Its control precision must fit a certain extent standard . now , proportional hydraulic valve which developed from the general hydraulic valve is applied in ali kind of control scopes . it uses proportional electromagnetic iron to change the electron signal into mechanical signal instead of the manual adjuster or general switch electromagnetic iron 现在工业生产中得到广泛应用的比例液压阀多是在普通液压阀的基础上，采用廉价而可靠的比例电磁铁作为电-机转换元件，把电气控制信号转为机械信号，以代替原阀内的手动调节器或普通开关式电磁铁。
In order to have the more proper application of constant power variable - volume pump in hydraulic system of drilling rig , the performance test of its proportional electromagnetic valve has carried out , and tested results indicate that the electric proportional variable - volume pump can be successfully used to the hydraulic system of drilling rig 为了使恒功率变量泵更好的应用于钻机的液压系统，对其比例电磁铁的性能进行了测试，测试结果表明，电控比例变量泵能够成功的应用于钻机的液压系统。
