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SeisMaCalibrate Frequently Asked Questions
- Q: How accurate is the Sudden Motion Sensor?
- A: The Sudden Motion Sensor seems to be quite precise, and when calibrated
it can be pretty accurate as well. On my MacBook Pro 15", calibration gets
to within about 1% of the expected value with the laptop level, and tipped
at 30, 60 and 90 degrees. Pretty darn good. I expect other MacBooks to have
similar precision, but G4 laptops have a lower-resolution accelerometer.
- Q: How many samples a second does SeisMaCalibrate display?
- A: SeisMaCalibrate samples 100 times a second, but displays a running average 10 times a second.
- Q: I used SeisMaCalibrate to calibrate my Sudden Motion Sensor while SeisMac is running, but SeisMac's graphs still aren't centered on 0g and 1g.
- A: For SeisMac to read SeisMaCalibrate's saved calibrations, you must quit SeisMaCalibrate before you start SeisMac.
- Q: Where is the calibration stored?
- A: In the defaults database maintained by OS X. To see this, open Terminal.app and type
defaults read com.suitable.SeisMacLib
- Q: What is this "calibration email" button?
- A: The default calibration values shipped with SeisMac and SeisMaCalibrate are collected from the web, and some are mere guesses. I know for a fact that some current values are just wrong, in both sign and magnitude. If you use SeisMaCalibrate to calibrate your SMS, and then send me a calibration email, over time I'll be able to greatly improve the default calibration values.
- Q: My G4 Mac laptop has SMS, but SeisMaCalibrate suddenly stops working on
it.
- A: On some models of G4 laptop, the access method SeisMaCalibrate uses may
fail suddenly, not working again until the computer is rebooted. Since Apple
doesn't support this API, and I don't own such a laptop, it would be difficult
for me to fix this. Sorry.
- Q: May I have the source code for SeisMaCalibrate?
- A: I've released the source code for the underlying SMS access library, SMSLib,
but I won't be releasing the source for SeisMaCalibrate as a whole.
- Q: Did you figure out how to access the Sudden Motion Sensor all on your own?
- A: Although the code is all my own, I used techniques discovered by a number of other people. For details, see the Credits and Links page.
- Q: I've got another question that you haven't answered here.
- A: You can contact me at griscom@suitable.com.
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