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4.4 Switching behaviuor
With 8800 process controller, configuration parameter CYCL (ConF/ Cntr/
CYCL) can be used for matching the cycle time of 2-point and 3-point
controllers. This can be done using the following 4 methods.
4.4.1 Standard ( CyCl= 0 )
The adjusted cycle times t1 and t2 are valid for 50% or -50% correcting
variable. With very small or very high values, the effective cycle time is extended
to prevent unreasonably short on and off pulses. The shortest pulses result from
¼ x t1 or ¼ x t2. The characteristic curve is also called "bath tub curve"
T / T
6,0
5,0
4,0
3,0
2,0
1,0
0,0
Parameters to be adjusted:
( PArA/ Cntr)
4.4.2 Switching attitude linear ( CyCl= 1 )
For heating (Y1), the standard method
(see chapter 4.4.1) is used. For
cooling (Y2), a special algorithm for
cooling with water is used. Generally,
cooling is enabled only at an
adjustable process temperature
(E. H 2O), because low temperatures
prevent evaporation with related
cooling, whereby damage to the plant is avoided. The cooling pulse length is
adjustable using parameter t. o n and is fixed for all output values.
The "off" time is varied dependent of output value. Parameter t. o ff is used for
determining the min "off" time. For output of a shorter off pulse, this pulse is
suppressed, i.e. the max. effective cooling output value is calculated according to
formula t. o n / ( t. o n + t. o ff) w 100%.
8800 process controller
1
5
10
15
20
25 30
35
49
40
45
50
55
60
65
Controller output [%]
t1 : min. cycle time 1 (heating) [s]
t2 : min. cycle time 2 (cooling) [s]
t. o n
Configuration level
4 x t1
3 x t1
2 x t1
t1
70 75
80
85
90
95
t. o ff
Switching behaviuor
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