Abstract: A portable monitoring device and method are disclosed for monitoring a predetermined parameter, such as temperature. The portable device, or probe, is miniaturized and includes a sensor and an associated electronic unit encased within a housing. The sensor senses the parameter to be monitored and produces signals indicative thereof, while the electronic unit includes a converter for converting signals received in analog form to digital signals, a memory for storing the digital signals, and a microprocessor for controlling the sensing and signal storing operations. The probe is a self-sufficient unit, is electrically isolated while at the monitoring area, and is caused to operate in an active mode during periods of sensing and storing of information in memory that requires low power with even lower power consumption being achieved when the probe is inactive.