YOKOGAWA UT350, Instruction Manual

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5-8
<Toc> <5. Parameters>
IM 05D01D02-41E 1st Edition : May 31,2000-00
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Hysteresis (for Target Setpoints (On-Off Control) and Alarm Setpoints)
Hysteresis can be set in on-off control setpoints and alarm setpoints as well. With the
hysteresis settings, it is possible to prevent relays from chattering.
• When hysteresis is set in a target setpoint
PV value
Point of on-off action
(Target setpoint)
Hysteresis
Output
On
Off
• When hysteresis is set in an alarm setpoint
Output
On
Off
PV value
Point of on-off action
(Alarm setpoint)
Hysteresis
Example of hysteresis set in PV high limit alarm
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Target Setpoint Ramp Setting Function
Use this function to prevent the target setpoint from changing suddenly. The ramp setting
function works when:
[1] the target setpoint is changed (example: change in “1.SP” from 100°C to 150°C);
[2] the target setpoint number is switched (example: switch from “1.SP” to “3.SP”);
[3] the power is turned on or the controller is recovered from power failure;
[4] a change is made from manual operation to automatic operation; or
[5] a change is made from the STOP state to the RUN state.
If the target setpoint before switching is smaller than the target setpoint after switching, the
controller operates according to the settings of the Setpoint Ramp UP (UPR) and Ramp
Time Unit (TMU) parameters. If the target setpoint before switching is greater than the
target setpoint after switching, the controller operates according to the settings of the
Setpoint Ramp Down (DNR) and Ramp Time Unit (TMU) parameters.