Hello! I would really appreciate some clarifications about the nominal bias terms of ICM-20689. On the data sheet (https://invensense.tdk.com/download-pdf/icm-20689-datasheet/), I can see that there is the term 'Initial ZRO Tolerance' for gyroscopes and 'Initial Tolerance' for accelerometers. Do these terms refer to the initial bias term? What exactly does 'tolerance' mean here? In addition, is there any chance that I am provided the bias instability for gyroscope and accelerometer of this type of IMU, please?
Thank you very much for your time.
Best regards,
Rozerin.
Hi Rozerin,
Initial ZRO Tolerance for gyro is the initial zero-rate offset (component) after we perform the final test in our factory. This is how much off the device is from the true angular velocity. For example, if the device is perfectly still, there should be 0 dps on all three gyroscope axes, but any reading from 0 dps would be considered the offset. A calibration step can be performed to zero out these offsets after it is soldered down to the board, and this is recommended.
Initial tolerance for the accel is the the same concept. This indicates the initial offset after final test in the factory. This is how much the device is off from the true acceleration. For example, if the device is perfectly still with gravity acting on only the Z-axis accel, the X and Y-axis should output 0 mgee, and the z-accel should output 1gee. Any difference between the output and this is the offset. This can also be calibrated out.
Enclosed are two application notes that will help you with calibration.
Thanks,
David N.