Wuxi, May 24, 2016 / PRNewswire / - Amex, a company based in Andover, Mass., Recently released a white paper to unveil its new MEMS sensor with reduced vibration, reduced impact and smaller dimensions And higher reliability solutions to provide dependable and accurate measurement results in high-intensity vibration environments. In addition, Midea is the only company in the world that has both MEMS sensor and sensor system integration technologies.
Design engineers often need to make a choice between different types of accelerometers in the development of heavy equipment. For example, in heavy machinery such as cranes, tractors, wood cutting machines, and construction works, designers need to measure the pitching and roll angle of the equipment during operation by using acceleration sensors.
Application of MEMS Thermal Convection Sensor in Industrial Field
In most applications, device designers often choose between capacitive and thermal MEMS accelerometers. They are usually based on the sensor's main characteristics, such as structure, resonant frequency, reliability, stability, bandwidth, power consumption and cost to make a choice. What is more, what they need to understand is that both types of the respective advantages and disadvantages of measuring inclination in a high-intensity vibration environment.
The accelerometer can directly measure the three components of the gravitational acceleration, which can be obtained by mathematically calculating the three components of the gravitational acceleration. A biaxial acceleration sensor determines the current pitch and roll angle by measuring the slanted sine angle. The theoretically measurable range of angles is 0 +/- <90 degrees. Since the rate of change of the sine function becomes smaller in the range of nearly 90 degrees, higher accuracy can only be provided in the range of 0 +/- 70 degrees. However, a biaxial acceleration sensor can measure pitch or flip angles up to 0 +/- 180 degrees. The pitch angle (0 +/- 90 degrees) and roll angle (0 +/- 180 degrees) can be measured over the full range using a three-axis or two-axis accelerometer. Because of the slightly lower Z-axis performance of the tri-axial accelerometer than the XY, two biaxial accelerometers are still used in most applications.
A cantilever-based triaxial capacitive MEMS accelerometer calculates acceleration by measuring the force acting on the mass. Under the action of acceleration, the distance between the mass and the fixed electrode is changed, which leads to the change of the capacitance between them. Since the rate of change of capacitance is proportional to the magnitude of acceleration. Therefore, the acceleration can be determined by calculating the amount of change in capacitance.
Typical biaxial thermal MEMS accelerometers are based on single-chip integration. The sensor and control circuit chips are integrated in a hermetically sealed package. The sensor contains a cavity created by silicon etching and a set of heaters and temperature measuring cells placed in the cavity. Unlike capacitive devices, thermal sensors measure acceleration by monitoring the movement of the heated mass within the package cavity. In the absence of acceleration, hot air masses are symmetrically distributed above the heaters. Under acceleration, the hot air mass moves in the direction of acceleration. Since the device does not contain a structure that can be bent or displaceable, very high device reliability can be provided.
The biggest difference between the two technologies lies in their different sensing technologies. Capacitive MEMS accelerometers use a displaceable cantilever structure. For low-acceleration devices used for dip measurements, the inherent bandwidth of cantilever structures is typically greater than 5 kHz and the resonant frequency is around 2 kHz. When the vibration energy is too large or the frequency of the vibration is close to the resonant frequency of the cantilever structure, the output signal of the capacitive acceleration sensor may be distorted or resonated. In most cases, distorted or resonant signals can cause large zero shifts (especially the Z-axis), making the sensor unable to properly reproduce the true signal in a high-intensity vibration environment. Zero drift in high-intensity vibration environments is an inherent disadvantage of capacitive accelerometers and often requires additional techniques to isolate or mitigate the effects of vibration.
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