Google wasn't feeling very helpful, so I will probably go home this weekend and to the experiments myself, but until then I'm curious to hear you guys' predictions of the effect on an inductor by being submerged in water. I have a growing curiosity with using springs as a position feedback mechanism by measuring the change in inductance as they stretch. Products such as TI's LDC1000 seem to make it easy. But what if your application is subsea? Assuming you coat the spring and the electrical terminations with an insulator to prevent current flow through the water, to what degree will the water itself induce eddy currents and change the inductance? My gut says the effect would be negligible, but that might just be wishful thinking.

 

it depends on the conductivity of the water. there will be loss due to coupling to the conductive water and wilool act like a shorted turn if too conductive.

 

Google wasn't feeling very helpful, so I will probably go home this weekend and to the experiments myself, but until then I'm curious to hear you guys' predictions of the effect on an inductor by being submerged in water. I have a growing curiosity with using springs as a position feedback mechanism by measuring the change in inductance as they stretch. Products such as TI's LDC1000 seem to make it easy. But what if your application is subsea? Assuming you coat the spring and the electrical terminations with an insulator to prevent current flow through the water, to what degree will the water itself induce eddy currents and change the inductance? My gut says the effect would be negligible, but that might just be wishful thinking.

I think you have very valid reason to suspect that the inductor's behavior will be affected... Pure distilled water is almost non-conducting, but saltwater is highly so... Maybe the inductor will behave as if it had a solid conductive core to some degree, but it's also being heavily shielded by the saltwater surrounding it... My suggestion: There's only one way to find out... test it, Test It, TEST IT! and have lots of fun while doing so...

 

Air has a relative permeability of 1.00000037. Water is 0.999992 (from Wikipedia). Ignoring conductivity, you'd be hard pressed to see a difference, I think.

 

I think you have very valid reason to suspect that the inductor's behavior will be affected... Pure distilled water is almost non-conducting, but saltwater is highly so... Maybe the inductor will behave as if it had a solid conductive core to some degree, but it's also being heavily shielded by the saltwater surrounding it...

I don't know everything that I should know about high frequency impedence or electromagnetism, so I don't know if there is a distinction to be made between electrical conductivity and magnetic reluctance, or if reluctance is the important factor. Are they directly related? Because if they are a 1:1 relationship, and if this list is accurate, then it seems the saltwater shouldn't pose much of a threat, being 12 million times less conductive than copper. But I tend to think that there is more at play than simply electrical conductivity.

My suggestion: There's only one way to find out... test it, Test It, TEST IT! and have lots of fun while doing so...

Agreed, and I will test it as soon as I can.

 

There you go, Relative Permeability. A good keyword for me to google. Thank you

 

There you go, Relative Permeability. A good keyword for me to google. Thank you

If you think about it, those metal detectors some use on the beach seem to work as well on land as submerged in water.

 

and trhe "relative permeability" is different from pure water to salt water. pure water isnt conductive, and salt water is. has anyone tried the sensativity of metal detectors in salt water as compared to dry ground? why dont the navy search for submarines with metal detectors?

 

Actually, I wish someone, someday, could explain to me how "free space" can have a magnetic permeability, as:

[T]he auxiliary magnetic field H represents how a magnetic field B influences the organization of magnetic dipoles in a given medium, including dipole migration and magnetic dipole reorientation. Its relation to permeability is

I am well aware of Maxwell's Equations, and I know that a specific value of permeability is required in order for light to propagate at velocity c, but where are these dipoles that are influenced by B? Virtual particles?

 

and trhe "relative permeability" is different from pure water to salt water. pure water isnt conductive, and salt water is. has anyone tried the sensativity of metal detectors in salt water as compared to dry ground? why dont the navy search for submarines with metal detectors?

Magnetic Anomaly Detection

 

Actually, I wish someone, someday, could explain to me how "free space" can have a magnetic permeability...

Duh. I think I answered my own question. The Magnetic Permeability of free space is simply a constant that relates B to H in the absence of magnetic dipoles. Someone tell me if I am wrong.

I've been out of college too long.

 

You might enjoy reading about this. I found quite a bit of interesting stuff by just searching on "effect of saltwater on magnetic field". Some of it would make for a good science fair project.

 

Actually, I wish someone, someday, could explain to me how "free space" can have a magnetic permeability..

It took science quite a while to accept the notion that there doesn't need to be an "ether" to propagate EM, so you're not alone in finding it hard to grasp.

 

You might enjoy reading about this. I found quite a bit of interesting stuff by just searching on "effect of saltwater on magnetic field". Some of it would make for a good science fair project.

You might as well also enjoy reading this, since it's somewhat related to what we've been discussing. I do believe that Einstein once worked on this concept, among many other small projects of his.

 

Google wasn't feeling very helpful, so I will probably go home this weekend and to the experiments myself, but until then I'm curious to hear you guys' predictions of the effect on an inductor by being submerged in water. I have a growing curiosity with using springs as a position feedback mechanism by measuring the change in inductance as they stretch. Products such as TI's LDC1000 seem to make it easy. But what if your application is subsea? Assuming you coat the spring and the electrical terminations with an insulator to prevent current flow through the water, to what degree will the water itself induce eddy currents and change the inductance? My gut says the effect would be negligible, but that might just be wishful thinking.

Years ago I used to repair TVs for someone who got them from the local tip.

One black & white battery/mains portable was put on the bench before me - despite taking the back off before getting started, I failed to notice the puddle of rainwater on the PCB around the horizontal transformer core.

When set was powered up; the puddle was instantly transformed into an impressive cloud of steam.