Wanted: Small-Scale DAQ Solution

What should you look for in a software package? Tools, wizards, other special features?

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I need helpful DAQ software. I’m a controls engineer proficient in hardware, PLCs, and ladder logic. I don’t have any other software programming experience, and I don’t want to get into large-scale SCADA packages like Citect or Wonderware. What should I look for in a software package in terms of tools, wizards, and other special features that would most easily allow me to implement some basic data acquisition?

—from September ’07 Control Design


Connections, Systems, and Reporting
Today, automation software extends far beyond the reach of basic data acquisition, offering users real-time data-capturing and visualization options. These packages are relatively easy to configure and install.
First, you need to evaluate what parts of your control system you’ll need to connect with to retrieve the data—and where you’d like to send the information. Software solutions that easily integrate with your control system will help your control-and-information layer communicate best. Features such as PLC programming and system setup tools will help you streamline the production process.


Data Monitoring
Once logging starts, a real-time trace is displayed to keep the operator informed.

Top-of-the-line automation software programs have tools needed to collect manufacturing information at the machine, line, plant and enterprise levels. Real-time information reporting tools help you gauge machine performance by identifying the root causes of production inefficiency quickly and easily. Data historian programs offer you the ability to capture time-series data, for accurate batch comparisons and improved order/product tracking across the enterprise.

A number of display formats and analysis tools can help you extract the most value out of the production information. When paired with an operator interface—placed directly on-machine or in the back office—advanced automation software solutions provide a window into operations. In fact, many programs feature fully customizable production dashboards, so users can compare key performance indicators using graphs and charts.

SCOTT MILLER, business manager
Rockwell Software, www.rockwellautomation.com

Know Your Data

Ask yourself these five questions.

  1. What data is important?
  2. What data is useful to display to the machine operator?
  3. What data is worthwhile to acquire?
  4. How fast does the data change, how often should you sample, and how much data should you acquire?
  5. What is the budgeted time and cost for an HMI/SCADA software tool?

For example, say an OEM mixer builder’s customer wants a graphical user interface to capture data, perform calculations, and trend it after the fact. A PLC is used for A/D conversion of the sensor inputs. Four variables are of interest: hp (0-2) and rpm (0-300) on one screen, and product temperature (50-450 °F) and barrel temperature (0-500 °F) on another screen. The cycle time of the continuous mixing process (test cycle) is one hour. The data to be collected and logged is manually triggered by the operator after the barrel temperature has reached a sufficient level and the mixing can start. Once logging starts, the real time trace is displayed to keep the operator informed. Data logging stops when triggered manually by the operator when the test is deemed finished.

The purpose of data acquisition is to understand machine behavior, improve efficiency, and perform diagnostic troubleshooting. With these objectives in mind, it’s desirable to log data at least every 6 sec (600 samples per hour), recall recent trend history on screen, save data, and do detailed historic trending analysis at a later time. It’s also useful to let the operator redline or mark any sample times of interest for further study.
A sample plot produced with InstantHMI software (see figure) illustrates the features described above. The screen includes temperature data fields and legend for plot variables, plot scales, buttons to trigger datalog, mark chart, and status LED. All these elements including plot should be available as widgets for easy pick-and-place screen creation. In addition, it should be easy for you to define tags to identify PLC memory locations—same as in ladder logic—that store the A/D values for the sensor data.

RAMAL MURALI, president
Software Horizons, www.InstantHMI.com

Intuitive Interface

This question is typical for many controls engineers, who don’t have time to learn a high-end SCADA software package. What users look for is a product that provides an intuitive, easy-to-learn, and easy-to-use interface with the functionality they need now and in the future.

Consider these questions:

  • Can the software support data acquisition from the various data sources you’re using, and is there any cost to support this interface? For example, can you use existing sensors connected to a PLC or RTU, or is proprietary hardware required? Does the software have drivers to interface to the PLC (RTU) or is a third-party OPC server required?
  • Does it support data acquisition by batch or continuous stream?
  • Does it have the means to scale the measurement data?
  • What options are available to store the streamed acquisition data? Is data stored in a proprietary file format? Can it be stored to Microsoft Excel, Access, or relational databases such as Microsoft SQL Server?
  • Does the software have the ability to easily configure data acquisition rates?
  • Are tools provided to display the acquired data (both online and historical) and provide dynamic configuration of the pens?
  • Can the product support data analysis either through internal functions or add-on software such as ActiveX controls?
  • Does it have an intuitive, configurable interface with appropriate configuration wizards?
  • Is remote viewing of the data required?

JOHN DUNLAP, vice president, marketing

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