A sensor alone does not meet the definition of a pressure accessory, as per Article 2 (5) (see PED Guideline A-08), nor the definition of a safety accessory, as per Article 2 (4). Consequently, no CE marking (due to the PED) is to be put on the individual sensor.
The conformity assessment procedure and essential safety requirements of the directive relate to the complete safety system. The requirements to the sensor may be different depending upon the safety concept employed (for example redundancy or fail safe, see Annex I point 2.11.1).