4
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4 - Functions
input and output at all.
A channel is not just a passive con-
tainer for data – it can also modify
the information owing through it. It
can be used to scale the information
and carry out conversions, for exam-
ple volts to kPa for a pressure sensor.
There are more advanced conversion
functions, allowing the value from a
temperature sensor input to be scaled
to temperatures in degrees Celsius or
Fahrenheit. Channels can also be used
to calculate mean values, lter the
data, calculate runtimes, etc.
Other functions in the WMPro use information from the channels. Examples in-
clude databases and alarms, which connect to channels to obtain information.
Databases store historical data so it can be analysed later on. Alarms are func-
tions that monitor a channel, and they are triggered when specied conditions
are met.
Some functions connect to channels in order to add information to channels, for example alarms
with an output channel. The only way channels connected to outputs alone – or not connected at all
– can receive information is from an alarm or from a script. Find out more about channels in section
11.
The whole system is controlled by scripts, which can add and remove data without restriction. A
script is a small program specifying what you want the device to do. All controllers are implemented
as scripts, and graphical programs, too, are in fact scripts.
USER SCRIPT 1 BEGIN
ROUTINE P_Controller
ALIAS
ControllerActive = PARAMETER[1];
PFactor = PARAMETER[2];
SetValue = PARAMETER[3];
InSignal = CHANNEL[1];
ControlSignal = CHANNEL[2];
ControlError = CHANNEL[3];
BEGIN
IF ControllerActive > 0 THEN
ControlError <- InSignal - SetValue;
ControlSignal <- ControlError * PFactor;
ENDIF
END;
END;
Databases
Alarms
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