It is getting really tiresome to click on this forum and see no less or no more than the same proposed 4 or 5 electronic engineers debating the same subject...I don't care what makes it work as long as it does and most probably is turning a few people off as well to have to read it...Why don't you electronic buffs get your own forum?More than likely 90 to 95 percent of the folks on this forum does not understand what or care what your talking about,I don't but I do not care as long as the machine works and we enjoy it...
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pi debates? new forum
- Thread starter hoss3500
- Start date
Charles (Upstate NY)
Well-known member
n/t
Dear Hoss...Your view is respectfully noted, but may I for one, remind you, that the title of this forum is the Explorer CLASSROOM'
As such, technical or implied technicalities are the substance of its existence.
Surely you Hoss should be the one who exercises the liberty to visit the forum most appropriate to your interests.
-------------
To Charles and all of those who found my earlier post on the generalities of forum readers etc. as offensive:-
Here we have a post, which in part, echoes my comments precisely, but for which I was criticized.
Cody was also unreasonably berated for defending me.
I feel vindicated, but not encouraged to debate, for why invite agro, when time can be better spent.
I still cannot understand why some folk feel offended at being taught.
For all my abilities, I still read EVERY contribution.
I believe in FREE SPEECH.
I also passionately believe, that ORIGINAL IDEAS are as likely to be discovered, coming from the thoughts of those NOT encumbered by tradition teachings.
So there is room for all peoples opinions.
As such, technical or implied technicalities are the substance of its existence.
Surely you Hoss should be the one who exercises the liberty to visit the forum most appropriate to your interests.
-------------
To Charles and all of those who found my earlier post on the generalities of forum readers etc. as offensive:-
Here we have a post, which in part, echoes my comments precisely, but for which I was criticized.
Cody was also unreasonably berated for defending me.
I feel vindicated, but not encouraged to debate, for why invite agro, when time can be better spent.
I still cannot understand why some folk feel offended at being taught.
For all my abilities, I still read EVERY contribution.
I believe in FREE SPEECH.
I also passionately believe, that ORIGINAL IDEAS are as likely to be discovered, coming from the thoughts of those NOT encumbered by tradition teachings.
So there is room for all peoples opinions.
Charles (Upstate NY)
Well-known member
n/t
I'm sorry matt but you lost me also on this...If I have offended you in some way I apologize to you an all who read that post,but I will stand behind that post...It is most refreshing to listen to what a learned person has to say,but in a way said so that it can be understood by most...There are folks on this forum from 13 to 80 years old that do feel intimidated when theory's start flying around...You are right Matt this a classroom on the exp2 and maybe most of us me included find it very hard to understand the text in which these electronic engineers are trying to explain their selves and at times I know that is difficult to do...Have good day Matt
I don't know the best answer but the forum has threads for topics. In "theory" one can only follow the topics by threads that are of interest. That should allow engineers to communicate and at the same time allow new user to do the same. I go to the site and set my preferences for CURRENT VIEW: Threaded. It can be set to flat view and that way can follow topics by threads. I think this is standard for a forum where we can expect to have engineers, very experienced users and newbies. They have taken it a step further and have the regular forum where they do not go into theory, or it is assumed they will not, but MattR is correct in that the Classroom will work for advanced to beginner with the Explorer.
It really is very easy to simply follow a threaded topic and when an engineer posts and a person is not interested then don't follow that thread. The same is true when we start to kick sensitivity around all over again then just don't bother with that topic thread and go on to something else. I often wonder around the other forms looking for interesting information when this one has little action and I know many others do the same thing.
It really is very easy to simply follow a threaded topic and when an engineer posts and a person is not interested then don't follow that thread. The same is true when we start to kick sensitivity around all over again then just don't bother with that topic thread and go on to something else. I often wonder around the other forms looking for interesting information when this one has little action and I know many others do the same thing.
I thank those that post educational info and explanations of the theory behind metal detectors. The technical side of these instruments is almost as interesting as making finds with them. Charles I wanted to get back to you and ask you if you are still selling the plastic coil forms used to make search coils? I thought that this forum was setup for the purpose of discussing the technical aspects of these instruments. Many thanks for this forum and God Bless all.
John T., CET
John's Detectors
John T., CET
John's Detectors
We will continue to do both theory and application and participants can follow the topics and threads that interest them. I will be post a technical explanation of how the sensitivity, as far as I understand at this time, which I think will take some of the "mystery" out of the application side of the question. We can learn to increase and decrease this or that function and never know how or why and do great with the Explorer. That is great and makes a powerful detector usable by a newbie. We can also know why increased sensitivity will get better depth in one situation and less in another. We don't have to guess although it is fun to do. I agree with you completely in that I like to know why and how but I certainly understand just mastering the how of the Explorer. Somehow I want to have accomplished more in life than how to use a hobby detector. It is just a fun hobby and I try to keep it from becoming my life's work. It is easy to fall into getting way to serious about how to use or how the Explorer works. Mr. Bill has posted several times that participants need to keep in mind we are just talked about a hobby detector.
It would be nice if more guys would risk and explanation of the theory of operation instead only critiquing those of others. I go from forum to forum and some participants never step out and say this is what I think. Instead it is picking apart the theory and application of others. I am still waiting for some of them to give us some idea of how they think it works or even venture a suggestion as how to use it that is original.
Anyhow, we shall plug away with both and users can follow the topics and threads that are of interest to them.
It would be nice if more guys would risk and explanation of the theory of operation instead only critiquing those of others. I go from forum to forum and some participants never step out and say this is what I think. Instead it is picking apart the theory and application of others. I am still waiting for some of them to give us some idea of how they think it works or even venture a suggestion as how to use it that is original.
Anyhow, we shall plug away with both and users can follow the topics and threads that are of interest to them.
The front end receiver of the Explorer is very interesting. The receiver coil is direct coupled to 6 preamplifiers. There are all kinds of basic ideas of how a capacitor works, most incorrect, but they do not actually pass DC or AC signals. They do not block DC if the DC changes amplitude. A capacitor would be damaged if it passes AC or DC. What a capacitor does is charge and discharge to the voltage difference between its plates. We can sum that up as a capacitor is voltage sensitive and charges or discharges to the difference of potential across the plates. (A tech tip would be that a coil is current sensitive and charges and discharges stored energy based on changing current in a circuit.)
The direct coupled receiver coil means no loss of signal across what would be a coupling and filtering capacitor or combination for coupling and filtering section. Very small signals can be lost in this process so but with the Explorer these smallest signal is amplified. It has nothing to do with where we set the sensitivity or if we use semi-auto or manual. The 6 preamplifiers are in pairs with each pair have one inverting amplifier so we have 3 of the six inverting the signal. The output of the preamplifiers is fed to three sets of demodulators. The demodulators are in pairs and connected to a set of preamplifiers. The demodulators output is three signals that are filtered and summed. In that respect there are three filters but on the outputs of the demodulators.
The amplifiers and demodulators connected to the receiver coil can be thought of as the front end of the detector. Notice there are three signals from the demodulators. The Explore does not use a square wave or a rectangular but a sequence of rectangular waves. The transmitter has a square wave and two rectangular waves of different time periods. Although these are generated continuously and a specific sequence is a cycle of operation the input preamplifiers are gated ON and OFF by sampling pulses so the transmitter is never on when the receiver is open to receive a signal. Signals are allowed to pass through the preamplifiers only when the transmitter is off.
If we consider an example such as turning the transmitter ON for one second and then OFF for two seconds and repeat this operation for a minute then the transmitter is OFF more than it is ON. We can see this with a digital circuit and a LED that will blink as the circuit is turned ON and OFF. However, if we start to increase the speed at which the ON and OFF occurs we reach a point where the light is ON to our eyes all the time. The point is the transmitter of the Explorer has an electromagnetic field all the time even though it is actually pulsed as does any PI detector.
A really neat operation of the Explorer I to use sample pulses to turn the front end ON and OFF. Ground signal is strongest right after the transmitter pulses the TX coil so the receiver is OFF. The signals induced into soil minerals immediately starts to die off and the receiver is sampled ON. The residual ground signal is fed to the preamplifiers and demodulators and filters and outputs three ground balanced signals. The front end has three signals, one that looks at the long time constant, one for the short time constant, and one for the medium time constant. The soil and targets have components of all three, lone, medium and shot TC. Time constants are critical to the identification of soil minerals and targets ID.
Notice we have done nothing to adjust the sensitivity of the detector to signals in the receiver coil. The receiver coil has components of ground noise and signal noise which is called the target volume. Pure soil volume will cause a specific induction between the receiver and transmitter coils. Free air is a good example of a constant to use as a measure of soil minerals. Soil minerals change not only due to magnetic minerals but also due to contamination and conductive targets in the target volume.
The challenge is to separate targets from the target volume when soil contamination can be considerable and also to discriminate between targets. Also, the target volume is constantly changing so it becomes even more complex.
The front end uses the three ground balanced signals to generate an instantaneous soil mineral signal based on the target volume at that instant in time. The previous instant in time is a historical soil mineral signal. The two ground signals processed and a predicted soil mineral signal is generated. We see that not only does the Explorer balance to the current soil minerals but also predicts what is ahead in the next instant of soil mineral target volume.
We can see how critical the soil minerals and contamination which is often grouped into ground noise is to our interest in refined metals in the target volume. The induction of voltages into the receiver coil cause currents to flow in the receiver coil as do contaminations, salts, refined metals and other conductive materials. BY ADJUSTING ONE LEG OF THE FRONT END WHICH IS THE HEART OF THE RECEIVER the negative effects of contaminations of the targets volume can be greatly reduced. The end results is refined metal signals are better identified form the composite signal fed to the microprocessor. This is similar to a third coil or other means to keep the TX and RX coils balanced so the faintest targets of interest are amplified.
The Explorer uses an adjustment called SENSITIVITY which can be adjusted by the users or it can be automatically adjusted. If adjusted by the use than there need to be some kind of reference for the user to know when to adjust the control. When the detector becomes unstable is a practical way to do this or allow the electronics to make the adjustment. For most users it is considered best to allow the electronics to make the adjustment. Experienced users however can do a pretty good job of this and that is called manual adjustment. A problem is the users need to be aware of soil minerals. In heavy soil minerals the adjustment is best, in general, if balanced by the electronics of the detector. In light minerals it can be adjusted with little problem by the user. What we come down to is if noise is a problem in the composite signal and the soil minerals are heavy then Auto-sensitivity is most likely the best option.
Now we have the problem of soil target volume from one instant to the next which can and does change dramatically. Not because the minerals necessarily change dramatically but due to contamination, co-located targets and discrimination. Semi-auto is designed to balance the front end for maximum detection of wanted targets from the composite based on sampled data by the microprocessor. An experienced operator can be very efficient in making the adjustment but when one considers the changes from one instant in time to the next thy would need to constantly adjust the sensitivity depending on the target volume and this does not happen. What most do is simply set the sensitivity as high as they can stand it and run on what they consider to be the ragged edge of stability. On the plus side is if the target volume is fairly constant then manual works just fine.
A problem is not knowing or trusting the electronics to work properly. However, with a correct sweep speed and takes ones time the detector
The direct coupled receiver coil means no loss of signal across what would be a coupling and filtering capacitor or combination for coupling and filtering section. Very small signals can be lost in this process so but with the Explorer these smallest signal is amplified. It has nothing to do with where we set the sensitivity or if we use semi-auto or manual. The 6 preamplifiers are in pairs with each pair have one inverting amplifier so we have 3 of the six inverting the signal. The output of the preamplifiers is fed to three sets of demodulators. The demodulators are in pairs and connected to a set of preamplifiers. The demodulators output is three signals that are filtered and summed. In that respect there are three filters but on the outputs of the demodulators.
The amplifiers and demodulators connected to the receiver coil can be thought of as the front end of the detector. Notice there are three signals from the demodulators. The Explore does not use a square wave or a rectangular but a sequence of rectangular waves. The transmitter has a square wave and two rectangular waves of different time periods. Although these are generated continuously and a specific sequence is a cycle of operation the input preamplifiers are gated ON and OFF by sampling pulses so the transmitter is never on when the receiver is open to receive a signal. Signals are allowed to pass through the preamplifiers only when the transmitter is off.
If we consider an example such as turning the transmitter ON for one second and then OFF for two seconds and repeat this operation for a minute then the transmitter is OFF more than it is ON. We can see this with a digital circuit and a LED that will blink as the circuit is turned ON and OFF. However, if we start to increase the speed at which the ON and OFF occurs we reach a point where the light is ON to our eyes all the time. The point is the transmitter of the Explorer has an electromagnetic field all the time even though it is actually pulsed as does any PI detector.
A really neat operation of the Explorer I to use sample pulses to turn the front end ON and OFF. Ground signal is strongest right after the transmitter pulses the TX coil so the receiver is OFF. The signals induced into soil minerals immediately starts to die off and the receiver is sampled ON. The residual ground signal is fed to the preamplifiers and demodulators and filters and outputs three ground balanced signals. The front end has three signals, one that looks at the long time constant, one for the short time constant, and one for the medium time constant. The soil and targets have components of all three, lone, medium and shot TC. Time constants are critical to the identification of soil minerals and targets ID.
Notice we have done nothing to adjust the sensitivity of the detector to signals in the receiver coil. The receiver coil has components of ground noise and signal noise which is called the target volume. Pure soil volume will cause a specific induction between the receiver and transmitter coils. Free air is a good example of a constant to use as a measure of soil minerals. Soil minerals change not only due to magnetic minerals but also due to contamination and conductive targets in the target volume.
The challenge is to separate targets from the target volume when soil contamination can be considerable and also to discriminate between targets. Also, the target volume is constantly changing so it becomes even more complex.
The front end uses the three ground balanced signals to generate an instantaneous soil mineral signal based on the target volume at that instant in time. The previous instant in time is a historical soil mineral signal. The two ground signals processed and a predicted soil mineral signal is generated. We see that not only does the Explorer balance to the current soil minerals but also predicts what is ahead in the next instant of soil mineral target volume.
We can see how critical the soil minerals and contamination which is often grouped into ground noise is to our interest in refined metals in the target volume. The induction of voltages into the receiver coil cause currents to flow in the receiver coil as do contaminations, salts, refined metals and other conductive materials. BY ADJUSTING ONE LEG OF THE FRONT END WHICH IS THE HEART OF THE RECEIVER the negative effects of contaminations of the targets volume can be greatly reduced. The end results is refined metal signals are better identified form the composite signal fed to the microprocessor. This is similar to a third coil or other means to keep the TX and RX coils balanced so the faintest targets of interest are amplified.
The Explorer uses an adjustment called SENSITIVITY which can be adjusted by the users or it can be automatically adjusted. If adjusted by the use than there need to be some kind of reference for the user to know when to adjust the control. When the detector becomes unstable is a practical way to do this or allow the electronics to make the adjustment. For most users it is considered best to allow the electronics to make the adjustment. Experienced users however can do a pretty good job of this and that is called manual adjustment. A problem is the users need to be aware of soil minerals. In heavy soil minerals the adjustment is best, in general, if balanced by the electronics of the detector. In light minerals it can be adjusted with little problem by the user. What we come down to is if noise is a problem in the composite signal and the soil minerals are heavy then Auto-sensitivity is most likely the best option.
Now we have the problem of soil target volume from one instant to the next which can and does change dramatically. Not because the minerals necessarily change dramatically but due to contamination, co-located targets and discrimination. Semi-auto is designed to balance the front end for maximum detection of wanted targets from the composite based on sampled data by the microprocessor. An experienced operator can be very efficient in making the adjustment but when one considers the changes from one instant in time to the next thy would need to constantly adjust the sensitivity depending on the target volume and this does not happen. What most do is simply set the sensitivity as high as they can stand it and run on what they consider to be the ragged edge of stability. On the plus side is if the target volume is fairly constant then manual works just fine.
A problem is not knowing or trusting the electronics to work properly. However, with a correct sweep speed and takes ones time the detector
Instead of thinking in terms of amplifying all signals how about reducing all signals to a lower level OTHER than the GOOD ones. If the signals in the receiver are a composite of noise, contamination, ground signals and faint good targets we can reduce the bad signals to a lower level and then the good ones are easy to process.
That is what I think noise cancel, the front end of the receiver, and sensitivity does. Gain on the other hand controls amplification of all signals. The idea being to attenuate the "bad" signals and then use gain to amplify the results.
Have a great day and I look forward to any help in understanding this area.
That is what I think noise cancel, the front end of the receiver, and sensitivity does. Gain on the other hand controls amplification of all signals. The idea being to attenuate the "bad" signals and then use gain to amplify the results.
Have a great day and I look forward to any help in understanding this area.
Hi Cody and thank you so very much for your post on sensitivity. So is the Explorer II sort of a hybrid PI/VLF? I have noticed that the user needs to have a fairly slow sweep to get good readings. I get the idea that this instrument is built for the very analytical mind or user. It is not a cruiser is it? I know it is an excellent instrument because Minelab has put a lot of R&D engineering into it. Even I have critisized it at times but if the user knows the instrument it is quite a piece of engineering I would think and will yeild many good find's. Ok Cody thanks for the write up and look forward to more. Where are you finding the patents Cody? I had the address at one time. God Bless and CU later.
John T., CET
John's Detectors
John T., CET
John's Detectors