How to calibrate multiple magnetometers for mass production
How to calibrate multiple magnetometers for mass production
(OP)
How would one go about calibrating several magnetometers in a production environment? The magnetometer is being used for the purposes of a compass.
Currently I'm calibrating them one-by-one in an open field free from magnetic interference (i.e. no hard or soft iron around) by rotating my magnetometer, and associated electronics, in all three dimensions and then compensating, through software, for the inherent magnetic interference of the on-board electronics.
I'm curious though how large companies scale this process without introducing magnetic interference. I am also assuming they don't go outside into an open field and do this so I wonder how you can control magnetic interference inside a building presumably with ferrous metal in the walls.
Currently I'm calibrating them one-by-one in an open field free from magnetic interference (i.e. no hard or soft iron around) by rotating my magnetometer, and associated electronics, in all three dimensions and then compensating, through software, for the inherent magnetic interference of the on-board electronics.
I'm curious though how large companies scale this process without introducing magnetic interference. I am also assuming they don't go outside into an open field and do this so I wonder how you can control magnetic interference inside a building presumably with ferrous metal in the walls.





RE: How to calibrate multiple magnetometers for mass production
Dan - Owner
http://www.Hi-TecDesigns.com
RE: How to calibrate multiple magnetometers for mass production
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: How to calibrate multiple magnetometers for mass production
RE: How to calibrate multiple magnetometers for mass production
> accuracy and matching of field intensity measurements
> orthogonality of the 3 axis magnetometers
> alignment to fiducials of the case
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: How to calibrate multiple magnetometers for mass production
There's a clue in the universal approach used in mobile phones, where the user is directed to move the phone around in a Figure-8 pattern of movement to calibrate the internal magnetic compass. It seems obvious that such an approach would allow the software to adjust-out the device's own field (as it would be a constant offset during the movement).
I wonder how they deal with variability of the device's own field? More software? A bespoke magnetometer system might be designed with a constant current (in the circuits) to avoid this question.
A strong local field will allow calibration of the relative alignment of the sensor onto the device's circuit board. That would seem to also be a requirement as part of the Factory ATP.
RE: How to calibrate multiple magnetometers for mass production
This method though, also looks at the field around the device as well as the magnetic field generated by the internal electronics. Since the end application is a digital compass, the readings are taken in a outdoor environment so as not to skew the final compass reading when it is used outdoors.
RE: How to calibrate multiple magnetometers for mass production
What accuracy are you trying to achieve?
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: How to calibrate multiple magnetometers for mass production
RE: How to calibrate multiple magnetometers for mass production
This is similar to what we used for compass calibration, but the actual volume of controlled magnetic environment is pretty tiny.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: How to calibrate multiple magnetometers for mass production
Since the goal is to do this indoors, could I simply perform the tumble test using the Helmholtz coil with my current method of calibration, with respect to the Least squares method? Basically I'm wondering if I can perform the calibration using the Helmholtz coil without having to change my software. I'm guessing that I probably can't do that because the strong magnetic field will skew the current calibration curve.
RE: How to calibrate multiple magnetometers for mass production
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: How to calibrate multiple magnetometers for mass production