Magnetometer in aliuminium box

Hi Linus, Aluminum is not Ferromagnetic so it will not block the Earth's Magnetic field entirely. Aluminum is a paramagnetic material with a susceptibility of 2.2. I will attach the Wikipedia article on Paramagnetism.

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

Paramagnetic means that the magnetic field does interact with aluminum to a minor extent and as such some field energy is lost. I do not know if it will be enough to matter to your project. A good experiment would be to see if you can detect the difference by testing with the sensor inside the aluminum and outside the aluminum case.

John

Yes, i do understand about properties para/dia/ferfo magnetic materials, only problem is that i can found many threads about sensors nonfunctional inside aluminum boxes, and because at the moment i can't make pcb only to test sensor ( i only have one shot to make pcb ) i need to know will it work or not.

Can't you design the board for an internal mounting and then use some coax to move that sensor off the board and outside the enclosure if necessary. My experience is that construction before testing my designs usually costs me more time than it saves. If you are working with a project to measure the Earth's magnetic field you will likely want the sensor away from your board anyway because of the magnetic fields generated by the currents in its circuitry.

John

i like to make stuff right from the start, and usually it works first time.

This will be used for GPS/GSM car alarm system. I want to generate trigger event based on car rotation in space, or minor impact based on accelerometer data

Basically if some one try to park his car inside of mine, i will get g sensor error/impact warning. If car for some reason will be towed, based on magnetometer data, if it change rotation at least 20-90 degrees from where i left my car, i get error message from that. So it just have to work, no need precision. But it cannot drift in time alot.

Multipurpose custom GPS/GSM alarm

Hi Linas, It sounds like a great project. Let me know how it turns out.

John

I would agree with jw0752.

If you experience any interference from the Aluminium enclosure you could interface the Magnetometer via an external connection. The device could then be housed in a better environment within a plastic enclosure. This external enclosure could even be mounted onto the exterior of the Aluminium enclosure.

Perhaps something like this:

This might sound stupid, but why not use a different material for the box. Maybe a hard plastic?

it should be safe and robust, since box will have lithium battery, and i don't want it to burst into flames that easy. Also, i already have one

Hi Linas,

I'm not sure a LiPo is an appropriate battery for this. Is it a backup battery?

There are well-proven (20+ years) technologies like NiCd or Lead Acid for long-term trickle

or long-term harsh environments (e.g. hot or cold. Although perhaps you've got some industrial or automotive LiPo

like Tesla may be using, in which case I know nothing about them. I'd probably go for NiCd unless you really do need to

go cutting edge on the battery choice, but I don't see that this scenario needs cutting-edge.

Furthermore, typical consumer LiPo is not known for low-temperature operation - I don't know where you're based, but that

may be a huge concern in some parts of the world.

Fist, temperature should be above zero. Second, I need as much energy density as I can get. Third, it should fit inside that tiny box. Yes, I understand, I could make use of larger box, mount sensors outside, but I need very compact and robust system, that could be hidden inside car, and can still function even if someone try to remove it, or do other bad things.

Also, current drain will be very small, in range of 100mA, so any lipo battery can supply this current, yes not for long, but can.

Also, 99.99% of the time system will be using main lead acid battery, and only if someone stole my car, and park inside garage or whatever he do, my system should work. (MEMS device in red circle)