By default, three of the UI-type Ndio points (ResistiveInputPoint, ThermistorInputPoint, VoltageInputPoint) include a “linearCalibration” slot containing 4 properties, as shown in Figure 14.

These properties allow you to “calibrate” the calculated value before is applied to the Out slot, where: [(calculatedValue x Scale) + Offset] = Out value.Usage is optional, although Offset and Units are commonly configured.

In most cases where the parent Ndio proxy point’s facets have been edited from defaults, note you must edit the Units value in the Linear Calibration Ext to match the units in the point facets, otherwise the parent proxy point will have a fault status!Typically, you see this fault status immediately after you add a new input point, for example a VoltageInputPoint or ResistanceInputPoint, and configure it with a Linear conversion type (including a scale and offset), and then specify the point’s facets. It may not be immediately clear that the problem is in this Linear Calibration Ext, where you must match its Units value to the units in the point’s facets.

You can also copy the linearCalibration extension without error to other Nrio points based on Numeric points. For example, a CounterInputPoint where a “scaled total” out value is desired. Consider a CounterInputPoint for a flow rate meter that provides a contact closure for every 0.15 gallons, configured as:

By copying a LinearCalibrationExt to the CounterInputPoint and specifying the item quantity/pulse as the Scale value (in this case, 0.15), the count output value will read in gallons, rather that number of pulses. Note that the “rate calc” setup provides the “gallons per minute” scaling that will reflect in the Rate slot of the point’s ProxyExt, where Scale was calculated as 60 (sec/min) * 0.15 gal/pulse = 9.