Burkert Type 8620 - Manual (Page 90)

mxCONTROL Type 8620
Page 90
• charact 1 • For simple control output limitation
• charact 2 • For control output limitation with scaling of the control output on the
control range
• e.g. to select actuators a specific only approximately linear operating
range
• e.g. selection of proportional valves with PWM signal
•
Figure 32: Control output limitation COMMON_PID: Characteristic curves 1 and 2 (with control range)
Characteristic curve 1 (charact 1)
The control output is restricted only in automatic mode by the lower and upper control output limitation
and output accordingly on the module output.
Characteristic curve 2 (charact 2)
The module output is limited in automatic mode by the lower and upper output limit. At the same time,
the lower and upper output limitation Lim- and Lim+ define the control range in automatic mode. This
means, the control output 0…100% calculated by the controller is not put out directly as output signal
0…100% but relates to the control range and is put out as control output 0… 100% within the control
range.
Certain actuators, e.g. proportional valves selected via PWM signal, work only approximately linear in
a specific operating range. The selection of an actuator often causes the change of the process
variable only from a specific minimum selection value Lim- just as the selection above a specific max.
selection value Lim+ no longer causes a change of the process variable.
Characteristic curve 2 is thereby especially used when selecting proportional valves to tune the
module output signal as optimally as possible on the actuator used.