Reply by DS

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Posted on "Homemade" digital bevel gauge

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3619 posts in 3392 days

#1 posted 12-13-2011 06:18 PM

Another word of caution: ALL accellerometers are inherently NON-LINEAR!
Even though, by design, they attempt to be as linear as possible, there is ALWAYS an error.

An application can attempt to correct this in two different ways. It can offset and scale the transducer readings for a best-fit curve to minimize the error along its entire range, or, it can characterize the transducer with a digital lookup table. The latter requires a precision reference table and gauges, which is not likely to be the case with your smart phone.

(Setting the phone at zero and setting it there, then setting it at another known angle creates offset and scale.)

The question is, how linear IS the smart phone transducer and will it be good enough for what you are trying to do? If it is linear to within a degree at 45 degrees, I would be very surprised.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

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