> 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/rechengroesse/register_verdichtung/intervallwerte.md).
# Interval values
Compression level to which the calculation result is compressed by the selected compression method.
Note
The intervals can only be selected in ascending (hierarchical) order: Secondary interval requires primary interval, additional interval requires secondary interval, and so on.
The intervals enabled in Plant Management/ [Database](/acron-9.3/en/anlagenverwaltung/register-datenbank.md) are available.
## Primary interval
The [primary interval](/acron-9.3/en/anlagenverwaltung/register-datenbank.md#verdichtungsstufen) is the first compression level to which the process data are 'compressed'.
If process data occur every 5 seconds, and the primary interval is set to 1 minute, the Database Engine generates a primary interval value from the 12 process values in each minute. The preset compression method (e.g. weighted average value) dictates how this value is calculated.
## Secondary interval
The secondary interval is the next compression level after the primary interval to which the process data can be 'compressed'.
If process data occur every 5 seconds, and the primary interval is set to 1 minute, the Database Engine generates a primary interval value from the 12 process values in each minute. The preset compression method (e.g. weighted average value) dictates how this value is calculated.
Consequently, for an interval of 1 hour an hour value is calculated on the basis of 720 process values per hour.
## Additional interval 1 to 6
Analysis level Additional interval; additional compression level to which the process data are 'compressed'.
## Limit value range from/to\*
Start/end of the limit value range of the interval values
Note
The limit value range must be within the measuring range.
## Unit\*
Unit at this compression level
## Decimal places\*
Number of decimal places to output
* Positive values indicate the number of decimal places to output.
* Negative values specify rounding of the process variable values to tens, hundreds, thousands, etc.
DP = -1
402
1007
is rounded down to
is rounded up to
400
1010
DP = -2
1007
4162
is rounded down to
is rounded up to
1000
4200
DP = -3
2234
3657
is rounded down to
is rounded up to
2000
4000
## Compression method
Compression methods indicate the way in which the data are compressed into a process variable, such as when forming the monthly values from the day data.
### - Arithmetic median
The arithmetic average is formed from the single values.
### - Arithmetic median (5-95%) *0*
Calculates the arithmetic average value in the range of 5% to 95% of the measurement values. The arithmetic average is formed from the single values. The lowest and highest 5% of the values are ignored.
### - Logarithmic median
The logarithmic median compresses average values of logarithmic measurement variables such as pH values. The Base 10 logarithm is used. For process variables with this compression the measuring range should be limited to -100 to +100, as this already corresponds to a regular measuring range of 1E-99 to 1E99.
### - Weighted average value *0*
In contrast to the arithmetic median, this method takes into account the time for which a variable had a specific value. That is useful whenever values are not recorded cyclically but only sporadically, as in the case of [Delta Event recording](/acron-9.3/en/acron_der_anlagenchronist/datenaufzeichnungsverfahren.md#deltaeventaufzeichnung).
### - Last value / First value
Only the last or first value of all values is determined for the time frame. Use this compression method where the process variable is a count value and when you want to output the value in ACRON as a meter reading (as opposed to a meter difference).
* **Floating maximum / Floating minimum** *0*\
A floating maximum or minimum of all values is formed with the specified time interval. A floating maximum/minimum is not tied to fixed intervals.
Usually an interval of one hour (3600 seconds) is specified. In this case the hour is searched for at which the averaged or totaled single values produce the maximum. This might be the time range from 12:34:10 to 13:34:10 hours for example.
### - Frequency
In this compression mode the measurement values are searched according to the frequency of their occurrence, and the measurement value which occurred most frequently is carried over into the next stage. This method is used, for example, when analyzing weather charts.
### - Sum
All single values are totalized.
### - Median
The median is the value which exactly 50% of measurement values are below and 50% above. It may differ widely from the average.
The median is formed from the following series of numbers: *1 2 3 8 9*
The result is *3*, because two values are less than it and two greater (the average value produces 4.6).
### - [Percentile value](/acron-9.3/en/acron_der_anlagenchronist/datenverdichtung.md#perzentilwertberechnung) X
The percentile value is the value under which X% of all values fall.
### - Standard deviation – totality / sample
The standard deviation measures the spread of a distribution of values. A distinction is made between:
| | |
| -------------------------------- | -------------------------------- |
| *totality* | *sample* |
|  |  |
| | | |
| --- | ---------------------- | -------- |
| *0* | With calculation basis | Process |
| *1* | With calculation basis | Interval |
| *2* | With calculation basis | Day |
| *3* | With calculation basis | Month |
---
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