An apparatus for measuring humidity or moisture, such as in concrete, is described comprising a sensor module comprising a humidity or moisture sensor in electrical communication with a first set of terminals and a hand-held reader module comprising a controller in electrical communication with a second set of terminals that are mateable with the first set of terminals such that the hand-held reader module is electrically connectable to and electrically disconnectable from the sensor module. The hand-held reader module is configured to read data from the sensor in response to making electrical connection with the sensor module. One set of terminals can comprise plural connector pins and the other set of terminals can comprise plural landing pads, such that the plural connector pins and the plural landing pads make a same electrical connection regardless of the rotational orientation of the hand-held reader module relative to the sensor module.