2 cents

I am unclear as to which one should be insulted.
If you check around here enuf you will find at least one member that bought a Sand Shark in part because of his recommendations only to learn that it did not work on the black sand beaches in California where he detects. He had to sell it at a loss to buy a different machine. If he wants he can speak up.He tends to be shy on here.

I for one am not in a power struggle I just don't like to see good people misled. A bad first detector choice can easily ruin this hobby for someone just starting out. The Sand Shark is not a bad machine but it's not what he says it is.