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Very Hot Topic (More than 25 Replies) 3rd Edition Coming Soon (Read 21198 times)
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Re: 3rd Edition Coming Soon
Reply #15 - Aug 11th, 2003 at 3:59am
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aldo_huxley wrote on Aug 9th, 2003 at 10:33pm:
Sorry, but I did not make myself clear. Tesla coil was just and idea, the 13.56 MHz generator I was speaking of is a linear design. We had a near disaster due to 13.56 MHz system which had RF leakage affecting a system about 150 feet away where the CPU was "frozen" as were the sensors of a hot acid bath and the critical temperature was almost reached before I used the old fashioned method of  a mercury thermometer. Gee, I ramble. Funny thing, the leakage and effect was due to 1 screw missing from a cooling fan. I think you can image what you could do intentionally if you so desire. To clear things up a bit, the generator is 1KW design. 

Yep, 1kw of rf there can easily lock up an ad hoc lab setup. I have had lab kludges lock-up from ESD and leaking RF from an unbalanced ham xmtr.  Not so though on a properly shielded design which commercial equip tends to have to pass for FCC and ECMA standards. Modern stuff is surprisingly resistant to high RF fields though this is not true of stuff designed 30 years ago and a lot of poly's have been around a long time.

-Marty
  

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Re: 3rd Edition Coming Soon
Reply #16 - Aug 12th, 2003 at 7:06am
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and if you load it through the AC line?
  
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Re: 3rd Edition Coming Soon
Reply #17 - Aug 13th, 2003 at 2:24am
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Maybe you should take the tin foil off your head. Cheesy
  
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Re: 3rd Edition Coming Soon
Reply #18 - Aug 15th, 2003 at 1:24am
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Your probably correct, took the foil off;  tried out a high power Tesla and WHAM! East coast went dark......

And now for something completely diffent...............

Smiley
  
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Re: 3rd Edition Coming Soon
Reply #19 - Aug 15th, 2003 at 11:42pm
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aldo_huxley wrote on Aug 12th, 2003 at 7:06am:
and if you load it through the AC line?


RF loads into the AC lines in 2 ways, common mode and differential. The latter, won't be a problem as the impedance mismatch with a Tesla is huge. The former is typically shunted to gnd by capacitance in various devices along the path.

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Re: 3rd Edition Coming Soon
Reply #20 - Aug 16th, 2003 at 1:40am
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Gee Marty, methinks we got away from the suject here. Sorry everone!

So..........If we realistically look at a problem there is always a solution. I have been gining the Tesla as an example, but looking for real feed back as how to do it, not "it can't be done". I was always told can't can't do anything.

Anyway, other approaches to jamming can include harmonic amplification( as in h of n(x) = A of n cos(n omega t+thea of n) are the harmonics, let's see how about a 25ns 500V P-P spike in the line? on and on......


any EE's out there?


Aldo

  
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Re: 3rd Edition Coming Soon
Reply #21 - Aug 16th, 2003 at 1:41am
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giving, sorry typo.......

Aldo
  
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Re: 3rd Edition Coming Soon
Reply #22 - Aug 19th, 2003 at 6:13am
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Sorry Marty, I find that you are an EE.  I'm an engineer producing 95nm gates curently running 37 GHz technology. How about you?

Aldo

  
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Re: 3rd Edition Coming Soon
Reply #23 - Aug 21st, 2003 at 5:50am
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aldo_huxley wrote on Aug 19th, 2003 at 6:13am:
Sorry Marty, I find that you are an EE.  I'm an engineer producing 95nm gates curently running 37 GHz technology. How about you?
Aldo


That's nice. How does that relate to Tesla's disrupting polygraphs at 13 MHZ? I seem to have off put you. Sorry. Why not use a real name and not an alias? Perhaps you been subject to polygraphs? They sure have their downsides.

-Marty
  

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Re: 3rd Edition Coming Soon
Reply #24 - Aug 21st, 2003 at 6:29am
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No relationship between Tesla coils and linear 13.56MHz amps, no experience with polys to date.

I guess my main point is that polygraphs are sensitive pieces of equipment and should inherently be subject to EMI if purposely designed to do just that. Of course $$$ is always a driving force to any new innovation.

Electronic jamming is not new, nor confined to specific areas. 

Search the following:

Skin Conductance and Cardiac Responses to Masked Presentations of Fear-Relevant and 
-Irrelevant Conditioned Stimuli

Changes in human skin conductance are frequently used as an indirect measure of a subject’s cognitive effort, emotional arousal, or level of attention.  Recording skin conductance responses (SCRs) is useful during 

"Psychologists have been trying to identify universal patterns of physiological response since the early 1900s, but without success. We believe that the lesson to be learned there is that there are no such universal patterns," said Smith. 

Galvanic Skin Response is a measure of the skin's conductance between two electrodes. Electrodes are small metal plates that apply a safe, imperceptibly tiny voltage across the skin. The electrodes are typically attached to the subject's fingers or toes using electrode cuffs (as shown on the left electrode in the diagram) or to any part of the body using a silver-Chloride electrode patch such as that shown on the EMG. To measure the resistance, a small voltage is applied to the skin and the skin's current conduction is measured.

Skin conductance is considered to be a function of the sweat gland activity and the skin's pore size. An individual's baseline skin conductance will vary for many reasons, including gender, diet, skin type and situation. Sweat gland activity is controlled in part by the sympathetic nervous system. When a subject is startled or experiences anxiety, there will be a fast increase in the skin's conductance (a period of seconds) due to increased activity in the sweat glands (unless the glands are saturated with sweat.)

After a startle, the skin's conductance will decrease naturally due to reabsorption. There is a saturation to the effect: when the duct of the sweat gland fills there is no longer a possibility of further increasing skin conductance. Excess sweat pours out of the duct. Sweat gland activity increases the skin's capacity to conduct the current passing through it and changes in the skin conductance reflect changes in the level of arousal in the sympathetic nervous system.

The electromyographic sensors measure the electromyographic activity of the muscle (the electrical activity produced by a muscle when it is being contracted), amplify the signal and send it to the encoder. In the encoder, a band pass filter is applied to the signal. For all our experiments, the sensor has used the 0-400 microvolt range and the 20-500 Hz filter, which is the most commonly used position.

Most people cannot mentally control their skin conductivity response in any kind of rapid and fine-tuned way. The response can take seconds to arise and longer to decay. However, you can experiment with thinking of exciting or calming thoughts and watch how your galvactivator responds. Once you have dialed it to your proper baseline, the galvactivator should be sensitive enough to respond to internally-generated imagery in a broad way. 

The startle reflex is a characteristic spike in the galvanicskin response that usually occurs 1-3 seconds after the onset of a startleprobe or a novel stimulus. Typically, a startle probe refers to a loudnoise, bright light, or puff of air designed to “startle” or suddenly divert the attention of the subject. A similar spike in conductivity can be generated when a subject "orients" to a new stimulus -- a person suddenly standing next to you, for example. 

Can someone tell if I am lying? 
Not with the galvactivator, though the galvanic skin response is one of the measures commonly used as part of a lie detecting apparatus. However, detection of deception requires a thorough experimental setting which does not compare to everyday’s use of the galvactivator. 

More later, Nuff to chew on.

Aldo
  
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Re: 3rd Edition Coming Soon
Reply #25 - Aug 22nd, 2003 at 9:06pm
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aldo_huxley wrote on Aug 21st, 2003 at 6:29am:

I guess my main point is that polygraphs are sensitive pieces of equipment and should inherently be subject to EMI if purposely designed to do just that. Of course $$$ is always a driving force to any new innovation.

Electronic jamming is not new, nor confined to specific areas. 

The polygraph, including the galvanic skin resistance component, is not intrinsically vulnerable to electronic jamming measurement though each instrument may have defects that produce specific sensitivities. They would not be consistent from one design to another however due to the above.

-Marty
  

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Re: 3rd Edition Coming Soon
Reply #26 - Aug 24th, 2003 at 1:48am
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So how many manufactures are they? What components are common? Just curious. Mainly interested in the type of sensors and IC's utilized.

Oh yes, a friend of mine is replacing a cap in an old stereo system. Question posed is which type is best, electrolytic, mylar, or ceramic? The former is best for filtering but I'm not sure about it's general effect on the sound. Any ideas?

Gee, went off the subject.......

So you think the EMI protection within the unit exceeds the ability to disrupt it's functionality?

On the subject of conductivity sensors, what if you went to a poly with a tinge unit on?



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Re: 3rd Edition Coming Soon
Reply #27 - Aug 24th, 2003 at 5:57am
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The oldest analog polygraphs are the least sensitive to external EMI. They didn't have any electronics except for the GSR which was typically passive, Wheatstone bridge based. The ones most sensitive were likely designed 30 years ago or so using electronic transducers (strain gauges) requiring significant amplification.. The types of capacitors make little difference, rather pcb layout and capacitor lead lengths (series inductance) are the important factors. Newer designs would have much more resistance as a side effect of stringent emitted EMI regulations.

As for the amplifier, resistors and capacitors in an RIAA equalization network should be highly accurate (or batch selected) and polystyrene types are quite good there. Low memory, linear, low leakage. For EMI, ceramic caps are normally best, available inline and with low series L.

-Marty
  

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Re: 3rd Edition Coming Soon
Reply #28 - Aug 24th, 2003 at 6:10am
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Marty wrote on Aug 22nd, 2003 at 9:06pm:

The polygraph, including the galvanic skin resistance component, is not intrinsically vulnerable to electronic jamming measurement though each instrument may have defects that produce specific sensitivities. They would not be consistent from one design to another however due to the above.

-Marty


Actually, I think it stands to reason that the GSR instrument would be the most vulnerable to externally-generated electric fields.  It's likely that those fields would need to be fairly strong and low frequency, though.

In my experience, the wires connecting the GSR (ohmmeter) to the fingers are not shielded, which would probably be the weak point for messing with the recorded signal.

Skeptic
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Re: 3rd Edition Coming Soon
Reply #29 - Aug 24th, 2003 at 6:18am
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aldo_huxley wrote on Aug 24th, 2003 at 1:48am:
So how many manufactures are they? What components are common? Just curious. Mainly interested in the type of sensors and IC's utilized.


I'm not sure how many manufacturers there are, but Lafayette Instrument Co. is one of the biggest suppliers of polygraph instrumentation:

http://www.lafayetteinstrument.com

Quote:
Oh yes, a friend of mine is replacing a cap in an old stereo system. Question posed is which type is best, electrolytic, mylar, or ceramic? The former is best for filtering but I'm not sure about it's general effect on the sound. Any ideas?


Was the cap in the audio path to begin with, or in the power supply?  In general, I would replace it with something close to what you took out.

For the record, electrolytics aren't necessarily "the best for filtering".  Again, it depends: upon the frequency range of noise you're looking to filter, the noise amplitude, and how much you're looking to spend.  Usually for power-supply-pin bypassing, you'll find both electrolytic and ceramic in parallel to cover a larger frequency range for noise filtering (most electrolytics are pretty much useless by the time you get into the tens-to-hundreds of kilohertz range).

Quote:
Gee, went off the subject.......

So you think the EMI protection within the unit exceeds the ability to disrupt it's functionality?


Absolutely not.  But it all depends upon the strength of the disruption practially available, of course.

I would imagine some sort of high-voltage spark-gap device would likely induce significant noise in the GSR channel, at least.  Whether the noise-induced nature would be obvious is another question.

It would be an interesting experiment to do, and could be tested using a common multimeter, unshielded leads and spade connectors strapped to the index and ring fingers using velcro straps (yes, I made my own crude GSR meter).

Skeptic
  
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