Example: Using a scaling object to convert Fahrenheit to Celsius

Purpose

We are going to monitor the temperature in a basin. However, the actual meter we are using can only use the Fahrenheit scale and our operator is more used to the Celsius scale. This, of course, we could work around in our PLC programming but using a scaling object can save quite a few lines of PLC code.

Procedure

  1. Select Objects ® Rectangular Field. The Object Browser dialog box appears.
  2. Select Scaling and enter the name Fahren.toCel in the Name field.
  3. Click OK. The scaling object properties dialog box appears.
  4. On the Scaling Specification tab, enter the Fahrenheit values in the I/O value column and the corresponding Celsius values in the Real value column as shown in the figure.

    images\D_SCA_FAHR.gif
  5. Click OK. The scaling object is now complete.
  6. Open the object representing the temperature meter, click the Data Management Definitions tab, open the Scale As drop-down list and select Fahren.toCel.
    The temperature meter is now linked to the scaling object and will report Celsius values.