MAG3110 calibration of devices that don't move

[michaelcallahan]

I have a device that doesn't move after being turned on but I would like to know which direction it is facing.  The MAG3110 magnetometer calibration instructions involve moving devices around (figure 8 or similar) to fit a solution to the resulting range of measurements.  How reasonable is it to assume that I could determine the hard and soft iron calibration for a small sample of PCBs/devices and use it for all others with the same layout?

[172809727]

Hi.

   i use the calibration way refer to the demo. But i don`t know why this way can calibration, if i am wrong. how i can use mag3110 enbedded offset?

   the screenshot is my calibration way

[anthonyduhamel]

Hello Mandy,

This software function is supposed to calibrate the HardIron (offset brought by the board and the magnetometer). But this will work with one essential condition : you need to rotate the board/MAG31110 over the 3-axis during the execution of the calibration !

Look at the chart below (here, the board rotates at a constant speed, but you don't need to do that)

By rotating the magnetometer, you will change the magnetic field (induced by the Earth, like a compass). By capturing the min and max values, you will by able to calculate the offset of the MAG3110. By writing theses values in the OFF_axis_xSB register, the MAG3110 will be able to apply this hardiron vector compensation to the raw measurements: that's the calibration.

Hope this helps you,

Anthony

[172809727]

if i just want to know the angle between to the horizontal. how can i do with mag3110? need i calibrate? please tell me how to do detailed

发自我的iPhone

[anthonyduhamel]

Yes you need to calibrate. If you don't, you will have inacurrate results.

[172809727]

if i just want to calculate the angle between the horizontal how can i do?

发自我的iPhone

[anthonyduhamel]

Please check the Tomas' response. 

how to deal the data from mag3110 

With the additional information I give to you, you should be able to understand how to do it : use the hardiron calibration, then apply arctan(Y/Z). You have all the pieces, you just need to merge it altogether.

Anthony

[anthonyduhamel]

Hello Ben,

Did you use the MAG3110 embedded offset calibration or a real magnetic external calibration? If it is the auto-calibration, it's going to work on 1,2 or 3 axis.

It's hard to say how reasonable is it to perform a "static(non dynamic) calibration" I would say no, but it depends on your final application. Can you tell us more about it?

Thank you,

Anthony