Inertial sensors are semiconductor devices that are used to measure acceleration, changes in inclination, and gyration. There are several basic types of inertial sensor products. Sensor elements or chips are "raw" devices that lack signal conditioning or packaging. Complete sensors or transducers are more complex devices that include packaging and/or signal conditioning. These inertial sensors are powered and provide an output such as direct current (DC) volts (V), or a current loop such as 4 to 20 milliamps (mA). Instruments and meters are inertial sensing devices with a local or remote display. They are usually self-contained and may include signal processing and signal conditioning features. Gauges and indicators are inertial sensors with a handheld, usually analog display. Records and totalizers log several data points and/or totalize measurements. They may also be capable of more sophisticated functions such as statistical analysis.
Mechanical specifications for inertial sensors include measurement range, minimum resolution, sensitivity, sensitivity change vs. temperature, zero-g level, non-linearity, self-test output change, bandwidth, operating temperature, and product weight. Minimum resolution is the smallest unit of resolution of distinction for the measurement. Sensitivity describes the gain of the inertial sensor and is a function of acceleration. Typically, this value remains relatively stable over changes in temperature. Zero-g level is the deviation of an actual output signal from an ideal output signal in the absence of acceleration. Linearity is steady-state on a horizontal axis and measures 0 g on the X-axis, 0-g on the Y-axis, and 1 g on the Z-axis. When a linear sensor’s self-test feature is activated, the output level is expressed as the algebraic sum of the resulting signals.
Selecting inertial sensors requires an analysis of electrical specifications and absolute maximum ratings. Electrical specifications include supply voltage, supply current, high-level input and output voltages, low-level input and output voltages, output data rates, turn-on time, and operating temperature range. Absolute maximum ratings for an inertial sensor include maximum powered and unpowered acceleration, maximum supply voltage, and electrostatic discharge (ESD). Storage temperature and product handling requirements are additional factors to consider when selecting inertial sensors.