Abstract
This article tackles the challenge of the dynamic calibration of modern sensors with integrated data sampling and purely digital output for the measurement of mechanical quantities like acceleration, angular velocity, force, pressure, or torque. Based on the established calibration methods using sine excitation, it describes an extension of the established methods and devices that yields primary calibration results for the magnitude and phase of the complex transfer function. The system is demonstrated with a focus on primary accelerometer calibrations but can easily be transferred to the other mechanical quantities. Furthermore, it is shown that the method can be used to investigate the quality and characteristics of the timing for the internal sampling of such digital output sensors. Thus, it is able to gain crucial information for any subsequent phase-related measurements with such sensors.
Highlights
More and more applications and appliances in both the industrial and the consumer fields are integrating micromechanical sensors with a direct digital output
Whenever the digital output sensor (DOS) signals the availability of a new sample via the data ready output
In order to test the above-mentioned concept, the digital acquisition unit (DAU) was used to perform a primary calibration of the z-axis of a 6-degreeof-freedom MEMS sensor of the type MPU-9250 following [6]
Summary
More and more applications and appliances in both the industrial and the consumer fields are integrating micromechanical sensors with a direct digital output. That means the measured value of a quantity like acceleration, air pressure or force is accessible via a digital interface like SPI, I2C or CAN in terms of a binary number Those values can be directly fed into control units or digital displays for further processing without any need for traditional signal conditioning by amplifiers or sampling by discrete AD converters. As soon as the focus shifts onto dynamic signals, the timing of signal acquisition is of high importance, and the integrated sampling and signal conditioning of such sensors creates new challenges for the calibration lab. While the calibration of the magnitude of a sensor's complex transfer function only needs the technical interfaces and a stationary excitation signal [5], the phase or group delay calibration is strongly dependent on either the synchronicity of the channels or other precise knowledge of the sample timing
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