When you create Lon proxy points under a Lon device, by default, each parent point’s facets are the same as the “device facets” in its Lon ProxyExt (SI units).
This occurs regardless of your Workbench “option” settings for unit conversion display. See Workbench (display) unit conversions for more details.
For example, if you add Lon proxy points for a device’s nci “nciTempSetPts”, for each data element (using SNVT_temp_setpt), each of the corresponding Lon proxy points default to facets of ˚C.
In U.S. installations, you typically edit the points’ facets to English equivalents. Otherwise, without any further change, as shown in Figure 4 top, (with your Workbench option set to English unit conversion), point “Out” values display in English units (such ˚F) in the Lon Point Manager. However, the actual (numeric) Out values remain in SI units (such as ˚C). If you link point outputs to other components, and/or add history extensions to these proxy points, the SI unit values are used.
Therefore, in a U.S. installation you should set the facets of Lon proxy points to the needed English equivalents, to avoid any control issues or other confusion. As shown in Figure 4 middle and bottom, you can do this with a “gang edit” of multiple (related) proxy points from the Lon Point Manager, or even in the initial Add dialog when you first create the proxy points.
In cases where proxy points are added for nvs or ncis known to have a “temperature differential” (delta) application, yet the point is using “absolute temperature” facets/units (e.g “fahrenheit”), you should change the proxy point’s facets/units to differential type, i.e. “degrees fahrenheit.” This prevents issues with unit conversions performed by Niagara. This also modifies the proxy units, device units, and the element qualifiers in the LonPrimitives in the associated Lon Component.
Note that you can also edit the Lon Xml (lnml) file for a device, if needed, to accomplish the same thing. See Differential temperatures and lnml file edits.