Just researching for better and improved technique of coupling of capacitors.
Either, what can be the ways in which I can improve its range of distance from the subject from where it stores charge (that might be the distance b/w its plates)
OR, anything which may be better than that doin the same work but at the same time maintaining a considerable distance.
First of all thank you for responding, I am glad to hear You!!
Yeah, non-invasive, I just wanna use it to record surface potential charges of a human body & I think Inductive coupling would never do it....right?
So, is there any parameter which can improve capacitive coupling in this regard or any other system which can do better than that?
Inductive coupling would require di/dt. Without a fast changing current you won't have anything to measure.
Perhaps a bridge circuit could be used to achieve the sensitivity desired assuming the bridge currents are very, very small and safe.
Sorry to be a bit negative, but capacitance is pure physics. Increasing the capacitance (with given dimensions) is achievable by increasing the relative permittivity - by inserting a dielectric into the gap.
Whether this helps in your application: I don't know.
Further information regarding capacitors, capacitance, permittivity etc. is easily obtained from wikipedia.
You may consider sacrificing/buffering your pulse of charge into a photo-diode driving a fibre optic line, recovering the pulse into a photo transistor such that the output replicates the initial charge energy.
Have you looked at these:
http://www.plesseysemiconductors.com/epic-plessey-semiconductors.php
"Epic" electric potential sensing technology?
High sensitivity electric potential sensor that can be used in either contact or non-contact mode.
Contact mode: measures bio-electric signals like ECG, EMG, EOG and EEG
Non-contact mode: measures disruption in the electric field caused by human body movement.
Best,
Susan.
Yeah Susan, I know about this electrometer.This is also used in many research works.
But, thanks for suggesting , cause till now I have never got into its detail and now I will....
& Remi, its about upto 1mv surface potentials which I have to measure & yes I'll work on your suggestion.
Yes, I have done this at 20 cm and got a good ECG wave shape. At 2m you can still get the heart rate. The problem is static electricity. I didn't need to have a shielded chamber but did need for the person to sit still for the wave shape. Brainwaves however are possibly too low in voltage to see in this way. Although I was never funded to see if it was possible. Their frequency is higher which makes it easier. The "Epic" technology was developed by Dr Terry Clarke, retired Uni of Sussex( Brighton, UK). I am also located in Brighton and have done similar independent work for 25 years.
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