Propylene is one of the building blocks of the modern industrial mansion, which is the feeding stock for polypropylene, acrylonitrile, and other important chemicals. Propane dehydrogenation (PDH) is one of...
This paper introduces a fiber-optic microelectromechanical system (MEMS) seismic-grade accelerometer that is fabricated by bulk silicon processing using photoresist/silicon dioxide composite masking technology. The proposed sensor is a silicon flexure accelerometer whose displacement transduction system employs a light intensity detection method based on Fabry–Perot interference (FPI). The FPI cavity is formed between the end surface of the cleaved optical fiber and the gold-surfaced sidewall of the proof mass. The proposed MEMS accelerometer is fabricated by one-step silicon deep reactive ion etching with different depths using the composite mask, among which photoresist is used as the etching-defining mask for patterning the etching area while silicon dioxide is used as the depth-defining mask. Noise evaluation experiment results reveal that the overall noise floor of the fiber-optic MEMS accelerometer is 2.4 ng/
H
z
at 10 Hz with a sensitivity of 3165 V/g, which is lower than that of most reported micromachined optical accelerometers, and the displacement noise floor of the optical displacement transduction system is 208 fm/
H
z
at 10 Hz. Therefore, the proposed MEMS accelerometer is promising for use in high-performance seismic exploration applications.
Temperature sensors are one of the most important types of sensors, and are employed in many applications, including consumer electronics, automobiles and environmental monitoring. Due to the need to simultaneously measure temperature and other physical quantities, it is often desirable to integrate temperature sensors with other physical sensors, including accelerometers. In this study, we introduce an integrated gold-film resistor-type temperature sensor for in situ temperature measurement of a high-precision MEMS accelerometer. Gold was chosen as the material of the temperature sensor, for both its great resistance to oxidation and its better compatibility with our in-house capacitive accelerometer micro-fabrication process. The proposed temperature sensor was first calibrated and then evaluated. Experimental results showed the temperature measurement accuracy to be 0.08 °C; the discrepancies among the sensors were within 0.02 °C; the repeatability within seven days was 0.03 °C; the noise floor was 1 mK/√Hz@0.01 Hz and 100 μK/√Hz@0.5 Hz. The integration test with a MEMS accelerometer showed that by subtracting the temperature effect, the bias stability within 46 h for the accelerometer could be improved from 2.15 μg to 640 ng. This demonstrates the capability of measuring temperature in situ with the potential to eliminate the temperature effects of the MEMS accelerometer through system-level compensation.
Most spaceborne scientific experiment
applications require a microgravity
environment. The current high-precision accelerometers used for the
spaceborne vibration isolation system generally have a noise floor
of sub-μg/√Hz, which cannot meet the demand of higher-level
microgravity measurements. This article introduces a micro-electromechanical
system (MEMS) acceleration sensor that has a noise floor of 2–5
ng/√Hz and an input range of more than ±2 mg. Its three-component
version, the MEMS microgravity measurement module (MEMS-M3), is designed to measure accelerations in the space microgravity
environment and might be used in the active vibration isolation system
for higher-level microgravity scientific experiments in the future.
The MEMS-M3 has a volume of 105 × 90 × 115 mm3, a weight of 1.2 kg, and power consumption of 3 W. The performance
of the MEMS-M3 has been characterized on the ground and
a series of preflight reliability experiments have been conducted.
Then, the MEMS-M3 installed inside the test spacecraft
has been carried by the Long March 5B rocket (CZ-5B) to the low Earth
orbit at 10:00 on May 5, 2020, and returned to Earth ground at 5:00
on May 8, 2020, both in UTC time. During the on-orbit period, the
MEMS-M3 has been switched on for 11 h. After data processing,
the transient, periodic, and steady accelerations can be observed
by the MEMS-M3 and a much noisier shelf product IMU STIM300,
verifying the functionality of the MEMS-M3. Apart from
application in active vibration isolation systems for spaceborne scientific
experiments, it can also be used for drag-free control of satellites
and other space applications.
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