Expression
The Expression processor evaluates a custom mathematical formula against your input tag values, for example converting a temperature reading from Celsius to Fahrenheit or calculating a custom formula for furnace pressure.
Why use Expression
Use this processor when you need to perform a calculation on one or more incoming values, rather than writing custom code to do the math.
How it works
Connect each input tag you want to use and give its connection a variable name, for example A. Reference that variable in your expression as A_value, for example sin(A_value) or A_value * 100. If you need more than one input, give each connection its own variable name and combine them in a single expression, for example A_value + B_value.
For example, this expression converts a Celsius reading to Fahrenheit:
(Celsius_value * 9/5) + 32
If you're combining multiple inputs, use values-type connections.
Parameters
Parameter | Details |
|---|---|
Expression | The mathematical expression to evaluate, using the variable names you defined for each connected input. |
Output Field Name | The field name for the evaluated result in the output payload. |
Timer Interval | Sets a timer (in milliseconds) that continuously publishes the output when no event triggers the expression. Enter 0 to disable the timer. |
Pass Through Value | Determines whether the processor's output is the evaluated expression result or the original unchanged input value. |