A sensor system comprises a sensor adapted for transcutaneous insertion into a host's skin； a housing adapted for placement adjacent to the host's skin； an electronics unit releasably attachable to the housing； and an applicator configured to insert the sensor through the housing and into the skin of the host. The applicator is adapted to releasably mate with the housing. The system is configured to release the applicator from the housing when the electronics unit is attached to the housing. The sensor system is configured such that mating the electronics unit to the housing triggers the release of the applicator from the mounting unit.
