# Two scale factors in IMU

1. ## Two scale factors in IMU

Hi,

an IMU has two parameters:

scale factor repeatability = 1000 PPM (1-sigma)
and
scale factor in-run stability = 250 PPM (1-sigma)

Question: What is the difference between them?

Senmeis

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2. ## Re: Two scale factors in IMU

from https://en.wikipedia.org/wiki/Inertial_measurement_unit

repeatability is getting the same result from doing the same thing - say you use your IMU to fly a plane from dallas to tokyo
do this several times. the repeatability is a measure of your landing in the same spot each time

stability is sitting still and getting the same thing - say you park your plane in denver, and leave the IMU running. stability is it saying your still in the same place

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3. ## Re: Two scale factors in IMU

I’m not sure if the „scale factor in-run stability“ is related to the case when the IMU stands still. Attached is an example of both parameters. It seems scale factor in-run stability is measured with the roll = 180 degrees.

Senmeis

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