User Guide

8
Trends
Overview of Trend Application
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Siemens User Guide Version 2.1 A6V10415471_en_a_21
Building Technologies 2015-07-15
 Measured value trends based on intervals, or each time a value changes
(change-of-value).
 Data types analog, digital, and multistate are supported.
 Create trendlog objects in the automation station.
Restrictions
 Maximum 10 GB database memory for SQL Server Express or 250 GB of
database memory for SQL Server.
 Display 10 curves (max. recommended) within a Trend View.
Restrictions: Version 2.1
 No archive data can be generated.
8.1 Overview of Trend Application
The Trends application allows you to create online trends and display offline trends
from the automation station.
The Trend application contains a workspace with specific properties (for example,
name, gridlines, scaling, and so on) as well as data point references (properties,
and so on). Trendlog objects contain measured values. The collected values are
displayed in a common time range and saved to the trend database.
Regardless of the trend data, Trend Views can be saved, queried, deleted, and
edited as well as saved under a new name.
You can use Trend Views in two ways in the management station:
 During operation, trend data recorded in real-time and saved to the trend
database (management station is online).
 Trend data are recorded in the automation station (management station is
offline) and periodically loaded to the management station trend database.
You can display the trend data in the Trend Viewer any time, even if the
management station is not connected to the site (no real-time data available).
Methods to Record Data
Two methods to configure online and offline Trendlog objects to record data:
 Change-of-Value (COV)
This method allows you to record new data when the data point value within
the defined data point range is changed. No value is recorded or transmitted if
the value does not change over an extended period of time. Database
acquisition of several data points in a Trend View is asynchronous.
 Interval-based (offline trend only)
This method allows you to record current data as soon as the time stamp is
reached. The data values are recorded without impact of a defined COV
property.
70.0°F
71.0°F
72.0°F
73.0°F
1
70.0°F
1
70.8°F
2
70.3°F
3
70.8°F
4
72.5°F
2
71.0°F
3
72.0°F
4
71.0°F
5
72.0°F
6
71.0°F
Time
interval
based
COV
based
= 1.0
Room temperature
Interval
 Triggered
Refers to the BACnet reference names of the selected trigger from reaction,
scheduler or the BACnet reference.