A system is provided for monitoring the removal of blister pack contents. An array of spatially-extended, electrically parallel breakable traces made from electrically resistive material is formed behind a corresponding array of blisters of a blister card. Then this array is connected in series with a reference resistor to form a voltage divider. All resistive traces are formed from the same materials in a single operation. Blister breakage is determined using changes in the ratio of the resistances of the array and the divider. A predictive algorithm is used to adjust the threshold resistance ratio change that signals blister breakage and voltage ratios are used to adjust for battery output changes over time. Breakage events and their time of occurrence are recorded in nonvolatile memory for later retrieval. Additional resistors can be used for activating the system and detecting tampering.
