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I'm trying to become educated on IMU specifications, and my understanding is that when comparing IMUs, the Gyros make the big difference. I am looking at the InertialLabs IMU-Nav-100:

https://inertiallabs.com/wp-content/uploads/2021/10/IMU-NAV-100_Datasheet.rev1_.6_October_2021.pdf

They specify the "bias instability over temperature range" as being 15deg/hr. What exactly does this mean?

I have an understanding of what a regular gyro bias instability looks like: a wandering bias with some standard deviation and time constant. But I don't know what the "over temperature range" looks like or means.

Does this mean that, over the operating range, in the worst case (at a particular temperature) the moving bias has a standard deviation of 15deg/hr, and therefore some temperatures are better than others? Does it matter since the document also states that it is "internally calibrated for temperature?"

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  • $\begingroup$ So I don't have an exact answer, but I think I have a very good guess. Typically IMU bias instability is measured at a constant temperature. For bias instability over temperature, it means how unstable the bias is as the temperature changes. So in a constant temperature environment, you can expect the normal bias instability, and in a temperature changing environment, you can expect up to 15 deg/hr of change. $\endgroup$
    – edwinem
    Mar 10, 2022 at 22:28
  • $\begingroup$ Thanks for your comment @edwinem. That makes sense, but for some IMUs I've seen specs such as (x deg/hr/deg C) and even some such as (x deg/hr/degC/min)!!. In the first case it seems like it's deg C away from some nominal temp (presumably room temp?), but the second case seems like what you were describing. It's all very confusing!! $\endgroup$
    – JCB
    Mar 10, 2022 at 22:46
  • $\begingroup$ x deg/hr/degC/min. In a way, this actually makes more sense to me. deg/hr doesn't tell you as much because it doesn't tell you anything about the operating conditions. A rapid temperature change would increase the bias instability more then a slow one. Whereas (x deg/hr/degC/min) does tell you more. Something like the amount of bias change per hour dependent on the rate of temperature change(would have to dig deeper to know what exactly it is). $\endgroup$
    – edwinem
    Mar 14, 2022 at 21:51

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