Pulse Generator Pulsegen (Pulse_On) - Siemens SIMATIC Manual

2.2

Pulse Generator PULSEGEN (PULSE_ON)

The PULSEGEN function converts the analog manipulated variable value LmnN to
a train of pulses with the period PER_TM using pulse duration modulation.
PULSEGEN is activated with PULSE_ON=TRUE and is processed in the
CYCLE_P cycle.
(LmnN)
QPULSE
A manipulated variable value LmnN = 30 % and 10 PULSEGEN calls per PER_TM
therefore means the following:
•
TRUE at output QPULSE for the first three PULSEGEN calls
(30 % of 10 calls)
•
FALSE at output QPULSE for seven further PULSEGEN calls
(70 % of 10 calls)
The duration of a pulse per pulse repetition period is proportional to the
manipulated variable and is calculated as follows:
Pulse duration = PER_TM * LmnN /100
By suppressing the minimum pulse or break time, the characteristic curve of the
conversion develops doglegs in the start and end regions.
The following diagram illustrates two-step control with a unipolar manipulated
variable range (0 % to 100 %):
PER_TM - P_B_TM
PID Temperature Control
A5E00125039-02
Continuous Temperature Controller FB 58 "TCONT_CP"
100
50
30
0
1
0
Cycle PULSEGEN = CYCLE_P
PER_TM
Duration of positive pulse
PER_TM
P_B_TM
0.0 %
80
50
100.0 %
t
t
2-11