Apparatus (2) for sensing parameters, which apparatus (2) comprises a housing (4), a plurality of sockets (6) in the housing (4), a sensor (8) in each of the sockets (6), first electrical contacts (10) on the sensor (8), and second electrical contacts (12) in each socket (6) at an end of the socket (6) remote from the sensor (8), and the apparatus (2) being such that: (i) the sensors (8) are for sensing different parameters; (ii) the sockets (6) are such that when they contain their sensors (8) then the sockets (6) are sealed from each other whereby a liquid caused to be present in a socket (6) consequent upon an operator error is unable to pass to the other sockets (6); (iii) the second electrical contacts (12) define the type of sensor (8) that is appropriate for each socket (6); and (iv) the sensors (8) each comprise a flat sensor part (14), a transversely extending mounting part (16), and a body part (18), the transversely extending mounting part (16) being located in a bore in the body part (18), and the body part (18) being sealingly located in the socket (6) for the sensor (8).