Friday, April 1, 2011

Temperature calibration

It seems that this gyro is much less temperature sensitive than the last one. I sat it still for a while, and over the temperature range I tested it, it has a variation of about 4 DN, out of 16 bits. That might be good enough. It depends on the temperature range.

I need to run the linear Kalman filter a couple of times, once on the temperature data itself, and once on each axis of the gyro.

So, I need a way to somewhat regularly cycle through temperatures. My desktop computer's case is open, so I can stick the IMU next to the exhaust fan while periodically loading up the main computer with a ray-tracing or something for a few minutes, then going idle for a few minutes, etc.

Update: Well, I got a couple of degrees of temperature swing:

So from the bottom we see that we get about 1.5 DN per degC of temperature change. This is on the gyro zero offset, so it is really really important to get right. As I said, this screams out for a Kalman filter, so it shall get a Kalman filter.

So, upon running the Kalman velocity model on both the temperature and X gyro data, we get:

and running a linear fit through this says we get an offset of 751.4609-1.3843T, where T is in degC. More useful is that the offset is 637.7520-0.0049438T where T is in raw sensor DN.

In DN, the zero setting for all three axes is as follows:


z= 21.9189-0.0002229T

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