Method of manufacturing a pressure sensor

A pressure sensor for measuring a fluid pressure in a device, the sensor comprising:

• a port element including a sealing structure and a membrane with a fluid side to be exposed to the fluid pressure, a strain sensing side and a membrane central axis, the sealing structure providing a seal when the port element is affixed in an opening of the device;
• four strain gages attached to the strain sensing side, including a first strain gage attached to a first position, a second strain gage attached to a second position, a third strain gage attached to a third position, and a fourth strain gage attached to a fourth position, such that the first strain gage and the fourth strain gage are put in compression when the fluid pressure is applied to the membrane and the second strain gage and the third strain gage are put into tension when the fluid pressure is applied to the membrane, the four strain gages are electronically connected to form a Wheatstone bridge circuit,
• wherein the first position, the second position, the third position, and the fourth position are determined by a position determining action including:
• providing the port element, the port element having a port central axis;
• performing position determining action including generating a mathematical model of the port element;
• a first finite element action determining, on the strain sensing side of the membrane with a first finite element algorithm using the mathematical model, a first contour around the membrane central axis with a first strain sensitivity for pressure and a second contour around the membrane central axis with a second strain sensitivity for pressure wherein when the fluid pressure is applied to the membrane a degree of compression of the surface on the first contour is equivalent to a degree of stretching of the surface on the second contour;
• and
• a second finite element action determining, with a second finite element algorithm using the mathematical model on the first contour, the first position for the first strain gage of the four strain gages and the fourth position for the fourth strain gage of the four strain gages and, on the second contour, the second position for the second strain gage of the four strain gages and the third position for the third strain gage of the four strain gages, wherein when a characteristic parasitic force is applied to any location on the sealing structure or any other location of the port element the difference between a highest error signal and a lowest error signal measured by a simulated Wheatstone bridge comprising the first strain gage attached to the first position, the second strain gage attached to the second position, the third strain gage attached to the third position, and the fourth strain gage attached to the fourth position, is minimal,
• wherein the membrane is a circular membrane and the four strain gages are embodied as two half bridge strain sensing elements, each half bridge strain sensing element comprising two strain gages and a centre point in between, both half bridges measuring strain in a direction parallel to a line through the centre points;
• the centre points are at a defined distance from each other;
• the position determining action includes determining a first circle and a second circle such that a difference between a radius of the first circle and a radius of the second circle equals the defined distance, the first position and second position being determined by using a first radial line on the first and second circle, and the third position and fourth position being determined by using a second radial line on the first and second circle.

A method of manufacturing a pressure sensor for measuring a fluid pressure in a device, the method comprising:

• providing a port element, the port element comprising a sealing structure and a membrane with a fluid side to be exposed to the fluid pressure and a strain sensing side, the sealing structure providing a seal when the port element is attached in an opening of the device, the membrane having a membrane central axis and the port element having a port central axis;
• mathematically modelling a first contour around the membrane central axis with a first strain sensitivity for pressure and a second contour around the membrane central axis with a second strain sensitivity for pressure;
• positioning four strain gages to the strain sensing side, including a first strain gage attached to a first position, a second strain gage attached to a second position, a third strain gage attached to a third position, and a fourth strain gage attached to a fourth position, in such a way that the first strain gage and the fourth strain gage are positioned on the first contour and are put in compressive strain when fluid pressure is applied to the membrane and the second strain gage and the third strain gage are positioned on the second contour and are put into tensile strain when fluid pressure is applied to the membrane;
• and
• performing position determining action including generating a mathematical model of the port element,
• wherein the membrane is a circular membrane and the four strain gages are embodied as two half bridge strain sensing elements, each half bridge strain sensing element comprising two strain gages and a centre point in between, both half bridges measuring strain in a direction parallel to a line through the centre points;
• the centre points are at a defined distance from each other;
• the method includes determining a first circle and a second circle such that a difference between a radius of the first circle and a radius of the second circle equals the defined distance, the first position and second position being determined by using a first radial line on the first and second circle, and the third position and fourth position being determined by using a second radial line on the first and second circle.