Reason to use Positioners

1. Increase control system resolution: i.e. fine control.

2. Allow use of characteristic cams.

3. Minimize packing friction effects: i.e. high-temperature packing.

4. Negate flow-induced reactions to higher pressure drops.

5. Increase speed of response to a change in process.

           6. Allow split ranging.

           7. Overcome seating friction in rotary valves.

           8. Allow distances between controller and control valve.

           9. Allow wide range of flow variation: i.e. operate at less than 10% travel under              

              normal conditions.

          10. Allow increased usage of 4-20 mA electronic signal.

          11. Increase fast venting (unloading) capability.

          12. Permit use of piston actuators.

          13. Facilitate operation when the higher number in the bench-set range is greater than           

                15 psig: i.e. 10-30 psig, 6-30 psig, etc.