The CFM table tab enables changes to the valve flow curve and the feedback flow curve. The table has three columns for actuator position, feedback position, and valve CFM.
At the factory, the actuator position values and the CFM values populate the curve. With the attached UVM, valve, and feedback sensor, a calibration process occurs that places the feedback entries in the table.
The actuator requires a feedback curve. The relationship between the actuator position and the feedback sensor position through the valve linkages is non-linear. The relationship deviates around 5% in the middle of the curve.
To compensate for this non-linearity, the automatic feedback calibration process through the UVM creates the correct feedback values. The factory enters the actuator, feedback sensor, and CFM data for a UVM supplied with a valve.
For units supplied without a valve, you can enter the position and CFM values through the UVM. They come from the curve supplied with the valve, or from live position and CFM measurements set on site
The feedback calibration process takes an A/D reading from the up-going and down-going direction and calculates the average. This accounts for any hysteresis in the feedback sensor reading.
The DO hysteresis setting averages each curve point that enables the average up and down reading of the curve’s actuator positions for the feedback sensor. This improves accuracy but takes longer to execute.
Changing the valve flow and feedback flow
To enable changes to valve flow and feedback flow curve in the CFM table tab, see the following steps.
- Enter the actuator and feedback entries as a whole number 10 times the positional value. For example, enter a position value of 40.5% as 405.
- Enter the positional values and the CFM values in the table and click the Set CFM Entries button. Ensure the actuator stroke time value entered matches the time the actuator takes to travel from 0% to 100%. For a Triatek actuator, use 4 seconds.
- To ensure the tool computes the gain and offset for the feedback
sensor, and also enters the corrected position values for each of the defined
actuator positions, select the Auto Populate FB Entries
check box. Note: Before you proceed with the feedback calibration, ensure the LO field cal and HI field cal entries are acceptable. These two values define the low and high travel points to obtain the information to compute the gain and offset for the feedback curve. The 0% and 100% positions do not use these points, as they are not on the linear part of the feedback curve.
- Attach the feedback sensor and download the actuator position curve to the controller and click the Calibrate FB Sensor button. The tool automatically positions the actuator at the HI Field Cal and LO Field Cal positions. This calculates the average A/D reading from which to compute the gain and offset for the feedback sensor.
- Position the actuator at each of the position points in the table and take readings from the relevant sensor. A selected Hysteresis check box records readings of the position that approaches from both directions and calculates the average. The actuator converts that information into a feedback sensor position and enters it into the table.
When complete, the Set Feedback Entries button is enabled. To download the values to the controller, click the Set FeedBack Entries button.
- To view the entry chart, click the Phoenix Valve Volt to Pos button.