This article was printed in CONTROL's April 2009 edition.
By Rich Merritt
Trevor Stripling works with PLCs, HMIs and data acquisition equipment all day in his job as a control systems engineer at Contech Control Services in La Porte, Texas. Stripling supports engineering procurement contractors (EPCs) in Texas and along the Gulf Coast, providing front-end project definition, planning, estimating, detailed engineering, systems integration and programming of control systems.So, when Stripling needed a data acquisition system for his race car (Figure 1), he called on his own knowledge and experience with industrial equipment.
Stripling campaigns a 1967 Camaro with a 598-cu -in. engine in 1/8-mile drag races. Currently, he's the world record holder with a 5.11 sec elapsed time at 143 mph. Though Stripling attributes his success to his engine builder and crew, the real hero of the team is a data acquisition system that acquires and logs data, so the crew can analyze what happened after each run, and fine tune the engine for the next one.
What Stripling accomplished with off-the-shelf components is similar to the challenges of a control data acquisition project: overcoming electrical noise, increasing real-time acquisition speed, performing systems integration of all components, using PLC and HMI communications over Ethernet, making wireless connections, analyzing the data, managing menus and recipes, keeping historical records and handling diagnostics.
Figure 1. Trevor Stripling's 1967 Camaro hits a record 143 mph in 5.11 seconds in a 1/8th-mile drag race. The secret to his success is a data acquisition system based on industrial components, including a Direct Logic PLC, Maple Systems' industrial computer, and InduSoft's HMI/SCADA software.
The sidebar, "Race Car DAQ" (see end of story), explains in more detail how the system works, but the basic point is this: Acquiring and analyzing data is key to the critical setup and tuning of the race car—in much the same way as an industrial DAQ system can be key to the efficient operation of a process.
What Stripling did could be called "DIY DAQ"—that is, he assembled various pieces of hardware and software, integrated and connected them together, and built a data acquisition system. Modern DAQ hardware and software lends itself to this very nicely, thanks to standard interfaces like Ethernet, Modbus and USB. Putting a system together these days is almost a plug-and-play operation.
"There is a clear trend in the increasing use of digital communications with protocols such as Modbus TCP, EtherNet/IP, Profibus DP, DNP3 and others," says Todd Stanier, network solutions marketing manager at Yokogawa. "While the use of these protocols is certainly not new, I know we've have invested significant resources in having these protocols available in our products."
Internet access is becoming popular too. "With increased reliance on immediate access to process data from anywhere at any time, the Internet connection is mandated," says Dave Parks, marketing manager at Logic Beach. "In the process industry, many non-DCS connected applications abound, from pilot plant/process data acquisition to environmental monitoring. A data logger such as Logic Beach's IntelliLogger can be assigned an IP address, allowing it to sample and process inputs, log to local memory, send FTP data to FTP servers for data archiving, email reports and alarm messages, and even serve custom Web pages directly to browsers."
To OPC or Not OPC
Tim Donaldson, director of marketing at Iconics, attributes software's easy connectivity to OPC. "We're delivering software related to data logging and acquisition today. OPC servers help provide connectivity from the data logger and data acquisition equipment level to high-level analysis software throughout an enterprise. Once data is captured through the hardware, HMI/SCADA software helps to visualize it and put it to use."
Donaldson says DAQ vendors should incorporate OPC drivers with their hardware. "When they deliver the hardware, there are no proprietary drivers for users to spend time trying to hook up," he explains. "Without OPC integration, a user might have considered: ‘I have my hardware piece. I have my software piece. Will I have to spend time finding a proprietary driver to have them talk to each other? Is there one that already exists? Do I have to write it?' If the vendor delivers hardware with an OPC server, then an OPC client can then connect to it."
Ed Stern, vice president of Canary Labs agrees wholeheartedly. "Our Trend Historian and Trend Link software obtains data via OPC interfaces to PLCs, DCSs, RTUs, video surveillance and other hardware and software packages," he says. "We have 10,000 packages installed worldwide, all running with OPC, so we know it works."
On the other hand, DAQ hardware that comes with standard (non-OPC) drivers means a system can run much faster. All you need to do is make sure that the DAQ hardware has a driver that connects to whatever PC software you will be using to process the incoming data. This could be a consideration when speed is at stake.
Bob Judd, director of sales and marketing at United Electric Industries agrees with the need for easy integration. "We see the push for easier to use, more integrated and more reliable products," he notes. However, he doesn't like wireless or USB, two communication methods that make things easy to connect. "We see a definitive bias against wireless and USB. People don't like USB because there is no cable-locking mechanism on the USB interface, and there is concern the cables will vibrate out. We see hesitance on wireless for two reasons. The first is concern over the reliability and integrity of the wireless link. Interestingly, this reliability is a smaller issue than security. Many companies we work with won't allow DAQ and control data to be sent wirelessly for fear that the data's privacy can't be assured."