The invention relates to a pressure sensor including an electromagnetic resonator with waveguide having a dielectric material with a dielectric permittivity that varies with temperature. There is an excitation circuit configured to propagate an electromagnetic field through the resonator and a device for heating the resonator. There is also a device for detecting the electromagnetic resonant frequency of the resonator and a device for determining the pressure of the gas surrounding the sensor as a function of the detected resonant frequency of the resonator.

A fluid 10 is contained within a chamber 12. The chamber wall 14 has an inner surface 16 exposed to the fluid 10 and an outer surface 18 separated from the inner surface 18 by the material 20 of the wall 14. Ultrasound 22 is introduced into the material 20. Measurement of the time of flight of the ultrasound 22 through the body 20 allows a measurement to be made of the pressure of the fluid 10.

A fluid 10 is contained within a chamber 12. The chamber wall 14 has an inner surface 16 exposed to the fluid 10 and an outer surface 18 separated from the inner surface 18 by the material 20 of the wall 14. Ultrasound 22 is introduced into the material 20. Measurement of the time of flight of the ultrasound 22 through the body 20 allows a measurement to be made of the pressure of the fluid 10.

Disclosed herein is a carbonated water producing apparatus which guides a replacement of a cylinder using sound generated when carbon dioxide is supplied from the cylinder, and a refrigerator having the same. In accordance with one aspect of the present disclosure, a carbonated water producing apparatus comprising: a carbonated water producing unit including a cylinder configured to store carbon dioxide and configured to supply the carbon dioxide to a container; a microphone configured to obtain sound generated in the carbonated water producing unit; a filter configured to pass a signal having a frequency of a predetermined cutoff frequency or more of signals obtained by the microphone; a user interface unit configured to display information related to carbonated water production; and a controller configured to obtain the sound generated in the carbonated water producing unit by driving the microphone when the carbonated water producing unit operates, and configured to display a message which requests that the cylinder which stores the carbon dioxide be replaced on the user interface unit when an intensity of a signal passing through the filter is less than a predetermined reference value.

The present invention relates to system for measuring pressure and temperature based on change in the characteristic properties of a medium for ultrasound under the effect of pressure and temperature. The invention is based on two waveguides where geometry is adapted to the medium's characteristic properties for ultrasound such that only planar pressure waves are generated in the waveguides. The first of the waveguides is arranged for measuring temperature due to thermal expansion of the medium, where the medium is pressure-compensated by means of an internal compensator to prevent thermal pressure accumulation, and where measuring temperature is based on the medium's specific known characteristic data for ultrasound under the effect of temperature under constant pressure. The second waveguide is arranged for measuring pressure, based on waveguide and the medium's known characteristic properties for thermal expansion and pressure, and where the thermal effect is corrected analytically based on measurement of temperature in the first channel. The physical principle of the invention is based on the properties of a medium (oil) where the stability for high temperature and pressure is crucial for long-term properties. Long-term properties of ultrasound sensors are not physically linked to the medium's properties, such that change in characteristic properties of ultrasound sensors does not impair the accuracy of the medium unless the function of the ultrasound sensors ceases. The physical principle of the invention allows an arrangement where ultrasound sensors can be separated from measuring channels by a pressure barrier, such that the integrity of the pressure barrier is not broken.

The present invention relates to system for measuring pressure and temperature based on change in the characteristic properties of a medium for ultrasound under the effect of pressure and temperature. The invention is based on two waveguides where geometry is adapted to the medium's characteristic properties for ultrasound such that only planar pressure waves are generated in the waveguides. The first of the waveguides is arranged for measuring temperature due to thermal expansion of the medium, where the medium is pressure-compensated by means of an internal compensator to prevent thermal pressure accumulation, and where measuring temperature is based on the medium's specific known characteristic data for ultrasound under the effect of temperature under constant pressure. The second waveguide is arranged for measuring pressure, based on waveguide and the medium's known characteristic properties for thermal expansion and pressure, and where the thermal effect is corrected analytically based on measurement of temperature in the first channel. The physical principle of the invention is based on the properties of a medium (oil) where the stability for high temperature and pressure is crucial for long-term properties. Long-term properties of ultrasound sensors are not physically linked to the medium's properties, such that change in characteristic properties of ultrasound sensors does not impair the accuracy of the medium unless the function of the ultrasound sensors ceases. The physical principle of the invention allows an arrangement where ultrasound sensors can be separated from measuring channels by a pressure barrier, such that the integrity of the pressure barrier is not broken.

An environmental condition may be measured with a sensor (10) including a wire (20) having an ultrasonic signal transmission characteristic that varies in response to the environmental condition by sensing ultrasonic energy propagated through the wire using multiple types of propagation, and separating an effect of temperature on the wire from an effect of strain on the wire using the sensed ultrasonic energy propagated through the wire using the multiple types of propagation. A positive feedback loop may be used to excite the wire such that strain in the wire is based upon a sensed resonant frequency, while a square wave with a controlled duty cycle may be used to excite the wire at multiple excitation frequencies. A phase matched cone (200, 210) may be used to couple ultrasonic energy between a waveguide wire (202, 212) and a transducer (204, 214).