A solid ring made of aluminium oxide (Al2O3) forms the base body of a ceramic thickfilm sensor and the front side is a closed membrane, also called a circular ring membrane. The base body and membrane form one part. On the outer side of the membrane (the side that is not subjected to pressure), the strain gauges are applied as a thick-film resistor paste using the screen printing method. These are then burned-in at high temperatures and coated with an additional protective lacquer or glass.
Compensation resistors are also often integrated into the printed electrical circuit in addition to the strain gauges in order to directly counteract temperature influences atthe sensor element. This kind of compensation is referred to as passive temperature compensation.
The thickness of the membrane varies depending on the pressure range. For ceramic thick-film sensors, this typically ranges from 0 to 1.6 bar – 0 to 100 bar. The resistance of the ceramic to corrosion and abrasion is an advantage of this sensor, but an additional seal is required for assembling in the housing of the pressure transmitter. Therefore, in the finished pressure transmitter, ultimately 3 different materials come into contact with the medium: the ceramic of the sensor, the seal, and the process connection. As a result, all components need to be included when checking for media compatibility. A great advantage of ceramic is its virtually hysteresis-free elasticity. The finished sensor also stands out due to its excellent price-performance ratio.