Abstract: A coating providing high abrasion and chemical resistance composed of a barrier layer from vanadium, molybdenum, niobium, tantalum and the like, and an outer layer of diamond-like carbon. The coating is especially applicable for acoustic wave device (AWD) based sensors, and for passivating an electrode such as an electrode deposited on the AWD sensing area. The coating provides excellent mechanical and acoustical characteristics for coating acoustic wave devices allowing the sensor to operate in harsh environments.

Abstract: A composite acoustic wave device (AWD) which is adapted for operation at high ambient pressures is provided. The AWD comprises two piezoelectric plates in back to back relationship, with electrodes disposed between the plates. The plates are bonded so as to neutralize the effects of external pressure. Further disclosed is a sensor utilizing the AWD and methods for utilizing such AWD for physical measurements in high pressure environments. An optional cavity formed between the piezoelectric plates offers the capability to measure the pressure and to further neutralize the residual effects of the pressure on measurement accuracy.

Abstract: An apparatus and a method for controlling the shear rate at which an acoustic wave device measures viscosity, by utilizing an automatic level control or an automatic gain control circuit to control power input to the sensor as a function of the sensor's output power. Further improvement is provided by measuring the input power and combining the input power and output power measurements, preferably by averaging, to control the input power to the sensor. A method is also provided for characterizing the fluid under test by providing a set of viscosity measurements at various shear rates.

Abstract: A diode detector comprising a detector network adapted to detect and multiply the detected voltage coupled to a divider network that comprise diodes in equal number to the number of diodes in the detector network, provides a passive detector applicable to any application requiring a small, efficient, high output, inexpensive temperature compensated detector for use as demodulator or as power to voltage converter. Integrating a portion of the divider network in the detector/multiplier network allows control over the minimum input impedance of the detector.