Instruction Manual

i.LON 100 Internet Server Programmer’s Reference 6-1
6 Data Loggers
You can use Data Loggers to monitor activity on your network. Each Data Logger will record
updates to a group of user-specified data points into a log file. The information recorded for
each update includes the value and status that the data point was updated to.
Each i.LON 100 supports up to ten Data Loggers. The log files for each Data Logger are
stored in the /root/Data directory of the i.LON 100 with the file name logX, where X
represents the index number assigned to the Data Logger.
You can create two kinds of Data Loggers: historical Data Loggers, and circular Data
Loggers. A historical Data Logger stops recording data point updates when its log file
becomes full. A circular Data Logger removes the records for older updates when its log file is
full, and new updates occur. The Data Logger can save either type of log file in an ASCII-text
(.csv file extension) or binary (.dat file extension) format.
You can specify the minimum amount of time that must elapse, and the minimum change in
value required, between log entries for each data point your Data Logger is monitoring.
When an update to a data point is logged, a subsequent update for that data point will not be
logged until the minimum time period specified for the data point has elapsed, and the
minimum value change specified for the data point has been met. If an input data points is
updated more than once before the minimum time period has elapsed after a log entry has
been recorded, the older values will be discarded. Only the most recent update will be
recorded by the Data Logger when the minimum time period elapses. This allows you to
throttle the data entry into a log.
You can also define a threhold level for each Data Logger. The threshold level represents a
percentage. When the Data Logger’s log file consumes this percentage of the memory space
allocated to it, the Data Logger will enunciate that it is time to upload the log, and clear out
some of the data. The Data Logger makes this enunciation by updating the Data Logger’s
alarm data point (called NVL_nvoDlAlarm[X], where X represents the index number
assigned to the Data Logger) to the status AL_ALM_CONDITION. This feature may be
useful when working with historical Data Loggers, which are disabled when they become
full. You could create an Alarm Notifier to trigger an alarm notification when a log becomes
full. For more information on Alarm Notifiers, see Chapter 9 of this document.
You can access the data in a log file by manually opening the log file, or by using the
DataLoggerRead SOAP function. You can clear data from a log using the DataLoggerClear
function, or by sending an update to the data point NVL_nviDlClear[X], where X represents
the index number of the Data Logger to be affected. This is described in more detail later in
the chapter.
6.1 DataLogger.XML
The DataLogger.XML file stores the configurations of each Data Logger that you have added
to the i.LON 100. Each Data Logger is signified by a <Log> element in the XML file. The
configuration properties contained in each <Log> element define the configuration of a Data
Logger, and are described later in this chapter.
You can create newData Loggers using the DataLoggerSet SOAP function, or by manually
editing the DataLogger.XML file. The sections following this example provide instructions
and guidelines to follow when doing so.
The following represents a sample DataLogger.XML file for an i.LON 100 with three defined
Data Loggers.