The system sampling interval of 0.05s, the control module by changing the pulse frequency of the motor to control the motor fuel tank sight glass speed by changing the phase of the pulse sequence to change the rotation of the motor. Stepper motor speed v = f * n, where f is the input frequency of the motor pulse, sight glass indicator is the motor's step size. Level input signal, i.e. the distance from the image center position of the digital signal obtained by the image processing computer. Stepper motor driven camera gradually close the image center, in general, "acceleration - constant - deceleration - stop" process. Since the oil tank gauges start-up phase stepper motor starter lower limit frequency, and requires a constant rate of frequency is greater than the starting frequency, there will be a short acceleration process.