System for measuring pressure and temperature

摘要

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.

主权项

1. A system for measuring pressure and temperature based on ultrasound, the system comprising:
a sensor comprising two separate measuring channels being in the form of a space or gap, and an ultrasonic transducer, the ultrasonic transducer being arranged in recesses to transmit and receive ultrasound to and from the two separate measuring channels, said measuring channels containing a medium in liquid state whose pressure and temperature properties are known, wherein a first measuring channel of the two separate measuring channels is separated from a surrounding pressure of the measuring channels and wherein the first measuring channel is filled with a flexible medium and has an internal pressure compensator by a bellows for eliminating pressure accumulation due to temperature expansion, and wherein temperature is measured due to change in the properties of the medium for ultrasound, said change being measured by transit time or resonance frequency, a second measuring channel of the two separate measuring channels comprising a flexible bellows being open to a surrounding medium and wherein the flexible bellows in the second measuring channel transfers ambient pressure into a change in the properties of the second measuring channel for transit time or resonance frequency in the medium, and wherein temperature measurement in the first measuring channel is used to correct temperature effect on pressure measurement in the second measuring channel.