Ascon Tecnologic - K31D - OPERATING INSTRUCTIONS - PAG. 7
5.5 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 pro-
grammed respectively as
1.rEG
and
2.rEG
and the parameter
Cont
=
nr
.
The
Neutral Zone control
is used to control plants in which
there is
an element
which
causes a positive increase
(e.g.
Heater, humidifier, etc.) and
an element
which
causes a
negative increase
(e.g. Cooler, de-humidifier, etc.).
The control functions work on the programmed outputs de-
pending on the Process Value (PV), the active Set Point
SP
and the
HSEt
hysteresis.
The control works in the following way:
deactivates the out-
puts
when the
PV reaches
the
Set Point
and it
activates
the
output
1.rEG
when the
PV
goes
below
the [
SP
-
HSEt
]
value, or
activates
the
output
2.rEG
when the
PV
goes
above the [
SP
+
HSEt
] value.
Consequently, the element causing a
positive increase
must be
connected to the output programmed as
1.rEG
while the element causing a
negative increase
must be
connected to the output programmed as
2.rEG
.
HSEt
HSEt
SP
PV
time
Out 1.rEG
(heating)
Out 2.rEG
(cooling)
off
off
off
ON
ON
ON
If
2.rEG
output is used to
control a compressor
, it is possi-
ble to use the “
Compressor Protection
” function that is used
to avoid compressor “
short cycles
”. This function
allows a
time control
on
2.rEG
output activation
, regardless of the
temperature control requests. The protection is a “
delayed
after deactivation
” type.
This protection
avoids the output activation
for a
time
programmable
at parameter
CPdt
(in seconds); the output
activation occurs only after the
CPdt
time has elapsed.
The
CPdt
protection time count starts from the last
2.rEG
output deactivation.
Obviously, whether during the time delay caused by the com-
pressor protection function, the control request should stop, the
output activation foreseen after time
CPdt
would be erased.
The function is deactivated by programming
CPdt
=
OFF
.
The LED relative to
2.rEG
output 2 blinks during the output ac-
tivation delay, caused by the “
Compressor Protection
” function.
5.6 Single Action PID Control (
1.rEG
)
All the parameters referring to
PID control
are in
]
rEG
group.
The
Single Action PID
control can be obtained by program-
ming parameter
Cont
=
Pid
and works on
1.rEG
output depend-
ing on: the active Set Point
SP
, the functioning mode
Func
and
on the instrument
PID algorithm
with
2 freedom degrees
.
If the Out1 analogue output is present (0/4 ÷ 20 mA; 0/2 ÷ 10 V)
the output will operate as a regulation output providing a
value proportional to the regulation power calculated by the
instrument.
PV
SP
100%
0%
time
ON
ON
ON
ON
ON
ON
ON
off
off
off
off
off
off
off
Digital
OUT1
1.rEG
(HEat)
Analogue
OUT1
1.rEG
(HEat)
tcr1
tcr1
tcr1
tcr1
tcr1
tcr1
tcr1
In presence of fast processes, in order to obtain a good
PV
stability, the
tcr1
cycle time must have a low value with a
very frequent intervention of the control output. In this case
we recommend to use a Solid State Relay (SSR) for driving
the actuator.
The Single Action PID control algorithm foresees the setting of
the following parameters:
Pb
Proportional Band;
tcr1
Cycle time of
1.rEG
output;
Int
Integral Time;
rS
Manual Reset (only if
Int
=
0
);
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.
PV
SP
time
2
1
3
1
FuoC
Value OK;
2
FuoC
Value too high;
3
FuoC
Value too low.
5.7 Double Action PID Control (
1.rEG
-
2.rEG
)
All the parameters referring to
PID control
are in
]
rEG
group.
Double Action PID control
is used to control plants where
there is an element which causes a positive temperature in-
creases (ex. Heating) and an element which causes a nega-
tive temperature increases (ex. Cooling) and can be obtained
when
2 outputs
are programmed respectively as
1.rEG
and
2.rEG
and setting
Cont
=
Pid
.
The element causing the
positive increase
must be con-
nected to the output programmed as
1.rEG
while the element
causing the
negative increase
must 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
2 freedom degrees
.
In presence of fast processes, in order to obtain a good Process
Variable stability, cycle times
tcr1
and
tcr2
must have a low
value with a very frequent intervention of the control outputs.
In this case we recommend to use Solid State Relays (SSR)
for driving the actuators.
