Pressure sensor for measurement of gas pressure in a cylinder of a combustion engine, including a tube shaped in cross section as an hourglass. In the axial direction the tube consists in part of a section connected to the cylinder and open to the cylinder, in part of a measuring section and in part of a final section the end of which is closed. The measuring section of the tube is shaped so that in the tubes axial direction two parallel measuring surfaces are established against which are two beams connected to force transferring yokes arranged to influence force measuring organs for the determination of the force with which the gas pressure influences the parallel measuring surfaces of the tube. In this pressure sensor and other embodiments the influences of temperature fluctuations and any shunting effects of the material of the measuring tube are reduced to a minimum.