6 GHz True RMS Power Meter with Bus-Powered USB Connectivity NI USB-5680 NEW! • • • • • • • • • • • • • True RMS power measurements Diode power meter -40 to +23 dBm power range 50 MHz to 6 GHz frequency range 10 and 100 Hz typical channel bandwidth ±0.13 dB accuracy at <+18 dBm ±0.18 dB accuracy at ≥+18 dBm Internal zeroing capability <3 percent sensor linearity Standing wave ratio <1.2 to 6 GHz 100 mA typical power consumption USB bus connectivity N-type connector Operating System • Windows Vista/XP/2000 Recommended Software • LabVIEW • LabWindows™/CVI Driver Software (included) • NI-568x Calibration • Gain and offset self-calibration • 1-year external calibration cycle >> For complete specifications, visit ni.com/manuals and search for USB-5680 Specifications. Overview Architecture The National Instruments USB-5680 is a 6 GHz true RMS (root-meansquare) power meter that features high measurement accuracy and wide dynamic range. As a true RMS power meter, the NI USB-5680 is ideal for measuring the power of continuous wave (CW) signals. In addition, it offers better than ±0.18 dB of linearity across all frequency ranges and all power levels. This functionality, combined with a flexible API, makes it ideal for measuring path loss in automated test applications. In addition, its small size (less than 9.6 cubic in.) frees up valuable rack space without sacrificing performance. One of the biggest benefits of the USB-5680 is its USB connectivity. Powered solely from the USB cable, it consumes only 100 mA of current. Thus, you can use this power meter in both production test and field applications with a laptop. Moreover, USB connectivity helps you easily integrate the power meter with PC and PXI systems in an automated test environment. The USB-5680 RF power meter features a dual-path architecture to achieve 63 dB of dynamic range. This architecture improves power measurement accuracy by ensuring that the diode sensors are used in their most linear region. A block diagram of the USB-5680 architecture is shown in Figure 1. As Figure 1 shows, the first measurement range is from -5 to +23 dBm and the second is from -40 to -5 dBm. This accounts for a combined dynamic range of -40 to +23 dBm with a single power head. 27 dB Attenuator Detector A Averaging Pre-Amp (-5 to +23 dBm) Input DC Block 10 dB Attenuator 6 dB Splitter ADC (-40 to -5 dBm) 6 dB Attenuator Figure 1. Block Diagram of the NI USB-5680 Detector B Averaging Pre-Amp Microprocessor USB 6 GHz True RMS Power Meter with Bus-Powered USB Connectivity Flexible Software You can operate the USB-5680 as a benchtop instrument or as an automated measurement device. For benchtop use, the soft front panel (see Figure 2) helps you configure multiple instrument settings on the fly. This program runs in Windows Vista, Windows XP, and Windows 2000 operating systems. Figure 2. Soft Front Panel Screenshot As Figure 2 illustrates, the soft front panel not only returns power measurements but also helps you configure settings such as autozero, number of averages, and predetermined power offsets. In addition, you can fully program the USB-5680 with the NI-568x driver in languages such as LabVIEW, LabWindows/CVI, C, C++, and .NET. Using the NI-568x driver, you can fully control the instrument and integrate it into existing automated test applications. A screenshot of the API is shown in Figure 3. most linear region when power levels are less than 18 dBm. Thus, the sensor is able to provide more accurate measurements at this power Power level <18 dBm Power level ≥18 dBm ±0.13 dB ±0.18 dB Table 1. Sensor Linearity According to Power Level level. Linearity across all power levels is illustrated in Table 1. Note that sensor linearity is only one of many factors that contribute to the absolute accuracy of an RF power measurement. Because impedance mismatch (standing wave ratio, or SWR) and noise can also add uncertainty, it is important to consider all of these characteristics when determining overall measurement uncertainty. National Instruments recommends downloading the Power Uncertainty Calculator on the USB-5680 product page at ni.com to determine your absolute measurement accuracy. With the uncertainty calculator, you can enter signal characteristics such as power, frequency, and signal type. You also can enter measurement characteristics such as number of averages and aperture mode. In addition to providing the absolute accuracy, the uncertainty calculator highlights individual sources of error. As Figure 5 shows, you can attribute an absolute accuracy of 4.45 percent to a wide range of Figure 4. USB-5680 Uncertainty Calculator Screenshot Figure 3. NI-568x Driver API Screenshot factors, the most significant of which include sensor nonlinearity and mismatch uncertainty. Note that the USB-5680 uses an internal auto-zero calibration routine to reduce errors associated with zero offsets. To do this, an internal source is used to calibrate the power meter, and external connectivity is not required. Absolute Accuracy Power meter linearity is one of the most important characteristics of a power meter because it greatly influences absolute accuracy. In addition, linearity is dependent on the power level of the signal you are measuring. As Table 1 illustrates, you can use the power meter in its Figure 5. Expanded Sources of Error from the USB-5680 Uncertainty Calculator BUY ONLINE at ni.com or CALL 800 813 3693 (U.S.) 2 6 GHz True RMS Power Meter with Bus-Powered USB Connectivity Averaging and Noise Level Low-Aperture Mode Because noise can have a significant effect on the accuracy of RMS power measurements, settings such as aperture time and averaging are often employed to mitigate the effects of noise on measurement accuracy. To improve flexibility, the USB-5680 features two aperture time settings to offer both high-speed and high-accuracy options. In “Low-Aperture” mode, the power meter features 15 measurements per second and in “High-Aperture” mode, the USB-5680 features 1 measurement per second. With these two options, you can choose the aperture mode and, number of averages to obtain the desired noise level of measurement. Table 2 shows the number of averages required in both aperture modes to achieve less than ±0.10 and ±0.01 dB noise levels. Input Power (dBm) >10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 Input Power (mW) >10.0 3.2 1.0 0.32 0.10 0.032 0.010 0.0032 0.0010 0.00032 0.000100 Number of Averages Needed for <±0.10 dB Noise 1 1 1 1 1 1 1 1 7 62 — Number of Averages Needed for <±0.10 dB Noise 1 2 16 78 1 1 7 61 — — — Table 3. Number of Averages, Low-Aperture Time Mode High-Aperture Mode Input Power (dBm) >0 -5 -10 -15 -20 -25 -30 -35 -40 Input Power (mW) >1.00 0.32 0.100 0.032 0.0100 0.0032 0.00100 0.00032 0.000100 Number of Averages Needed for <±0.10 dB Noise 1 1 1 1 1 1 1 4 39 Number of Averages Needed for <±0.10 dB Noise 1 5 1 1 1 4 38 — — Table 2. Number of Averages, High-Aperture Time Mode Ordering Information NI USB-5680 ..........................................................................780167-01 Includes NI-568x driver featuring soft front panel and API for LabVIEW, LabWindows/CVI, C, C++, and .NET. BUY NOW! For complete product specifications, pricing, and accessory information, call 800 813 3693 (U.S.) or go to ni.com/rf. BUY ONLINE at ni.com or CALL 800 813 3693 (U.S.) 3 IN TA PL AN MA IN NI Services and Support P DE LO Y EL OP SERVICE NEEDS V DE NI has the services and support to meet your needs around the globe and through the application life cycle – from planning and development through deployment and ongoing maintenance. We offer services and service levels to meet customer requirements in research, design, validation, and manufacturing. Visit ni.com/services. Training and Certification NI training is the fastest, most certain route to productivity with our products. NI training can shorten your learning curve, save development time, and reduce maintenance costs over the application life cycle. We schedule instructor-led courses in cities worldwide, or we can hold a course at your facility. We also offer a professional certification program that identifies individuals who have high levels of skill and knowledge on using NI products. Visit ni.com/training. 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Find immediate answers to your questions at ni.com/support. We also offer service programs that provide automatic upgrades to your application development environment and higher levels of technical support. Visit ni.com/ssp. Hardware Services NI Factory Installation Services NI Factory Installation Services (FIS) is the fastest and easiest way to use your PXI or PXI/SCXI combination systems right out of the box. Trained NI technicians install the software and hardware and configure the system to your specifications. NI extends the standard warranty by one year on hardware components (controllers, chassis, modules) purchased with FIS. To use FIS, simply configure your system online with ni.com/pxiadvisor. Calibration Services NI recognizes the need to maintain properly calibrated devices for high-accuracy measurements. We provide manual calibration procedures, services to recalibrate your products, and automated calibration software specifically designed for use by metrology laboratories. Visit ni.com/calibration. Repair and Extended Warranty NI provides complete repair services for our products. Express repair and advance replacement services are also available. We offer extended warranties to help you meet project life-cycle requirements. Visit ni.com/services. *351555A-01* 351555A-01 2007-9226-101-D ©2008 National Instruments Corporation. All rights reserved. CVI, LabVIEW, National Instruments, National Instruments Alliance Partner, NI, ni.com, and SCXI are trademarks of National Instruments. The mark LabWindows is used under a license from Microsoft Corporation. Other product and company names listed are trademarks or trade names of their respective companies. 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