Echelon LonPoint Application and Plug-In - Manual (Page 77)

The LonPoint Application and Plug-in Guide 8-5
Analog Input network variable is formatted as SNVT_temp_f#US_diff, this
option is disabled and Differential is automatically selected.
This option can only be modified by the user if you are using a Logic function
(see the Function tab). All temperatures are internally represented in degrees
Celsius and all calculations are performed in Celsius, therefore, if you are using
Fahrenheit values, you must indicate whether the Fahrenheit temperature from
each input is to be interpreted as an actual temperature or a differential. For
example, if you were comparing a Fahrenheit temperature input to a setpoint
constant to determine which one was greater, select the Absolute setting. If
you were comparing the difference between two Fahrenheit temperatures (as
calculated by another AFB functional block) to a constant to determine whether
the difference between them was larger than the constant, select the
Differential
setting.
If the Add or Subtract Math function is chosen (see the Function tab), this option
is automatically set to Differential. If the Multiply or Divide Math function is
chosen, this option is automatically set to
Absolute for input network variables
(input constants will be treated as unitless). Multiplying temperatures displayed
as Fahrenheit may yield unexpected results, since calculations are performed in
Celsius and 32 * 2 is not equivalent to 0 * 2.
Note:
The Absolute/Differential setting is not saved by the plug-in. When
you start the plug-in, the default setting is Absolute. If you previously
entered a constant value using the Differential setting, you need to
reselect this setting each time you start the plug-in for the value to be
interpreted correctly.