Abstract: A system for monitoring a fluid in an environmental control system includes a mechanical resonator positioned for contacting a thermal change fluid. In some embodiments, the mechanical resonator is positioned in a passage for containing the thermal change fluid. Suitable thermal change fluids include an R-134A refrigerant, a mineral oil, an ester lubricant or a mixture thereof; a superheated refrigerant; or an elevated pressure and elevated temperature vapor, an elevated pressure liquid, a reduced pressure liquid, a reduced pressure vapor and combinations thereof. The mechanical resonator can be a flexural resonator or a torsion resonator. In some embodiments, the mechanical resonator is a tuning fork resonator. Methods of the invention include monitoring a response of the mechanical resonator to the thermal change fluid. In some embodiments, at least a portion of the mechanical resonator is translated through the thermal change fluid and the response of the resonator to the fluid is monitored.

Abstract: Methods for monitoring a fluid composition include placing a mechanical resonator in the fluid composition and oscillating the resonator. The resonator can be a tuning fork resonator having tines oscillated in opposite directions and in opposite phases. A variable frequency input signal can be varied over a predetermined frequency range and oscillate the mechanical resonator at less than 1 MHz. A frequency-dependent resonator response curve can be stored in a computer memory and fitted to a model curve to monitor the fluid. The resonator can be coated with a protective coating. The resonator can be treated with a functionality designed to change a resonance frequency of the resonator after being exposed to a selected target chemical and the resonance frequency monitored to detect presence of the target chemical.

Abstract: A sensor for sensing one or more properties of a vehicle fluid has a tuning fork resonator adapted to contact the fluid. The tuning fork resonator comprises two tines and is operable to oscillate so that the two tines move in opposite phase at a frequency of less than 1 MHz while contacting the fluid to generate a resonator response indicative of one or more properties of the fluid. In another aspect, a sensor includes a substrate and a flexural resonator on the substrate and adapted to contact the fluid. Circuitry for operation of the resonator is on the substrate. The resonator is adapted to receive an input signal and to oscillate while contacting the fluid to generate a resonator response indicative of one or more properties of the fluid. One suitable application for the invention is monitoring the condition of a vehicle engine oil.

Abstract: Fluid monitoring methods, systems and apparatus are disclosed, including a portable subassembly that is in electrical communication with a sensor in contact with the fluid being monitred. Preferred embodiments for the sensor include one or more flexural resonator sensing elements. In preferred embodiments the sensor subassembly is ported to multiple fluidic systems to monitor the fluid properties in an effecient manner.

Abstract: A sensor for sensing one or more properties of a vehicle fluid has a tuning fork resonator adapted to contact the fluid. The tuning fork resonator comprises two tines and is operable to oscillate so that the two tines move in opposite phase at a frequency of less than 1 MHz while contacting the fluid to generate a resonator response indicative of one or more properties of the fluid. In another aspect, a sensor includes a substrate and a flexural resonator on the substrate and adapted to contact the fluid. Circuitry for operation of the resonator is on the substrate. The resonator is adapted to receive an input signal and to oscillate while contacting the fluid to generate a resonator response indicative of one or more properties of the fluid. One suitable application for the invention is monitoring the condition of a vehicle engine oil.