View Full Version : Comparison of Overhauser and Cesium
Jan,
I think that using a buffer is a very good idea. This way you spread out the transmit time over the cable so bandwith is reduced. Also, digitizing early seems like a good idea. Digitizing in itself will help reduce errors by making the system less sensitive to noise.
My only concern is that the more electronics that are on the fish, the more upset I'll be if the cable snaps or the fish gets flooded!
One idea I had was to put a whole industrial PC down there. This would make life simple, because all kinds of values could be tweaked from the surface, using a remote control program, but suppose things went wrong?! I quickly scrapped that idea!
I guess what I am trying to say is that I feel the cheaper the fish electronics the better.
Cheaper doesn't mean less funcional though. That is why I thought of the Ethernet idea. I figured that using a standard part would give us more functionality for less.
I know virutally nothing about using fiber optic transmissin lines, but I suspect it may require expensive electronics in the fish, and/or an expensive cable.
If I am wrong then please let me know! My only point is that I want to avoid putting expensive parts where they might get damaged.
-Bob
Bob,
The electronics in the fish is not very expensive.
It extensive use of PIC's will reduce the amount of parts.
Sending signal over lightpipe is nearly as easy as sending it through a copper wire.
The main difference is that lightpipe is connected to xmit/receive diode via special connector.
You cannot just put lightpipe in connector but need special tools for it. (Glassfiber end must be polished and very wel fitted)
Normally when one orders a length of pipe one can also let them put the connectors on it.
The major problem I have at the momement is to know what I need to send topside.
I hope that time between sending and echo + amplitude is enough, but am not sure about it.
Hope Sture will give answer to this.
If that is all, I will got for standard RS232 setup.
There are inexpensive chips using a stripped RS232 protocol which will do the trick.
I believe that the whole communication electronic will be below $50
This is for both sides, but without lightpipe and connectors
At the moment the transducer electronics do not seem to be very expensive (a PIC + some odd bits)
But this can change depending on what Sture says what we need from the echo.
I hope I can start the process flow diagram for the electronics next week.
Then I will start on transducer and start writing the PIC program.
This will be difficult at first because eventhough I am a programmer I never programmed a PIC before.
I do not suppose its difficult otherwise they will not sell these things in the quantity they do.
Regards, Jan
Hi Jan,
If you use a lightpipe are you also going to have power going down the cable? The transducer will want a fair amount of power or at least lots of volts (100 to 1000). You need a tank circuit or something to drive the volts as high as possible. The volts are what make the piezo ceramics expand. The more volts the stronger the wave. I like designing around PICs. It makes the design very flexible. I like every thing I hear so far, I think we’re making progress.
Tod
Tod,
I have a seperate powersupply in fish.
I was not planning to have an electrical connection between boat ancd fish.
All is done via fiber optics.
I have no idea what voltage I am going to need for transducer, am still gathering information about them.
If they need several hundred volts than that is no problem (assuming there is no big current involved)
I will then charge a capacitor with high voltage and discharge it over transducer.
Regards, Jan
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>RE: "...if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?"
------------------
It is not optimized for copper. The frequency (range) selected has everything to do with optimizing and compromizing the design parameters to achieve the desired functions most reasonably, and nothing at all to do with a specific metal. The frequency could as well have been 20 kHz or 16.999 kHz, or less. This is not a MFD type magic frequency device.
If this post shows up more than once, I apologize in advance. I seem to get into trouble when I try to "preview" a post.
>RE: "...if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?"
------------------
It is not optimized for copper. The frequency (range) selected has everything to do with optimizing and compromizing the design parameters to achieve the desired functions most reasonably, and nothing at all to do with a specific metal. The frequency could as well have been 20 kHz or 16.999 kHz, or less. This is not a MFD type magic frequency device.
If this post shows up more than once, I apologize in advance. I seem to get into trouble when I try to "preview" a post.
>RE: "...if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?"
------------------
It is not optimized for copper. The frequency (range) selected has everything to do with optimizing and compromizing the design parameters to achieve the desired functions most reasonably, and nothing at all to do with a specific metal. The frequency could as well have been 20 kHz or 16.999 kHz, or less. This is not a MFD type magic frequency device.
If this post shows up more than once, I apologize in advance. I seem to get into trouble when I try to "preview" a post.
>Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?
I don't think he was saying 18KHz is the optimum copper frequency. It appears that he pulled 18KHz out of the bag and then showed it to be acceptable for copper, and only from a skin depth perspective. (He also showed 100KHz to be acceptable as well.) Skin depth is important for good amplitude response.
He did not consider the phase response of the target vs. frequency, which is just as important. This aspect will determine sensitivity and the ability to discriminate. He also did not account for earth penetration vs. frequency, esp. under mineralized ground conditions.
There are a lot of things to consider when choosing the frequency, and Rick's approach of having several makes sense. I plan to eventually use a multi-frequency method with sampler and DSP so that I can see the response of a target to several different frequencies simultaneously. I think this is the approach Minelab uses.
- Carl
>Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?
I don't think he was saying 18KHz is the optimum copper frequency. It appears that he pulled 18KHz out of the bag and then showed it to be acceptable for copper, and only from a skin depth perspective. (He also showed 100KHz to be acceptable as well.) Skin depth is important for good amplitude response.
He did not consider the phase response of the target vs. frequency, which is just as important. This aspect will determine sensitivity and the ability to discriminate. He also did not account for earth penetration vs. frequency, esp. under mineralized ground conditions.
There are a lot of things to consider when choosing the frequency, and Rick's approach of having several makes sense. I plan to eventually use a multi-frequency method with sampler and DSP so that I can see the response of a target to several different frequencies simultaneously. I think this is the approach Minelab uses.
- Carl
>Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?
I don't think he was saying 18KHz is the optimum copper frequency. It appears that he pulled 18KHz out of the bag and then showed it to be acceptable for copper, and only from a skin depth perspective. (He also showed 100KHz to be acceptable as well.) Skin depth is important for good amplitude response.
He did not consider the phase response of the target vs. frequency, which is just as important. This aspect will determine sensitivity and the ability to discriminate. He also did not account for earth penetration vs. frequency, esp. under mineralized ground conditions.
There are a lot of things to consider when choosing the frequency, and Rick's approach of having several makes sense. I plan to eventually use a multi-frequency method with sampler and DSP so that I can see the response of a target to several different frequencies simultaneously. I think this is the approach Minelab uses.
- Carl
Sam Scafferi
10-23-1999, 11:33 AM
I've seen some of the references, and even brought up a couple of the sites, but really haven't had the time to study it in any depth.
One site indicated that it was not a particularly new concept, so perhaps it's already been "kicked around" some by the scientific community, however, I'm not aware of any other site references --other than those on the "Pro" side of the concept. (That doesn't mean there aren't any out there.)
As I get more time, I'll try and poke around and see what I can find out, from sources other than those which we already know about.
Carl and Evan may have some info on the subject also, and will share it with us.
Naturally, there are a great many theories and hypotheses out there, and some may be able to be advanced to axioms, with the correct amount of testing and analysis. However, just because something sounds like it is already validated, because of the terminology associated with it, doesn't mean it IS validated. We have a shining example of that sort of fallacy in a very close neighbor of ours.
I took a quick look at a couple of on-line torsion field articles. What I read was some highly contradictory statements followed by leaps into the metaphysical realm, such as "pyramid energy" and dowsing. Like most pseudoscience, it appears as if some people are taking legitimate science research (esp. leading edge and poorly understood by the public) and contorting it to support their superstitious beliefs. I'll be a bit more receptive of this kind of stuff when it starts getting published in mainstream peer-reviewed journals instead of the fringe "free energy" publications.
- Carl
Don Pierce
02-27-2002, 07:46 PM
I am looking for any papers on the comparison of Overhauser versus Cesium magnetometers. Nice if it was objective and not a manufacturer publication
Greg Hollyer
08-14-2002, 11:16 AM
Hi Don:
In response to your request for a paper that compares Overhauser and Cesium magnetometers, you may be interested in a 15 page technical paper that we recently published.
The paper is entitled, "A Brief Overview of Quantum Magnetometers" and is intended to provide as objective as possible an assessment of the various systems and their capabilities. We have tried to keep the commercial "spin" to a minimum, although, it does of course, have some discussion of specific GEM systems.
You can access the paper by visiting www.gemsys.ca and selecting the "Paper on Quantum Magnetometers" link in the "Whats New from GEM" section.
Sincerely,
G. Hollyer, M.Sc.(Eng)., P.Eng.
GEM Systems Inc. Advanced Magnetometers
GEM Systems Inc. Advanced Magnetometers (http://www.gemsys.ca)
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