Meggitt (United States)

Relaxor ferroelectric behavior occurs in many disordered ferroelectric materials but is not well understood at the atomic level. Recent experiments and theoretical arguments indicate that Anderson localization of phonons instigates relaxor behavior by driving the formation of polar nanoregions (PNRs). Here, we use inelastic neutron scattering to observe phonon localization in relaxor ferroelectric PZN-5%PT (0.95[Pb(Zn1/3 Nb2/3)O3]–0.05PbTiO3) and detect additional features of the localization process. In the lead, up to phonon localization on cooling, the local resonant modes that drive phonon localization increase in number. The increase in resonant scattering centers is attributed to a known increase in the number of locally off centered Pb atoms on cooling. The transition to phonon localization occurs when these random scattering centers increase to a concentration where the Ioffe-Regel criterion is satisfied for localizing the phonon. We also model the effects of damped mode coupling on the observed phonons and phonon localization structure.

The design of a seismic piezoelectric (PE) accelerometer with integral electronics (IEPE) having probably the lowest noise floor (for its size and weight) and lowest (near-dc) operating frequencies ever reported to date among this type of sensors is presented. The accelerometer frequency range is from 0.003 to 200 Hz at the ±3 dB level. The noise floor (equivalent input noise acceleration) is about 600, 55, 37, 7 and 3 nG/√(Hz) at frequencies 0.1, 0.5, 1, 10 and 100 Hz, respectively. The sensor incorporates the ultra-low-noise FET-input charge amplifier and the PE transducer operated in the flexural, circular bender bimorph mode. Key factors for low-noise operation are discussed. The contribution of the PE transducer noise and charge amplifier noise is shown at a frequency range from 0.1 to 200 Hz. In addition to ultra-low-noise and near-dc frequency response, the designed accelerometer has other parameters impressive for the seismic IEPE sensors: output impedance ≤ 10 Ω, 100°C maximum operating temperature and 250 G pk shock limit. The sensor's noise floor was measured directly at the National Institute of Standards and Technology (NIST). The experimental results have good correlation with the noise values evaluated based on the measured charge amplifier noise and the theoretical PE transducer thermal noise. The ultra-low-noise floor of the designed sensor allowed using it in the stabilization platform, which carries the world's most frequency stable laser system used for the atomic clock research conducted by NIST.

Meggitt Sensing Systems (formerly Endevco) pioneered the commercialization of a shock tube calibration system by taking an established laboratory tool capable of imparting near-instantaneous pressure stimulus and incorporating this capability into active product development for the purpose of providing quantifiable frequency response of pressure transducers. These activities commenced in 1996 in a cooperative effort with Texas Christian University, and results were reported extensively through 1998. After 15 years of successful new product introduction, empirical data has been used to model more accurately the 1-D compressible gas dynamics occurring within the shock tube so that the time interval of the reflected shock—the most critical parameter in determining the transfer function for the pressure transducer under test—can be optimized for varying amplitudes. The existing Meggitt Sensing Systems shock tube (102 mm diameter × 3.7 m length) operates up to a pressure of 6895 kilopascal gauge (kPag) and sustains up to 8 ms reflected shocks. Recent modelling suggests that these parameters can double. Accordingly, effort is currently under way to bring this enhanced capability to the marketplace, offering both increased performance and ease of user operation.

High-temperature hybrid miniature silicon-based charge amplifier has been designed, fabricated, and tested. The charge gain Gqap30 mV/pCplusmn1 dB at the reference frequency of 100 Hz. Frequency response deviation is plusmn1 dB at frequency range from about 0.5 Hz to about 10 kHz over the temperature range from -55degC to 175degC. The maximum change in gain is plusmn5% over that temperature range. The maximum output signal is 5 V peak at voltage supply of +24 V. The charge amplifier compromises standard components, and it is built on the ceramic disk substrate with a diameter of about 8 mm. This circuit made possible the development of the industry's first 100-mV/G miniature (cube with side of 14 mm), lightweight (12.5 g), low-cost, and low-noise piezoelectric triaxial accelerometer with integral silicon-based electronics having operating temperature from -55degC to 175degC. In the long-term active (with power supply) test, the circuit and the accelerometer operated at temperature of 175 degC for 1000 h without any signs of degradation