L-VIS User Manual
194
LOYTEC
Version 6.2
LOYTEC electronics GmbH
underlying BACnet objects are enabled. Alarm conditions can be specified for analog input,
output, value objects (AI, AO, AV), for binary input, value objects (BI, BV), and for multi-
state input, value objects (MSI, MSV).
Alarm servers in the BACnet technology are mapped to BACnet Notification Class (NC)
objects. Each alarm server is mapped to one NC. The notification class number can be
configured in the object instance number property of the alarm server object.
Remote alarms in the BACnet technology refer to a remote NC object. When the device
starts up, the remote alarm object reads out the current alarm state of the remote NC and
reporting objects. To get notified about alarm transitions during run-time, the device
registers in the
Recipient_List
of the remote NC object.
Some BACnet devices do not send a usable text in their alarm notification messages. For
those devices, the alarm client provides the option
Ignore alarm message text
. If this
option is enabled, the alarm client ignores the message text of an alarm notification and
reads the description property of the alarmed object instead.
10.5.4 BACnet Trend Logs
Trending in the BACnet technology is based on the BACnet TrendLog object. A number of
restrictions apply to trend log objects in BACnet. Trend log objects must be created by the
configuration software. These objects are accessible over the BACnet network for other
BACnet devices and operator workstations (OWS). All configuration properties can be
modified by the configuration software as well as an OWS. The number of trend log objects
cannot be changed at run-time. Therefore, if it is intended that an OWS configures the trend
logs, a suitable number of empty trend log objects (i.e., without attached data points) must
be created in the configuration software.
In BACnet trend logs, only one data point can be trended per trend log object. The trended
data point can either be a local BACnet server object or a remote BACnet object accessed
through a client mapping, showing the referenced property for trending to the OWS. Data
points of other technologies and the min/max/avg algorithms can be trended as generic data
points without having a BACnet property reference.
BACnet trend logs support interval, COV, and trigger-mode logs, aligned intervals are
available in interval mode. The settings for linear and ring-buffer logging are mapped to the
Stop_When_Full
property of the underlying BACnet trend log object. This setting in the
configuration software is a default and can be overridden by writing to the
Stop_When_Full
property by the OWS. The trend log object adheres to BACnet revision 12.
If an enable data point is configured in the project, the
Log_Enable
property is written with
the value of that data point. If no enable data point is configured, the
Log_Enable
property
is set to TRUE as a default and can be modified over the network.
The fill-level action is mapped to generating a
buffer event notification
in the BACnet trend
log object. The fill-level trigger can still be used for e-mails even if no notification class is
configured in the BACnet trend log object. The fill-level percentage maps to the
Notification_Threshold
property. The percentage setting in the project is a default and can
be changed by the OWS over the network.
The BACnet technology also supports
remote trend logs
. A remote trend log is basically a
BACnet trend log client, which accesses trend data on another device. The remote trend can
load the trend data from the remote device and supply it to trend controls, the OPC server,
or make it accessible via the trend CSV files.
10.5.5 Dynamic Polling in BACnet
Read client maps in BACnet rely either on COV subscriptions or on polling. Polling can be
configured as a fallback, if COV is not supported, by setting the poll cycle (see section