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4.4 – NEUTRAL ZONE ON/OFF CONTROLLER (1rEG - 2rEG)
All the parameters referred to the Neutral Zone ON/OFF control are contained into the group
“
]
rEG”.
This type of control is obtainable when 2 outputs are programmed respectively as 1rEG and 2rEG and the par.
“Cont”
= nr .
The Neutral Zone control is used to control plants where there is an element which causes a positive increment (ex. Heater,
humidifier, etc.) and an element which causes a negative increment (ex. Cooler, de-humidifier, etc).
The control functioning works on the programmed outputs depending on the measure, on the active Set Point
“SP”
and on
the hysteresis
"HSEt
".
The controller works in the following way : it deactivates the outputs when the process value reaches the Set Point and it
activates the output 1rEG when the process value goes below value [SP - HSEt], or it activates the output 2rEG when the
process value goes above [SP + HSEt].
Consequently, the element causing a positive increase has to be connected to the output programmed as 1rEG while the
element causing a negative increase has to be connected to the output programmed as 2rEG.
4.4 – SINGLE ACTION PID CONTROLLER (1rEG)
All the parameters referred to the PID control are contained into the group
“
]
rEG”.
The Single Action PID control is obtainable programming par.
"Cont"
= Pid and it works on the output 1.rEG depending on
the active Set Point
“SP”
, on the functioning mode
"Func”
and on the instrument’s PID algorithm with two degree of freedom.
In order to obtain a good stability of the process variable, in case of fast processes, the cycle time “tcr1” has to have a low
value with a very frequent intervention of the control output.
In this case it’s recommended to use a solid state relay (SSR) to drive the actuator.
The Single Action PID control algorithm needs the programming of the following parameters :
"Pb"
– Proportional Band
"tcr1"
– Cycle time of the output 1rEG
"Int"
– Integral Time
"rS"
– Manual Reset (if “Int =0 only)
"dEr"
– Derivative Time
“FuOC” -
Fuzzy Overshoot Control
This last parameter permits to avoid the variable overshoots at the start up of the process or at the changing of the Set Point.
It’s worth to remember that a low value on this parameter reduces the overshoot while a high value increase it.
