MC-TAMT12
例如，在冷却系统中，控制器设置为在空间温度达到78F时打开冷却阀，在温度降至76F时关闭阀。两个温度（2华氏度）之间的差值就是差分间隙。受控变量在两个温度之间波动。基本的双位置控制适用于许多应用。然而，为了进行严密的温度控制，必须加速或定时循环。基本两位控制在基本两位控制中，控制器和终控制元件相互作用，无需来自机械或热源的修改。其结果是受控设备的循环运行，以及受控变量在两个值（开和关点）之间来回循环的情况，并受系统滞后的影响。在受控变量达到差速器两个极限中的一个或另一个极限之前，控制器不能改变终控制元件的位置。因此，差速器是受控变量的小可能摆动。图21显示了典型的加热系统循环模式。温度（°F）OFF ON 75 74 73 72 71 70 69 68时间欠调条件差分刻度盘设置过调条件C2088

An example of differential gap would be in a cooling system in which the controller is set to open a cooling valve when the space temperature reaches 78F, and to close the valve when the temperature drops to 76F. The difference between the two temperatures (2 degrees F) is the differential gap. The controlled variable fluctuates between the two temperatures. Basic two-position control works well for many applications. For close temperature control, however, the cycling must be accelerated or timed. BASIC TWO-POSITION CONTROL In basic two-position control, the controller and the final control element interact without modification from a mechanical or thermal source. The result is cyclical operation of the controlled equipment and a condition in which the controlled variable cycles back and forth between two values (the on and off points) and is influenced by the lag in the system. The controller cannot change the position of the final control element until the controlled variable reaches one or the other of the two limits of the differential. For that reason, the differential is the minimum possible swing of the controlled variable. Figure 21 shows a typical heating system cycling pattern. TEMPERATURE (°F) OFF ON 75 74 73 72 71 70 69 68 TIME UNDERSHOOT CONDTION DIFFERENTIAL DIAL SETTING OVERSHOOT CONDTION C2088