在玻璃圆盘上刻划几个同心圆带，每一个环带表示一位二进制编码，称为码道(如下图所示）。如果再将全圆划成若干扇区，则每个扇形区有几个梯形，如果每个梯形分别以“亮”和“黑”表示“0”和“1”的信号，则该扇形可用几个二进数表示其角值。例如，用四位二进制表示角值，则全圆只能刻成24＝16个扇形，则度盘刻划值为360o/16=22.5o，如图所示，这显然是没有什么实际意义的。如果最小值为20”，则需刻(360×60×60)/20=64800个扇形区，而64800≈216个码道。因为度盘直径有限，码道愈多，靠近度盘中心的扇形间隔愈小，又缺乏使用意义，故一般将度盘刻成适当的码道，再利用测微装置来达到细分角值的目的。
动态光栅度盘测角原理如下图所示。度盘光栅可以旋转，另有两个与度盘光栅交角为β的指标光栅S和R，S为固定光栅，位于度盘外侧；R为可动光栅，位于度盘内侧。同时，度盘上还有两个标志点a和b，S只接收a的信号，R只接收b的信号，测角时，S代表任一原方向，R随着照准部旋转，当照准目标后，R位置已定，此时启动测角系统，使度盘在马达的带动下，始终以一定的速度逆时针旋转，b点先通过R，开始计数。接着a通过S，计数停止，此时计下了RS之间的栅距（φ0）的整倍n和不是一个分划的小数Δφ0，则水平角为β=nφ0+Δφ0。事实上，每个栅格为一脉冲信号，由R、S的粗测功能可计数得n；利用R、S的精测功能可测得不足一个分划的相位差Δφ0，其精度取决于将φ0划分成多少相位差脉冲。
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Characterization of the glass disc with several concentric circles, each with a ring that a binary code, known as the code channel (as shown). If you add to the whole circle divided into a number of sectors, each fan-shaped area there are several trapezoidal, respectively, if each ladder in order to "bright" and "black" means "0" and "1" signal, then the fan can be used for several a binary number indicates the angle value. For example, using four binary representation of angle values, then the whole circle can only be carved 24 = 16 fan-shaped, then the degree of plate depicts the value of 360o/16 = 22.5o, as shown, it is obviously of little practical significance . If the minimum is 20 ", you need engraved (360 × 60 × 60) / 20 = 64800 Ge fan-shaped area, and 64800 ≈ 216 Ge code channel. Because the dial diameter is limited, the more yards Road, near the center of the fan-shaped dial interval smaller, they lack the use of meaning, and therefore will generally carved dial the appropriate code channel, re-use of sub-micrometer devices to achieve the purpose of angle values.
Dynamic grating-degree angle-measuring plate theory as shown below. Dial grating can be rotated, and another two with the degree of obliquity of plate grating grating targets β S and R, S for a fixed grating, located in the outer dial; R for the movable grating, located inside the dial. At the same time, there are two marks on the dial points a and b, S is only receiving a signal, R only receives b, signals, measuring angles, S on behalf of any one of the original direction, R awarded with the Department of rotation, when the photo quasi-target, R location has been scheduled at this time start angle measuring system that allows dial in the motor driven, and always with a certain speed counterclockwise rotation, b points to pass R, start counting. Then a through S, counting to stop, this time under the terms of the RS between the pitch (φ0) times n the whole, and not a partition of the decimal Δφ0, then the horizontal angle of β = nφ0 + Δφ0. In fact, each grid is a pulse signal, from R, S of the coarse features count too n; the use of R, S refined measurement function can be measured less than a partition of the phase Δφ0, its accuracy depends on the φ0 divided into the number of phase pulse.
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