Specifications accelerometers

Frequency is defined as the number of repetitions of a specific forcing function or vibration component over a specific unit of time. Take for example a four-spoke wheel with an accelerometer attached. Every time the shaft completes one rotation, each of the four spokes passes the accelerometer once, which is referred to as four cycles per revolution. Therefore, if the shaft rotates at 100 rpm, the frequency of the spokes passing the accelerometer is 400 cycles per minute (cpm). In addition to cpm, frequency is... 

Three basic types of vibration transducers that can be used for monitoring the mechanical condition of plant machinery are displacement probes, velocity transducers, and accelerometers. Each has limitations and specific applications for which its use is appropriate. 

Most silicon accelerometers are based on a micromachined variable capacitance element (g-cell) that is converted to a voltage using a C-V converter and then amplified, filtered, and buffered to provide an analog output as shown in Fig. 7.1.4. To date, open-loop implementations for capacitive read-out circuits are more widely employed than closed-loop systems, primarily as a result of the stability of such systems [16]. Interface electronics for micromachined sensors depend not only upon the transduction technique (input specification) and the product requirements (output specification) but also on the packaging approach, as parasit-ics are introduced when a multiple-die packaging technique is used. 

With the advent of acceleration detection over longer timeframes or satellite sensors near the perimeter of the vehicle, problems began to surface with signal distortion from the accelerometers. These occurred due to several specific sources. 

Accelerometers generally fall into two application categories of impact or motion measurements. The specifications for each type of application vary with regard to sensitivity, zero-g offset, frequency range and noise. In all cases there is a desire to have the smallest possible package size and lowest power consumption. 

Orientation of Sensors. Tissue-, interface-, and structure-mounted sensors may be aligned as closely as possible with the axes of a biodynamic coordinate system (see, for example, Fig. 10.2), even though these may have inaccessible origins that are anatomical sites within the body. In practice, sensors are commonly oriented to record the component accelerations defined by the basicentric coordinate systems shown in Fig. 10.2 (ISO 2631-1, 1997 ISO 5349-1,2001), which have origins at the interface between the body and the vibrating surface. The location of accelerometers to record the handle vibration of specific power tools is described in an international standard (ISO 5349-2, 2001). 

The ALMS detects leaks at specific locations or within specific components in the primary coolant system. This system uses accelerometers to detect the presence of a primary leak. The system follows, in part, the guidance identified in Regulatory Guide 1.45, as discussed in CESSAR-DC, Section 7.1.2.20. The system functions, theory of operation and description are given in CESSAR-DC, Section 7.7.1.6.2. Other leak detection methods employed in the System 80+ Standard Design are discussed in CESSAR-DC, Section 5.2.5. 

In the following, the fabrication and characterization of micromachined high frequency focused polymer ultrasonic transducers in a manner that is compatible with CMOS microelectronics, and MEMS batch fabrication techniques, are described. The specifics of the electronics are not described here, but the interested reader may find more details elsewhere [75, 76, 81-84]. The transducer is capable of being manufactured on silicon wafers after the completion of CMOS electronics. These two key elements enable the eventual creation of a monolithic transducer chip that does not require modification of the standard circuit fabrication process. This type of transducer chip will likely follow the path of other MEMS devices such as accelerometers, gene chips and digital micromirror arrays, where batch production, high yields and... 

Since the integrated gyro value is limited (in this case to 32 Bit) the maximum angle of turn is fixed (at around 6600° which correspond to approx. 18 turns in a specific direction). After the data is processed, it is send over a serial connection to a high level system where the data of the gyroscope and accelerometer is converted into system angles with the following Eq. 2. 

Similar holds for the accelerometer outputs (not shovm) where both IMUs have shown to satisfy the manufacturer specifications, although an increased variability has been observed for FOG IMU accelerometers in the region of bias instability. 

For both the accelerometers and the gyroscopes the EKF noise values were selected according to the manufactiu er specifications as AV analysis confirmed a close match of the experimentally extracted parameters to those given in the associated datasheets. 

The same principles described so far are valid regardless the size of the accelerometer, but accelerometer sensors of micrometric size have specific characteristics, so a brief description follows. 

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