PRESSURE SENSOR ASSEMBLY

A pressure sensor assembly (10) for measuring the pressure of air in a compression ignition internal combustion engine is disclosed, the pressure sensor assembly comprising: an external housing unit (50); a sensor unit (20) received within the external housing unit (50), the external housing unit comprising an external surface (22) including a mounting surface (24); a sensing element (28) mounted within the sensor unit (20) and comprising a pressure-sensing surface (30); a substrate (40) upon which the mounting surface (24) is mounted; an air passage (54) to enable air to impinge on the sensing element (28), in use; and a filling passage (68), separate from the air flow passage (54), for the introduction of an encapsulation material (84) onto the sensor unit (20), during assembly. The encapsulation material (84) covers at least a part of the external surface (22) of the sensor unit (20) but does not cover the pressure-sensing surface (30) of the sensing element (28) which remains directly exposed to air withi