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User Manual
Piccolo Range
4.12 Timer Operation
An internal timer can be configured to operate in one of three different modes or types. These are Dwell Timer,
Delayed Switch on Timer and Soft Start Timer and are described in the following three sections. The timer types are
configured by ‘P’ code P41 section 5.2.15.
The Timer Resolution is configured using ‘P’ code P42.
4.12.1 Dwell Timer
P41 = D.LL.
A dwell timer is used to control a process at a fixed temperature, set by SP1, for a defined period.
When Run is selected the setpoint will servo immediately to the current PV, and the display will show rUn
immediately.
If setpoint ramping is enabled, then the setpoint ramps to SP1 at the set rate.
Timing starts when the temperature is within the threshold of the setpoint, set by parameter ‘t.thr’ in Operator
Level 2. If the threshold is set to OFF the timing starts immediately. Heating or cooling will come on as appropriate
during the timing period. Once the timer is running, it will continue to run even if the temperature falls below the
threshold.
When the timer has timed out the controller behaviour depends on the configuration of the END state parameter.
This is set up in Conf Level using P code ‘P43’.
OFF:
SP2:
dLL:
res:
When the timer completes its dwell, the instrument will be put into Standby mode. The output power will
be set to 0%, and the standard home display will display PV and OFF instead of setpoint. The PV will revert
towards ambient since no power is being applied.
When the timer completes, the target setpoint will switch to setpoint 2. Setpoint 2 may be a lower or a
higher temperature. If the Setpoint Rate Limit is enabled, then the controller will ramp to the setpoint 2 at
the SPrr rate. During this ramp, the Timer status will indicate RUN. Once the setpoint 2 is reached the
status will change to EnD. This configuration can be used to provide a simple ramp/dwell/ramp/dwell
sequence.
Dwell. When the timer completes, the controller will continue to control at setpoint.
Reset. The timer will reset on completion reverting to SP1.
Temperature
Timer end type (P43)
OFF SP2 DLL res
t.tHr = + n
SP1
Timer Duration
t.dUr
SP2
Ramping
Setpoint
PV
Time
Flashing display message
rUn
End/OFF
rUn
End
rUn
End
rUn
RUN Digital Output = t.run
END Digital Output = t.End
Run
Notes: The dwell period can be reduced or increased while the timer is running by adjusting t.re (Time Remaining)
in Level 2.
The parameter t.thr is a deviation band from setpoint value. It is set by the user in Level 2. Timing starts when the
process value reaches the deviation limit. Because it is set as a deviation band the operation will apply to both
increasing (heating) or decreasing (cooling) values.
38 Part No HA031260 Issue 1 May -12