When output pressure of regulator is high or diameter of that is big
Use regulator spring to adjust pressure, spring stiffness must be much too big
Dimension of valve will increase for big flections of output pressure caused bye change of flow
Order to overcome these shortages, select pilot-regulator
Adjusting air of this kind of valve is provided by small-type direct-acting regulator
Put it inside valve, internal pilot regulator will be called
Compared with direct-acting regulator, this valve has an increase of nozzle baffle larger area made up of nozzle, baffle, fixed orificel
Distance between nozzle and baffle changes little, big changes will happen to pressure in aircel, will cause large displacement of diaphragm so as to control movement of spool and to make intake valve port open bigger or close smaller, which in this way increases the sensitivity of spool control, namely increasing the precision of stable pressure
