The thesis firstly presents the market of pressure sensors for comparison in economical and technical view. The analysis of a pressure sensor in hydraulic systems, which can be separated in two individual sensing elements is presented. The first sensing element is mechanical, specifically a circular plate with clamped edge, which deforms under hydraulic pressure. The second, electrical sensing element is an assembly of strain gauges, which are glued to the surface of the plate and because of the plate deformations it changes their electrical resistance. The research of the mechanism of functioning of a pressure sensor in the form of a circular plate, distribution of deformations on its surface because of hydraulic pressure and the research of the mechanism of functioning of the Wheatstone bridge is presented. The procedure and calculation of autofrettage, calculation of the sensor head due to the load of the torque of the wrench and a basic control for pressure vessels is introduced. For the stress-strain analysis of a pressure sensor we used theoretical and numerical approach. The results of the theoretical and numerical calculations are validated with the measuring of a change in resistance of strain gauges in the Wheatstone bridge.