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Cooling (direct) action
When the process variable is higher than the setting value, the control output is turned on, and when the process variable is lower than the setting value, the control output is turned off.
For instance, freezer performs cooling (direct) action.
Reset in PD action
This is the function of correction by eliminating the offset which is created in P (Proportional) action or PD (Proportional and Derivative) action.
Input sampling period
This is the processing time it takes to convert input analog signal to digital signal, and is peculiar to the digital controllers.
Hysteresis (in ON/OFF control action)
If control output is frequently turned ON or OFF, relay chatter may occur.
To prevent the relay chatter, certain span is provided between control output ON point and OFF point. This span is called hysteresis.
Sensor burnout alarm
this warns of thermcouple or RTD burnout.
If the sensor is burnt out, a safety function for turning all control outputs off is provided.
Setting value memory function
The setting value and other setting parameters can be saved and called up as one file.
The CPU is monitored by a watchdog timer, and when any abnormal status is found on the CPU, the controller is switched to warm-up status with all outputs turning off.
Setting value lock function
All setting values or other setting values except for main setting value can be locked so as not to be changed.
Simplified program controller
By setting a simple program with temperature and time, the same control action like a programmable controller can be performed.
In this communication system, data is transmitted one bit by one bit.
(typical rating : RS-232C, RS-422A, RS-485)
PV filter function
This is the function of cutting high frequency element of PV input signal.
If the filter is applied, the instrument becomes strong against input noise, however, control response speed becomes slow.
This is the range in which the control ouput varies in proportion to the deviation between the SV (setting value) and the PV (process variable)
ON/OFF time ratio of control output in the proportional band varies according to the deviation between the SV (setting value) and the PV (process variable). This one cycle of ON/OFF time is proportional cycle.
In the P (Proportional) action or PD (Proportional and Derivative) action, the system is often stabilized without the SV (setting value) corresponding to PV (process variable).
The diffference between the SV (setting value) and PV (process variable) is called offset.
Warm-up indication function
When power to the controller is turned on, the selected sensor type is indicated for the multi-range input type.
Various setups such as sensor input, alarm action, direct/reverse action alternation can be performed as desired.
ARW function (Anti-reset windup)
When PID control action is rising, overshoot may occur due to excessive integral (I) action. ARW is the function for reducing the overshoot on start-up.
Alarm action delayed timer function
The alarm is not activated even if the process variable enters the range in which the alarm is turned on of off, and the alarm action is delayed until the set time is passed.
For example, if alarm action delayed timer is set to 10 seconds, the alarm is activated in 10 seconds after the process variable enters the range in which the alarm is turned on of off.
Autumatic cold junction temperature compensation
This detects the temperature at the connecting terminal between thermocouple and the instrumen, and always keeps it on the same status as when the reference junction is located at 0℃ (32℉).