Data Acquisition

In its purest form, data acquisition (DAQ) is the process of gathering information in an automated fashion from analog and digital measurement sources and presenting that information in a meaningful way. Depending on your industry, DAQ means different things to different people. For example, to the utility industry, DAQ is part of the SCADA (supervisory control and data acquisition) system and ...


In its purest form, data acquisition (DAQ) is the process of gathering information in an automated fashion from analog and digital measurement sources and presenting that information in a meaningful way.

Depending on your industry, DAQ means different things to different people. For example, to the utility industry, DAQ is part of the SCADA (supervisory control and data acquisition) system and implies that data is gathered from remote locations via telephone, microwave, radio, or satellite communications. To the manufacturing or process industry, DAQ is part and parcel of the control system. To a scientist, DAQ is a quick, flexible, efficient way of gathering experiment results, often at very highspeed and with exceptional accuracy. To the business executive, DAQ is knowing, in real-time, the status of production capabilities, work in-progress, inventory, and shipments.

As a result, the people likely to respond to a survey inquiring about their DAQ needs and uses are possibly the most diverse group you'll find specifying, recommending, and purchasing instrumentation and control equipment.

Thirty-two percent of respondents to the most recent Control Engineering and Reed Research Group DAQ survey said SCADA is their primary application for DAQ hardware and software, followed by testing and diagnostics at 23%.

Changing patterns

Among those buying, specifying, or recommending DAQ systems, 56% do so for in-plant needs, 22% for OEM (resale) requirements, and 21% for both.

Pricing appears to be changing—either that or DAQ deployment is decreasing. Survey results show respondents spent 44% less on DAQ systems in 2005 than they did in 2003. (See "DAQ Annual Spending" graph.)

Instrumentation and Sensors

From 2002 to 2003, spending for DAQ systems increased nearly 20%, but declined 44% between 2004 and 2005.

As in the past three DAQ surveys, Rockwell Automation, National Instruments, and GE Fanuc Automation remain the top suppliers of DAQ hardware. However, Opto 22 is a DAQ manufacturer on the move.

Less than 1% of responders indicated purchasing hardware from Opto 22 in 2002. By 2003, some 5% of responders had purchased from Opto 22, and in 2005, that number had jumped to 13%, just behind GE Fanuc at 15%.

DAQ communication preferences are almost as diverse as the DAQ applications supported. For the third straight survey, Ethernet TCP/IP, RS-232, RS-485, and any form of Modbus ranked first through fourth, respectively; however universal serial bus (USB), a recent addition to the list of survey responses, is solidly positioned in fifth place, edging out more traditional choices, such as DeviceNet, ControlNet, Profibus, FOUNDATION fieldbus, and RS-422.

Copper wire continues to be the DAQ communication medium of choice, but one in five users indicated they are using wireless (IEEE 802.11) technology (see "Wireless DAQ basics" sidebar.)

Changing requirements

Though DAQ data are still intended to provide operators and users with real-time information about a particular measurement and/or application, the data's destination (the software application where data ultimately reside) is definitely changing.

In 2002, Microsoft Excel was the number one application choice, followed by commercial data-acquisition software-packages, and manufacturing execution systems (MES). In 2005, commercial data-acquisition software-packages are the first choice, followed by MES. Microsoft Excel has dropped to a distant third.

Reviewing the software manufacturer portion of the three DAQ product-focus surveys, Rockwell Automation continues to hold the top position with GE Fanuc/Intellution, Invensys/Wonderware, and National Instruments holding positions two, three, and four, respectively.

While DAQ software supplier positions in the Control Engineering survey haven't changed much over the past few years, DAQ software features certainly have.

Seven in 10 respondents indicate Microsoft Windows XP is today's DAQ operating system of choice, followed by Microsoft Windows NT, 2000, and Windows 95/98. Linux and Sun continue to garner some DAQ use, but less than Microsoft DOS.

Features and capabilities that respondents seek most often when selecting DAQ software are:

  • Data logging (93%);

  • Control and simulation (91%);

  • SQL (database connectivity, 78%);

  • Historian (70%);

  • ActiveX (69%);

  • OPC (OLE for process control, 67%); and

  • SQC/SPC (statistical quality/process control, 66%).

Unchanging requirements

Among DAQ capabilities that remain fairly stable across the three surveys are the average number of variables per minute, A/D resolution, and the preferred form factor. Despite a handful of survey respondents indicating a need for DAQ systems to collect tens of thousands of variables per minute, 60% require 1,000 variables per minute or less.

Accuracy receives a lot of discussion, but more than half the respondents indicated 16-bit resolution meets their DAQ application needs, with 20% indicating 12-bit resolution is satisfactory.

Another stable in the world of DAQ hardware is form factor. The networked PLC remains the DAQ hardware platform of choice, followed by stand-alone and networked PC-based platforms, while the free-standing PLC ranked fourth.

The intangibles that users expect from their suppliers remain unchanged across the DAQ surveys. Things like ease of use (98%), responsive and helpful technical support (97%), breadth of supported devices (86%), and a configuration-based interface (83%) never go out of vogue.

DAQ products

For more manufacturers, visit . For more information on the products described here, visit the Web sites listed.

High-performance DAQ

Designed to monitor high-speed or application-critical machinery, such as steam and gas turbines, centrifugal compressors, boiler feed pumps, and electric motors, Entek Entrx data-acquisition system helps users maintain the highest levels of operation and production using predictive maintenance tools. Entrx can perform data acquisition, database management, and data analysis functions in portable/test or permanent/online monitoring installations. It can also simultaneously monitor the behavior of several machines under various conditions, including startups and shutdowns. System comprises: Entrx software, a PC workstation or laptop—running Microsoft Windows NT or 2000 operating system, and Agilent VXI data acquisition instrumentation. , Rockwell Automation

Networks & Communication

PCI Express DAQ

NI PCIe-6251 and NI PCIe-6259 DAQ devices combine PCI Express bus with National Instruments' M Series DAQ, providing fast analog- and digital-I/O connections with the dedicated per-slot bandwidth of PCI Express. Devices feature up to 32 analog channels with 16-bit, 1.25 MS/s sampling speed and 10-MHz digital-I/O capabilities on up to 32 lines. PCI Express is a high-performance, point-to-point serial interconnect with a scalable architecture said to provide bandwidth from 2-30 times that of traditional PCI. , National Instruments


Real-time portal

Proficy Real-Time Information Portal (formerly infoAgent) enables users to visualize, analyze, and report on iHistorian data using a Web browser. Version 2.0 expands the business analysis tools available in v1.1, letting production teams make plant-wide decisions in real-time. Proficy v2.0 includes more plant-wide connectivity capabilities (relational databases, OPC, Proficy HMI/SCADA—iFix, Proficy Historian, OSI PI), easy-to-use analysis tools (graphic statement builder, hierarchical data control, data-bound forms controls), and a set of other client components (grids, charts, and graphics). , GE Fanuc Automation

PC-based Control

Programmable automation controllers

Two versions of Snap Pac provide multi-domain, Ethernet-based industrial automation controllers suitable for applications in automation and control, remote monitoring, and data acquisition. Snap-Pac-S1 is a stand-alone controller suitable for distributed control systems and applications with high I/O point counts or complex Ethernet network architectures. Snap-Pac-R1 is an "on-the-I/O-rack" controller designed for cell control and smaller point count applications where the I/O needs are geographically contained. Both feature a 32-bit multitasking processor with floating point unit and two independent, auto-negotiating 10/100 Mbps Ethernet interfaces. Snap-Pac-S1 includes 32 MB of RAM, 16 MB of flash memory, and 8 MB of battery-backed RAM. Snap-Pac-R1 includes 16 MB of RAM, 8 MB of flash memory, and 2 MB of battery-backed RAM; and one RS-232 port with handshaking control. , Opto 22

Embedded Control

No-programming Web data

DataNet OPC uses open connectivity technology to communicate live data from industrial devices to a Web page, with no HTML programming required, making data available anywhere the Internet or company intranet is accessible. For plants that use multiple PLC brands, DataNet OPC is said to provide a unified approach to data display and logging. Dynamic colors allow users to determine the status of their plant operations at a glance and can be used to alert personnel of abnormalities in operations. DataNet OPC is compatible with any industrial device that runs on an OPC 1.0- or OPC 2.0-compliant server. , AutomationDirect

Machine Control & Discrete Sensors

Touchscreen terminal

Magelis XBT-GT 1000 series 3.8-in.-wide monochrome HMI graphic terminal features six function keys to reduce implementation time, includes an embedded FTP server for easier diagnostics, supports Ethernet communication, and can be simultaneously connected on Modbus, Modbus TCP/IP, and Unitelway. Other features include trends and procedures for integration and an audible buzzer that acknowledges operator commands. The terminal has a 320 x 240-pixel resolution screen-image in eight levels of gray scale and a red tint option to help identify display faults and alarms. , Schneider Electric

Process Control and Advanced Control

Paperless data recorder

Minitrend QX electronic data acquisition paperless recorder features up to 16 universal analog inputs and 90 MB of available on-board memory in a DIN standard 144-mm format. It uses a digital color TFT LCD screen with wide viewing angles. The touchscreen operator interface provides access to the recorder menus for set up and data analysis. Navigation through the menus and text entry are said to be direct and intuitive. , Honeywell

I/O Modules

Multi-function RTU

ROC809 is said to combine the ruggedness, low-power consumption, and broad communications capabilities of an RTU (remote terminal unit); the audit trails and historical data archival of a flow computer; and the scalability, speed, and control of a PLC in one package. It includes capabilities for up to 12 meter runs of orifice metering and/or turbine-meter gas-flow calculations using AGA 3, AGA 7/ ISO 9951. AGA 8/ISO 9951 is used for super compressibility factoring and compliance with API Chapter 21. PID (proportional, integral, and derivative) loop control is configurable for up to 16 control loops. User-developed control strategies with logic, math, comparison, time-related, control-related, database, and general commands can be set in up to six function sequence tables. , Emerson Process Management


Simultaneous input USB module

DT9836 Series family of high-performance data-acquisition modules for USB 2.0 provides simultaneous analog input operation at up to 225 kS/s per channel. Each analog input has its own A/D converter to eliminate phase shift between channels and allows correlation of measurements. Twelve 16-bit A/D channels on the DT9836 module are said to guarantee less than 1-ns aperture uncertainty. All analog and digital subsystem functions are sampled simultaneously to yield a data throughput of 225 kHz per channel. Additional features include six or 12 simultaneous, 16-bit analog inputs at 225 kHz per channel; and two 16-bit analog outputs for waveform generation at 500 kHz per channel. , Data Translation

Wireless DAQ basics

Two types of wireless technologies being used in DAQ applications are, according to Kristi Hobbs, data acquisition product manager, National Instruments:

High performance, high power (802.11b/g), which is best suited for applications such as high-speed testing and diagnostics, vibration monitoring, and mobile DAQ; and

Low performance, low power (802.15.4 ZigBee), which is best suited for applications such as environmental monitoring, embedded machine monitoring, and portable testing and data logging.

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