9
Theory of Operation - Software
While the AV-Trend software provides the interface for all configuration, reporting, data
annotation, logbook, etc, it does not perform the realtime functions normally associated with
the data logger, such as:
Instantaneous scans of I/O, Modbus, GSI connections
Short-term averaging and validation / flagging
Calibration Control
Short-term alarm generation with relay output control
To fulfill these requirements, the AirVision Service runs a plug-in called the Site Node Logger.
The addition of this plug-in distinguishes an 8872 from an AV-Trend PC. This service scans the
configuration within the 8872 (channels, calibrations, etc) and loads processes and threads to
perform the realtim functions, inserting averaged data, calibrations results, etc, into the 8872
database at the required time.
The Site Node Logger operates at a general scan rate of 3 seconds (for internal I/O modules
and external Modbus/GSI devices). Consult Agilaire for applications where higher scan rates
are required.
Agilaire 8872 Manual
Chapter 1 Theory of Operation
Digital Module
Analog Module
Site Node Logger
Service
GSI
Modbus
Averaging
Calibrations
Other
AVData
Database
AirVision
Service
AV-Trend