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MCT-CM
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NOTE: Guaranteed soak is typically not used during set point ramping steps as the ramp rate will be affected
if any process variable deviates from its soak band because the program will be placed into hold.
When the program is in hold, the step length will be extended and all set points will no longer ramp at
the desired rate. They will maintain their current value until the timer starts again. Guaranteed soak
is primarily used on soak steps to make sure that the process stays at the desired set point, within
the soak band, for the full time duration of the step.
6.1.3 Setting Wait Conditions
The “Wait” function is a powerful tool for pausing a program until selected process variables (loops and/or
monitors) reach a predefined set point. This differs from the guaranteed soak function by being a single shot
monitor. With the guaranteed soak, the process variable is monitored throughout the whole step. If the process
exceeds the limit, the program will pause until the process returns to within the limit setting. The wait for function
pauses the program and waits for the process to reach a particular value that is set for the step. Once the
process reaches this set point value, the program automatically resumes operation.
The program can also be set to wait for a digital input. This allows any of the available inputs on the MCT
control module to be selected (input must also be configured as a wait for input). When the step is reached, it
will wait for the input to change state before continuing the step. Any combination of loops, monitors and inputs
can be set for a step, but all of them must meet the wait for condition of the step for the program to continue.
To enable a wait condition in a step, press the
“Wait” button on the Entry screen to display the wait settings
screen. The process selections, as shown below, allow you to select which loops and/or monitors (if any) will
be used as a wait for condition.
The loop and monitor selections share two common settings, the “Wait Type” and “Wait SP”. These settings
are used to set the trigger point for the wait condition, i.e., the value that each loop and/or monitor must meet
for the program to continue.
The
Wait SP is the set point value that each selected loop and monitor must reach.
The
Wait Type setting selects how MCT determines if the loop or monitor input has reached the wait set point.
There are three possible selections that can be made from the drop-down list box; Edge, Increase and
Decrease.
The default setting is Edge. With this selection, MCT samples each loop and monitor input selected and
determines that the wait for condition is met when each input crosses the set point value, either rising or falling.
If the selected wait type is Increase or Decrease, each input must be above, or be below the set point for the
wait condition to be met.
If any analog or digital wait selections
or delta selections are made for the
current step,
an asterisk ‘*’ will
appear before the word on the
corresponding list selection button.
Th
e ‘Wait’ button on the Entry screen
will also display an asterisk if any
wait or delta selection is made. This
allows the user to know that a wait
condition has been entered for the
step without the user having to
access the wait screen and check
each step of the program.