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PEB/Semi-auto

A

Anonymous

Guest
I talked to Minelab today about semi-auto sensitivity and what a PEB is. The simplest one first is that PEB should have been PCB as several suggested. <STRONG><span style="background-color:#ffff00;">Sensitivity is an adjustment for detector stability and is user input to the microprocessor. The operation of the microprocessor is based on their algorithm. </span></STRONG>Therefore, we cannot relate this in the same way that you can by turning the sensitivity up or down on a guitar amplifier as an example. <STRONG>However, run the sensitivity as high as one can with stability in manual or semi-auto.</STRONG> I assumed this was what was going on and posted this down the page so will not repeat what several of us have already said.
<span style="background-color:#ffff00;">
I ran these tests so will make some suggestions based on those tests.</span> With Audio Gain set to 10, Sensitivity at 1,and using a TV as a source for noise the following results were obtained:
#1 In manual sensitivity the detector responds to where the sensitivity is set pretty much as we would expect. At a sensitivity of 1 the detector can be operated right up to the TV with very little noise induced. However, if Semi-auto is activated then the noise is excessive. This appears to be a situation where there is a "saturation" point so that the algorithm will not allow loss of sensitivity below a specific level and it looks to me to be around 16.Someone called this wrap around which is an interesting way to see this. If we get out and run into heavy EMI this prevents the detector from going just about dead from strong external noise as semi-auto compensates.
#2 The presets are outstanding but if less sensitivity is desired then use manual as semi-auto starts to compensate by increasing the sensitivity. <span style="background-color:#ffff00;">This is my suggestion to a new user for some kind of referece.</span> While this depends on external noise the sensitivity setting of 16 may be a good reference point. <STRONG>They could not tell me how far semi-auto slides the sensitivity from the set point due to microprocessor control and the algorithm. </STRONG>
#3 Underground electrical services can make the detector go nuts in semi-auto but by using manual and adjusting the sensitivity one can get past the problem. This is also true close to electrical fences, under high power lines, etc.
<span style="background-color:#ffff00;">So, the bottom line is stability</span> and go for the highest setting for deep coins. What that means to me is that I will use the highest setting I can in manual and if necessary go to semi-auto. The preference is does the user want to adjust the sensitivity up or down for stability or have the detector do it. I have been using semi-auto but am going to see what happens with manual and adjust down from 28 in steps for stability and go from there. This also takes me to an old habit of using a threshold so I know what is going on with the detector.
HH, Cody
 
Cody, you are the typical academic. You know that Varmint answered first on the PCB question. You also know he is the one that mentioned wrap-around. Are you trying to come across as the prime example of what has gone wrong with today
 
OK, first, thanks (I think) for the support, but that was uncalled for.
Cody was probably just trying to acknowledge that several people arrived at the same conclusion on the PCB thing. As for the wrap-around, this is unconfirmed at this point so the point is mute.
Next time you feel the need to comment, don't do so on my behalf. M'kay?
DAS
 
Thanks Cody, for checking that spelling issue out for me. I really appreciate all your hard work on this, and other matters as well.
Thanks again.
Tom Weaver
 
Have a good evening and try to relax and enjoy life.
HH, Cody
 
Glad to help and enjoyed the talk with Minelab. They are interested in helping and understand our desire to know how the detector works. We will have to guess at some of this as they don't tell all they know to protect their process.
HH, Cody
 
<img src="/metal/html/grin.gif" border=0 width=15 height=15 alt=":grin"> <img src="/metal/html/grin.gif" border=0 width=15 height=15 alt=":grin"> <img src="/metal/html/grin.gif" border=0 width=15 height=15 alt=":grin">
 
and due to some of my own testing, I'm convinced there is a codeing error in the "semi-auto" algorythm. Long story made short, I'm sticking with my assertion that it does NOT try to keep the gain as close to your selection that it can, rather it "adjusts" in the manner described in my previous post. You pretty much elude to it with your comment "does the user want to adjust the sensitivity up or down for stability or have the detector do it" key words of course "up or down". To read the manual would give one the impression that it adjusts only downward while keeping it as close to your selection as possible, but we have all verified it does go UP.
On to the TV test. I think the tests should be limited to the detector responding to real world conditions, i.e., the detector generates a signal and processes the response generated by target in the field. Using the TV uses a great deal of "out of band" noise, that is neither frequency or phase related to the detectors emmissions, therfore hopelessly confusing the results. Another issue is frequency and amplitude changes in the TV signal are high dependant on the image displayed, scene changes which include wild variations from light to dark, color to B&W, reds to greens, etc... all have a huge impact on the emissions from the TV. If we still want to use the TV as some sort of signal generator, the image must be static, or even completely random like tuned to a blank channel where the TV displays pure "static". Most TVs nowadays go to bluescreen and muted audio on blank channels, so that might even be of some use, so long as we keep the frequency/phase problems in mind. Again, I feel any meaningful test would need to be performed with the detoector processing responses by targets to it's own signals.
Again, thanks for making the call, too bad they can't be a bit more forthcoming with solid info though, it sure would help us get past the guessing stage!
DAS
 
I agree as the TV test is only good to the extent that I could see how the detector responded to EMI. I thought a lot about that and wondered how it responded to real world EMI when hunting. Several people have posted that the noise was worse with semi-auto ON and I did not expect that. I now see how that can happen depending on how strong the EMI is such as over underground electrical services.
HH, Cody
 
Let me think..I wonder who you are???? Hmmmmm.... <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=":)"> <img src="/metal/html/tongue.gif" border=0 width=15 height=15 alt=":b">
 
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