The invention concerns a body-mountable device (12) for a medical sensor assembly (10) and a method of using the same, wherein the device (12) comprises a patch (20) configured for adhesive attachment to a body (16) of a user and a mounting unit (24) arranged on the patch (20) for connecting a disposable transcutaneous sensor (14) to a reusable electronics unit (18). In order to facilitate sterile handling, the mounting unit (24) comprises an electronics compartment (26) which is closed by a sealed cover (28) for fully encasing an internal space (44) adapted for receiving the electronics unit (18), wherein the cover (28) is operable for insertion or removal of the electronics unit (18).
