Static Gravity Reference Vector Determination for Sensor Calibration
Static gravity reference determination requires site gravimetric surveying and arcsecond stage indexing to isolate true sensor bias from facility tilt errors.
Bearing Wobble
Rotational Error
Mechanical deviation where the axis of a spinning component drifts from its theoretical center leads to premature wear and measurement inaccuracy. The bearing wobble introduces a cyclical noise pattern into the output of attached sensors. High precision spindles require minimal runout to maintain the integrity of the data.
This deviation is typically measured in arcseconds or as a linear displacement at a specific radius.
Periodic Runout
Periodic motion of the shaft causes the sensor to experience an unintended tilt or translation. During a test, bearing wobble appears as a sine wave that repeats with every full rotation. This effect is often confused with sensor bias, but the frequency dependence allows for its identification.
Precision bearings use ceramic or high grade steel components to keep this error below one micron. The magnitude of the runout is often dependent on the rotational speed of the assembly.
Signal Noise
Measurement electronics detect the parasitic motion and incorporate it into the primary signal. The bearing wobble creates a false indication of movement that can saturate high gain amplifiers. To isolate the true signal, calibration routines must characterize the rotational profile of the bearing assembly.
Monitoring the phase of the wobble relative to a fixed trigger point enables software compensation. This characterization is performed during the initial setup of the instrument.
Mounting Tolerance
Strict limits on the fit between the shaft and the housing reduce the magnitude of the error. A bearing wobble that exceeds the specified tolerance indicates a failure in the mounting process. Quality control teams verify these levels using a dial indicator or a laser interferometer.
Correct installation ensures that the rotational axis remains stable throughout the life of the instrument. The stability of the bearing determines the long term reliability of the sensing system.