LSM9DS1 Gyro drifting while shutdown

PRebo.1 · ‎2021-01-24

I have an application with a LSM9DS1 that is powered up for a few minutes at a time and then shutoff. It might be powered up again for a few minutes within the same day, or be used only the day after or a few days later. The purpose is to get angular speed information from the gyro.

During testing, I noticed that each time I turn it on, I might get an initial reading that differs progressively from the last time I turned it on. Specifically, during a period of 2 weeks, the speed reported varied progressively up to 0.1 rpm or about 0.6 dps. This was measured against a reference source, that was calibrated with other means (laser tach).

This seems too high a drift to me, especially as is not "continuous" drift while measuring. Is this expected or normal ? Any clue on what might be causing this ?

Thanks

Eleon BORLINI · ‎2021-01-27

Hi @PRebo.1 ,

my suggestion is to always discard the first few samples when you start to acquire data after a power on, especially if these data are the input of an algorithm including integration steps.

You should also control the environmental variables on the long time, even if the datasheet doesn't mention explicitly the time and temperature drift of sensitivity / ZRL parameters (just states that "the sensitivity value changes very little over temperature and over time. The sensitivity tolerance describes the range of sensitivities of a large number of sensors", see datasheet, p.). For this reason, I suggest you to perform some initial measurement of the Zero Rate Level after every power on of the device (before starting a long acquisition), and subtract it via software to the raw data.

Please note by honesty that excursions on LSM9DS1 might be effectively large (although should be not so large as you monitored) if compared to more recent devices such as the LSM6DSx family (e.g. LSM6DSO), that I suggest you to use for application that requires particular accuracy, such as very long acquisitions with little drift.

-Eleon

PRebo.1 · ‎2021-01-27

Thanks for the answer, I might look into the LSM6DSx family.

Are all LSM6DS equivalent in terms of accuracy, sensitivity and temperature/time drift ?

Or some are better than others ?

These are my main criteria. I don't need additional sensor integration or motion recognition features.