In this example ventilation fans are operated to lower the
indoor temperature when it exceeds the specified ranges. A temperature
sensor (thermocouple or Pt100) and the ALPHA series' analog input (0 to 10
V), Offset Gain, and Schmitt Trigger are used to control the ventilation
fans.
The second fan is controlled via a Delay Timer which sets a certain
time difference between the starting time of the two fans.
Contents of Control:
-
When the automatic mode button (S1) is pressed, the
automatic operation of the ventilation fans starts. If the indoor
temperature exceeds 40 °C, the fans rotate until the temperature falls
below 30 °C. This automatic operation continues until the stop automatic
mode button (S2) is pressed.
-
When the manual mode ON/OFF button (S3) is pressed
during the automatic operation, manual mode is entered. The fans operate
according to the status of the button (S3).
-
When the manual mode ON/OFF button (S3) is set to ON,
the fans rotate, and when it is set to OFF, the fans stop.
-
Fan 2 starts 30 seconds after fan 1 has
started.
How to use a temperature sensor (thermocouple or Pt100)
with the ALPHA series and how to convert a value into degrees
[°C]:
a) Using a temperature sensor (thermocouple) with the ALPHA
series The electromotive force is too small. Therefore, it needs to be
converted into 0 to 10 V using a dedicated signal converter (available
from specialist suppliers).
b) Converting the value into degrees [°C] In this example
-20 to 80 °C have to be converted into 0 to 10 V. Set the following linear
function calculation in the Offset Gain function block to convert the
input voltage into an analog value.

Installing and Wiring:
Refer to the ALPHA/ALPHA2 Hardware Manuals for correct
installation and wiring procedures.

Program:
Refer to the ALPHA/ALPHA2 Programming Manuals for
explanations concerning function blocks and program input. Refer to the a
Software Manual when using the AL-PCS/WIN-E programming software.

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