SITEC S.r.l. Industrial electronics
Pag. 18
R2.A
User Manual TRG 72x72
5.7 P
ROPORTIONAL BAND
In order to set up the proportional band you have to enter the configuration menu (see paragraph
), then
enter the
Pb
level (see paragraph
), and select the desired value, to then save the new value by the OK
key.
The proportional band is displayed in centigrade: within the proportional band the output power (duty cycle of
the PWM) will be proportional to the error (setpoint
– feedback), outside this band the power will be maxi-
mum if the oven temperature is lower than the setpoint temperature; it will be minimum if the oven
temperature is higher than the setpoint temperature. If you reduce the proportional band, the accuracy of the
controller improves, since a smaller error is enough to cause a certain change in the output power.
There is however a limit to the reduction of the proportional band: at a certain point the system starts to
self-oscillate and the band must be increased.
In the diagram you can see how the power (duty cycle of the PWM) is slowly decreasing as the oven tem-
perature (feedback) gets close to the setpoint temperature, while outside the proportional band the power is
maximum (100%) when the feedback is lower than the setpoint temperature and, minimum (0%), when the
feedback is higher than the setpoint temperature.
Please note
:
The proportional band can be set up only if the temperature setting by PID (see paragraph
has been enabled beforehand.
