reaches [SP - HSEt] in case of symmetrical hysteresis, or [SP] in
case of asymmetrical hysteresis and is activated again when the
process value goes above value [SP + HSEt].
4.4 - NEUTRAL ZONE ON/OFF CONTROL (1.rEG - 2.rEG)
All the parameters referring to Neutral Zone ON/OFF control are
contained in the group
“
]
rEG”.
This type of control can be obtained when 2 outputs are
programmed respectively as 1.rEG and 2.rEG and the par.
“Cont”
= nr .
The Neutral Zone control is used to control plants in which there is
an element which causes a positive increase (ex. Heater,
humidifier, etc.) and an element which causes a negative increase
(ex. Cooler, de-humidifier, etc).
The control functions works on the programmed outputs depending
on the measurement, on the active Set Point
“SP”
and on the
hysteresis
"HSEt
".
The control 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 2.rEG when the process value goes above
[SP + HSEt].
Consequently, the element causing a positive increase has to be
connected to the output programmed as 1.rEG while the element
causing a negative increase has to be connected to the output
programmed as 2.rEG.
0N
OUT 2.rEG
(cooling)
OUT 1.rEG
(heating)
SP
PV
off
0N
off
off
off
0N
time
HSEt
HSEt
4.5 -SINGLE ACTION PID CONTROL (1.rEG)
All the parameters referring to PID control are contained in the
group
“
]
rEG”.
The Single Action PID control can be obtained by programming
par.
"Cont"
= Pid and 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.
0 N
0 %
( H E A t )
1 . r E G
A N A L O G .
1 0 0 %
t c r 1
1 . r E G
( H E A t )
D I G .
S P
P V
t c r 1
o f f
tc r1
tc r1
tc r1
tc r 1
0 N
o f f
o ff
0 N
o f f
o ff
0 N
0 N
tc r1
o f f
0 N
0 N
tim e
In order to obtain good stability of the process variable, in the event
of fast processes and with control by digital output, the cycle time
“tcr1” has to have a low value with a very frequent intervention of
the control output.
In this case use of a solid state relay (SSR) is recommended for
driving the actuator.
The Single Action PID control algorithm foresees the setting of the
following parameters :
"Pb"
- Proportional Band
"tcr1"
- Cycle time of the output 1rEG (digital output only)
"Int"
- Integral Time
"rS"
- Manual Reset (if “Int =0 only)
"dEr"
- Derivative Time
“FuOC” -
Fuzzy Overshoot Control
This last parameter allows the variable overshoots at the start up of
the process or at the changing of the Set Point to be avoided.
Please remember that a low value on this parameter reduces the
overshoot while a high value increase it.
2
1
3
S P
P V
t im e
1: “FuOC” OK
2: “FuOC” too high
3: “FuOC” too low
4.6 - DOUBLE ACTION PID CONTROLLER (1.rEG - 2.rEG)
All the parameters referred to PID control are contained into the
group
“
]
rEG”.
The Double Action PID control is used to control plants where there
is an element which causes a positive increment (ex. Heating) and
an element which causes a negative increment (ex. Cooling).
This type of control is obtainable when 2 outputs are programmed
respectively as 1.rEG and 2.rEG and the par.
“Cont”
= Pid.
The element causing a positive increase has to be connected to
the output programmed as 1.rEG while the element causing a
negative increase has to be connected to the output programmed
as 2.rEG.
The Double Action PID control works on the outputs 1.rEG and
2.rEG depending on the active Set Point
“SP”
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 and with control by digital outputs, the cycle times
“tcr1” and “tcr2” have to have a low value with a very frequent
intervention of the control outputs.
In this case it’s recommended to use solid state relays (SSR) to
drive the actuators.
The Double Action PID control algorithm needs the programming of
the following parameters :
"Pb"
- Proportional Band
"tcr1"
- Cycle time of the output 1rEG
“tcr 2”
- Cycle time of the output 2rEG
"Int"
- Integral Time
"rS"
- Manual Reset (if “Int =0 only)
"dEr"
- Derivative Time
“FuOC” -
Fuzzy Overshoot Control
"Prat"
- Power Ratio or relation between power of the element
controlled by output 2.rEG and power of the element controlled by
output 1.rEG.
4
.7 - PID CONTROL FOR MOTORIZED ACTUATORS WITH TIME
POSITIONING (1.rEG - 2.rEG)
All the parameters concerning the PID control for motorised
actuators are contained in the group
“
]
rEG”.
This type of control is used to control installations that have a
motorised actuator with digital opening and closing controls that
remain at the point they have reached if no command is received
and which are started up when 2 outputs are configured as 1.rEG
and 2.rEG respectively and the parameter
“Cont”
= 3 Pt is set.
The opening command for actuation will be supplied by the output
configured as 1.rEG while the closing command will be supplied by
the output configured as 2.rEG.
The PID type control for motorised actuators therefore acts on the
outputs 1.rEG and 2.rEG depending on the active Set point
“SP”
TECNOLOGIC spa - TLK 94
-OPERATING INSTRUCTIONS - Vr.01 - 01/10 - ISTR-MTLK94ENG1 - PAG. 6
