> 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/anlagenkonfiguration/verfahrensgroessen/handgroesse/register_allgemein/prozessdatenverknuepfung.md).

# Process data linkage

## External variable

Display of assigned external variable

## Value handling of process data <a href="#wertebehandlung" id="wertebehandlung"></a>

If you want to link the consecutive result values of a calculation, or of the assigned external variables, various value handling methods are provided here.

## Value handling methods

* **No value handling**
* **Difference from previous value**\
  The difference relative to the previous value is formed in each case. According to the configured compression method, the individual differences are then compressed.
* **Counter difference (\*Info on manual variables, see below as appropriate)**\
  If the process variable is an ascending count value imported as such from a control system/PLC driver or as a manual entry, and in ACRON you want to evaluate the individual differences rather than the meter reading, you should check this checkbox. If your meter does not overflow during the lifetime of the plant, you can ignore the adjacent "Overflow" field. If your meter overflows at a specific value (returns to 0), you can optionally enter the value at which the overflow occurred in the "Overflow" field.

  ACRON handles such values as follows:

  The difference relative to the previous value is formed in each case.

  If this difference is negative the overflow value is added. If no overflow value is specified, the negative difference is set to 0. As a result this then produces a slight inaccuracy, because the difference between two values in the write interval of the Provider could not be determined. If the previous value is not present in the preceding day, the result is zero.

  In the following compression stages you can totalize the values to produce the "daily, monthly and annual consumption".\
  If your count value does not return to zero in the event of an overflow, but turns negative, you must use the "MakeDWord" function. This function interprets the parameters as unsigned 16-bit values and returns only positive values. Note that this produces twice the overflow value.

  Note

  When an overflow is recorded / 'Meter management' tab, the overflow value entered under Base data/Value handling of process data is ignored.
* **Consumption from container contents**\
  With this method ACRON approximates the consumption from a container with a level indicator or from a weighing scale or the like. If, for example, it is a container containing a liquid substance, with a level indicator attached, ACRON forms the negative difference between two consecutive level measurements and in this way is able to determine the "consumption". If the container is refilled - the level rises - ACRON ignores the rising values. So during filling no consumption can be determined. But as the filling process usually only takes a short time, this inaccuracy can be ignored in many cases. Under Hysteresis you record a fluctuation range of the measurement, resulting from vibration on a level measurement for example, or due to wind impact on an outdoor weighing scale.

  Differences less than the hysteresis are not evaluated by ACRON.
* **Operating hours from status bit**\
  If you are using an external variable to record a digital value indicating whether an entity is running (1 = entity running, 0 = entity off), you can employ this method to determine the elapsed time in hours. The Delta Event recording method should be applied to the assigned external variable. For very fast switching entities this method is too inaccurate however.
* **Form integral**\
  In this compression mode the area beneath the resultant value curve is determined. The time difference relative to the previous value in hours is multiplied by the value itself. In the next compression stage you can then totalize the values for example.
* **Use predecessor value**\
  The entire value series is moved by one value. At each point in time in the value series the value is replaced by the predecessor value.

Noteon manual variables

If counter readings are not recorded daily, though the counter difference between the readings is to be distributed evenly across all days, the 'Fill in missing process values' option must be enabled.

![](/files/iTRHslfH8VtTcRA6Zj9G)

## Handling of differential values / Difference from previous value

Selection from

* Use all difference values
* Differences as absolute values
* Ignore negative differences

<details>

<summary></summary>

| No value handling | Use all difference values | Differences as absolute values | Ignore negative differences |
| ----------------- | ------------------------- | ------------------------------ | --------------------------- |
| 36.05             | ...                       | ...                            | ...                         |
| 43.36             | 7.31                      | 7.31                           | 7.31                        |
| 34.93             | -8.43                     | 8.43                           |                             |
| 42.30             | 7.37                      | 7.37                           | 7.37                        |
| 24.76             | -17.54                    | 17.54                          |                             |
| 28.5              | 3.74                      | 3.74                           | 3.74                        |

</details>

## Overflow value / Meter difference with fixed overflow

If the meter has a defined overflow, you can specify the value here. As soon as a negative difference relative to the previous count value occurs, the overflow value is added to the difference.

Note

When meter management is enabled, the overflow value entered here is ignored.

## Maximum permissible difference from the previous value / Counter difference with variable overflow

Optional input of a maximum permissible difference amount.

Note

If this amount is exceeded, the value is replaced by Novalid (= invalid value / empty field).

Depending on the custom settings, these exceedances (empty fields) are identified by the failure marker, or are populated with the substitute value in the event of a failure.

## Hysteresis value / Consumption from container contents

Record a fluctuation range of the measurement, resulting from vibration on a level measurement for example, or due to wind impact on an outdoor weighing scale.

Note

Differences less than the hysteresis are not evaluated by ACRON.


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