Sunday, December 30, 2007

Integrated Receiver For High Frequency Applications On A Tiny Chip

The receiver is just a few square millimetre and is suitable for new safety systems, image sensors, and radio communication for high bitrates. The receiver is an electronic circuit including antenna, low noise amplifier, and frequency converter monolithically integrated on gallium arsenide.

The receiver is just a few square millimetre and is suitable for new safety systems, image sensors, and radio communication for high bitrates. The receiver is an electronic circuit including antenna, low noise amplifier, and frequency converter monolithically integrated on gallium arsenide. (Credit: Image courtesy of Chalmers University)

"This is a breakthrough in our research. Our result opens the possibility to manufacture systems for very high frequencies within the so called 'THZ-electronics' area, to a relatively low cost. In the next phase of this project even more functions can be integrated on the same chip", according to Herbert Zirath, professor at the department of Microwave Electronics.

This circuit can be used, for instance, in radiometer systems in future safety systems looking for concealed weapons without personal intrusive search. Other applications for this circuit are imaging sensors that can look through darkness, smoke or fog. This is an important safety function for vehicles such as cars and aircrafts.

"Thanks to this technology, we now have the possibility of integrating imaging sensors by using circuits of a few square millimetre which is much smaller that the present technology at a lower cost. For automotive applications such as cars, aircrafts and satellites, the size and weight is of utmost importance. The present systems consist of many pieces and demands several cubic decimetres volume", says Herbert Zirath.

The new circuit is designed to work at the frequency of 220 gigahertz, but this is not an upper limit. According to professor Zirath, the technology can be used up to and above 300GHz in a near future.

The technology is also interesting for wireless data communication because, due to the very high bandwidth, data rate well above 10 Gbit/s is possible to realize in future radio links. Together with Omnisys Instruments in Gothenburg, we are also implementing receivers for future earth observation satellites for environmental studies and weather forecasts at frequencies 118 and 183 GHz, using the same technology.

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Five key tips for using an oscilloscope

The oscilloscope is one of the most widely used pieces of test equipment. It is used my many engineers almost every day and as a result it sometimes helps to recap some simple but important tips that enable the best to be gained from this type of test equipment.

When making measurements using an oscilloscope there are a number of pitfalls that result in measurements not being as accurate or useful as they might otherwise be. Taking a few simple precautions when using an oscilloscope, it is possible to ensure that the measurements taken are as accurate as possible and that the measurements are as useful as possible.

Some of the precautions result from knowing the limitations of using an oscilloscope. However other precautions can be reflected in the way the oscilloscope is used, and the equipment, including probes that are used with the test equipment.

Beware of oscilloscope bandwidth limitations
As with any item of test equipment used for making measurements of signals and waveforms the bandwidth of the oscilloscope is particularly important. If the oscilloscope is to be able to reproduce the image of the waveform accurately then it must have sufficient bandwidth to accommodate the frequencies within the signal.

For sinusoidal type waveforms, measurements should not be made near the 3dB bandwidth as operating in this area will give a 30% reduction in the signal level. For digital measurements, the expected rise time of the signal can be used to determine the bandwidth requirements of the oscilloscope.

Ensure the correct triggering
In order that any waveform can be seen clearly when using an oscilloscope, it is necessary to ensure that the oscilloscope triggers correctly. If it does not trigger properly then the waveform will not be seen clearly. In view of the fact that it is necessary to view many complex waveforms on an oscilloscope, it is not always possible to enable it to trigger correctly when using the automatic trigger facility taken from the input channels. When looking at the best methods it is necessary to consider using the external trigger, and using a pulse of other suitable waveform from another point on the circuit under test. In this way it is often possible to gain a much better signal so that the oscilloscope can display the optimum image of the waveform.

Use the right oscilloscope probe
In the same way that the performance of any piece of test equipment can have its performance limited by some of the peripheral equipment, the same is particularly true when using an oscilloscope. While it is common to focus on the specification of the oscilloscope as this is the item into which the major investment is made. However the performance of the oscilloscope probe is just as important. If a poor oscilloscope probe is used then the performance of the whole test equipment will be impaired.

The oscilloscope probe should provide a simple way of presenting the signal on the board or item under test to the input of the oscilloscope, and ideally being totally transparent. A typical probe will consist of three major elements: probe tip; length of shielded wire; and a compensation network.

The most common types of oscilloscope probe are the passive probes. Of these there are two major types that are used namely a X1 and a X10. The X1 probe presents the signal as it is to the oscilloscope. Normally the oscilloscope input impedance is 1 Mohm. However this can load the device under test and distort the waveform. In addition to this tip capacitance of a x! oscilloscope probe can be as high as 100 pF. To overcome some of these problems and load the circuit under test less, a X10 probe can be used. Providing an input impedance of 10 Mohms and a capacitance which may be typically around 10pF, it will distort the waveform much less. Where even greater levels of performance are required, active oscilloscope probes may be sued. Having the active element very close to the tip of the oscilloscope probe, these have much higher levels of input impedance and lower levels of capacitance.

Remember to calibrate the oscilloscope probe
When using an oscilloscope, it is very easy to plug the oscilloscope probe in and start to make measurements. Unfortunately oscilloscope probes need to be calibrated before they are sued to ensure that their response is flat. There is a built in calibrator on virtually every oscilloscope for this purpose. It provides a square wave output, and there is a small preset adjustor on the probe. With the oscilloscope probe connected to the output of the calibrator the shape of the waveform displayed on the screen should be adjusted until it is perfectly square. If the high frequency response of the probe is down then the edges of the square wave will be rounded. If it is up then the square wave edges will show overshoot.

Although a simple adjustment, it is essential that it is undertaken to ensure that the performance of the probe is correct.

Beware using ground clips for high speed measurements
Oscilloscope probes normally come with a clip that is removable, and an earth or grounding clip that provides the earth return to the circuit under test. The clip can normally be taken to a convenient earth test point on the board. While this is perfectly adequate for most low frequency measurements and tests, when high speed tests are to be made, it is not satisfactory. The wire to the clip introduces inductance and this can introduce ringing into the circuit and this affects the measurements.

The only way to overcome this problem is to significantly reduce the length of any return path, and also reduce the length of wire to the actual probe tip. This can be done by removing the ground clip and its associated wire. In addition to this the clip on the centre of the probe can also be removed. This leaves a short exposed coaxial style connection. The centre connection or pin is for the signal and the surrounding connection is for a direct connection to an earth plane. While this may present some physical problems in making connections, it provides a far better level of electrical performance.

Using the oscilloscope
Oscilloscopes are easy to use, and with the developments in recent years oscilloscopes, along with many items of electronic test equipment have become even more versatile. It is possible to use them to see waveforms that might not have been at all easy even a few years ago. However the basic knowledge of using oscilloscopes is only gained from years of using them, but it is hoped that these few tips will enable them to be used in a better way and to be able to gain more from them.

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Friday, December 28, 2007

Dual Multiband Transceiver with FPGA Offers Improved Signal-to-Noise, SFDR

Dual Multiband Transceiver with FPGA Offers Improved SNR and SFDRPentek released its Model 7141 Dual Multiband Transceiver with FPGA. It is a complete software radio system for connection to HF or IF ports of a communications system. The device's signal-to-noise ratio and the spurious free dynamic range are improved by 10 dB, when compared to many competitive products, according to the company. It accepts two full scale analog HF or IF inputs on front-panel MMCX connectors at +10 dBm into 50 ohms with transformer coupling into Linear Technology’s LTC2255 14-bit 125 MHz A/D converters. A/D output samples are delivered into the Virtex-II Pro FPGA for signal processing or for routing to other module resources. A TI/Graychip GC4016 quad digital downconverter accepts either four 14-bit inputs or three 16-bit digital inputs from the FPGA, which determines the source of GC4016 input data. These sources include the A/D converters, FPGA signal processing engines, SDRAM delay memory and data sources on the PCI bus. Each GC4016 channel may be set for independent tuning frequency and bandwidth. A TI DAC5686 digital upconverter (DUC) and dual D/A accepts baseband real or complex data streams from the FPGA with signal bandwidths up to 40 MHz. When operating as an upconverter, it interpolates and translates real or complex baseband input signals to any IF center frequency between DC and 160 MHz. It provides real or quadrature (I+Q) analog outputs through two 320 MHz, 16-bit D/A converters to two front-panel MMCX connectors at +4 dBm into 50 ohms. The Xilinx XC2VP50 Virtex-II Pro FPGA serves as a control and status engine with data and programming interfaces to each of the on-board resources including the A/D converters, GC4016 digital downconverter, digital upconverter and D/A converters.

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Thursday, December 27, 2007

Sony becomes latest to quit rear-projection TVs

Sony Corp said on Thursday it would stop making rear-projection televisions, becoming the latest company to distance itself from a technology once seen as a promising rival of LCD and plasma displays in the flat-TV market.

Sony said it would focus its resources on liquid crystal display (LCD) and organic light-emitting diode (OLED) technology to address the flat-TV market, which is growing rapidly as consumers trade in their boxy tube sets for sleeker flat screens.

The consumer electronics firm plans to stop making rear-projection TVs at three plants in Japan and overseas in February, company spokesman Shinji Obana said.

Seiko Epson Corp said earlier this month that it had halted production and sales of its rear-projection TVs, while Hitachi Ltd withdrew from the North American rear-projection TV market earlier this year.

Demand for rear-projection TVs, which were once dominant in the large-sized flat-TV market, has been dwindling as electronics makers in recent years started offering larger and cheaper LCD and plasma models.

In October, Sony cut its rear-projection TV sales target for the year to March by 43 percent to 400,000 units.

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Wednesday, December 19, 2007

Integrated Circuits And How They Affect You

Integrated circuits have played a large role in the development of all the technological wonders that populate the world today. But what is an integrated circuit? How does it apply to you? How has their development changed your life? To answer these questions, we must first work to understand them as a whole.

Integrated circuits, or chips, simply perform as a very powerful electric circuit. Their makeup should not be too far from your grasp, as they are constructed from basic electronic parts. The technology that makes your computer able to run everything from Word to Half-Life is just run by connected transistors, diodes, capacitors, and resistors. The transistors act as amplifiers for all of our household electronics, while the resistors focus on tuning back the effect.

Capacitors allow electricity to be stored and released in varying amounts for special effects, and the diode works to cut off electricity. Through these simply changes to electric current, we are able to send information throughout the device to make everything just work.

Now that you understand the basics, you should probably at least understand how we went from basic circuitry in the 1950s to the supercomputers of the 21st Century. The 1950s saw a very important change in the field of electronic parts. Transistors were invented to replace the bulky and ineffective vacuum tubes that were once necessary for circuits. This let smaller electronics be practical and possible, since you finally didn't need your own power plant to run advancing technologies.

The chips were still held back by old circuitry though. Computers require the electric signals to flow quickly between the different parts. Old methods of production meant that the chips were just too large to actually be fast enough for practical computing. A new method for building a faster and smaller chip had to be found.

The answer came through the development of the integrated circuit by Jack Kilby. He was just a new researcher left alone in the Texas Instruments laboratory while several of his colleagues were on vacation. While alone, he came up with a radical new way to actually craft chips. The different parts could just be made out of one block of a semi-conductive material.

Metal connections would then just connect the different pieces together. Gone were the days of unwieldy and ineffective wires for transmitting information from point A to point B. This technique allowed for smaller integrated circuits to be made later on, which ultimately led to the development of the microprocessor.

In the end, this simple development opened the door for years of refinement that have led us to our current position. One integrated circuit led to another until it ended with the mind shatteringly fast chips of today. Hundreds of millions of basic electronic parts are now able to fit on one chip that is no larger than an average fingernail.

Pretty amazing, especially when you consider that this chip powers your life through its advanced methods of calculation that paved the way for the information age.

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Monday, December 17, 2007

SiBar™ Devices Help Protect High Data Rate Telcom and Datacom Equipment

Tyco Electronics expands its Raychem™ brand SiBar™ thyristor series to include new bi-directional transient voltage surge suppressors with an expanded range of voltages and lower capacitance to help protect high-speed ADSL/VDSL modems, Ethernet and Power-over-Ethernet and other high data rate communications equipment.

Product Features
  • GR-1089 Core, ITU K.20/K.21, IEC61000-4-5, FCC part 68, and UL60950 compliant
  • F, bi-directional protection in industry standard surge current families of 50A, 80A and 100A (10/1000µs)
  • Voltage ranges from 6V to 400V, capacitance values as low as 12pF, maximum leakage current of only 2µA and a minimum hold current of 150mA
  • Housed in surface-mount SMB (JEDEC DO-214AA) and SMA (JEDEC DO-214AC) package options
  • Small form factor, low on-state power dissipation, and accurate foldback voltage shunting
  • RoHS-compliant
  • Analog and Digital Linecards
  • xDSL and ISDN Modems
  • Set-top Boxes
  • T1 Equipment
  • Voice over IP (VoIP) Equipment
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New Scale Debuts World's Smallest Linear Motor

At 1.5 x 1.5 x 6 mm, Latest Piezoelectric SQUIGGLE Motor is Half the Size of Other Micro-Motors; Offers Ten Times the Precision and Push Force

May 25, 2006 - Victor, NY - The latest SQUIGGLE motor from New Scale Technologies, Inc. is the smallest linear motor on the market, the company announced today. At 1.5 mm x 1.5 mm, the new SQL-1.5 piezoelectric motor is half the size of competing micro-motors. It also offers a 20 gram push force and sub-micron position resolution, performing ten times better than its closest competitor on both counts.

"The SQL-1.5 opens a whole new range of performance for miniature electronic systems such as phone cameras and medical devices," said New Scale president David Henderson. "Designers of leading edge mobile devices finally have a precise, reliable linear motor that fits within their size and power budgets. They can add motion – and hence new capabilities – where they were unable to do so before."

A description of the SQUIGGLE motor operating principle is available at

Typical applications: phone cameras and medical devices

The SQL-1.5 has been designed into next-generation auto focus and optical zoom assemblies by leading camera module developers, who support the top tier handset manufacturers. Focus and zoom capabilities have become an essential ingredient in the drive to deliver smaller, thinner handsets with the image quality of digital still cameras.

"Even by the most conservative handset sales forecasts, phone cameras alone represent a new market for one billion motors a year," Henderson said. "The requirements of these cameras can not be met by current motor technologies."

The SQL-1.5 is also of interest to medical device manufacturers for a new class of implantable drug pumps and micro-valves. The motor itself is tiny, but its high precision is what enables the most dramatic reduction in overall device size. It provides more precise valve control, which permits more concentrated medications and therefore smaller fluid reservoirs. The patented ceramic motor design generates no magnetic fields and can be made of non-ferrous materials, making it MRI-safe and image compatible.

SQL-1.5 SQUIGGLE Motor Specifications

- Motor body dimensions 1.5 mm x 1.5 mm x 6 mm
- Stroke 10 mm (customizable)
- Resolution Better than 100 nm
- Speed (no load) Up to 10 mm/s
- Force > 20 grams
- Typical input power (moving) 400 mW (< 40 V)
- Input power (stationary) 0 mW (0 V)

See complete SQL Series specifications and downloadable data sheet on the website. The SQL-1.5 SQUIGGLE motor evaluation kit is $950 and will be available to qualified OEMs for delivery in July 2006.

The evaluation kit includes an SQL-1.5 SQUIGGLE motor, drive electronics card, cables, and computer control software including an ActiveX command library.

About the SQUIGGLE Motor

The patented SQUIGGLE motor design uses a threaded nut and screw to create precise linear movement in a very small space. Piezoelectric ceramics create ultrasonic vibrations in the nut, causing the screw to rotate and translate with high precision. SQUIGGLE motors are smaller, more precise, less expensive and more efficient than conventional electromagnetic motors. In addition, they use 90 percent fewer parts and require no gear reduction, which eliminates many failure modes. The patented ultrasonic motor design has much lower power consumption than miniature electromagnetic motors and holds its position when the power is turned off, further conserving battery life. This ceramic motor is fundamentally compatible with high magnetic fields including MRI chambers.

SQUIGGLE motors are used in nanotechnology research, microelectronics, optics, lasers, biotechnology, medical devices, aerospace and defense, fluid control, and office/consumer products including mobile phone cameras.

About New Scale Technologies, Inc.

New Scale Technologies, Inc. ( makes miniature ceramic motors that enable our customers to create smaller products and research tools. Our piezoelectric SQUIGGLE motors are smaller, more efficient and more precise than conventional motors. With very few parts and no gears, this patented piezoelectric motor design uses ultrasonic vibrations to create precise linear motion. New Scale's miniature motors are compatible with extreme environments including vacuum, very low (sub-Kelvin) temperatures, and high magnetic fields.

SQUIGGLE is a registered trademark of New Scale Technologies, Inc.

For more information contact:

Fred Haas, Sales Manager, New Scale Technologies
Phone 585-924-4450 x 112

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New High-Power LED Driver from Catalyst Semiconductor Optimized for Rapidly Growing, Mid-Size LCD Panel Market

Catalyst Semiconductor, Inc. (NASDAQ:CATS) a supplier of analog, mixed-signal and non-volatile memory semiconductors has expanded its line of high-power LED drivers with a new device optimized for the rapidly growing mid-size LCD panel market. The new CAT4139 boost converter provides a switch current up to 750mA and drives LED strings up to 22V, making it an ideal choice for digital photo frames and other backlighting applications where high LED counts (up to 40 LEDs) are emerging.

Many high-voltage boost converters typically use a simple variable-frequency switching scheme. This approach results in a wide range of unwanted harmonics, which are not easy to filter or eliminate. The CAT4139 uses a fixed frequency (1MHz) switching architecture making it ideal for low noise applications. A high voltage CMOS output stage in the device allows 5 LED strings (up to 22V) to be accurately biased and regulated from a low voltage input supply while still delivering efficiency levels of up to 87%. The CAT4139 follows Catalyst's CAT4240 high-power boost converter introduced earlier this year, which drives 10 LED strings up to 38V each.

To eliminate excessive "in-rush" currents which can occur during initial power-up, the CAT4139 offers an integrated soft-start control. In the event of an open-LED fault condition, an internal over-voltage protection circuit will place the device into a low-power operating mode restricting the output voltage to safe levels without the need for external circuitry. Both of these features are fully integrated, eliminating the need for external components and the associated cost and board space overhead.

Designers have a choice of controlling LED dimming in the CAT4139 using a DC voltage, logic signal, or pulse width modulation (PWM) signal.
Product Features
  • Switch current limit 750mA
  • Drives high voltage LED strings up to 22V
  • 1MHz fixed-frequency, low-noise operation
  • Fully protected
  • Packaging: 5-lead TSOT23 (1mm max height)
Price and Availability
The CAT4139 LED driver is priced at $0.64 each in 10,000 piece quantities. Samples are available now. Projected lead-time for production quantities is currently 6 to 8 weeks ARO.

About Catalyst Semiconductor
Headquartered in Santa Clara, California, Catalyst Semiconductor designs and markets analog, mixed-signal and non-volatile memory products, including Digitally Programmable Potentiometers (DPP™), white and color LED drivers, DC/DC converters, LDO regulators, voltage supervisors, bus expanders, serial and parallel EEPROMs, Flash and NVRAM. Many of Catalyst's products incorporate the Company's Quantum Charge Programmable™ technology, to deliver Adaptive Analog™ products, which offer a new level of customer flexibility, lower power and smaller die size. Catalyst products are used in telecommunications, computer, automotive, industrial and consumer markets. Typical applications include LCD displays, automotive lighting, optical networks, printers, modems, wireless LANs, network cards, DIMM modules, cellular telephones, navigation systems, set-top boxes and Internet routers.

Forward-Looking Statements
This press release contains forward-looking statements that are subject to uncertainties and risks including, but not limited to statements relating to lead times and product availability for Catalyst Semiconductor's LED drivers. These statements are based on current information and market conditions and, as such, are subject to uncertainties and risks that could cause actual results to differ from those described in these forward-looking statements. Factors that may affect product availability and lead times include manufacturing process interruptions at Catalyst's or our vendors' production facilities, fluctuations in customer demand and changes in market supply. Additional information about factors that could cause actual results to differ materially from those in the forward-looking statements is contained under the heading "Certain Factors That May Affect the Company's Future Results of Operations" listed from time-to-time in reports Catalyst files with the Securities and Exchange Commission including, but not limited to, Catalyst's Annual Report filed on Form 10-K and Quarterly Reports filed on Form 10-Q. Catalyst disclaims any obligation to update information contained in any forward-looking statement.

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Tuesday, December 11, 2007

Link Partners

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Monday, December 10, 2007

Rohde & Schwarz unveils fast production tester for wireless devices up to 6 GHz

The R&S CMW500 non-signaling tester delivers high speed, accuracy, and high scalability when used in the production of wireless devices. Featuring a frequency range up to 6 GHz and an IF bandwidth of 40 MHz/70 MHz (analyzer/generator), the production tester has been designed to anticipate future technological developments, This ensures minimum test costs and high safety of investment.

The R&S CMW500 one-box tester includes a powerful RF analyzer and generator. This combination plus a new test concept ensures maximum test performance, minimum space requirements, and comparatively low power consumption.

"Modern mobile phones are becoming more and more complex", says Anton Messmer, Director of the Mobile Radio Testers Subdivision. "The test effort increases with every new technology and every additional frequency band. To curb the growth in test times and costs, completely new approaches are needed. That's the reason Rohde & Schwarz developed the R&S Smart Alignment test concept for manufacturers of chipsets and wireless devices. By applying this test concept, alignment times are up to ten times faster than with conventional methods."

A prerequisite for minimum production costs is maximum first pass yield. Yield depends on optimizing the entire production process, where the measurement accuracy of the individual components involved is crucial. For this reason, very high standards – especially with regard to absolute accuracy, repeatability, and linearity – were set during the development of the R&S CMW500.

The R&S CMW500 presently supports GSM, GPRS, EDGE, WCDMA, mobile WiMAX, CDMA2000, and TD-SCDMA as options. Further technologies will follow. Rohde & Schwarz provides applications that allow extremely fast measurements.

With a frequency range of 3.3 GHz, the base unit supports all important mobile radio bands used today. Since the range can be easily extended from 3.3 GHz to 6 GHz with software, the tester is excellently positioned for future developments.

Due to the high stability of the R&S CMW500 design, users can extend the calibration interval to two years, generating further cost savings.

Source : Click here

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NI intros high-performance Smart Camera family

National Instruments has announced the NI 1722 and NI 1742 Smart Cameras to provide engineers and scientists with high-performance systems at a low cost. The NI Smart Cameras are embedded devices that combine an industrial controller with an image sensor and integrate with NI vision software to offer image processing directly on the cameras, making them ideal for applications such as locating parts, inspecting packaging, verifying assembly and reading 1-D and 2-D codes.

The new cameras are shipped with National Instruments Vision Builder for Automated Inspection (AI), an interactive software environment for configuring, benchmarking and deploying machine vision applications without programming. With this intuitive, menu-driven software, engineers can build complex machine vision applications incorporating not only vision algorithms but also state-based execution with looping and branching using the built-in state diagram editor. For more advanced applications, NI Smart Cameras also integrate with National Instruments LabVIEW software and the full NI library of image processing and machine vision algorithms such as edge detection, pattern matching, 1-D and 2-D code reading and optical character recognition. Machine vision applications can migrate between platforms with few modifications because LabVIEW and Vision Builder AI support this entire range of hardware.

"The NI Smart Camera represents a significant step forward for the vision industry by achieving high performance at a low cost while expanding the NI vision hardware platform beyond PC-based systems and compact vision systems to the sensor itself," said John Hanks, NI vice president of industrial product marketing. "From inspecting silicon wafers to packaging food products, NI Smart Cameras provide machine builders and process engineers with easy-to-use, all-in-one inspection solutions that deliver the capabilities of a full-featured vision system."

Built for use in harsh industrial environments, the NI 1722 features a 400 MHz PowerPC processor and the NI 1742 features a 533 MHz processor. The monochrome VGA (640 x 480) image sensor used in both cameras is a high-quality Sony charge-coupled device. The cameras also provide built-in industrial I/O, including two opto-isolated digital inputs and two opto-isolated digital outputs, one RS232 serial port and two gigabit Ethernet ports with support for industrial protocols, including Modbus TCP.

In addition, the NI 1742 includes quadrature encoder support and a built-in controller featuring NI direct drive lighting technology. With quadrature encoder support, engineers can easily synchronize inspections with linear and rotary drive systems. The NI direct drive controller features a built-in LED lighting drive that provides up to 500 mA constant current and up to 1 A strobed current. Strobe lighting offers increased lighting intensity by up to four times without harming the light head.

Source : Click here

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Sunday, December 09, 2007

Nanotube-producing Bacteria Show Manufacturing Promise

The research team believes this is the first time nanotubes have been shown to be produced by biological rather than chemical means. It opens the door to the possibility of cheaper and more environmentally friendly manufacture of electronic materials.

The team, including Nosang V. Myung, associate professor of chemical and environmental engineering in the Bourns College of Engineering, and his postdoctoral researcher Bongyoung Yoo, found the bacterium Shewanella facilitates the formation of arsenic-sulfide nanotubes that have unique physical and chemical properties not produced by chemical agents.

"We have shown that a jar with a bug in it can create potentially useful nanostructures," Myung said. "Nanotubes are of particular interest in materials science because the useful properties of a substance can be finely tuned according to the diameter and the thickness of the tubes."

The whole realm of electronic devices which power our world, from computers to solar cells, today depend on chemical manufacturing processes which use tremendous energy, and leave behind toxic metals and chemicals. Myung said a growing movement in science and engineering is looking for ways to produce semiconductors in more ecologically friendly ways.

Two members of the research team, Hor Gil Hur and Ji-Hoon Lee from Gwangju Institute of Science and Technology (GIST), Korea, first discovered something unexpected happening when they attempted to remediate arsenic contamination using the metal-reducing bacterium Shewanella. Myung, who specializes in electro-chemical material synthesis and device fabrication, was able to characterize the resulting nano-material.

The photoactive arsenic-sulfide nanotubes produced by the bacteria behave as metals with electrical and photoconductive properties. The researchers report that these properties may also provide novel functionality for the next generation of semiconductors in nano- and opto-electronic devices.

In a process that is not yet fully understood, the Shewanella bacterium secretes polysacarides that seem to produce the template for the arsenic sulfide nanotubes, Myung explained. The practical significance of this technique would be much greater if a bacterial species were identified that could produce nanotubes of cadmium sulfide or other superior semiconductor materials, he added.

"This is just a first step that points the way to future investigation," he said. "Each species of Shewanella might have individual implications for manufacturing properties."

Study results appear in the December 7 issue of the early edition of the Proceedings of the National Academy of Sciences.

Myung, Yoo, Hur and Lee were joined in the research by Min-Gyu Kim, Pohang Accelerator Laboratory, Pohang, Korea; Jongsun Maeng and Takhee Lee, GIST; Alice C. Dohnalkova and James K. Fredrickson, Pacific Northwest National Laboratory, Richland, Wash.; and Michael J. Sadowsky, University of Minnesota.

The Center for Nanoscale Innovation for Defense provided funding for Myung's contribution to the study.

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