Data Acquisition In Your Pocket

Data acquisition, or DAQ, brings to mind the recording of test or manufacturing data in real time on a personal computer (PC) or data logger.

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But new adjectives are beginning to describe the current state of data acquisition, such as smaller, faster, easier-to-use and virtual.

“Really, DAQ is taking [a measurement of] a real-world phenomenon, such as temperature or pressure; passing a signal through a transducer; digitizing it in a PC-based or stand-alone device; and then saving it to a disk and/or displaying it on a panel,” explains Jared Aho, technical product manager, DAQ Group, for automation vendor National Instrument (NI, www.ni.com), Austin, Texas.  

Doing all this requires more than just a device. Signal conditioning is needed to connect different sensors, and usually some electrical protection, such as isolation, is required, Aho says. “And then the other part of the system is the software.”  

That software—or how end-users employ it—differentiates PC-based and stand-alone systems, Aho explains, adding that there is vendor-defined or user-defined software. An example of the former is NI’s LabView, a 21-year-old programming platform.  

So what is DAQ’s current challenge? Providing smaller devices that provide the same type of measurements as the larger ones, but more dynamically, Aho suggests. That will lead to more systems, rather than just devices, to measure things such as temperature, pressure, strain and acceleration, he forecasts. One example is NI’s Compact DAQ system, which is 10 inches long, about three inches deep and about three inches high. “It’s a blank chassis into which you plug modules. It’s easier to use for different types of measurement,” he explains. 

Smaller devices do exist that maintain the performance expected from traditional DAQ. For stand-alones, Aho mentions universal serial bus (USB)-based newcomers to the low end of the general market. There are also vendor-defined USB data loggers “the size of a woman’s lipstick.” The emergence of the USB 2.0 specification has “enabled the low-cost lipstick-sized data loggers all the way to the high-performance DAQ systems,” Aho says.  

Capitalizing this year on USB 2.0, automation provider Advantech (www.advantech.com) released its USB-4700 series DAQ family. It needs no external power or wiring terminal, explains Juan Peishan, product manager with Advantech’s e-Automation Solutions Group, Cincinnati. “It moves the DAC [data acquisition and control] device out of the chassis, and adapts the advantage of distributed modules.” With a plug-and-play feature, the USB-based system makes the new series “not only faster—up to 200,000 samples per second—but also easier to use,” he notes.  

Is smaller easier to use, though? It can be, Aho suggests. “But when mixing all these types of measurements, if it’s not easy to program, then it won’t be successful.” So all measurements need to be more transparent. “And the user needs to understand how to set up to measure, how to start it and then acquire it—no matter whatever type of signal,” he says.  

Choose your bus  

Regardless of DAQ size, though, there is no “silver bus” for DAQ connections, meaning “you can’t standardize on one bus for all applications,” Aho remarks. For quick, portable measurements, he asks, “What’s easier than USB?” For something distributed across the factory floor, “Ethernet is the perfect solution.” And for very high speed, data-intensive applications, he suggests, “There’s nothing better than PCI [peripheral component interconnect] Express or PXI [PCI extensions for instrumentation] Express.”  

Two coming milestones foreshadow more changes in DAQ. “We believe we are at a tipping point in the adoption of virtual instrumentation,” Aho says. And regarding the current DAQ instrumentation market, “we are seeing the tipping point where PC-based equipment may soon be more prevalent than traditional stand-alone-based.”
 

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