Pressure transducer with reduced temperature sensitivity

Claim 1

A pressure transducer comprising a piezoelectric sensing element, a pressure diaphragm mechanically coupled to said sensing element for stressing said piezoelectric element in response to fluid pressure acting on said diaphragm, a heat shield mounted on said diaphragm on the side remote from said sensing element for protecting said diaphragm from heat, said heat shield having a low coefficient of thermal expansion and a low thermal conductivity, a heat shroud surrounding but spaced from said heat shield, said shroud and heat shield defining an annular groove communicating with said diaphragm, said groove being stepped to a smaller dimension at its end adjacent said diaphragm, said sensing element having first and second mutually perpendicular electrically sensitive axes, said pressure diaphragm being mechanically coupled to stress said element along said first axis, and temperature compensating means mechanically coupled to said element for applying compensating stresses to said element along said second axis in response to variations in temperature, said temperature compensating means comprising a pair of side-by-side masses positioned along said first axis, one of said masses engaging one side of said element, the temperature coefficient of thermal expansion of one of said masses being higher and the other lower than the coefficient of thermal expansion of said element along said second axis.