The pressure dependence of resonance impedance of a wristwatch oscillator made it possible to estimate ambient gas pressures from 1 atm to 1 Pa. A thermometer-type oscillator provides a practical basis for compensating thermal variation of the intrinsic impedance and lowers the minimum detectabale pressure to 10 mPa. Based on the theory of the gauge, a digital data processing method was developed for an 8-bit microprocessor to realize automatic pressure indication with errors of less than around 10% in a full pressure range for any gas with given values of mass and viscosity constant. By utilizing the pressure dependence of the resonance frequency and the impedance, automatic discrimination of hydrogen from air was successfully demonstrated.