SITEC S.r.l. Industrial electronics
Pag. 20
R2.A
User Manual TRG 72x72
5.9 D
ERIVATIVE TIME
To set up the derivative time you have to enter the configuration menu (see paragraph
), enter the
dEr
lev-
el (see paragraph
), and then select the desired value and save the new value via the OK key.
The derivative action gives a response according to the speed with which the feedback is changing,
therefore gives an anticipative action.
The idea is to rapidly compensate the variations of the control variable if we see that the feedback is
increasing, the derivative action tries to compensate this deviation as a result of its changing speed,
preventing the system from moving too sharply.
Moreover, we should consider that the derivative action, differently from the proportional and integral, is
independent from the setpoint, namely the derivative gives a contribution only according to the changing
speed of the feedback without considering the setpoint position,
therefore a step change of the setpoint
will not involve any change on the derivative
.
To disable the derivative time, you have to set it to 0.
Please note
:
the derivative time can be set up only after having enabled the temperature setting via PID
(see paragraph
Hereafter we show the behaviour of the derivative in the presence of a step change (of +20°C) of the feed-
back temperature and then the derivative immediately replies outputting a negative power (around -95%),
that then will be added to the proportional and integral effect of the PID.
You can easily notice that, as the derivative time increases, also increases the time necessary for the
derivative contribution to be again equal to 0, therefore, as the derivative time increases, also increases the
contribution of the derivative in the PID.