ABB ES/S 4.1.2.1, User'S Product Manual

Page: 31 / 60

ABB i-bus
£
KNX Commissioning
© 2010 ABB STOTZ-KONTAKT GmbH 29
Control value is received as
Options: 1 bit
1 byte
This parameter defines how the sent control value is received by the ther-
mostat. Depending on the selection made, the communication object for
the
Control value , page 43, (1 bit or 1 byte) is displayed.
x
1 bit: The control value is sent by the thermostat as a PWM signal
or a two-step signal (ON/OFF). The parameter for setting
the PWM-cycle time is displayed.
PWM = pulse width modulation.
Note
Pulse width modulation
With pulse width modulation, the valve is operated as with 2-point control
exclusively in the positions fully opened and fully closed. In contrast to
a 2-point control, the position is not controlled via limit values, but rather
by calculated control values similar to continuous control.
The control value is fixed for a timed cycle and recalculated for the switch
on duration of the output. The control value 20 % at a cycle time of 15 mi-
nutes, for example, will be recalculated for a switch on duration of three
minutes.
The control value 50 % results in a switch on duration of 7.5 minutes.
Using pulse width modulation, a relatively exact control of the temperature
can be achieved without high levels of overshoot. Simple, attractively-
priced thermoelectric valve drives can be used.
x
1 byte: The control value is sent by the thermostat as a continuous posi-
tioning telegram (0…255).
Note
1 byte control
For 1 byte control, a value of 0…255 (corresponds to 0 %…100 %) is pre-
set by the room thermostat. This process is also known as
continuous
control . At 0 % the output switches off (the valve is closed), at 100 %
the output switches on (the valve is fully opened).
Further parameters are displayed if the option 1 byte is selected:
Convert control value to
Options: PWM-Signal
ON/OFF-Signal
This parameter determines how the received control value (0…255)
can be processed. The control value can be converted to a PWM sig-
nal or an ON/OFF signal.
x
PWM-Signal: With this option, the continuous control value
is converted to a PWM signal. The parameter for entering
the PWM-cycle time is displayed.