An accelerometer is an electronics component that detects movement along one, two, or three dimensions. It converts the physical properties of motion into electronic signals for digital processing. This technology is used in manufacturing, safety-critical equipment, computers, and many other contexts. Accelerometer calibration is employed using many techniques in order to accommodate the many different applications in which the devices measure acceleration and orientation changes. Methods essentially consist of determining orientation and acceleration under field-use conditions. Procedures involve evaluating performance goals, calibration measures and processes, and implementation.
Accelerometer calibration is the comparison of the component using a standard instrument or testing process to detect, correlate, or eliminate inaccuracies. It relates to metrology, or the study of measurement systems, and depends upon traceability, which is the relationship between standard and performance. Some accelerometers are mass produced and rely on common techniques to detect motion, while others are custom built and require specialized techniques and analysis. Most protocols adhere to national or international standards of measurement or performance.
Each method of accelerometer calibration depends upon its constituent technology. Types of accelerometer detection include piezoresistive, variable capacitance, micro-electromechanical systems (MEMS), and integrated circuits. Some even use bubbles, like a carpenter's level. These components assess movement along two or three axes in physical space. Careful positioning of the x,y, and z axes aligned with known local verticals permits readings of orientations and forces; as well as inaccuracies, bias, and errors of scale.
Whether devices are high tech or low tech, all require an accelerometer calibration that allows for the natural resting state of gravity. This is the one gee, or 9.81 m/s^2, of gravitational force already applying itself to a detector. An accelerometer affixed to a calibration bar might be launched and struck to measure the stress wave of its impact; this may be recorded onto a stress gauge.
A comparison can be made between the readings of the gauge and the characteristic output measures of the accelerometer. Additional techniques include tipping a device in regular increments and recording the angle outputs, compared to trigonometric values for gravity. Data is correlated among multiple tests to allow for varied object masses, speeds, and forces.
As accelerometer technology has worked its way into an increasing number of technologies and safety-systems, accelerometer calibration has become an issue of increasing value. Specialized equipment is designed to provide these measurements for more accuracy and consistency, and less cost. These devices allow system designers to evaluate equipment performance levels and manage expenses. Calibration processes examine these performance versus cost curves to decide between outsourcing calibration services or developing a company's own in-house processes.
