wtw DIQ/S 182-MOD, System Operating Manual

Page: 93 / 150

System 182 Relay outputs
6 - 9 ba75504e07 04/2012
Pulse width output The output via the pulse width is used, e.g. for controlling valves.
Pulse-width regulation changes the duration of operation (ton) of the
output signal. Depending on the position of the measured value in the
proportional range, the relay is operated for a longer or shorter period.
Fig. 6-4 Relay output of the pulse-width output
The cycle duration (T) is made up of the turn-on and turn-off switching
duration (t
on
, t
off
) of the relay together. While the selected cycle
duration (T) remains constant, the turn-on duration (t
on
) changes
depending on the measured value and, with it, the pulse width (v). The
pulse width can be set from 0 % to 100 %.
v = (t
on
/ T) * 100 %
v = pulse width, T = cycle duration, t
on
= turn-on duration

If the measured value is at the end of the proportional range ( End
value ), the turn-on duration (t
on
) is long, the turn-off duration is short.
This means the relay operates for a longer period.

If the measured value is at the beginning of the proportional range
(
Start value ), the turn-on duration (t
on
) is short, and the relay
operates for a correspondingly shorter period.
Note
If the duration of the closing or opening pulse is shorter than 0.1 s, the
relay remains open or closed for the complete cycle duration.
T
Time [s]
Relay
Off
On
t
On
t
Off