Meter In Circuit diagram
The circuit connection of a meter-in circuit is shown in the figure.
|Meter-In circuit diagram|
In the meter-in circuit, the flow control valve is placed in the primary line, directly before the load.
The following pressure measures are taken at three different points
Pressure Gauge P1: It indicates the Place set by the pressure relief valve. This pressure is the input pressure to the throttle valve.
Pressure Gauge P2: It indicates the load pressure P2, which varies between 0 to Pmax, depending upon the load status.
Pressure Gauge P3: It indicates the cylinder output pressure P3=0.
Meter-Out Circuit | Advantages, Disadvantages, and Applications
In a meter-in circuit, speed control is achieved by changing the flow adjustment of the flow control valve, which controls the oil going to the head end of the cylinder.
It should be noted that the flow control in the given circuit is achieved in the forward direction only i.e. in return stroke the return flow from the head of the cylinder bypasses through the check valve.
Advantages of Meter In Circuit
- The main advantage of the meter in circuit is that the cylinder undertakes one side pressure with a valve corresponding to the real load.
- The relatively small friction due to pressure on one side, decided by the load of the piston sealing ensures it’s long life.
- The uniform motion of the piston rod even at a very slow speed.
- Flow rate estimation is made based on the large piston area, which is a significant advantage when very small piston-rod speeds are to be achieved.
Disadvantages of Meter In Circuit
The major disadvantage of the meter-in circuit lies in the fact that there is no pressure on the piston rod side of the cylinder, due to this the load actuated by the piston rod is not held firmly in position.
This means that in the case of “Pulling” type loads if the load suddenly collapses, the piston rod shoots forwards causing the uncontrolled shift.
Special counter balance measures are to be taken if the above circuit is to be used for such applications.
Meter In Circuit Applications
Meter-in circuits are generally used when the load characteristics are constant and positive. If the load is erratic or negative, the actuator will have jerky motion. Hence, meter-in circuits are ideally applied on a surface grinder, milling machines, etc.
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