Glossary
input failure, or a heater or load failure.
Loop Break Time - the time interval from when the controller detects a loop break condition and the initiation of the failsafe state.
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 set- point. 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.
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
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 capac- ity. 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.
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