National Instruments BridgeVIEW Historical Data Logging and Extraction

Historical Data Logging and Extraction

This chapter explains the concept of a trend, how to log and extract

historical data, and how to use the Historical Trend Viewer (HTV), a utility

that displays historical data that has been logged to disk with BridgeVIEW.

A trend is a display of tag values against time. BridgeVIEW displays tag

values with two types of trends: real-time trends and historical trends. You

can find these trends in the Controls palette.

A real-time trend is a display of tag values as they are collected in real time

over a relatively short period of time. You can display a real-time trend in

your HMI by using the Trend Tags VI in the Tags palette in the block

diagram. You also can use the HMI G Wizard to create a real-time trend.

For more information about the HMI G Wizard, see Chapter 4, Human

Machine Interface.

A historical trend is a display of tag values that have been logged to disk.

This is usually over a relatively long period of time. You can display a

historical trend in your HMI by using the Get Historical Tag List VI and

Read Historical Trend VI from the Historical Data palette from the block

diagram. You also can view historical data by launching the HTV utility.

You can use the HMI G Wizard to create a historical trend display.

Citadel is a high performance historical database. With Citadel,

BridgeVIEW can log tags while continually servicing data queries.

BridgeVIEW also includes the Citadel ODBC driver that has special

commands to perform data transforms, making it easy for you to retrieve,