12-16
12.3
Initial Setup and Calibration
Using
the
Performance
Tuner
Note The performance tuner is not available for instrument levels AC and HC.
The performance tuner is used to optimize the tuning of DVC5000 and DVC5000f Series digital valve controllers. It can be used on most sliding-stem and rotary designs, including Fisher Controls and other manufacturers’ products. Moreover, because the performance tuner can detect internal instabilities before they become apparent in the travel response, valves can be tuned remotely. Typically, the performance tuner takes 3 to 5 minutes to tune an instrument, although tuning instruments mounted on larger actuators may take longer. When tuning a digital valve controller, the performance tuner detects the instrument revision level and tunes the system accordingly. In most cases, the performance tuner selects a tuning set that has a gain margin around 2. As with most self-tuning control algorithms, there are limitations to the use of the performance tuner. It should not be used on instruments mounted on valves with graphite packing at room temperature. The high friction of such packing causes severe stick-slip friction. The performance tuner also does not detect or adjust for flow restricting accessories placed between the digital valve controller and the actuator. This includes devices such as volume boosters, solenoid valves, and under–sized connecting tubing. The exception to this limitation are actuators equipped with Type 2625 volume boosters. The bypass screw on the volume booster should be set to no less than 1/2 turn of the seat. PS Sheet 62.1:FIELDVUE(H) Guidelines for Manually Tuning FIELDVUE Instruments with Firmware Revision 5 provides more information on tuning instruments used with flow restricting accessories. However, if the performance tuner is used on actuators equipped with flow restricting accessories, it will find and report a stable—although suboptimal—tuning set. In VL2000 Series
July 2000