The File - Nov 16, 2008 - (Page 11)

In Focus | Data acquisition Function gens simplify measurement continued from page Events BIG Expo 200 Nov. 21-23, 2008 Chennai Trade Centre, Chennai and improve the IGBT’s immunity to noise injected through the rate of change of the collector-to-emitter voltage, which can be substantial for inductive loads, the gate drive circuitry must include substantial on and off biasing. The IGBT’s best performance varies by application, and the gate drive circuit must be designed accordingly. In hard switching applications such as motor drives or UPS, the gate drive parameters must be selected so that the switching waveform does not exceed the IGBT’s safe operating area. This can imply a sacrifice in switching speed at the expense of switching loss. In softswitching applications where the switching waveform is well within the safe operating area, the gate drive can be designed for short switching times and lower switching loss. To optimise the design of an IGBT gate drive, the design engineer must understand the device’s switching characteristics under the actual load conditions. To analyse these switching characteristics, the gate of the IGBT is stimulated with a series of single pulses while the gate-to-emitter voltage, collector-to-emitter voltage and collector current are measured with an oscilloscope. An arbitrary/function generator with high amplitude pulse capabilities is suitable for this task. Since the IGBT’s collector-toemitter voltage has a very high dynamic range for inductive loads, the measurement requires a high-voltage differential probe. The gate-to-emitter voltage can be measured with a standard passive probe, and the collector current with a non-intrusive current probe. From the switching waveforms of an IGBT with inductive load (figure 3), the design engineer can determine the switching energy, on-state losses and whether the IGBT is operating within the safe operating area. Based on the measurement data, the engineer can then determine whether the selected pulse rep- etition frequency, amplitude and edge transitions are adequate to achieve the design objectives. If adjustments are necessary, the generator should allow easy modification of pulse parameters without interrupting the test. A variety of factors must be considered during the measurement, such as the propagation delay (skew), offset and noise inherent to the probes. The engineer will find it beneficial to use an oscilloscope with a software tool that takes care of the probe related issues, automatically calculates the switching power losses and determines the safe operating area of the IGBT. Read the full article to learn more about arbitrary/function generators, their signal amplitude and load impedance, how they can simplify test and measurement, and more. Online | The Zak Batteries Inverters & Generators Expo showcases products and services related to power generation and distribution, electrical technology, energy infrastructure and solar energy. Get more information. Broadband Tech 200 Nov. 21, 2008 The event brings together industry leaders, customers, venture capitalists, analysts and government officials to share case studies and best practices and broadband technology trends. More information here. Wind India 200 Nov. 25-26, 2008 Chennai Trade Centre, Chennai conference-cum-exhibition on wind power Click here for more information. National Conference On E-Governance Nov. 27-28, 2008 Dayananda Sagar Institutions, Bangalore Choose the right tools for high-speed serial data analysis Why a scope’s update rate matters Digital telemetry advances torque measurement continued from page The event explores availability of E-features in remote India through information and communication technologies. The conference highlights secure, trustworthy and reliable systems that enable better applications to better governance. Go to event site. ICSST Dec. 3-4, 2008 NMAM Institute of Technology, Nitte You normally have to set both a zero and a known load point. During the process, you need to read it and verify that you are in the range. It takes a lot of “back and forth” to manually dial the pot so you are in the right range. More importantly, all this adjusting will work only for the original range of 1,000 footpounds. You cannot scale for different ranges, including the desired 500 foot-pound scale in our example. The new generation of digital systems eliminates the headache of adjusting potentiometers and switches. These systems are completely software-driven, and output range is factory-set. However, the software allows this range to be changed, within certain limits, to any output level. They are almost plug and play. You can upload separate calibration runs from a disc into the signal-processing module using software like Toolkit. Scale ranges for these separate calibration runs are typically limited to between 50 per cent and 150 per cent of the full-scale range. It is important to note that the resolution for separate calibration runs will be different from the resolution of the factory calibration. With this new generation of digital telemetry, you can adjust your voltage output to interface with your existing data acquisition system through the software and also make changes “on the fly” during a test. You can also upload a new scale from your software “on the fly.” You can establish multiple scales to create a library of scales and corresponding output voltages. When you want to change scales, you just upload and reset it. For instance, if you are measuring 0-1,000 foot-pounds, you can set up your system so 10 volts is equivalent to 1000 foot-pounds. There is minimal set up. Read the full article to learn how digital telemetry eliminates difficulties related to mounting and wiring, torque range, maintenance, size, and more. The International Conference & Symposium on Storage Technologies (ICSST) brings together researchers, scientists, engineers and students to share research results on information storage and management. View event agenda. NGSA - 0 Dec. 5-6, 2008 Karunya University, Coimbatore Online | Telemetry encoder targets airborne apps M easurem ent m eth o ds sp ur au to capacitive sensor usea The International Conference on Next Generation Software Application (NGSA -08) aims to support multidisciplinary software research. Topics include object based storage, OFDM, distributed computing, data mining, wireless networks, location management, distributed instrumentation, cryptography and embedded systems. Learn more. 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Table of Contents for the Digital Edition of The File - Nov 16, 2008

EETimes India - November 16, 2008
Contents
Farnell
Embedded System Eases Rail Maintenance
National Semiconductor
Working With IT for Networked DAQ
Digital Telemetry Advances Torque Measurement
Events

The File - Nov 16, 2008