单项选择题
A.moisture in the compressed air supply
B.excessive dryness in the compressed air supply
C.pressure surging in the compressed air receiver
D.insufficient lubrication of the system components
单项选择题 In a pneumatic automation system, a unit producing a signal to govern the position of the controller of the measured variable, relative to the value of the measured variable, is said to have（）.
单项选择题 In an automation system, the effect of a control action sensed by a controller is known as （）
单项选择题 The value of the controlled variable, which under any fixed set of conditions the automatic controller operates to maintain, is known as （）