hi jeremy adding to Urs' comments to caliberate, u should get a +1/-1 mGauss when the +ve/-ve X/Y axis is facing towards the earth or vice versa. if that is different, u have to caliberate the values to get this reading.
On 9/19/07, Urs Hunkeler <[EMAIL PROTECTED]> wrote: > > 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 > _______________________________________________ > Tinyos-help mailing list > [email protected] > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > -- Sougata Sen Bangalore
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