A digital sensing apparatus includes a sensing unit capable of providing a sensing response associated with an environmental parameter, and a digital readout module including a reading unit for generating a pulse signal having a pulse width associated with the sensing response, and a converting unit. The converting unit includes a clock signal generator for generating a variable-frequency clock signal, and a counter operable to count a width value of the pulse width of the pulse signal using the clock signal, so as to generate a digital sensing code. The frequency of the clock signal from the clock signal generator is adjustable to adjust resolution of the width value of the pulse width of the pulse signal.