Cla-Val 131VC Series - Manual (Page 5)

VALVE RESPONSE TIME
DEVIATION BAND DEVIATION BAND
Faster
Slower
Higher
Lower
Dead
Band
VALVE SENSITIVITY
SET-POINT
SOLENOID
CYCLE TIME
Feature in blue
are user programmable
PROPORTIONAL
OUTPUT CIRCUIT NO.2
PROPORTIONAL
OUTPUT CIRCUIT NO.1
Valve Solenoid
"On" Time
SOLENOID
CYCLE TIME
100%
75%
50%
25%
0%
Full Programmable Control of Valve Sensitivity and Valve
Response
Designed with duplex output circuits (one to control the valve
opening solenoid and one to control the valve closing solenoid ).
The 131VC-1 Electronic Control System can be programmed to
maintain precise control of any process. Each output circuit has
an independently programmable proportional band and solenoid
cycle time. By adjusting these control algorithms in combina-
tion, the response time can be varied over a wide range.
Proportional Band
The proportional band can be programmed from 1 to 999 per-
cent of transmitter scale. Programming a narrow deviation band
will result in faster valve response, whereas a wider band will
result in slower response.
Proportional Response Time
The response time of the valve is proportional to how far the
process variable is from the set-point. If there is only a small
deviation, the solenoid “on-time” will be short and the valve will
move slowly. For large deviations, the “on-time” will be longer
and the valve speed will be faster.
Solenoid Cycle Time
The opening and closing solenoid pilots operate in “on-off”
cycles. The cycle time is programmable to allow the valve to
make a smooth transition to the set-point and avoid overshoot-
ing.
Dual Output Circuits
The two output circuits can be programmed independently to
respond at different rates. For example: fast response above
the set-point; slow response below the set-point.
Set-Point Rate of Change
The controller has a ramping function that will further control
valve speed of operation. This feature is especially useful in
applications where valve speed is critical and pipeline surges
are possible. When turned on, the set-point rate of change
feature is operational under the following conditions:
On power up, the set-point will ramp from the process
variable value to the set-point value at a specified rate.
On a transfer from manual to automatic control, the set-
point will ramp from the process variable to the set-point
value at a specified rate.
On any set-point change, the set-point will ramp from the
current set-point to the new target set-point.
Programmable Control Features