Scaling a Value

Scaling a Value




What Is Scaling?

Scaling is the process of converting a raw signal (the numeric value sent by a PLC or sensor) into a real-world engineering value that operators can understand and use.

Scaling is used when a system receives a raw input from a sensor—commonly 4–20 mA or 0–10 V—and needs to convert it into a meaningful measurement, such as tank level, flow rate, or temperature.

This is done by defining:

  • A minimum and maximum raw value, and

  • A corresponding minimum and maximum real-world value

Once these endpoints are known, the system can calculate (scale) any intermediate raw value into its real-world equivalent.

Example

A water tank level sensor provides:

  • A raw value of 500 when the tank measures 5 ft

  • A raw value of 10,000 when the tank measures 22 ft

By establishing these minimum and maximum reference points, the system can scale any raw reading between 500 and 10,000 into an accurate tank level in feet.

Now, if the sensor sends a reading of 5,250, the system can estimate the tank level and display it as about 11 ft.


How to Scale a value in Simpliscada:

Select the Tag that you wish to apply the Scaled Formatted Value to and click the green "Edit" icon in the top-right corner of the "Tags Editor"



Scroll down in the "Tags Editor" and click on the green "Select Formats & Formulas" icon.



Select the large green "Select Format/Formula" button from the Formats & Formulas pop-up window.
The "Scale" selection from the fly-out menu has several presets as well as a custom option. For this exercise, select the "Custom" option.



Using the example values we used above, we have filled in the "Raw Low", "Raw High", "Scale Low", and "Scale High" values. After entering the values used to define the scale, click the green "Add" button to close the "Scale" window.



Click the green "Apply" button from the Formats & Formulas window to add it to the tag that is being editted.



Finally, you will need to click the green "Save" button in the Tags Editor to save your changes to the tag.



You should now see a formatted value in the tag list for your controller.



To use the formatted value in your HMI, be sure to choose the "Formatted" bullet point when selecting the Tag Object. For more info see our HMI knowledgebase article.



























 

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