PRECISE POSITIONING

Does a tighter setpoint improve the process? Billions of dollars have been spent upon electronic sensors and microprocessor based controllers. The expected return for this expenditure was improved control. In most cases, these upgrades only allowed better information gathering. This result was worthwhile in serving to indicate the poor performance of existing actuation.

Regardless of the sophistication of a loop, control still depends on the position, speed and stability of a mechanical element (valve plug, damper or speed control). The actuator is the component that supplies response and stability to the final control element. The greater the sensitivity and the shorter the time lag, then the better the control. As a rule of thumb, a deadband of 1% will result in a 1 percent error band for the process.

Bringing instrument level performance to the final control element, the Xpac provides positioning resolution as fine as 0.05%, instantaneous response and hydraulic stiffness. Flatline setpoint control with the Xpac has shown direct results to the bottom line for many users.

For additional information related to this subject see: Theory of Operation ( PDF files), Smart Positioners, Flow Match Valve System, Stability of Position, Advanced Control Options (PDF file), Time Lag, and Resolution and Positioning (PDF file).

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