A sensing apparatus includes a reference voltage generation circuit for generating a first and a second reference signals having different constant voltage levels, an A/D conversion circuit having a ring-gate-delay circuit, and a correction circuit for correcting an output value of the A/D conversion circuit. The A/D conversion circuit converts a load signal and the first and second reference signals to digital data based on the number of times a pulse signal input to the ring-gate-delay circuit circulates through the ring-gate-delay circuit. The correction circuit corrects the output value based on a ratio of a first difference between the digital data to a second difference between the digital data.