Systems for sensing pressure and temperature at a common location

Claim 1

A sensing system that provides an output in respect of both pressure and temperature changes in an optical sensing element at a common location, comprising a source of alternating optical radiation, said optical sensing element having a resonant frequency that is dependent on pressure and a Q that is dependent on temperature, a probe disposed in a flowing fluid and having an inlet and an outlet, said common location being a location in said flowing fluid, said optical sensing element being located in said probe between said inlet and outlet such that said flowing fluid flows through said probe over said optical sensing element, means supplying optical radiation from said source to said optical sensing element to excite said sensing element optically so as to cause said sensing element to vibrate, an optical radiation detector, means supplying radiation from said sensing element at its frequency of vibration to said detector, and processing means responsive to an output from said detector and operative to provide separate indications of pressure and temperature changes at said common location in accordance with the frequency and Q respectively of said sensing element which are substantially independent of variations in amplitude of the radiation from said source.