L-DALI User Manual
129
LOYTEC
Version 5.2
LOYTEC electronics GmbH
by controllers for optimum start algorithms (e.g., pre-heat a room for the scheduled
occupancy state). Use the SNVT_tod_event in CEA-709 to accomplish this task. With
generic schedulers and BACnet schedulers use the scheduler’s property relations
timeToNext and nextState (see Figure 118).
Figure 118: Property relations of a scheduler object.
When a scheduler is executing the schedule on the local device, it is called a
local
scheduler
. Such a scheduler is configured to schedule data points and later its daily
schedules can be modified. When accessing the daily schedules of a scheduler, which
executes on a remote device, the object is called a
remote scheduler
. A remote scheduler
has the same interface to the user to modify daily schedules. A remote scheduler object can
be used as a user-interface for schedulers that execute on different devices.
6.4.4
Trending
Trending refers to the ability to log historical values of data points over time. A trend log
object is responsible for this task. The generic trend log object provides the maximum set of
features and can be accessed by L-WEB and the Web service. It can be configured to record
historical data of any data point on the device. Log records are generated either in fixed
time intervals, on change-of-value (COV) conditions, or when a trigger is activated. The
fixed intervals can be optionally aligned to the wall time (e.g., to the top of the hour). After
a reboot the recording is resumed at the aligned intervals. Trend log objects can trend either
local or remote data points. Technology trend log objects can be used to record historical
values of the respective technology data points and expose them to network technologies
that support it. These historic logs are separate from the generic trend logs and certain
restrictions of the technology may apply.
The trend data is stored in a binary format on the device. The capacity of a given trend log
is configured. The trend log can be operated in one of two modes: In
linear mode
the trend
file fills up until it reaches its capacity. It then stops logging. In
ring buffer
mode the oldest
log records are overwritten when the capacity is reached.
Devices with SD cards also allow backups of the trend logs on external Flash storage. This
backup can be triggered by the user over the LCD display or be triggered by certain actions.
The trend data is stored in CSV format under a folder identifying the device by serial
number and the trends sub-directory, e.g. '016101-8000000DEA51/trends'. The SD card can
be used on different devices. In this case different device directories will be created. The
trend backup files can be opened directly on a PC. The backup on external storage can be
enabled individually per trend log.
A fill-level action can be activated, whenever the trend log has logged a percentage of its
log size with new log records. A fill-level condition of 70% on a trend log with 1000 items
capacity will activate the fill-level trigger every 700 logged records. This trigger can be
used to send E-Mails or backup trend data on external storage if available.
Trended data points can be logged as their actual values at given time instants or as an
aggregated value over the defined log interval. Aggregation can be calculated as minimum,
maximum, or average. Aggregation can be beneficial, if the trended value changes more