Badger Meter SRD/SRI Valve Positioners - Manual (Page 42)

Custom Curve
The Custom Curve lets you define up to 22 input/output pairs . To add a
new pair of values:
1 . Select Custom .
2 . Enter the X-Value and Y-Value .
3 . Click Add .
The input value pair will be sorted in increasing order of the X-Values . To
modify a value pair:
1 . Select the X-Value in the list box .
2 . Modify the value and press Modify .
To delete a value pair, select the X-Value in the list box and press
Delete .
A custom curve which is stored in the device can be activated by selecting Custom or deactivated by switching to Linear,
Equal Percentage (1:50) or Quick Open (50:1) .
NOTE: N The flow characteristics of the valve depend on both the positioner and valve trim characteristics . For example, if
the positioner Characteristic is set to Linear and the valve has an Equal percentage trim, then (Cv/Cv .max) vs . input
signal will also be Equal percentage .
Number of Points
This is a single byte field . You can specify how many straight line segments will comprise the characterization curve . If custom
characterizer is enabled, this value sets the number of points . The default value is 2 (one line segment) . This is also the
minimum . If one of the standard options is selected, the custom points are disabled and turned off .
Select Point
Use this Combobox to select the Points for output and input .
Xn Characterizer Input Value
This is a 4-byte real that is used as the input to the custom characterizer function . It is only enabled if the characterization is
custom, not for any other option . Xn and Yn represent the input signal and the valve position respectively . Between Xn and
Xn+1, a straight line interpolation of Yn to Yn+1 is defined . Similarly, between Xn-1 and Xn, a straight line interpolation of Yn-1
to Yn is developed . Xn must be larger than Xn-1 .
Yn Characterizer Output Value
This is a 4-byte real that is used as the input to the custom characterizer function . It is only enabled if the characterization is
custom, not for any other option . Xn and Yn represent the input signal and the valve position respectively . Between Xn and
Xn+1, a straight line interpolation of Yn to Yn+1 is defined . Similarly, between Xn-1 and Xn, a straight line interpolation of Yn-1
to Yn is developed . Xn must be larger than Xn-1 .
Characterization
This is a single-byte field . The Valve’s position characteristic is determined here . There are four options:
• Linear
• Equal percentage
• Quick opening (inverse equal percentage)
• Custom
If you choose Custom characterization, you can freely define up to 22 points to create a new characteristic for the setpoint
changes . Linear is the default .
Configuration / Parameter
Page 42 August 2014 POS-UM-00011-EN-02