Abstract: In an apparatus for measuring variable quantities such as fluid pressure, stress and strain there are provided an electric pulse generator for generating an electric pulse during a measuring interval in which the quantity to be measured exceeds a preset value, a counter for counting the number of pulses and a time measuring apparatus for cumulatively adding the measuring intervals. By providing a plurality of sets of the elements described above responsive to different set values, the variation of the quantity over a long period of time can be precisely supervised.