The buses roll on: PCI gets competition from PXI and USB in DAQ applications
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 2/1/2007 2:00:00 AM
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PCI data-acquisition cards have been around for more than a decade. They handle a wide range of the measurement tasks, but PCI expansion slots are vanishing from commercial PCs. Those remaining slots are moving to the faster PCI Express serial bus. Thus, building measurement systems with PCI cards is getting harder to do.
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PCI data-acquisition cards face vanishing slots in commercial PCs. Courtesy of Measurement Computing. |
PCI also gets competition from PXI and USB, the latter of which is partly responsible for the loss of expansion slots. “USB is the hot bus right now,” said Bill Kennedy, sales and marketing manager at Measurement Computing. Engineers are, however, building plenty of new systems with PCI cards.
In spite of the vanishing slots on PCs, PCI card makers report brisk sales. Industrial computers and expansion chassis help because they provide plenty of slots. Industrial computers also make it possible to use ISA cards, which card makers continue to build, although the rate has slowed significantly. Many ISA-based systems, though, require replacement cards, or engineers are asked to build duplicates of old systems.
Jon Tucker, lead marketing engineer for nanotechnology, research, and education at Keithley Instruments, said that card makers still build ISA cards because customers don’t want to incur the costs associated with switching an ISA-based system to one that uses a different technology. “That’s especially true with software,” he added. Field wiring is another reason for not changing to a newer technology: A new card may use a different I/O connector that would be incompatible with the existing wiring.
Although engineers who need ISA cards can often still get them, card makers don’t promote these cards anymore. “We still get orders for cards that use the ISA bus, the STD bus, and the Q bus,” said Tim Ludy, product manager at Data Translation. “One person found an old card where the analog-to-digital converter (ADC) was a module instead of an IC and asked if we could build more boards with these modules. We’ll make legacy boards for as long as we can get the parts.”
“Customers pay a premium for ISA cards,” added Kennedy. “We have to get parts made in through-hole packages, often from brokerage houses. If the part is available in a surface-mount package, then card makers may change their product to accommodate the newer parts, provided that there’s enough sales volume to support an engineering change.”
Often, manufacturers of data-acquisition cards have to discontinue older products because IC makers discontinue their ADCs. When that happens, IC makers notify their customers (the card makers) to make a last-time buy. Card makers do the same for their customers to give them time to redesign their systems with newer technology.
Who uses PCI data-acquisition cards in new systems? All three people I spoke with mentioned machine builders who embed the cards into PCs to use as controllers. Other applications I’ve run across include test systems for automotive components where cost reigns supreme. Other applications include measuring systems where engineers don’t want the measurement hardware accessible to operators.
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| For more on PCI and ISA cards, including past predictions, see my “Rowe’s and Columns” blog at www.tmworld.com/blogs. |
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