7 benefits of integrating human-machine interfaces, historians
Cover story: Human-machine interfaces (HMIs) and historians differ but need to be tightly integrated to provide company operations with optimal value. Big data has little value without analysis and access in real time. Seven application examples explain HMI-historian integration benefits, including troubleshooting, analysis, and regulatory compliance.
Human-machine interfaces (HMIs) and historians differ in purpose but need to be tightly integrated to provide great value to companies' operations. HMIs provide effective control and interactions between humans and machines. Historians collect high-speed time-series data to maintain a chronology of events. Seven applications examples help explain integration benefits.
Connecting to data
HMIs typically connect to programmable logic controllers (PLCs) to get their real-time data. Historians typically can connect to a HMI or directly to PLCs via OPC servers. Sometimes users want to connect to the HMI because certain tags have calculated values within the HMI. The preferred method should be that the historian connects directly to the PLC or source of the data. The objective for the historian is to have a complete chronology of process events for future analysis. HMI screens are typically being updated with new displays and graphics and may be shut down or restarted on occasion. When this happens, the data is not being collected properly and there are probably "holes" in the data-if the historian is connected to the HMI. By connecting directly to the PLC source, there is an independent connection that still collects data whether the HMI is running or not. Well-engineered historians also incorporate store and forward capabilities within the logger/collector components and should be located on the same machine as the source. This allows no data to be lost if network connections or communications go down between computers due to network failure or unreliable remote connections via satellite, cellular, or wireless connections. Also, data will not be lost when updating software to the latest software revisions.
Historian storage, performance
With today's PC standard technology and capabilities, a typical historian system should be able to store and access more than 10 years of raw data. Aggregated manufacturing big data is good for certain reports, and historians should have the features to get access to this data, but it should not be stored as aggregates. Raw data streams are needed for true analysis. A well-performing historian should be able to easily exceed 1 million updates per second when storing data while retrieving more than 3 million updates per second at the same time. Users become quickly frustrated if they cannot get access to the data they need for analysis within a few seconds.
Historian ease of use
Users need intuitive tools to leverage historical data. They need easy access to the data tools that don't require weeks of training. This historical data needs to be accessible to the operators within the HMI via client applications that use Microsoft ActiveX controls or preferably Microsoft .NET applications. If operators and engineers could view how different values were moving and setpoints were being changed, they could identify the rippling effect through the entire system and determine problems and solutions more quickly. The value is creating information that leads to faster decisions from this data as opposed to having a bunch of data.
The key is easy access to this data. The value of the trend data is that the user can ask "what if?" and pull the data together to verify the theory immediately. If they must go through IT to get data from the archives, which could take one or two days, they have lost that thought process. In reality, if analysis doesn't happen in almost real time, it is not going to happen.
See the following HMI-historian benefits and application examples.