Future Design MCT-MC 4.3, Руководство пользователя

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MCT-MC
4.3
Configuring the MCT-MC - 27 - FDC MCT-MC
The
Cooling on-off control function will turn on the output when the process value is above set point. When
the process value falls below the set point minus the on-off control hysteresis, the output will turn off.
The
Cooling time proportioning function uses the PID settings to cycle the output on and off according to the
percentage of cooling required using the cycle time configured for output 1. For example, if the percentage of
output is 50% and the cycle time is 6 seconds, the output will repeat on/off cycles of 3 seconds each. If the
output was only 25%, the output would be on for 0.75 seconds and off for 5.25 seconds of the 6 second cycle
time.
The
Cooling linear control function uses the PID settings to vary the Vdc or mA output from the minimum to
the maximum range of the output as a direct percentage of the cooling output.
4.3.11 Output 1 Failure Transfer
The output 1 failure transfer setting is used to set the value the output should go to if there is an input failure,
i.e., sensor break. The output can be set for bumpless (-1) operation or a fixed percentage of output (from 0 to
100%) if proportioning or linear control is selected fro the output function. When failure transfer is set to
bumpless, the output will remain at its previous percentage of output until the input condition is corrected. Note
that this should not be used for extended periods of time as a runaway condition could occur if separate limit
devices are not installed to insure safe limits of operation by turning off the system should a limit be exceeded.
If the output function is set for on-off control, the failure transfer can be set to have the output turn on (1) or turn
off (0) when a sensor break occurs.
4.3.12 Output 1 ON-OFF Control Hysteresis
The output 1 on-off control hysteresis can be set when the output 1 function is set for heating or cooling on-off
control. It is used to eliminate rapid cycling of the control output by applying a safe-sided dead band to the
control output. When the control set point is exceeded, the output will turn on. The output will not turn off until
the process rises above (for heating) or falls below (for cooling) the set point by the hysteresis value.
The hysteresis can be set from a minimum of 0.1 to a maximum of 50.0 for units of degrees Centigrade and to
a maximum of 90.0 for units of degrees Fahrenheit and when a linear input type is used.
4.3.13 Output 1 Cycle Time
The output 1 cycle time can be set when the output 1 function is set for heating or cooling proportioning control.
The cycle time can be adjusted from 0.1 to 90.0 seconds. For cycle times less than 18 seconds, it is
recommended that the loop control board be ordered with the triac or SSR drive output for output 1 to extend
the life of the control output.
4.3.14 Output 1 Low/High Limit Values
The output low and high limit values can be set when the output 1 function is set for heating or cooling time
proportioning or linear control. They are used to set the minimum and maximum percentage of output that the
output will control to with a default of 0% for the low and 100% for the high. By raising the low limit or reducing
the high limit, the output will not exceed the output value regardless of the percent output required by the PID
values.
For example, raising the low limit to 5% with the output set for heating proportioning control, even if the process
value is over set point and the PID values are calling for a 0% output, the output will continue to cycle on and
off at 5% heating output.