Operation and Configuration
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6.11.1
Deadband
Control deadband is the range through which an input signal can be varied without initiat-
ing any change in the output signal. To avoid an unnecessary output bouncing by small
signal deviations the deadband
db
should be set (see Fig. 6.9). The deadband must not
exceed the required control accuracy. The deadband should be set within the range
0.0…20.0°C for temperature sensors (RTD and TC) and within the range 0…200 in the
measuring units for linear signals.
6.11.2
Setpoint Ramp
The transition from one setpoint value to another during the process can be smoothed
using the parameter
vSP
(Setpoint Ramp), the maximum setpoint rate of change.
After switching on the device, the current process value is used as the initial setpoint and
then it cannot be changed by more than the value specified in the parameter
vSP
per
minute.
The higher the Setpoint Ramp, the slower the response time. Increase the value or set
vSP
= 0, if the process cannot be controlled properly.
6.12
Outputs
In the device with the digital output the PID control is applied as a pulse width modulation
(PWM) with Pulse period
CP
and Pulse duration of (Output signal x
CP
).
The device with the analog output is used for analog PID control or for retransmitting the
signal to other devices e. g. for recording.
Output circuits are galvanically isolated from other circuits, except the output type S, be-
cause the galvanic isolation is provided by the solid state relay itself.
6.12.1
Output signal limitation
The value and the rate of change of the output signal can be limited in following parame-
ters:
Fig. 6.10
oL-L
– Control signal lower limit in %
oL-H
– Control signal upper limit in % (see Fig. 6.10a)
orL
– Control signal ramp in %/s (see Fig. 6.10b)
6.12.2
Output pulse period
When the digital output with PID control is used, the output pulse period CP should be
specified. The higher the period, the faster the response to the process value variation.
oL-H
oL-H
oL-H
mv
mv
100%
100%
a)
b)
mv
∆
t
PID
oL-L
oL-L
oL-L
0
0
t
