Data Acquisition Systems Fit Wide-Ranging Applications
Quality data acquisition provides industrial users with the ability to optimize processes, maintain and/or improve product quality, ensure operational safety and environmental compliance, minimize downtime, and improve overall productivity. Control engineers have long depended on accurate data to provide their window into the manufacturing or testing process. Over the last couple of decades, data acquisition technologies have made great strides, including increasing measurement resolution and adaptation to a wide variety of platforms and networks. Flexibility has become a key word in data acquisition.
To investigate trends in this product sector, Control Engineering and Reed Research Group—both part of Reed Business Information ( www.reedbusiness.com )—polled data acquisition users among their subscribers about their preferences with an email/Web-based survey conducted in September 2003. Responses were received from 180 subscribers who evaluate, specify, recommend, install, and/or purchase data acquisition hardware and software. Selected survey results are discussed here.
According to survey data, primary applications for data acquisition hardware and software range widely. Supervisory control and data acquisition (SCADA) and testing and diagnostics form the bulk of the applications (see illustration). Some category overlap is evident, however. SCADA systems are used for statistical process control and work-in-progress testing in many industries, including utilities, continuous process, discrete, and batching applications. When applied this way, they are classified as SCADA systems and lose their identity as to the industry they represent. In any case, it is safe to say that data acquisition is certainly an integral part of many manufacturing operations and a mainstay of automated test data collection.
Selection criteria revealed
The survey also looked at factors that influenced the data acquisition (DAQ) hardware and software selection process. Hardware and software were considered independently of one another in the survey. Of the list of selection factors given, respondents were unanimous in their picks for “very important” reasons for selection in three of the top five reasons listed. The top five for hardware were ease of use, availability, technical support, price, and wide range of I/O device option. Software “very important” selection factors included—in descending order—ease of use, technical support, price, TCP/IP compatibility, and PLC device servers.
Reasons for ease of use, technical support , and price being high on both lists are easy to understand. In today’s shrinking manufacturing economy, emphasis on the bottom line makes it clear that expenses must be controlled. Many manufacturing technologies, including data acquisition systems, have improved to the point of allowing companies to do more with less, greatly increasing productivity while keeping labor costs under control. To maintain quality of operation, control engineering departments now count on vendors to provide products with increased emphasis on the other selection factors. A quality product must be easy to use, so that both installed and operating costs can be controlled. Providing technical support means that vendors must service what they sell and provide users with backup to staffs pared thin by cost-cutting measures.
How accurate, how large?
According to survey results, most system resolution requirements tended to be at or under the 16-bit mark (common for A/D card systems) with 16-bit resolution being the most used. Generally fewer numbers of systems fell in the categories above 16 bit except for those in the 32-bit category that put DAQ technology in the microprocessor, micro-controller, or DSP category. Few A/D card systems exist at or above 32-bit accuracy.
The average number of variables sampled on a per minute basis tended to be concentrated in smaller systems. According to the survey, 50% of the respondents sampled less than 500 variables. Sampling of 500-1,000 variables followed at 14.6% and 1,001-2000 variables came in at 13.5%. Data acquisition systems sampling 2,001-3,000 and 3,001-5,000 variables recorded 7.3% and 3.9%, respectively. A jump in number of variables sampled per minute came in the “more than 5,000” category where 10.7% of the respondents claimed to sample over 5,000 variables in a typical application.
Data acquisition system suppliers have done a yeoman’s job providing control engineers with accuracy and scalability in the systems they provide. According to Rahul Kulkarni, industrial control product manager at National Instruments, “Absolute accuracy of a system depends on the percentage of actual input voltage, offset, system noise, and temperature drift. In a high channel count system with multiple boards, accuracy will not degrade as long as the individual boards meet accuracy specs.”
Main considerations for large data acquisition systems include stream to disk rates, number of channels, sampling rates, data analysis required, and presentation in real time. The main elements governing these parameters include the drive software, processor speed, hard disk type, timing and synchronization across multiple boards, and the modularity of the system. Application of industry standards such as PXI ( www.pxisa.org ) has allowed systems to become quite large and quite fast.
Role of wireless
A considerable percentage of Control Engineering survey respondents (48.3%) do not use wireless technology in data acquisition at all. Most respondents (80.5%) use it sparingly—on less than 10% of applications.
Reasons wireless communication has not penetrated the data acquisition market include cost and perceived unreliability and/or lack of security. However, in today’s industrial climate, companies are hard pressed to cut costs and find alternate ways to get more data for less money. The fact that running conduit and wire costs approximately $30/ft makes wireless technologies and networks very attractive, especially at transmission distances of more than 250 ft.
According to Scott Saunders, technical application specialist for Moore Industries-International Inc. (Sepulveda CA), “RF networks were once viewed as unreliable and insecure. The fact is that wireless networks, if properly selected and designed, are actually more reliable, secure, and cost less to upkeep than hardwired ones.”
Data acquisition technology has made strides in many areas over the past decade. More are yet to come. However, as with any essential technology, for the control engineers and industries that rely on them, quality advances cannot come soon enough.
Data acquisition products
For more manufacturers, visit www.controleng.com/buyersguide . For system integrators go to www.controleng.com/integrators . For more information on products discussed, visit the individual company websites.
Model 2701 Ethernet-based DMM/data acquisition system is said to be the industry’s first multipoint measurement and control system that fully integrates instrument-quality, 22-bit (6-1/2 digit) resolution and sensitivity with Ethernet long-distance networking. Model 2701 also delivers high accuracy, high channel count, broad expansion potential, free software, and built-in Ethernet at a price comparable to less accurate Ethernet-based data acquisition products.
Keithley Instruments Inc.
AutomationDirect offers DataWorx software, an Ethernet-based PLC data collection and storage software package that works with its full line of PLCs. DataWorx PLC connects Ethernet-enabled DirectLogic PLCs or WinPLCs to stand-alone PCs or network servers for simple data logging. The software requires no PC programming or third-party HMI, SCADA, or DAQ software application. Prices start at $395 for the version that supports one PLC.
NI PCI-6509, NI PCI-6514, NI PCI-6515, and NI PXI-6528 are industrial digital I/O modules designed for high reliability industrial data acquisition applications. The low-cost modules feature digital I/O watchdogs, programmable power-up states, programmable input filters, isolation, and change detection. They offer a new price point for mission-critical control and automation applications, including discrete and batch process control, embedded machine control, and manufacturing production line automation. NI
DT9841 Fulcrum II Series intelligent DAQ system processes measurements that require high performance in real time. System combines the accuracy of Texas Instruments’ floating-point TMS3206711 digital signal processor (DSP) with the speed of two 24-bit sigma-delta A/D and D/A converters on a standard 6U card that communicates to the host via USB 2.0. Boards offer high-performance analog circuitry with peripheral-rich C6711 DSPs to provide a complete off-the-shelf, real-time test and measurement system. Each A/D and D/A subsystem has its own high-speed pathway in and out of memory so each can execute real-time measurements without processor intervention. Embedded C6711 DSP is software programmable and can be used in a standalone or system test operation.
Data Translation, Inc.
Fluke 2680A data acquisition system chassis is designed for small to large multi-channel applications requiring reliable Ethernet communications. Front-end chassis style system has six slots, allowing users to custom build a complete data-logging system. Five slots can accommodate any combination of 20-channel universal input modules compatible to the new 2680 Series and eliminating the need for, and the added expense of, external signal conditioning. The sixth slot may be used for an additional analog input module or for an available digital I/O relay module that adds an additional element of control to the system.
New platform offerings
RSView Enterprise Series 3.1’s HMI software family is said to help ensure system availability and ease regulatory compliance. Latest version, which includes RSView Supervisory Edition, RSView Machine Edition, and RSView Studio PC-based development tool, supports improved productivity through redundancy and information collaboration enabled by FactoryTalk. Featuring system-wide audit capabilities, the software can simplify the documenting process for users trying to comply with government regulations, such as 21 CFR Part 11. RSView Enterprise Series 3.1 is available as a stand-alone product or pre-installed on VersaView industrial computers and monitors to reduce time spent combining and configuring hardware and software.
Single-device DAQ, control
The ROC809 remote operations controller meets a wide range of data acquisition and control applications. Single-package format features ruggedness, low power consumption, broad communications capabilities, audit trail capability, historical data archival, scalability, speed, and control. It interfaces to a wide variety of measurement and control devices using low-density I/O modules that plug into expansion slots. Modules are designed for accuracy, ruggedness, and survivability, and their low point-count design allows I/O devices to be closely matched to the application for better cost-effectiveness. Standard package handles a wide range of applications, including PID loop control configurable for up to 16 control loops.
Emerson Process Management
Store data conveniently
Simatic PLC Micro Memory Card (MMC) lets users store, read, and write data to it while applications run, record measurements, and execute or edit recipes. It stores nearly any file type, so collected data important to users or their customers is accessible right from the PLC. The MMC needs no external power source from batteries; change programs simply by changing MMCs. MMC will store a complete project with symbols and comments on the CPU. Programs can be read from and written to the device while in run mode to record measurements or execute/edit recipes. MMC also allows field upgrading of a CPU (debugging, adding additional functionality, etc.) without having to use a programming device.
Siemens Energy & Automation
Process control, distributed I/O network
The NET Concentrator System (NCS) is a process control and distributed I/O network designed specifically for demanding industrial data acquisition and control applications. The NCS provides 20-bit measurement resolution and signal conditioning capabilities said to be equivalent to the highest-quality transmitters on the market. Data rates up to 100 megabits/sec provide the speed needed for applications requiring precise real-time readings or control. NCS features a robust design, which includes a DIN rail-mount metal enclosure that protects against RFI/EMI, high vibration, and shock common in heavy industrial applications. It uses a 10/100Base-T Ethernet or Modbus RTU network and connects existing “legacy” and new process variable transmitters, sensors, control valves, discrete devices, relays, and other distributed field devices, to a DCS, PLC or PC-based strategy.
Latest iFIX software (version 3.5) features new project management capabilities, data accessibility, and security features. According to its developer, the software can help reduce development time, improve enterprise connectivity, and gain greater overall control of their production processes. With companies implementing multiple automation solutions in each plant environment (such as one HMI/SCADA application controls the production line, another controls plant utilities, a third manages information flow to higher level business systems, etc.), today’s intricate manufacturing operations often require users to manage numerous and vastly different applications. Using iFIX 3.5, users can develop, manage, and alternate between multiple HMI/SCADA applications and projects from a single development station. As a result, corporations and system integrators can greatly increase the agility, productivity, and effectiveness of their development personnel.
GE Fanuc Automation Americas Inc.
Better production decisions
InformITInformation Manager software is said to raise data visibility from all control-system functions so manufacturers can use information to make better production decisions. Information Manager collects, stores, and retrieves historical and process business data from control and related systems and turns it into meaningful information, allowing manufacturers to map out a plan to achieve significant key performance indicator improvements. Information Manager serves as the information management solution for IndustrialITautomation systems, providing access to real-time and historical data from control and related business systems.
The isoLynx SLX100 data acquisition system is designed for laboratory, test and measurement, data acquisition and control, and machine monitoring applications. System is comprised of a 12-channel base system including an I/O controller module and optional 8- or 16-channel expansion backplanes—all of which can be panel- or DIN rail-mounted. System accepts single-channel digital or analog I/O modules, all of which are channel-to-channel isolated. It is intended for use with its developer’s SCM5B signal conditioning module family and SCMD miniature digital modules. Fully protected analog inputs feature continuous protection against overload up to 240 V ac sustained. All modules are certified to CSA/FM and CE requirements.
PC-less, modular DAQ
Field acquisition of data can be a problem if an application requires the equipment to be located in an environment not suited for a PC. EX Series portable data acquisition system with its memory recording module (RM-10) allows the user to be “PC-less.” The EX Series/RM-10 combination is portable and offers quick set-up and recording of data up to 2 GBytes. After field acquisition is complete, the EX Series can be easily connected to any PC using its two PCMCIA memory cards for downloading collected data. Modular design allows easy channel expansion up to 24 channels, four per module. A TEDS sensor interface is included.
Analog signal conditioner
PC/104 board solution for data acquisition, test and measurement provides 32 single-ended or 16 differential inputs with flexible gain for use with factory-configured options such as conditioning for thermocouples, RTDs, bridge type load cells and strain gauges, and 4-20 mA inputs with fault detection. Model 104-AIM-32A Kit features include software programmable channel by channel input range/gain, six standard analog input ranges, and complete system calibration with easy-to-use utility software. Priced at under $400, the board is suited for a variety of applications including temperature control and monitoring, power system data acquisition, and environmental monitoring.
Acces I/O Products Inc.
Additional Online Products
Easy paperless recording
eZtrend paperless recorder is a cost-effective, compact DIN-size recorder. Device eliminates the need for paper and pens along with their associated cost and maintenance. Its 5-in. color display presents simple-to-understand bar charts, digital values, and trends, allowing the user to easily interpret process data and take action. Its operator interface provides easy access to the recorder menus for quick set up and replay of the data. Data are stored in secure files under pen configurations. Data are directly related to a pen, so there is no need to remember file names and file structures. Standard Ethernet connection allows direct connection of the recorder to a Local Area Network (LAN) or the Internet. TrendManager software suite ties the process together, providing access to the recorders through a plant-wide LAN or the Internet.
Foxboro A2 Automation systems are said to provide a powerful, yet economical SCADA solution. System supervisory control is provided by Foxboro’s A2 T940 Process Supervisor and a Wonderware InTouch HMI. Together, they provide a fully functioning DCS at the price of a PLC. T940 Process Supervisor provides advanced continuous and sequential control for up to 200 control loops, has comprehensive alarm and data logging and a powerful operator display interface, and integrates with a central database. Data acquisition component of the system is the Foxboro A2 Series 2500 intelligent remote I/O modules. Systems operate as RTUs at process points, receiving sensor data and then transmitting to the control unit via wireline or wireless communications. Unlike traditional I/O modules, the Model 2500 units provide local PID, math, timer, totalizer, counter, and other control capability along with auto-tuning and gain scheduling.
The Foxboro Co.