摘要：The design and development of a timer based revolution per minute(RPM)measurement system were described in this *** rotating shaft of a dc motor was used to measure the RPM and timer integrated circuit(IC)555 was used in astable *** frequency of timer output waveform measured by a digital storage oscilloscope(DSO)is almost linearly proportional to the RPM of rotating shaft,and the RPM also linearly varies with the change of the external input voltage *** the linear relationship between the frequency of timer output waveform and the RPM can be *** main advantages of this developed system are linear input-output relationship,small size,easy to carry and cost effective.