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.
(Courtesy of Scott Singleton for RPM magazine)
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."
DCS as DAQ?
Why do companies install DAQ systems? Just about every process plant has a control system, field transmitters, network and other hardware and software that support the main process control system. If they need to gather more data from process units, it's a simple matter to tap into the existing system and process the data through their DCS, PLC, or HMI/SCADA system.
As Larry Wells, a systems integrator at Confidential Control Systems Assessment ([email protected]), puts it, "All my customers have full-blown DCSs. Even though from a hardware perspective buying a dedicated data logger can cost less, if the user has a DCS, it's much easier to use the DCS as the ‘data logger.' A little more expense for the I/O, but less training, less custom engineering, fewer spare parts, single service contract, etc."
So, unless a company owns a race car, why does it need a separate DAQ system? Harry Sim, CEO of Cypress Envirosystems says DAQ systems are installed for energy audits, condition-based maintenance, outright energy savings and better input variables for advanced control models, among other things. Note that process control is not on that list. This is probably because the cost of putting in sensors and transmitters on a process unit costs tens of thousands of dollars. "In talking with many industry customers, the cost of installing a transmitter into a legacy system is $4,000+, higher for regulated industries," says Sim. Such an installation involves a PLC, PC or DCS control system, and DAQ that will be incorporated in the control system. Therefore, many DAQs are used for non-control purposes, such as energy management or equipment diagnostics.
For these kinds of DAQ purposes, you may want to use temporary, wireless or non-invasive sensors. "One trend relates to ‘temporary' sensors, which are easy to uninstall and move," says Sim. "There are several drivers of this that we've observed, including energy audits. Some measurements of flow, pressure and temperature are only needed to get a good baseline, but not needed for permanent installation."
Though wireless sensors reduce wiring costs, some users are still skeptical about the technology. "In some cases, this is because they've looked at obsolete wireless technology that's not as reliable as today's equipment and mistakenly concluded that all wireless data loggers are alike," says Chris Sorensen, vice president of sales and marketing at Dickson. "Dickson invested a good deal of effort to develop wireless instruments that are reliable. Dickson's Wireless Wizard has an automatic data backup of nine days, real-time ongoing feedback to confirm that the wireless network is intact, and that the expected benefits of real-time data are there and that no more labor hours are required for data downloading. In our case, wireless technology is as reliable as hardwired models."
Figure 2. Wireless steam trap monitors.
Wireless DAQ worked for Genentech at its facility in South San Francisco, where it manufactures biotechnology-based drugs and performs R&D. The facility has about 500 steam traps. Chris Stubbs, senior director of corporate facility services, decided to install wireless steam trap monitors from Cypress Envirosystems (Figure 2) on 56 traps. The wireless monitors transmit data back to a receiver server, which connects to the plant's LAN. Any PC connected to the LAN can see the data. Between September 2008 and January 2009, the system detected 14 steam trap leaks. If undetected, Stubbs estimated the leaks would have cost $42,525. Based on this experience, the payback period was five months. For more details on the installation, see the sidebar, "DAQ Attacks Steam Leaks."
DAQs and Data Loggers
For those who don't want to integrate hardware from Vendor A and software from Vendor B over an XYZ interface, complete DAQ systems are available from many vendors. These vary from a simple battery-powered data logger that downloads into a mobile computer to a full-blown hardware and software system.
For example, Measurement Computing just released its USB-502-LCD data logger, which stores up to 16,379 relative humidity and 16,379 temperature readings. Users can plug its USB connection into a mobile computer and process the data with USB-500 Series Data Logging Application software.
A simple, inexpensive data logger can replace chart recorders, says Minoru Kobayashi, product marketing manager at Omron Electronics. "The electronic version of a paper-based chart recorder can measure a wide range of inputs, such as temperature, voltage, vibration and weight, on multiple channels," he says. "Critical factors in selecting such a data logger include range, measuring speed, how long the data can be saved, the method for saving data, price, size, portability and weight. Data transfer preferences for this type of data logger include USB memory stick, SD card and direct serial connection."
Moving up to bigger DAQ systems can cause problems. "Many end users want to purchase a complete solution from a single vendor," says Yokogawa's Stanier. "With cutbacks in corporate and plant engineering staffs, many customers look to us, not only for hardware but also for a fully designed, configured and installed system. This seems to be particularly true with small (20-500 I/O count) systems where end users know what they want, but don't feel the need to do specifications or internal project management, which would be more common on a DCS project."
"Tightly integrated hardware-software solutions are inherently more flexible than stand-alone systems," says Charlie Stiernberg, product marketing manager for remote data acquisition, at National Instruments. He says "retaskable" DAQ systems allow users to move a system from job to job without spending more money.
"In some cases, companies are testing for A and then B without having to buy any additional equipment. National Instruments customers, for example, can use the same C Series modules for measurement, control and datalogging applications over Ethernet, wireless or USB connections without changing their software," Stiernberg says.
EUtech Scientific Engineering in Germany used NI's hardware-software solution to build the EUcoalsizer system, a mobile DAQ and laser probe that measures coal particles in coal pipes. Instead of collecting samples from the coal pipe and taking them to a laboratory for analysis, EUcoalsizer does the measurement and analysis onsite. This helps EUtech's utility customers optimize coal combustion efficiency and lessen the effects of coal burning on the environment by reducing greenhouse gases such as nitrous oxide and carbon dioxide.
Max Starke, development engineer at EUtech, says, "We simplified and improved a formerly expensive and labor-intensive coal particle measurement process by using National Instruments' high-speed digitizers, multifunction DAQ devices and LabVIEW software." For more details on how EUcoalsizer works, see the sidebar "DAQ in the Stack."
Similar DAQ systems are available from a host of vendors to address everything from general-purpose to very specific applications. So, if you can't find one that meets your exact needs, you can always build one yourself from available hardware and software.
Rich Merritt is a Control contributing editor.
Racing great Mark Donohue called it "the unfair advantage." Rally racers in the U.K. call it "demon tweaks." In NASCAR, it's "getting the call." Whatever you call it, finding little secrets to make your car go just a teeny bit faster than everyone else's is what wins championships and sets records.
That's what Trevor Stripling did with his car: He found a way to use data acquisition to get the data he needs to tune his car to the ultimate, much like a process control engineer uses adaptive tuning and process optimization techniques. Essentially, Stripling gathers important data during a "batch run," analyzes it, compares it to previous runs and tunes the car accordingly, in the hope of finding "the golden batch."
Figure 3. DirectLogic DL06 series PLC
A DirectLogic DL06 series PLC (Figure 3) captures data from oil pressure,fuel pressure, engine vacuum, engine temperature, voltage, nitrous pressure, wideband O2, and engine and driveshaft RPM sensors during the five second drag strip run. All real-time functions of the car are handled by the PLC, including ignition timing.
"The most important engine parameters are the wideband O2 sensors," Stripling says. "They tell us how efficient the nitrous tune is for the given weather conditions.The second would be the engine and drive-shaft RPM; these tell us how the suspension settings are responding to the engine power and track conditions."
The PLC connects to Maple Systems' Ivory Series HMI with Windows CE, running Indusoft WebStudio HMI/SCADA software (Figure 4). The PLC and HMI connect via standard Ethernet. "One of the benefits of the HMI is that I was able to move some of mathematical conversions for the analog sensors to the HMI, which has decreased the scan time in the PLC, allowing it to respond quicker and make real-time control decisions," says Stripling.
Figure 4. Indusoft Web Studio HMI software displays data and downloads engine tunes to the PLC.
(Courtesy of Scott Singleton for RPM magazine)
HMI displays are used to tune the car before each run and to log and save settings after each run. "I can view and change any of the tune-up settings in the PLC and enter in any other manual or physical setting, such as shock settings and tire pressure for the race," he explains. "I've built a ‘recipe' database, as we call it in the control world, that saves these settings for each run.We can easily pull up a prior run and load the tune. We also use this when we are in line for a run and the track conditions change. At the last minute, we can pull up an alternate tune and load it with a touch of the HMI screen."
Like many process systems, the DAQ system connects to higher-level management software—in this case, a laptop computer in the race car trailer. "We used to have to get the laptop out of the trailer, connect it and download the run data, then convert, analyze and graph it," says Stripling. "With WebStudio's scripting and database connectivity and Maple System's USB communication ports, we now just touch a button on the screen and a script goes out to the PLC, gets all the log data, converts it to engineering units and loads it into a database on a USB thumb drive. We simply take the thumb drive to the trailer and plug it into the laptop where all the run data is analyzed and graphed in Excel. We're currently working on adding a wireless USB card to the HMI so we can wirelessly access the run data."
DAQ Attacks Steam Leaks
Genentech determined that leaking steam traps were costing the company hundreds of thousands of dollars per year. Chris Stubbs, senior director of corporate facility services, says Genentech performs manual audits of traps about once a year, and replaces traps that the audit discovers to be leaking. "Steam cost is about $15 per 1,000 lb, and a typical small 1/8-in. leaking trap would cost $5,000 or more per year," she says. "Larger traps would waste much more."
The manual audits were time-consuming and expensive, and—because they were done only once a year—it was impossible to detect steam traps that were just starting to leak and beginning to waste steam. Genentech wanted to install steam trap monitors in its plant, so it could detect traps that were leaking or starting to leak. They were faced with the choice of using wired or wireless devices.
Genentech did an analysis and discovered that using traditional hardwired monitors was expensive and disruptive to the process. Projected costs were about $3,000 to $5,000 per point. Wireless, on the other hand, was non-invasive, required no interruption to the process and cost $750 to $1,500 per point.
So Genentech installed 56 wireless steam trap monitors from Cypress Envirosystems as a trial. The monitors transmit data once every 10 minutes to a central "blue box" receiver, which displays the health of the different steam traps, provides notification alarms via email and text messages, and trends historical values. The blue box is connected to the plant's central local area network (LAN), allowing access from any PC on the LAN. "Looking at the past five months of data, we could actually sample just four times a day," says Stubbs.
Stubbs says the steam trap monitoring DAQ is part of an overall wireless plant monitoring scheme involving wireless monitors and DAQs on 20 freezers, four air handling units, one reverse-osmosis water treatment system and five other utility systems. Genentech has 100 wireless monitors installed and estimates that annual savings so far are more than $75,000. So far, the wireless DAQ systems have paid for themselves in the first year.
DAQ in the Stack
Measuring coal particle size helps utilities and large energy users tune their boilers for optimum performance. But the efficiency depends on the speed of analysis. "Taking coal particle samples to the lab for analysis makes direct correlations between operational mill and boiler settings impossible," says EUtech's Max Starke. "Furthermore, inherent variability in coal properties and measurements requires multiple analyses on the same sample to obtain accurate results."
In response to the industry's need for a mobile data acquisition and control system, EUtech developed EUcoalsizer, which uses laser-based online technology, as well as National Instruments' USB-5133 digitizer, a USB-6009 DAQ and LabVIEW software to measure coal pipe particle size, velocity distribution, mass flow, as well as the temperature inside the coal pipe.
The measuring probe is inserted into the coal pipe, and data is processed on the spot with a laptop loaded with LabVIEW software. "The PC uses LabVIEW for data processing and user interfacing, data analysis, evaluation and data storage," says Starke. "The system setup also includes automatic reporting that we can calibrate according to user-defined requirements. NI hardware and software formed a flexible, environmentally beneficial and cost-saving system that provides high sampling rates, accurate measurements and advanced processing capability."