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Offset accelerometers

In addition to the desired dependence on AC, it has a matching-dependent offset and gain that depends on parasitics. Any deviation of the reference capacitor Cref from the nominal value of the sense capacitance Cs appears as offset. Since in many applications AC is much smaller than C0, this offset often exceeds the signal. Offset cancellation should therefore occur early to minimize the dynamic range of the readout electronics. Care should also be taken for the trimming not to introduce a poor temperature coefficient. One solution fabricates the reference with the same process and in close proximity to the sense capacitor. The z axis accelerometer shown in Fig. 6.1.3 [7] utilizes two rnicromachined structures for the sense and reference. The suspension of the reference structure has been made intentionally stiff. [Pg.240]

In developing these new algorithms, the requirements for sensors added more of them outside of the central control module for two reasons. First, some types of crash were difficult to detect within the short time frame required for deployment (such as offset pole crashes) and the solution was to provide a high-g precrash sensor within the front of the vehicle. And second, the need for side-impact detection required deployment decisions even faster that the frontal crashes (within approximately 5 ms). Both of these requirements moved accelerometers to satellite positions closer to the perimeter of the vehicle where they are more likely to pick up impacts from small objects. [Pg.277]

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. [Pg.283]

J. Wu, G.K. Fedder, L.R. Carley, A low-noise low-offset capacitive sensing amphfier for a 50-pg/VHz monolithic CMOS MEMS accelerometer, IEEE Journal of Solid-State Circuits 39 (2004) 722-730. [Pg.176]

Apart from an adjustable rauge, current accelerometers also provide for configurable offsets, allowing calibration of the sensor at run-lime whereby the (X 1 ) offset values are kept in the sensor. An integrated low-pass filter can furthermore be controlled via the bandwidth parameter, going from 1 kHz down to 8 Hz for the BMA150. [Pg.175]

As an example of this class of sensors. Fig. 11 shows a MEMS triaxial accelerometer LIS 344 ALH (www.st.com/web/en/catalog/ sense power/FM89/SC444) from STMicroe-lectronics mounted on a small printed circuit board, which is sold as an evaluafimi board, since hand soldering the chip for prototyping is quite a difficult task. This chip accelerometer has a user-selectable full-scale 2 g or 6 g and comes with factory-trinuned sensitivity and offset Its bandwidth may be selected by an external capacitor. [Pg.2514]


See other pages where Offset accelerometers is mentioned: [Pg.284]    [Pg.241]    [Pg.542]    [Pg.177]   
See also in sourсe #XX -- [ Pg.283 ]




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