Data Acquisition, Trending, and Historians

Although a PLC and panel HMI may adequately control a system, the owner can improve his grasp of how the system is functioning by logging production data over long time intervals.

With data acquisition, important sensor values are sampled regularly and stored in a database. This data may be stored locally for a few months, or it may be stored on a server long term. In either case, the primary goal of data acquisition is the ability to produce trend plots, either in real time or historically.

Local Trending

SCADA systems such as Wonderware InTouch® and Rockwell's RSView32™ already come with trending capabilities built in. Data is stored locally and viewed locally.

Because local data has only limited usefulness, it is typically not retained more than a few months at a time.

trend plot

Sample trend plot using Wonderware InTouch

Plantwide Trending and Reporting

Due to the limitations of locally-based trending, larger plants benefit from server-based historians which collect data from multiple systems and store it long term. Not only does this shift the data to a more robust platform, it means the data may be accessed plantwide via a corporate intranet.

Another advantage is data is put into a more accessible format. Whereas local trend data is stored in a SCADA's proprietary format, historians use standard database solutions such as Microsoft SQL Server®. Consequently, you have a wider variety of reporting options.

Our staff has plenty of experience with Wonderware Historian (formerly known as Industrial SQL). We have also developed systems using Rockwell's historian, RSSql™.

See Web Reports for an idea of things we can do with this data.