Watlow F4T • 217 • Chapter 5 Function Reference
• Relative Temperature: Use this function to integrate a user-set, relative temperature
in to the application. When the Data Type is Analog and Units is Relative Temperature,
the Variable function appears as shown at the left. See Units below for more informa-
tion on when to use relative temperature vs. absolute temperature.
Signals
Direction Label Type Function
Transmitter - - - - Analog
The value set by the user with the Analog parameter in the
units specified with the Units parameter
Name
Uniquely identify this FB using up to 20 alphanumeric characters.
Data Type
To configure the variable to hold a user-set, analog value, set Data Type to Analog.
Units
Set the units of the function’s output.
Options:
• None: the output is a pure number without units.
• Power: the output is a percentage with 100% representing full power, 0% representing
no power and, for some uses, -100% representing full cooling.
• Process: the output is in units of measure other than degrees Fahrenheit, degrees Cel-
sius or relative humidity.
• Relative Humidity: the output is in percent relative humidity (%RH).
• Absolute Temperature: the output is a temperature on the Celsius or Fahrenheit scale.
For example, 33°F as an absolute temperature is one degree above the freezing point
of water. An absolute temperature can be used as a set point or compared with other
temperatures to determine which is hotter or colder.
• Relative Temperature: the output is a relative number of degrees, not an absolute
temperature. For example, the difference between the two measured temperatures,
120°C and 100°C is 20 degrees, but it is not the temperature 20°C. A relative tempera-
ture is appropriate for use as a calibration offset or a deviation alarm set point.
Analog
Set the value of the function’s output.
Range: -99,999.000 to 99,999.000
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