Abstract: A combination of an in-line pressure sensor and a portable gauge head are arranged such that they can be quickly connected and disconnected together and apart for giving a quick pressure reading of the pressure sensed by the sensor. The in-line sensor is semi-permanently installed in a fluid system. The portable gauge head, during a given use, is releasably connected or coupled to the in-line sensor to detect a message signal given off by the in-line sensor and convert that message signal into a visible indication of the pressure sensed by the in-line sensor. After a given use, the portable gauge head is disconnected or de-coupled from the in-line sensor and is transported elsewhere either for use with another in-line sensor at a different location or else for storage between uses.