Patent ID: 8538630

Claim:
An A/D conversion device comprising: a first A/D converter configured to receive an analog vibration signal corresponding to a vibration detected by a vibration detecting sensor and convert the analog vibration signal to a first digital value; a digital amplifier configured to digitally amplify the amplitude of the first digital value and output an amplified first digital value; an analog amplifier configured to amplify the amplitude of the analog vibration signal and output an amplified signal; a second A/D converter configured to convert the amplified signal to a second digital value; a determiner configured to determine whether an amplitude of the amplified signal input to the second A/D converter exceeds a range of amplitude that is convertible by the second A/D converter; and a selector configured to receive the amplified first digital value and the second digital value, output the amplified first digital value when the determiner determines that the amplitude of the amplified signal exceeds the range of amplitude, and output the second digital value when the determiner determines that the amplitude of the amplified signal does not exceed the range of amplitude, wherein the digital amplifier and the analog amplifier have a same gain, the gain causing the amplitude of the first digital value and analog vibration signal to be greater than the amplitude before amplification, and the amplified first digital value and the second digital value have a same change rate and a same zero point with respect to an amplitude variation of the vibration detected by the vibration detecting sensor wherein the determiner makes a determination based on whether the amplified first digital value or the second digital value exceeds a predetermined threshold.