Applies To:
  • CitectSCADA 5.xx

When displaying the value of a trend it shows -1.#QNB  

When you display the value of a trend and it shows -1.#QNB it represents that it is an invalid or gated value.

If this is not descriptive enough in your application or otherwise, instead of directly displaying or using this value you can pass it to the cicode function TrnIsValidValue() and it will return with a number indicating if the value is valid, invalid or gated.

You can then decide how to handle it. eg instead of displaying the invalid value you may choose to place the text "invalid" which would be more descriptive.