Test and Measurement

GPS TIMES DAQ SYSTEM

Symmetric Research Data Acquisition with GPS. Going beyond positioning, this system's GPS module time stamps and correlates the data streaming into its A/D module. Satellite-clock-based timing accuracy is within 10 microseconds with zero drift. In comparison, crystal oscillators typically drift about four minutes a month—similar to a desktop PC clock, says Kip Wyss, system design engineer. A proprietary algorithm integrates a PPS (pulse per sec) signal with A/D conversion for data stream synchronization. Another key technology is a 2 Mbyte deep DRAM buffer. This mitigates data losses to the one, four, or eight 24-bit channel A/D modules from any PC or network interruptions. (www.symres.com) Enter 582

SPRINGS ENSURE PROBE'S TOUCH

Agilent Technologies Soft Touch Probe. Capacitive loading can be deadly, degrading speed when measuring high-frequency signals. This probe not only requires no adapter/connector to probe targets on a printed circuit board, but it also reduces capacitive loading by roughly 75% compared to other connectorless designs, says Brock Lameres, design engineer. The probe fits into a retention module that holds the probe contacts against an array of pads on the PCB. In Agilent's design, microsprings on each contact and a 4-point crowned contact tip ensure electrical continuity. By locating the tip networking circuit in the probe behind the contacts and as close to the target as possible, engineers cut parasitic capacitance from around 3 pf to approximately 0.7 pf. (www.agilent.com/find/softtouch) Enter 583

OPTICALLY BASED LENGTH GAUGE

Heidenhain Corporation SPECTO Gauge. Unlike conventional electrically based LVDT (linear displacement velocity transducer) length gauges, these optics-based devices require no calibration. The reason: The internal chromium marked glass scale includes a reference mark. The gauge achieves ±1 micron accuracy, with repeatability to 500 nm, over the 12- or 30-mm length of the scale, says Kevin Kaufenberg, engineer and sales manager. He notes the challenge for engineers was packaging the 15-mm long optics package and circuits within the 11-mm inner diameter gauges. "We redesigned everything down to the component level," he adds. Such components include a flex circuit, LED light source, and spherical bearings for shock resistance. (www.heidenhain.com) Enter 584

PLATFORM LEVERAGES INTEGRATION

National Instruments 100 Msamples/sec PXI Instruments. For maximum usefulness of NI's analysis tools, developers tightly integrated several additions to the PXI instrument family and LabVIEW 7 Express analysis and development software, including the new Digital Waveform Editor. The high-resolution digitizer, arbitrary waveform generator, and digital waveform generator/analyzer (shown here), are designed around the new Synchronization and Memory Core (SMC), NI's common architecture for building mixed-signal test systems, says Product Manager Eric Starkloff. One benefit: By using the PXI backplane to sample module clocks, the SMC's synchronization engine tunes out clock skew (signal propagation delays along various length circuit paths), "locking" instrument modules together with sub-nanosecond accuracy. (www.ni.com) Enter 585

ISOLATION BOOSTS DAQ RELIABILITY

Yokogawa MX100 PC-Based DAQ. Reliability was the driver for engineers designing this platform, which competes with PLC-based systems in harsh-environment process monitoring, notes Data Acquisition Product Manager Joseph Ting. They developed a proprietary, high-isolation solid-state relay that can safely pass through 1,500V compared to only about 100V for a conventional solid-state relay. By combining the relay with a unique A/D converter chip and a planar, isolation transformer, the engineers obtained a 3,700V ac withstand isolation rating, and 600V ac channel-to-ground and module-to-module isolation. Such isolation voltages enable measurements, for instance, from thermocouples on bare ac power lines and for fuel cell testing. In the event of a network or PC crash, a CompactFlash memory card slot in the main DAQ module permits automatic and continuous data backup. (www.us.yokogawa.com) Enter 586

TIGHT TIMING PACES MID-PRICE ANALYZER

Tektronix TLA 5000 Logic Analyzer. With digital electronics pushing data rates upwards of 400 Mbit/sec, timing can be everything in test and measurement. To measure signal timing on fast digital signals, as well as slow signals with fast rising and falling edges, Tektronix engineers incorporated a three-chip set from their high-end modular, multibus correlation analyzers, but without such integration, for a $9,200 starting price (as opposed to upwards of $50k). TLA5000 Series uses the 8 GHz oversampling ASIC (125 psec resolution) to store a data stream in a 32 Mbit deep memory. While users see a 2 GHz sampled signal on the display, they can analyze any glitches by zooming in with a MagniVu^™ feature that mines the higher rate sampled data. (www.tektronix.com) Enter 587