Unipulse F805AT-BC, Operation Manual

Page: 92 / 202

6.SETTING AND ADJUSTMENT OF READING
77
6-7-2. Control limit
Use this menu item to specify the control limit: an alarm message appears when
absolute value of control deviation exceeds this limit value, and control rate is
automatically fixed to the initial control rate. PID control resumes when absolute value
of control deviation returns within the range defined by this limit value and
stabilization time elapsed.
The use of control limit is useful to reduce hunting of the control system due to external
disturbances. Control limit has no effect on the system if it is set to 0.0%.
Operation
6-7-3. Allowable control dev.
Use this menu item to set a limit value by which to determine if the system is over/
under the control deviation limit (effective only while RUNNING).
・ Control deviation over: control deviation > control deviation limit
・
Control deviation under: control deviation < - control deviation limit
Over scale alarm is displayed when either one of above conditions occurs. This alarm
function is disabled if the value is set to zero. Also, the function is disabled if
[DEVIATION LIM OVER ASC.] is set to zero.
Operation
6-7-4. Rate limit
Use this menu item to define a rate limit value, which control the next increment/
decrement value in control rate within a certain range. This method is effective to
reduce flow fluctuation caused by noise and external disturbances. Avoid unprepared
change of the rate limit: too small rate limit gives rise to slow tracking characteristics to
external disturbance. This parameter does not function if set to 0.0%.
Operation
Range: 0.0 – 500.0% (4 digits, decimal place fixed to the first place)
MODE CTRL. PARAMETER CNTRL.DEVIATION LIMIT
→ →
Range: 0.0 – 99.9% (3 digits, decimal place fixed to the first place)
MODE CTRL. PARAMETER ALLOWABLE CONTROL DEV.
→ →
Range: 0.0 – 99.9% (3 digits, decimal place fixed to the first place)
MODE CTRL. PARAMETER RATE LIMIT → →