[Tinyos-help] 2-axis Magnetometer MTS310CA

[Urs Hunkeler]

Hi Jeremy,

I see you have been posting this message several times and apparently
have not received a reply. So here is my unqualified reply. Maybe this
gets somebody so annoyed that they just want to correct me :-)

1. I think the sensors need to be calibrated. For instance this could be
done by turning the mote slowly around while simultaneously sampling the
magentic field. That way you'll get a maximum and a minimum value
corresponding to perfect (mis)alignment to the earth's magnetic field.
How you do this exactly I don't know (but would like to learn as well).

2. Based on the calibration you need to adjust the on-chip amplifier.
There is are some functions in the Mag interface that seem to allow
exactly this: gainAdjustX and gainAdjustY.

3. It should. But I seem to vaguely remember that the magnetic sensors
on the MTS310 sensor board only measure differences in the magnetic
field, so you could not measure a static field.

I hope this helps a bit. Please let me know if you find out more about
it. Maybe you could contribute these findings then also to the TinyOS
wiki? http://www.eecs.harvard.edu/~mdw/tinyosdocs/index.php/Main_Page

Cheers,
Urs


Tan Simin Jeremy schrieb:
> Hello ppl,
> 
> I'm currently working on the Honeywell HMC1002 Magnetometer which is located on 
> the MTS310CA sensor board. However I'm facing a few problems and hope that you 
> will be able to assist me.
> 
> 1. Why is it that my readings for the x and y-axis are different when I use 
> different sensor boards (MTS310CA) on the mote?
> 
> 2. My readings for the x-axis is changing but the readings for the y-axis does 
> not change in the room. WHy is this so? The y-axis only changes when I bring a 
> magnet near the magnetometer.
> 
> 3. Will the magnetometer still give us a reading if we do not bring a magnet 
> near it? I'm sure there is still the earth's magnetic field present in the room.
> 
> Thank you for your help. Have a blessed week ahead!
> 
> Cheers,
> Jeremy