The grating ruler, also called the grating ruler displacement sensor (the grating ruler sensor), is a measurement feedback device that uses the optical principle of the grating. Grating rulers are often used in closed-loop servo systems of CNC machine tools, and can be used to detect linear or angular displacement. The measured output signal is a digital pulse, which has the characteristics of large detection range, high detection accuracy and fast response speed.

For example, in CNC machine tools, it is often used to detect the coordinates of the tool and the workpiece, to observe and track the error of the tool, in order to play a role in compensating the error of the tool. According to different manufacturing methods and optical principles, grating rulers are divided into transmission gratings and reflective gratings.

The output signal of the grating ruler is an electric signal. When the moving ruler moves one grating pitch, the output electric signal changes one period. It measures the relative displacement of the movement by measuring the signal change period. Multiplying the count by the counter by the grating distance is the displacement of the linear motor.

When the output signal is 90o in phase angle, the direction is positive, otherwise it is negative. The Z signal is used as a calibration signal to eliminate accumulated errors. The movement direction can be determined by collecting the B signal at the falling edge of the A signal.

When the rising and falling edges of the A signal are 1/4W ahead of the B signal, the B signal collected on the falling edge of the A signal is "1", and it is moving in the positive direction at this time; the rising and falling edges of the A signal Both are 1/4W later than the B signal, and the B signal collected on the falling edge of the A signal is "0", and it is a reverse movement at this time.

According to the collected motion signal direction and the number of cycles of the A signal change, use a counter to count (forward or reverse), and then the total displacement can be measured.