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Test software enhances large data-set signal acquisition/analysis

Posted: 10 Mar 2006 ?? ?Print Version ?Bookmark and Share

Keywords:test software? oscilloscope? DIAdem? National Instruments? Agilent?

Just about every piece of test equipment uses software in some way, but some recently introduced software products stand out for their ability to address the problems associated with the acquisition of large data sets.

Long record lengths generated by digital storage oscilloscopes, for example, can easily represent thousands of screen's worth of signal activity. How do you wade through that and make sense of what your scope has acquired? Without a way to analyze and organize your data, you may be overwhelmed trying to extract meaningful information from a waveform data-set.

Packages such as National Instruments DIAdem 10.0 software can help. NI's $1,000 v10.0 software, installed on Windows PC platforms, can assist you in managing and mining large amounts of data.

DIAdem 10's DataFinder gives you a way to perform Internet-like searches across data files, regardless of format. DIAdem DataFinder lets you correlate test data, find trends, and troubleshoot problems. Even multiple engineers on a development team can organize and find information, and do that at different times, too.

Virtual memory management
DIAdem 10's algorithms give you fast file access, thanks to a virtual memory management scheme. Going beyond predecessor DIAdem versions, you get support for third-party file formats as well. The package encompasses files in Nicolet, PSpice, ADAMS, and Yokogawa formats.

You can also output reports in popular Windows applications such as Adobe Acrobat.PDF, HTML and JPEG images.

Users are enthusiastic about how the software works. DIAdem DataFinder user Raytheon Missile Systems, for one, says it recorded an overall time reduction of 90 percent since adopting NI's software.

Another user reports DIAdem's success in a test system designed to collect data on 16 channels. Challenges included formatting the data for optimal post-test use, handling the results from long-duration measurements, and correlating the sensor information back to the actual measurements.

Indeed, high channel-count tests impose more set-up problems that most applications. When dealing with dozens or even hundreds of sensors, inadvertently swapping sensor connections, or having to deal with broken transducers, can be a painful reality.

Self-identifying sensors such as TEDS (transducer electronic data sheet) types can reduce set-up times for high channel-count applications. However, this information may not be adequately captured with the actual test data.

Descriptor searches
DIAdem comes to the rescue. It lets you perform simple or advanced searches based on key descriptors. You can use DIAdem DataFinder to search for all tests with a specific serial number, status, or test type, for example.

After narrowing the data set, you can then use DIAdem to drill down for further analysis and reporting. DIAdem DataFinder gives you the ability to establish and uncover anomalies or trends that previously might have gone unnoticed.

NI isn't the only company addressing the problem of dealing with large sets of acquired data. Sifting through captured oscilloscope traces also distinguishes Agilent Technologies' latest N5414/5A InfiniiScan software.

This event identification software helps Agilent's popular Infiniium oscilloscopes identify signal integrity problems. It costs about $5,000, which may be a small price to pay if you can save countless engineering man-hours.

The mythical find-problem button
N5414/5A InfiniiScan works by scanning through thousands of acquired waveforms and then isolating anomalous signal behavior. That's a feat that brings the company's scopes closer to the ideal mythical Find Problem button. Such a button would presumably let a scope automatically inspect signals and inform you about any signal integrity problems it discovered.

Although not quite a one-button answer, Agilent's N5414/5A InfiniiScan software can help smooth the way to identify signal integrity problems that were previously difficult or even impossible to find with conventional hardware triggering or deep-memory approaches.

There's also no need to manually inspect waveforms. InfiniiScan scans waveforms automatically. It's able to identify a single waveform anomaly out of 10,000 screens of data, without programming.

Compare that with hardware triggering and its myriad limitations, including the number of events that can be monitored simultaneously, the number of occurrences of that event that can be identified and the variety of events that can be identified. Hardware triggering also limits the maximum speed of events that can be isolated, and makes for difficulty in defining the proper set-up to capture an event.

Automatic signal inspection
Finding an event of interest in a deep-memory capture can also be tough. InfiniiScan overcomes these limitations by automatically inspecting each signal it acquires. With InfiniiScan, you can monitor up to five different events or the same event on four channels simultaneously. The software isolates events as narrow as 70ps, well beyond the 300ps limitation of hardware-based approaches.

Two main components comprise InfiniiScan. One general component is called a software finder. The other is a measurement limit test.

The software finder can be used in conjunction with an Infiniium oscilloscope's hardware trigger using delays from hardware trigger control. In effect, this provides a two-level sequencer; a hardware trigger followed by software finder with a specified delay between events.

You can use the delay capability to get a higher percentage of pre-finder or post-finder information. The InfiniiScan software finder can also be used in conjunction with an Infiniium scope's hardware trigger via the delay from a hardware trigger control.

Finders include a measurement finder, a zone qualify finder, a generic serial finder, a non-monotonic edge finder and a runt finder.

The measurement finder sets boundary conditions to specified measurement results, such as inside/outside limits. In use, your scope then informs you if it finds such an event. You could, for example, set the measurement finder to have the scope identify a risetime that's been specified.

Pass/fail conditions
The InfiniiScan software's zone qualify finder lets you draw a Must Pass and a Must Not Pass zone on your oscilloscope screen. With that you visually determine an event identification condition. If you can see the event of interest on-screen, it can be isolated without having to figure out how to set up a trigger, or repeatedly press the scope's Single key.

For its part, the InfiniiScan's generic serial finder sets up to an 80bit serial pattern for the oscilloscope to identify, handling streams of acquired data as fast as 8.5Gbps. Hardware approaches are currently limited to 40bits and a maximum speed of 3.125Gbps. The InfiniiScan approach is also generic, so it works with any serial pattern, and the patterns can be expressed in hexadecimal or binary form.

User-definable clock data recovery (CDR) methods are also available; a fixed-frequency CDR is standard. Other methods, such as PLL are also available (in conjunction with jitter analysis or serial data analysis software).

The system's non-monotonic edge finder identifies non-monotonic edges that can be caused by impedance mismatches resulting in unwanted reflections. Using the edge finder can help you identify improper line terminations, for example. Keep in mind that finding a bad impedance match with hardware triggering is well nigh impossible.

The runt finder identifies under-sized signal pulses, and like the edge finder, does it with resolution that would be beyond the capability of hardware approaches. Agilent's technique uses hysteresis and threshold levels that you specify.

The InfiniiScan package also gives you a measurement limit test that counts the number of violations against specified measurement value conditions. This feature lets you set up to five different measurement conditions over all channels.

You can monitor the valid risetime window for Channel 1, for example, while monitoring the valid signal period window on Channel 3. You can monitor negative pulse width, positive pulse width, peak-to-peak levels, and rise-times and fall-times, all simultaneously.

The navigation capability of the measurement limit test will also move the display to the exact location of any and all anomalous events that have been identified on every waveform. The limit testing will also take action on a failure, where it can stop, print, send an e-mail, do a screen shot, or save a waveform or measurement.

Agilent competitor Tektronix is also dealing with the problem of reducing large digital storage oscilloscope data sets into meaningful engineering information. The firm's latest DPO4000 scopes, already equipped with powerful hardware-based search capabilities, now benefit from outboard software, too.

Thanks to National Instruments' SignalExpress Tektronix Edition PC-based measurement software, your Tek scope can acquire and analyze large amounts of data, and even assist you in prepping documentation of measurements. Like Agilent's InfiniiScan, it does this without any programming on your part.

Plug-and-play analysis
Relying on USB's plug-and-play capability, SignalExpress Tektronix Edition software provides seamless connectivity to DPO4000 series scopes, as well as Tek's AFG3000 series waveform generators.

Most of you probably manually transfer data from your benchtop instruments to your PC using "sneaker net" USB memory-stick transfers or even floppies. With SignalExpress that's not necessary. It lets you connect stand-alone instruments to your PC, and then immediately control, measure, analyze and document.

Thanks to USB, the SignalExpress software immediately detects a Tek DPO4000 scope and/or AFG3000 waveform generator as soon as it's connected to your system configuration. With nothing more than a mouse click or two, you can then configure instrument communication and also access a live view of captured waveform data and generated signals.

Within the familiar Windows drag-and-drop environment, SignalExpress lets you access more than 200 measurement, processing, analysis and reporting capabilities to apply to live data acquired from Tek's DPO4000 scopes. It works with other Tektronix oscilloscopes and signal sources, too.

In addition to USB, the package supports IEEE-488/GPIB and Ethernet/LAN connections. SignalExpress also offers automated sweeping and limit testing features. These functions are usually manual and tedious processes.

- Alex Mendelsohn

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