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View electric fields in real time?

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Advanced Member level 6
Dec 24, 2004
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Is there any way to view real time electric fields? You can "view" magnetic fields with iron filings in oil solution. How about something like that to view electric fields? It would be nice to point a camera at something, like a matching network on microstrip, and actually see the standing waves. Is there any way of devising such a thing? maybe scanning the circuit with electron beams? An array of hall effect sensors?

Any ideas? Is there something that we can scan the circuit with that the electric field will alter either in reflection off the microstrip surface or transmission thru the microstrip surface to the backside?

For instance, ions are electrically charged and should interact with an electric field. Can we scan a microstrip circuit with an ion gun, and measure the acceleration/deceleration and plot the Efield in real time?

It would be more useful if the method did not require that the microstrip circuit be inside of a vacuum chamber!
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Weak electric and magnetic fields in near field can be visualized by different kind of sensors but at least for electric field, it is hard to measure and avoiding that the measurement tool rotate the fields and same for magnetic sensors as they tend to become a part of the load.
For antennas I think the use of such tool are limited. See **broken link removed**. It can maybe be useful for finding bad EMI spots on a PCB or problems with leaking shields but so far have I found what I need with aid of simple homemade sniff-antennas, coils and electrical probes.
For antennas is the problem that if a probe is measuring in antenna near field, it will disturb this field. At some distance can also measurement be done by scanning or pinpointing but it is just the wave front that will be visible.
Optical fiber can be placed along a dipole and signals that are sent thru fiber becomes modulated in a such way that that voltages in different parts of dipole can be read. Much as how a electron beam is deflected in a CRT due to electrical fields.
If it works with one fiber, can probably many fibers be placed in parallel to build up a 2D view. Problem is that sensitivity and precision is a bit low for small antenna signals but have lately been improved in other areas: **broken link removed**

Thanks. I will investigate. I saw an EM scan at a show, and it looked interesting. But....I suspect the presence of that array of antennas would modify what I am trying to measure a good amount.

I am curious about the fiberoptic approach. Maybe you could use a non-linear media for the fiber, and get some microwave to optical modulation going on that could be hetrodyne detected with a very good dynamic range.

Testing with electron beams is a topic on it's own in IC test methods. Time resolved SEM intruments have been used to measure voltage waveform in chips. Optical measurements utilizing electrical active crystals have been developed at the Fraunhofer Institute for Microelectronic Circuits and Systems.

See appended an US patent describing electron beam measuring techniques.


  • US5444384A.pdf
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Distortion in CRT TV due to static magnetic fields are well known sciencephoto but I have never tested it with a RF TX-circuit placed on screen.
Have however seen similar effects at RF modulated LCD screens in cell phones as an EMI related problem. Do not know if these screens was of type FLCD (F=ferro) but if so can maybe ferrofluid be something to investigate further.
Ferrofluid, as its permeability probably is less then 10 and it is a very thin layer that is needed between two sheets of glass is it maybe possible to build some kind of RF scanner/detector. Total mass can be low, so it should not disturb electric field too much.
Static fields are somewhat simpler, How it works & **broken link removed**.
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