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Is there any electronic device that can measure the distance from a point in space to a wire with very low voltage running through it? The measurement of concern would be approx. 3 to 5mm . Its application would require the measurement to be made through a material such as bone.

Any ideas?

Connor Wolf
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Gregg Stein
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  • 'Very low voltage running through it'? Do you mean that there is a constant voltage on the wire? Is there any current flow? What sort of precision do you need? Any other knowns that we can work with? – Samuel Dec 02 '12 at 21:17
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    Depending on how much current flowing through it, you can measure the strength of the electromagnetic field the wire produces, which you can then calculate the distance from the data. I have no idea if this is feasible or can be made accurate enough for your particular application. – In silico Dec 02 '12 at 21:18
  • If the device is small and the current is very low, I doubt it would be detectable at any decent distance. A metal detector would probably give you better results. FYI, bone or bone like material won't have much if any effect on detecting active electronics, since they are detected by the magnetic field created by current flow. Just because I'm curious, are you trying to detect implanted electronics in a person? – Garrett Fogerlie Dec 02 '12 at 22:25
  • Keep in mind that while the wire has a small current running through it, that is not the only possibility for detection - acoustic, radiographic, active inductive, etc options might exist too. – Chris Stratton Dec 02 '12 at 22:28
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    I think a key question is: do you have any control over the current flowing in the wire? If you do, you have a much easier problem. –  Dec 03 '12 at 10:25
  • Voltage doesn't run through it appears across. Direct current produces a magnetic field. – JIm Dearden May 23 '13 at 14:23

4 Answers4

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Context

What others have rightly pointed out is that you have many modalities to choose from each with its own strengths and weaknesses.

If you want to pursue the electro-magnetic modalities, what you are trying to do is certainly possible and practical.

Interferometry ("High" Frequency)

If you can control the wire, EnSite NavX from St. Jude's uses a 20MHz RF signal to do localization by Time of Flight (via interferometry) if I recall correctly.

We use it in our interventional cardiology procedure rooms ("cath labs").

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Electrostatics ("Low" Frequency)

I developed a similar approach that works at near-DC (quasi-static).

enter image description here

DrFriedParts
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  • Xray works best for metal detection with transmission but doesn't work by reflection and tissue, bone, plasma is relatively transparent but this is not wrokable.
  • RF can detect metal but is also affected by plasma so this is not workable
  • Magnetic is more immune to plasma and bone but due to VLF has very poor resolution and accuracy and is more dependant on mass proximity,not precise but best method for locating. Miniature version can be made but wont measure distance, just getting closer.
  • 3D Ultrasonic would work best but requires lots of impedance matching goop so may not be workable. (this is hypothetical and I dont have any recommendations beyond this.
Tony Stewart EE75
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I cannot help being reminded of the Theremin, which is a kind of electronic musical instrument whereby pitch is controlled by the distance of the player's hand from the antenna, causing small variations in a tiny capacitance. The operational principle may be applicable to your problem. Different materials have different dielectric constants, though, which would precludes an absolute measurement scale.

Kaz
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Its an old question but worth adding this

http://en.wikipedia.org/wiki/SQUID

JIm Dearden
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