Fisher FIELDVUE DVC6200 Instruction Manual page 48

DVC6200 Digital Valve Controller
point pressure control. Setting this value to Not
Configured will disable partial stroke tests and end
point pressure control.
D Press Set Pt—Used in conjunction with End
Point Pressure Control, Pressure Set Point allows
the user to select a pressure to be delivered by the
instrument at the travel extreme. For a fail-closed
valve, this pressure must be sufficient to maintain
the fully open position. For a fail-open valve, this
pressure (which is automatically set to supply
pressure) must be sufficient to fully close the valve
and maintain its rated shutoff classification. For
double-acting spring return actuators, this is the
differential pressure required to either maintain the
4
fully open or fully closed position, depending on the
valve and actuator configuration. For a
double-acting actuator without springs with a
fail-close valve, this is 95% of the supply pressure.
If the valve is fail-open, the upper operating
pressure for all actuator is set to the supply
pressure.
D Press Sat Time—Pressure Sat Time is the
amount of time the digital valve controller stays in
hard cutoff before switching to pressure control.
Default is 45 seconds.
Input Char (1-2-2-3)
Input Characterization defines the relationship
between the travel target and ranged set point.
Ranged set point is the input to the characterization
function. If the zero power condition equals closed,
then a set point of 0% corresponds to a ranged input
of 0%. If the zero power condition equals open, a set
point of 0% corresponds to a ranged input of 100%.
Travel target is the output from the characterization
function.
To select an input characterization, select Select Input
Char from the Input Char menu. You can select from
the three fixed input characteristics shown in figure 4-1
or you can select a custom characteristic. Figure 4-1
shows the relationship between the travel target and
ranged set point for the fixed input characteristics,
assuming the Zero Power Condition is configured as
closed.
You can specify 21 points on a custom characteristic
curve. Each point defines a travel target, in % of
ranged travel, for a corresponding set point, in % of
ranged set point. Set point values range from −6.25%
to 106.25%. Before modification, the custom
characteristic is linear.
Define Custom Char (1-2-2-4)
To define a custom input character, from the Input
Char menu select Define Custom Char. Select the
point you wish to define (1 to 21), then enter the
40
125
100
0
−25
Ranged Set Point, %
−25
0
Input Characteristic = Linear
125
100
0
−25
Ranged Set Point, %
−25
0
Input Characteristic = Equal Percentage
125
100
0
−25
−25
Ranged Set Point, %
0
Input Characteristic = Quick Opening
A6535-1/IL
Figure 4-1. Travel Target Versus Ranged Set Point, for Various
Input Characteristics (Zero Power Condition = Closed)
100 125
100 125
100 125
September 2010