Resonances accelerometers

Aikele, M. Bauer, K. Picker, W. Neubauer, F. Prechtel, U. Schalk, J. and Seidel H. Resonant accelerometer with self-test. Sensors and Actuators A Physical, 92 (2001), pp. 161-164... 

The si/e of mass within the accelerometer determines the self-resonant frequency of the sensors. The smaller the mass, the higher the frequency Accelerometers are usually operated in a range below this self-resonant, freqncnc)/. 

Cantilever bimorphs (see Section 6.5.2 below) with small masses attached to their free end can be used as accelerometers provided that the frequency of the vibrations to be detected is well below the resonance frequency of the transducer. 

Though the measurement uncertainty of each device has been checked, and care was taken to minimize measurement errors, inaccuracies of measurement cannot be ruled out. The higher peak loss factor for the resonant apparatus for example may be due to vibrational energy propagating into the dangling accelerometer cable. 

Observation of the accelerometer signals shows that the support motion, x, is considerably smaller in amplitude than the shear displacement, y. In addition, the driven block mass, correction term, w m, is small in comparison with the ratio F/Y for tests at frequencies well below resonance of the sample. 

The complex mechanical impedance can be obtained by measuring force, velocity, and their phase difference using probes or pickups attached to the transducer at suitable points [144], This method is very convenient with solids [52] (sometimes the most accurate), but not with liquids, although in this case it can be a convenient method of checking the performance of a transducer. The output from an accelerometer or strain-sensitive pickup gives information on resonant frequency and vibrational amplitude. However subsequent correlation with the power transmitted to the sonicated medium is not straightforward. 

Noise and vibration measurements are made with microphones and accelerometers. Sometimes, sophisticated instruments like laser vibrometers are used for NVH work. Common noise fixes include cutting slots and/or chamfers on the brake pads and linings, the application of constrained layer damping noise insulators to the back of the brake pad shoe plates, and detuning the resonant frequency of mechanical brake corner components. 

Test and measurement sensors, pressure transducers, torque sensors, instrumentation, accelerometers, and displacement sensors An extensive array of instruments and systems for applications ranging from automotive R D, process and environmental monitoring, in vitro medical diagnostics Surface plasmon resonance biosensors for the determination of the affinity and kinetics of biomolecular interactions... 

Air-packaged microresonators are widely used in a variety of low-frequency applications such as accelerometers, gyroscopes, and sensors. In many of these applications, the quality factor of the resonator, defined as the ratio of total energy to energy dissipated per cycle, is a key performance variable but is very difficult to predict. The problem is that the dominant loss mechanism for many air-packaged resonators is viscous drag, and to predict drag, it is necessary to accurately determine the detailed airflow in these typically very complicated three-dimensional resonators. 

Acceleration Accelerometer, gyroscopes Suspended spring, capacitance, resonant piezoresistive effect, diaphragm... 

All thermal actuators have a reputation of being rather slow, due to thermal time constants typically in the upper millisecond range, particularly for the cooling phase. Large forces can usually be achieved at the expense of considerable power consumption. In small structures, however, it has been shown that substantially higher speeds can be attained, due to reduced thermal time constants. Thus, an accelerometer based on a thermally actuated resonant read-out principle was shown to operate at a frequency of 400 kHz [308],... 

Here, the whole shear cell is located on a vibrating plate, mounted on vertical leaf springs, see Fig. 3. On the shear base and the shear ring, there are located one piezoelectric accelerometer each for measuring the vibration acceleration a and a, respectively. The arrangement whole shear cell vibrated can be used for investigations on the resonance and damping characteristics of cohesive powders. 

Due to its robustness. PVDF has found application as an accelerometer (3334). Piezoelectric polymer aoceleroineteis have high sensitivity, low-frequency operation, large dynamic range, excellent linearity, high resonant frequency, low mechanical quality foctors (Q ), low transverse sensitivity, and small temperature dependence. 

This elliptical pattern is what in the past was called ovaling. Some towers display an oval movement in resonance more than others however, field accelerometers show that the movement may not be entirely elliptical it is random... 

For free-field stations, it is usual to build a small concrete pier on which the accelerometer (or accelerograph if the sensor is inside it) must be firmly anchored so a strong motion cannot move the instrument relative to ground Most commercial instruments include a suitable base with anchoring holes or a similar system. Other materials for pier, like a table made with steel bars, are not suitable since it may resonate with very low damping in the seismic band of interest. 

The complex dynamic Young s modulus can be determined from the response of a bar-shaped test specimen in a forced-resonance method (186). A shaker drives one end of the specimen (nominally 100 x 6 x 6 mm). Miniature accelerometers are used to measure the driving point acceleration at the shaker and the response of the test specimen as shown in Figure 6. The output signals from the accelerometers are analyzed by a dual-channel fast Fourier transform spectrum analyzer. The analyzer determines the acceleration ratio and phase difference of the two accelerometers, and also provides a random noise source to drive the shaker over... 

---