Pressure sensor assembly

A pressure sensor assembly for measuring pressure of air in a compression ignition internal combustion engine, the pressure sensor assembly comprising:

• an external housing unit;
• a sensor unit received within the external housing unit, the external housing unit comprising an external surface including a mounting surface;
• a sensing element mounted within the sensor unit and comprising a pressure-sensing surface;
• a substrate upon which the mounting surface is mounted;
• an air passage which enables impingement of air on the sensing element, in use;
• and
• a filling passage, separate from the air passage, which introduces an encapsulation material onto the sensor unit, during assembly;
• wherein the encapsulation material covers at least a part of the external surface of the sensor unit but does not cover the pressure-sensing surface of the sensing element which remains directly exposed to air within the air passage.

A method of encapsulating a sensor unit in a pressure sensor assembly for a compression ignition internal combustion engine, the pressure sensor assembly comprising an external housing unit for the sensor unit, the sensor unit comprising a sensing element defining a pressure-sensing surface, the method comprising;

• providing an air passage for the sensor unit which enables an airflow to be applied to the pressure-sensing surface, in use;
• mounting a mounting surface of the sensor unit on a substrate to leave at least a part of an external surface of the sensor unit exposed including a pressure-sensing surface of a sensing element of the sensor unit;
• providing a filling passage, separate from the air flow passage;
• and
• introducing an encapsulation material through the filling passage so that the encapsulation material surrounds the external surface of the sensor unit which is exposed but excluding the pressure-sensing surface of the sensing element which remains directly exposed to air within an air passage.