Universal Instruments Break Traditional Measurement Barriers
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New flexible hardware technology expands virtual instrumentation with universal measurement capability. The new NI PXI-4071 7½-digit FlexDMM and NI PXI-5922 flexible-resolution digitizer are universal instruments capable not only of replacing several traditional instruments at a fraction of the cost and size but also of making new types of measurements. For example, you can take advantage of the PXI-4071 FlexDMM to digitize picoamps to kilovolts at 1.8 MS/s, while using the PXI-5922 digitizer to acquire dynamic signals up to 100 kHz with more than -108 dBc spurious-free dynamic range (SFDR). These measurement capabilities are required to meet the needs of precision audio testing, analog-to-digital converter (ADC) characterization, and low-noise communication measurements.
26-Bit Universal DC Measurement Device
Digital multimeters (DMMs) have long been considered universal instruments for DC measurements because a single device is able to perform a variety of functions such as voltage, current, and resistance measurements. You can extend this traditional functionality with the new NI PXI-4071 FlexDMM by configuring it in software to operate as a full-function 7½-digit (26-bit) DMM or a 1.8 MS/s isolated, high-voltage digitizer.
When configured as a DMM, the FlexDMM is the industry’s most accurate 7½-digit DMM on any platform. It delivers 2.5 parts per million basic 24-hour DC voltage accuracy and measurement sensitivity from ±10 nV to 1,000 V (700 Vrms). The FlexDMM implements a novel solid-state current shunt configuration that offers eight DC current ranges from ±1 µA to 3 A and six AC rms current ranges from 100 µA to 3 A (4.2 Vp). In the 1 µA range, the FlexDMM provides you with ±1 pA (10-12 A) resolution. This measurement sensitivity is required for applications such as IV curve tracing and leakage testing on discrete semiconductor devices. You also can achieve accurate resistance measurements from 10 µΩ to 5 GΩ, as well as take frequency/period and diode measurements.
In the 1.8 MS/s isolated digitizer mode, you have the software flexibility to vary the resolution from 10 to 23 bits, so you can pick the exact point on the frequency-versus-resolution curve that meets your application requirements. A traditional DMM only provides a discrete set of resolutions from which to choose. At all resolutions, the FlexDMM can acquire DC-coupled voltage and current waveforms up to ±700 Vrms and up to ±3 A at a maximum sample rate of 1.8 MS/s. With the built-in isolation, you can use the PXI-4071 to measure differential waveforms up to 500 V common-mode voltage, which is often required in applications such as fuel-cell stack testing. You also can use this isolated digitizer capability and NI LabVIEW software to analyze transients, fly-back signals, or other aperiodic high-voltage AC waveforms in both the time and frequency domains.
24-Bit Universal Measurement Device
The NI PXI-5922 flexible-resolution digitizer is a universal instrument for dynamic measurements. Just as the DMM combined several DC measurements into one instrument, the PXI-5922 revolutionizes AC measurements by providing the capabilities of many instruments in one digitizer. Using this digitizer with LabVIEW, you can create a virtual instrument that achieves or surpasses the measurement performance obtained with many traditional instruments such as audio analyzers, spectrum analyzers, IF digitizers, DC and RMS voltmeters, and frequency counters.
While other PC-based digitizers and traditional instruments acquire data with a fixed resolution, the PXI-5922 is a flexible-resolution digitizer that gives you the capability to trade sample rate for resolution. For example, at 15 MS/s the module delivers 16 bits of resolution, which is ideal for IF and I/Q baseband digitization. Reducing the sample rate to 500 kS/s, the PXI-5922 delivers 24 bits of resolution and more than -108 dBc SFDR for signals up to 100 kHz, giving you higher performance than many traditional audio analyzers. This unparalleled flexibility, resolution, and dynamic range are achieved with the development of NI Flex II ADC technology, which uses an enhanced multibit delta-sigma converter and patented techniques for linearization. Refer to "Flex II ADC Technology -- A Novel Digitization Technique" sidebar for more information.
The PXI-5922 is built on the Synchronization and Memory Core (SMC) architecture, which helps you tightly synchronize multiple PXI-5922 digitizers for high-channel-count applications. This synchronization capability also is critical when building mixed-signal test systems including digitizers, signal generators, and high-speed digital waveform generator/analyzers. In addition, the SMC offers up to 256 MB per channel of onboard memory on the PXI-5922 digitizer.
Integrated Software Support
Both modules provide instrument drivers containing easy-to-use measurement functions for performing common measurements in LabVIEW and other development environments such as NI LabWindows/CVI, Visual Basic, and C/C++. Furthermore, you can enhance your analysis with application-specific toolkits such as the LabVIEW Sound and Vibration Toolkit, Modulation Toolkit for LabVIEW, and LabVIEW Spectral Measurements Toolkit.
For a more interactive measurement experience, you also can use these devices with NI SignalExpress to simplify your exploratory and automated measurement tasks through a drag-and-drop, configuration-based environment with little or no programming. With SignalExpress, you quickly take measurements using built-in steps for signal acquisition, processing, time and frequency domain analysis, and file I/O. SignalExpress supports a large number of NI modular instruments and data acquisition (DAQ) devices including DMMs, digitizers, signal generators, high-speed digital I/O, and M Series DAQ devices.
Future of Virtual Instruments
With the introduction of these new universal instruments, NI has again extended the reach of virtual instrumentation and provided you with the measurement capability to solve new and demanding test and measurement application challenges, as shown in the figure. In addition, you can use these devices to decrease your system cost, footprint, and complexity by creating software-centered systems that achieve or surpass the functionality of several stand-alone fixed-function instruments.
Kevin Bisking
DMM Product Marketing Manager
kevin.bisking@ni.com
Kaustubh Wagle
Digitizers Product Marketing Engineer
kaustubh.wagle@ni.com
Download the architecture white papers for these new instruments and see how these products lower cost and deliver unmatched accuracy.
This article first ran in the Q3 2005 issue of Instrumentation Newsletter.
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