There is often a requirement to take a raw analogue value from a PLC and scale it into engineering units on an HMI. For analogue input objects there can also be a requirement to limit the range of allowed input values. This document explains how both of these requirements can be met with any GT1000 GOT.

Design Considerations

The example below is for an analogue input object, however the scaling part will also apply to an analogue display object.

Once an analogue input object has been placed on screen, select the “Input case” tab then press the + button and finally, press the “EXP…” button.

At this point an expression can be entered to limit the allowable input range. In the example the input range limit is zero to 100.

To set-up scaling from the same analogue input object, select the “Operation” tab and then select the “Data Operation” radio button. At this point you can set a “Data Expression” for both the Monitor data and the Write data (input from the PLC and output to the PLC).

To input the scaling calculation the “Exp…” button must be pressed (the example shows the Monitor data expression). In the example the Monitor data is divided by 10 and the Write data is multiplied by 10.

NOTE: the values and calculation required for any scaling must be worked out by the user.

Further Information
For further information please see the screen design manuals provided with the GT Designer.

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