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# [ADIS16475] How does varying the frequency of the SYNC input change the gyro readings?

How does varying the frequency of the SYNC input change the gyro readings?

- ADIS16475-2 configured in direct sync mode.
- Input clock configured within the 1900-2100 Hz bounds.

Is there any way for the IMU to know the *actual* frequency of the SYNC input?
Does this affect the accuracy of the angular rate readings? The data sheet
indicates that the nominal rate of 2000 SPS is used when calculating the DELTA
ANGLES. I assume something similar is done when calculating the angular
velocities.

Consider page 22 of the data sheet where it shows that better precision on the
DELTA ANGLES measurements can be reached by "measur[ing] the internal sample
rate (fS) using the data ready signal on the DR pin (DEC_RATE = 0x0000, see
Table 108), divide each delta angle result (from the delta angle output
registers) by the data ready frequency, and multiply it by 2000."

Can a similar process be followed to increase the accuracy of the angular
velocity measurements?: measure the internal sample rate (fs), divide each
angular velocity result by 2000, and multiply by fs.

Suppose I place an IMU on a turntable and apply a known rotation (e.g. 100
deg/sec). Then I provide a 1900 Hz direct SYNC input. Next I provide a 2100 Hz
SYNC input while the IMU is undergoing the same physical rotation. Will the
GYRO registers provide different outputs in the these situations? Or will it
correctly report 100 deg/sec regardless?

Without having too much insight on the sensor internals, if I assume a similar
situation in the angular rate as with the DELTA ANGLES then there can be almost
a 10% percent difference in sensor readings [(100 / 2000) * 1900 = 95 deg/sec]
vs [(100 / 2000) * 2100 = 105 deg/sec] if the IMU incorrectly assumes a 2000 SPS.

typo
[edited by: heving at 9:23 PM (GMT -5) on 20 Jan 2022]