Tall and shallow or short and deep?
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 3/1/2006 2:00:00 AM
In January and February, LeCroy and Tektronix introduced oscilloscopes that feature large displays and shallow footprints (Ref. 1). Design engineers like this tall form factor because the instruments use little bench space. But what about test-system builders? Taller scopes consume scarce rack space while leaving the space behind them potentially unused. To find out what oscilloscope form factors work best in test systems, I spoke with several test-system integrators.
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What do you think about the new scope form factor? Tell Martin. For more information about the scopes mentioned here, read these T&MW articles: WaveRunner Xi: LeCroy moves large screen to the next scopes DPO7000: Get the big waveform picture DPO4000: Scroll through millions of waveform samples |
"My rack has no space for the tall form factor," claimed Curt Schlenker, systems engineer at Instrumentation Engineering. He has a customer with 10 installed systems that use a Tektronix TDS724D scope, which is no longer produced. When he had to duplicate the system, he had to find a used instrument.
Jay Nemeth-Johannes, CTO of CompleteTest, was more open to tall scopes. "The Tektronix DPO7000 is 17.75 in. wide, so it should fit nicely into a rack. If the system needs another tall instrument," he noted, "it may fit nicely side by side with the new large-screen scope. Instruments that don't fit in the traditional 19-in. rack are nothing new." He expressed some concern about vertical space consumed by the tall form factor. "If a physical display is important, then get a scope that's easy to use. If not, then use a modular scope and a virtual display."
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| The traditional short and deep oscilloscope form factor saves rack space over tall scopes designed for the bench. Courtesy of Instrumentation Engineering. |
For Tim Brooks, president of B&B Technologies, the form factor of box scopes is irrelevant. "We use PXI almost exclusively," he said. "We can find about 95% of what we need in this format."
Brooks isn't alone in his sentiment. "PXI digitizers and scopes are available from several suppliers," added N.D. "Buck" Smith, principal at Cal-Bay Systems. "They typically have 14-bit or 16-bit resolution and sample at up to 200 Msamples/s. Other PXI scope cards with 8-bit resolution sample much faster."
While modular scopes offer an alternative to box scopes, IE's Schlenker likes boxes because he can operate a scope offline to troubleshoot the system. "The best solution is to eliminate the display but provide a VGA output," he said. His colleague, senior software engineer Asish Shah, offered an alternative. He'd like to see a no-display scope that contains an Ethernet port and a Web server so he can operate the scope with a browser.
As I see it, the biggest problem with using a tall scope in a system isn't the form factor but the computer interface. IEEE 488 is still the I/O bus of choice for test-system builders because of its large installed base. An IEEE 488 port is standard on the DPO7000, optional on the LeCroy WaveRunner Xi, and not available on the DPO4000. I expect IEEE 488 ports to slowly disappear as designers switch to USB or Ethernet.
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Data-acquisition modules support Matlab
Data Translation's free DAQ Adaptor for Matlab software provides direct access to analog and digital I/O data through Matlab's Data Acquisition Toolbox. You can use the DAQ Adaptor to configure your hardware through Matlab and acquire data directly into the software. www.datatranslation.com.
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