Multi axis magnetometer sensitivity: what kind of detection range is possible?

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nitrous2000

Member
Hi folks,

What kind of detection range is possible with a magnetometer?
I realize magnet (detecting a neodymium magnet) strength will play a big factor, but what sort of range might one expect with a coin size N42 magnet?

Would a three axis device be superior to a 2 or even single axis device? I'd like to detect polarity as well.

Any advice would be welcome.
Thanks,
Nitrous
(I'm asking about an accelerometer application in an other thread but need to order both devices so I'm asking about this as well)
 
G

g6ejd

Senior Member
You can't get the z-axis without an accelerometer so 2-axis is adequate IMO? I use this type of device and obviously they can detect differences in the Earths magnetic field. When I've brought mine near a psu they have stopped working. What are you trying to do?
 
C

Colinpc

New Member
I have used a magnetometer in one of my projects (do a search). I was able to detect moving a standard paper clip from about 40mm. I only looked for a change in field rather than polarity but your code should be able to do what you want.

In a basic quick test, I put my cct about a metre from the front wheel of my car, then moved the car back and it detected the movement.

Fred
 
N

nitrous2000

Member
Thanks for that feedback. So, in the absence of another detection means (ie accelerometer), there is no value beyond 2-axis?
Nitrous
 
A

AllyCat

Senior Member
Hi,

What range are you looking for? Neodymium magnets may be very "strong", but the poles are quite close together so I think the field strength will fall off rapidly at larger distances.

Cheers, Alan.
 
N

nitrous2000

Member
About 1 metre or so.
I was also concerned about the proximity of the two poles affecting detection distance.
Thanks for your thoughts and comments on this question.
Nitrous.
 
A

AllyCat

Senior Member
Hi,

That sort of distance I'd consider "problematic". My pure guess is that 30cms could be possible and 3 metres impossible, but in between needs a detailed analysis of the environment. Magnetometers, like many scientific instruments, can be incredibly sensistive (are you actually considering a Hall device of some type?) so you probably need to consider if there are any interfering or "noise" sources (motors, transformers, etc.) in the vicinity, or large objects which might distort the Earth's magnetic field. If not, and the magnet moves at a moderate speed, then detection might be possible. But to be honest, I think I'd be looking for an alternative sensor method, or at least extending the magnetic field away from the poles.

Cheers, Alan.
 
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