Application of photoelectric encoder in gravity measuring instrument！

Using a rotary photoelectric encoder, connect its shaft to the compensation knob shaft in the gravity measuring instrument. The angular displacement of the compensation knob in the gravity measuring instrument is converted into a certain electrical quantity; the rotary photoelectric encoder is divided into two kinds of absolute encoders and incremental encoders.

Incremental encoders are sensors that are output in the form of pulses, which are much simpler and more resolving than the absolute encoder code. Generally only need three yards, where the code channel actually does not have the meaning of the absolute encoder code channel, but produce a count pulse. The outer and middle passages of the code plate have the same number of uniformly distributed light and opaque sectors (gratings), but the two sectors are offset from each other by half. When the code wheel rotates, its output signal is a phase difference of 90 ° of the A-phase and B-phase pulse signal and only one light transmission slit of the third code generated by the pulse signal (which is the reference position of the code, To provide an initial zero signal to the counting system). From the A, B two output signal phase relationship (lead or lag) to determine the direction of rotation. Figure 3 (a) shows that when the code is forward, A-channel pulse waveform than the B-lead ahead of π / 2, and reverse, A-channel pulse than the B-channel lag π / 2. Figure 3 (b) is a real circuit, with the A-channel rectangle wave to trigger the monostable state of the positive pulse and B-channel shaping wave phase 'and', when the code is only forward pulse pulse forward output, and vice versa , Only the reverse port pulse output. Therefore, the incremental encoder is based on the output pulse source and pulse count to determine the direction of rotation of the code and the amount of relative angular displacement. Normally, if the encoder has N (code) output signals, the phase difference is π / N, the countable pulse is 2N times the number of gratings, and now N = 2. The disadvantage of the circuit of Figure 3 is that there is sometimes a misinterpretation of the error, which occurs when a signal is in the 'high' or 'low' level and the other signal is in the 'high' and 'low' Between the round-trip change state, although the disk does not produce displacement, but will produce a one-way output pulse. For example, when the encoder is jitter or manually aligned

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