A measurement device is for use with a current-type sensor unit, which, when applied with a driving voltage, is capable of reacting with a target substance for generating a sensor current that corresponds to a concentration level of the target substance, and includes: a driving unit operable to generate the driving voltage that includes alternating current (AC) and direct current (DC) components; and a processing unit for receiving the sensor current from the current-type sensor unit, and operable to determine the concentration level of the target substance according to a peak-to-peak value of the sensor current received by the processing unit.