Best Targtet Material for Magnetic Sensing?
Best Targtet Material for Magnetic Sensing?
(OP)
I'm designing a sensor that needs to convert mechanical vibration in a target object to an electrical signal. The situation is very analogous to a guitar pickup, where a magnet or pole piece is surrounded by several thousand turns of wire, except that in my case I have some control over the materials selection of the object whose vibrations are being transduced.
I want to maximize the transfer gain of the whole system (Vout/TargetDisplacement) in order to maximize signal-to-noise ratio and to enable a coil-to-target distance large enough that manufacturing tolerances are not problematic.
I understand that I can increase coil output by increasing magnet strength and/or number of coil turns, but these have some limits due to cost, size, and undesirable damping of the target object. I want to first choose the best target material then find the lowest cost, smallest combination of magnet power and coil size that will do the job.
I would like some guidance on what magnetic parameter(s) is/are most important in the target object for maximizing the induced coil voltage for a given target displacement diatance. I believe I am looking for the highest possible permeability in order to have maximum impact on the flux lines going through the coil as the target object vibrates. Is this correct and are there other parameters I should be looking at?
Thanks,
Julia
I want to maximize the transfer gain of the whole system (Vout/TargetDisplacement) in order to maximize signal-to-noise ratio and to enable a coil-to-target distance large enough that manufacturing tolerances are not problematic.
I understand that I can increase coil output by increasing magnet strength and/or number of coil turns, but these have some limits due to cost, size, and undesirable damping of the target object. I want to first choose the best target material then find the lowest cost, smallest combination of magnet power and coil size that will do the job.
I would like some guidance on what magnetic parameter(s) is/are most important in the target object for maximizing the induced coil voltage for a given target displacement diatance. I believe I am looking for the highest possible permeability in order to have maximum impact on the flux lines going through the coil as the target object vibrates. Is this correct and are there other parameters I should be looking at?
Thanks,
Julia





RE: Best Targtet Material for Magnetic Sensing?
What are your requirements? Is this for school?
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RE: Best Targtet Material for Magnetic Sensing?
Thanks for the reply, IRstuff. No, this is not for school - I have 35+ years of experience in my field (which doesn't usually involve a whole lot of magnetics, hence my inquiry to this fine forum).
There are indeed many sensing modalities, and I've been through quite a few: experimentally, in production, and in my mind, and am pretty darned keen on a magnetic coil for the next iteration. It's been prototyped and is looking very promising; now I just need to work out some details and we'll be off and running.
I require frequency response out to 20kHz, which rules out a lot of techniques. I require a sensor cost in the vicinity of $2.00 in volume, which rules out some more. I require something that can be produced in volume by a fairly low-tech Asian OEM factory, which rules out some more. The magnetic sensor meets all the requirements, I just need to tell the metallurgists what to put into the mix.
I can't tell you all about the dingus because it's confidential to my client.
So what's the most important magnetic parameter when trying to induce the maximum possible current in a coil in a magnetic field by waving a chunk of ferromagnetic material around in the field?
Thanks,
Julia
RE: Best Targtet Material for Magnetic Sensing?
The answer to your last question of your 2nd post: The most important magnetic parameter would be the Remanence of the material.
RE: Best Targtet Material for Magnetic Sensing?
Julia
RE: Best Targtet Material for Magnetic Sensing?
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Best Targtet Material for Magnetic Sensing?
Electroplated nickel (sorry, I don't know the exact thickness at this point) actually works, marginally, at very close coil-target distance, say, around .062". A piece of 0.010" mu metal works great at distances up to about 0.375".
Re corrosion resitance, we will probably nickel-plate over everything for both appearance and corrosion resistance, if the sense material turns out to be something other than nickel.
Cost is a consideration, yes, but we'll spend what we need (within reason) to to make it work well.
I guess we'll have to experiment, but it's good to know that I need to look at saturation flux density as well as premeability, that's the kind of info I was looking for.
Julia
RE: Best Targtet Material for Magnetic Sensing?
400G is the field calculated for that distance in air only. The presence of a high-permeability material will re-distribute the field and increase its magnitude in that region.
MagMike, that is a myth regarding AlNiCo!
RE: Best Targtet Material for Magnetic Sensing?
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Best Targtet Material for Magnetic Sensing?
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Best Targtet Material for Magnetic Sensing?
Julia
RE: Best Targtet Material for Magnetic Sensing?
You could use electroless Ni to protect from rust.
If you want to boost field (ans output) then try adding pole pieces to the ends of you magnet. You would raise the operating point and you could taper them. It would raise the field strength.
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