or dry chemical etching to then be used to remove unwanted material, leaving behind only the desired parts of the wafer. Additionally, metal can be deposited on the surface of the silicon to form the actuators needed to have a variable structure that can move in response to acceleration or rotation, and the transducers which can detect those movements. Together, these steps produce a batch of MEMS accelerometer or gyroscope structures. New-generation silicon MEMS tend to appear with mass availability every few years, or faster; such is the speed at which MEMS fabricators improve on their older products, while still being able to leverage their existing photolithography and deposition machinery. Nextgeneration quartz MEMS accelerometers are not yet widely or mass-produced, but this may change over the next few years as new production facilities with laser-etching systems come online. As a side-effect of quartz-based MEMS being larger, they come with the prospect of being easier to manufacture (without such precise fabrication requirements as silicon), so investing in a quartz MEMS production line comes with a lower capital requirement, all other things being equal. Complex and exact Quartz MEMS accelerometers can be produced in various ways, with these sometimes being so complex as to require around 200 steps, but they typically start with a quartz wafer, from which multiple devices can be made. Chemical lithography and laser etching are among the techniques leveraged by successful manufacturers to etch the exact shape of the MEMS sensing structures. After these are formed and separated into individual units, processing chips can be mounted on their back sides and connected to them via circuitry for turning their capacitive or resistive signals into acceleration data. After the accelerometer is fabricated, it can be sealed inside a housing, save for an aperture for vacuuming the ambient air – a vacuum environment being highly desirable for ensuring reliable, free movement of the tuning fork inside. Following selection of MEMS accelerometers and gyros (which can mandate exhaustive testing on bench, simulator, and crewed and uncrewed aircraft to ensure systems perform as their datasheets claim), the systems can be integrated into a circuit board to form an IMU, and that complete system can then be calibrated. Calibration today, whether for MEMS or FOG devices, is increasingly automated, with the removal of human error essential for consistent quality. A multi-axis thermal chamber is ideal, within which an IMU can be spun or shaken on a rate table at known, controlled IMUs, gyros and accelerometers | Focus Inertial Performance Reimagined 0.076°/√hr ARW 600 Hz Bandwidth 10 kHz Output Rate <100 µs Message Delay 0.6 Cubic Inches www.gladiatortechnologies.com/sx2 Lower Noise. Higher Speed. SX2 Inertial Sensors with VELOX™ Technology +1 425.363.4180
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