> For the complete documentation index, see [llms.txt](https://docs.videc.de/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.videc.de/acron-9.3/en/acron_der_anlagenchronist/ersatzwerte.md).

# Substitute values

Substitute values are always formed when the value of a process variable moves out of the measuring range.

In this case normally a measurement error has occurred. In such cases, in order not to corrupt the statistical calculations it is useful to apply the substitute value instead of the measured value for further calculations. Substitute values are marked as such, and the marking is applied to the data compression under certain conditions:

A value is marked if the following conditions occur:

|                |                                                                                           |
| -------------- | ----------------------------------------------------------------------------------------- |
| Interval value | In a measure interval (usually 2 hours) more than 30% of the values are substitute values |
| Daily value    | For one day 30% of the interval values were created with substitute values                |
| Monthly value  | For one month 30% of the daily values were created with substitute values                 |
| Annual value   | For one year 30% of the annual values were created with substitute values.                |

The percentages are entered in Plant Management/ Database/ [Select compression data](/acron-9.3/en/anlagenverwaltung/register-datenbank/sonstiges.md#verdichtungsdaten_markieren).


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