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LOWEST READING
- records the lowest process value read by the controller. May be reset to zero by using
the Raise or Lower arrow keys.
LOWER SETPOINT LIMIT
- prohibits users from adjusting the setpoint lower than the selected value.
MANUAL RESET
- an adjustment that moves the Proportional Band up or down by a fixed percentage so that
more or less power is applied at setpoint. It is used to eliminate offset error.
ON/OFF OUTPUT TYPE
- In a heating application, the controller applies 100% output power if the process
temperature is below the setpoint and 0% at the setpoint. For a cooling application, the controller applies
100% output power if the process temperature is above the setpoint and 0% output power at the setpoint.
There are only two output states: fully on and fully off.
Applications for On/Off Control:
1. When temperature oscillation is acceptable.
2. When constant cycling of mechanical devices is prohibited (Compressors, Blowers, etc.)
3. Under-powered processes
OUTPUT LOW LIMIT %
- Prohibits the controller’s output from going below the specified percentage.
OUTPUT HIGH LIMIT %
- Prohibits the controller’s output from going above the specified percentage.
PID OUTPUT TYPE
(Proportional - Integral - Derivative) - The controller modulates output power by adjusting
the output power percentage within a proportional band. Power is proportionally reduced as the process
temperature gets closer to the setpoint temperature. PID control helps reduce overshoot on start-up,
enhances stability, and compensates for process lag. The PID parameters are automatically calculated for a
particular application during the autotune procedure.
Applications for PID Control:
1. Where process temperature lags exist
2. When load changes are present
3. When overshoot is prohibited
4. When very accurate control is required
PROPORTIONAL BAND
- the band (expressed in degrees of temperature) in which the controller modulates its
power percentage.
TEMPERATURE LAG
- The product of thermal resistance and thermal capacity. Also defined as delay of the
transmission of heat from the controlled element to the sensor caused by thermal mass of the process
material and/or process container, or the distance between the control element and the sensor.
UPPER SETPOINT LIMIT
- prohibits users from adjusting the setpoint higher than the selected value.