SysAdmin/Calculated-Fields.md

@@ -89,11 +89,13 @@ The `id_` prefix on the variable `val` indicates that the variable will be taken
 
 So, every 30 minutes BMON will gather up all of the `Burth158_firing_rate` sensor readings that have not already been used previously in this calculation, and BMON will multiply the by 1500 to create additional sensor readings for the `Burt158_boiler_gas` sensor.
 
-Here is a more complicated example, which also illustrates an additional feature:
+Here is a more complicated example that creates a Calculated Field that estimates the natural gas usage of a sidewalk snowmelt system based on measuring supply and return temperatures and the runtime of a circulating pump:
 
 [[images/calc_ex6.png]]
 
+The Calculated Function being used here is the `fluidHeatFlow` function, as described in the table above.  You can see in the `Function Parameters` box that the `heat_recovery` variable is *not* provided in the configuration of this Calculated Field.  Therefore, the `heat_recovery` variable will assume its default value of 0.0.  Three of the variables in the math expression for the `fluidHeatFlow` function come from existing sensor values: `flow`, `Thot`, and `Tcold`.  In the `Function Parameter` box, these variable names are prefaced by the `id_` prefix, indicating the values provided are Sensor IDs.  The `multiplier` variable is not a sensor value but instead the constant 14960.0.
 
+Finally, you can see that the `flow` variable appears in the `Function Parameter` box as `id_flow_sync`.  As explained before, the `id_` prefix indicates that the variable comes from a Sensor.  The `_sync` suffix indicates that the final calculated values for the new sensor (`manor_snw1_gas`) should be synchronized on the timestamps of this sensor. The other input sensor values (`Thot` and `Tcold`) will be interpolated to these timestamp values when the calculation occurs.  If you have multiple sensor values entering into a Calculated Field, you can add the suffix `_sync` to the variable whose timestamp values should be used for the resulting calculated values.
 
 
 ## Entering Sensor IDs for Calculated Fields