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Articles from 2003 In May


Sensors

Sensors

Level headed and then some

MTS Systems Sensor Div. Level Plus M-Series Digital sensor. Designed as a drop-in replacement for the company's analog liquid level sensors, this series features a digital Modbus output, which can also be interfaced with most Fieldbus and Profibus systems. No intermediate Modbus box is needed. The magnetostrictive-technology sensor not only senses inventory level, but also interface level and temperature. Leveraging the sensing technology (here in a low-profile control head thanks to surface-mount components) with processing was possible due to a proprietary, high-speed signal processing IC. "With a single 16-bit microprocessor, we were able to move intelligence to the sensor, closer to the sensing point, and integrate temperature sensing digital thermometers," notes Adrian Totten, product manager. The microprocessor-based design also features a flexible command interface, high noise rejection capability, built-in test, and automatic data error checking. (www.levelplus.com) Enter 696

Transducers with hart

Phoenix Contact loop-powered MCR temperature transducers. An addition to the company's line of MCR (measurement, control, and regulation) signal conditioners, these devices convert temperature readings into 4-20 mA analog signals. The microprocessor-based, Windows-programmed devices are available with HART-protocol compatibility (which superimposes digital data on the analog signal) for process control applications such as pharmaceuticals and petrochemicals. The analog signal current loop supplies the signal conversion power. "The transducer in itself is universal and can be programmed to be flexible in any temperature monitoring application, regardless of the type of RTD, thermocouple, temperature range, etc.," says Davis Mathews, product market manager for instrumentation products. "It is left to the customers to choose a sensor type and housing style to suit their application," he adds. The transducers come in a 12.5-mm DIN-rail mount housing or a standard head-mount version for DIN-B field installations. (www.phoenixcon.com) Enter 697

Tag team

"BALOGH Distributed by TURCK" RFID Systems. Using these reprogrammable RFID tags, a system can track components, and products, as well as manage process information within harsh industrial environments, including areas with high EMI. For security, users can select only specific transceivers to dialog with specific tags, cutting down on cross talk. Tag modes include Read Only and Read/Write, the latter permitting tracking of process steps using upwards of 32 kbits of onboard memory. Diagnostic features include executing an error bit (with a corresponding error code) if a data transfer error occurs between tag and transceiver-alerting the user to a problem and its possible cause. (www.turck.com) Enter 698

Stifle it

Omron Electronics E3Z-LS diffuse photoelectric sensor. This sensor offers either foreground and background suppression in a single package. Background suppression (BGS) is needed in applications where a highly reflective background can trigger false detections and should also insure that objects beyond a set distance will not be detected. Foreground suppression (FGS) is used where targets have a shiny or irregular surface. The single-package detector is possible thanks to development of two-part diode detectors, which feature areas for detecting near and far reflections, according to Mike Frey group sensor product market manager. Two of these diodes are used to cancel out any intermediate "dead zone" signals. "No mechanical adjustments are needed, say for a mirror that changes alignment, thus vibration is not a problem," he notes. A proprietary processing algorithm also minimizes interference from external fluorescent lighting. The E3Z-LS used a red LED's visible light beam to ease alignment. (www.info.omron.com) Enter 699

See your true colors

Banner QC50 color sensor. An ice-white LED light source is only one vital element that allows this sensor to analyze and identify user-programmed colors. A microprocessor and redesigned send/receive optics facilitate not only contrast detection but also electronic filtering of the reflected white light into its primary color components to determine true color. "What makes it possible is efficient algorithms and a microprocessor fast enough to analyze three independent values to determine true colors, at speeds suitable for automation equipment," says Chris Benson, product manager. A small, cost-effective package is also key, he adds. A color-plus-intensity mode allows gray-scale sorting within a color family. The processor permits the use of just two push buttons to adjust color channels, sensing modes, and tolerance levels. (www.bannerengineering.com) Enter 700

Sealed strain gauges

Texas Instruments 3PP8 hermetic pressure transducers. Using silicon MEMs technology, these strain gauge sensors are designed for pressures from 150 to 40,000 psig. Hermetic sealing in a stainless steel case allows for operation in most industrial applications and provides corrosion resistance in severe environments. Users can store details of each unit's calibration coefficients and serialization data in an EEPROM memory. A key feature is a proprietary ASIC for diagnostics of the sensor itself as well as its connection to a server, says George Verras, engineering supervisor. Such capability allows the sensor, for example, to keep a running tab on a refrigeration system, allowing performance tracking of food storage facilities under FDA regulations. The transducer is based on automotive brake pressure sensor technology, which has pushed down the cost of diagnostics and tightened tolerances. (www.ti.com/snc) Enter 701

NiMH Battery Monitor Touts Accuracy

NiMH Battery Monitor Touts Accuracy

The latest application of Microchip Technology's PowerSmart(R) technology, the PS402, integrates all rechargeable battery monitoring functions for nickel metal hydride (NiMH) cells onto a single chip. Included on the chip are a precision time base (eliminating need for an external crystal clock), a regulator, and temperature sensor. The battery being monitored powers the PS402, thus an external regulator is not needed. If a user chooses, an external thermistor can be used to monitor battery temperature.

Smaller size and reduced parts count are always cost-effective developments. But the company says the key advantage of the PS402 is the ability to determine, within plus or minus 1% accuracy, the remaining battery capacity. This allows maximum safe lifetime of the battery to be achieved before recharge is needed.

Engineer Doug Phillips notes the need for maximum device life. "The power consumption in portable electronics has grown. Meanwhile, the increase in battery capacity has lagged," he says. So it is a case of trying to squeeze the maximum energy out of the cell technology available.


Capacity Key: The PS402 Smart Battery System is designed to monitor NiMH battery capacity for stacks of six to twelve cells. For removable stacks, the device is onboard the battery pack and for embedded applications it can be part of the systems board.

To do this, Microchip uses its Accuron(TM) technology consisting of battery models, customized tables, and patented algorithms that are stored in the on-chip programmable memory. The remaining capacity of the battery is computed. The capacity is a dynamic number based on temperature, usage rate, and the specific chemistry of the battery. Phillips says conventional battery fuel gauges usually use only one parameter to try and assess remaining lifetime.

Phillips cites one algorithm in particular used to predict shutdown capacity, which is having enough energy left to close the device while safely protecting any information that must be saved. "It tells the device to shut down at a certain capacity, not a voltage or temperature. It takes into account the discharge curve differences between a fully charged and nearly empty battery," he notes.

Finally, Phillips says battery management is not just silicon and firmware. Implementation can be problematic so the company has a set of development tools for configuring, calibrating, and testing. "These wizard-driven implementations install like Windows with features like auto-configuration after a user inputs design parameters." Microchip Technology Inc.www.microchip.com Enter 688

Resolution and Accuracy: Cousins, not Twins

Resolution and Accuracy: Cousins, not Twins

While checking the Home Depot website for a new thermostat, I found a unit with a weight of 8.899999 oz. I doubt Home Depot has a scale that measures millionths of an ounce. But because those digits exist, some people will believe they represent an accurate measurement.

That's the problem with accuracy and resolution-people often think they represent the same thing. At its simplest, resolution tells you how finely you can represent a quantity and accuracy tells you how much of the measurement really has value.

Companies that sell instruments such as data-acquisition boards and digital multimeters (DMMs) often make a big deal of the fact that a given card provides a 16-, 18-, or 24-bit analog-to-digital converter (ADC). But they may not tell users, at least not clearly, how many of those bits they actually can use. In the thermostat example, it's safe to assume only the two most significant digits have any value.

Keep in mind that all ADCs have built-in inaccuracies because they digitize a signal in discrete steps. There's just no way the output can perfectly represent an analog input signal. So, a 12-bit converter would provide a least-significant bit (LSB) with a 2.44 mV step, so the ADC only can digitize values in 2.44 mV steps; 2.44 mV, 4.88 mV, 7.32 mV,


Perfection Please: A perfect ADC produces a unique digital code as an analog input increases through small voltage increments. Each increment equals the voltage represented by the converter's least-significant bit. For a 12-bit converter with a 0-10 V range, that comes to 2.44mV per step.

and so on. Through its entire 10-V range, a measurement never can be more accurate than plus or minus 1/2 LSB, or plus or minus 1.22 mV.

Today, the cost of a 16-bit ADC exceeds that of a 12-bit device by only a few dollars. So users ask, "Why can't manufacturers use 16-bit ADCs and give us four more bits?" They can, but adding four bits of resolution doesn't automatically guarantee more accuracy. The 2.44 mV steps in a 12-bit ADC shrink to 0.15 mV steps in a 16-bit ADC. Unless board manufacturers also improve the performance of the ADC's supporting circuits, which costs money, those extra bits amount to naught. In particular, they must pay careful attention to stability and noise reduction.

Watch for Errors

Several characteristics of the ADCs themselves, if not accounted for, can introduce errors and reduce accuracy. These errors stem from offset, gain, temperature drift, and non-linear performance.

Although they don't often measure such errors, users should know they exist. Offset refers to a fixed difference between an actual signal and what an ADC measures. The offset remains constant throughout the ADC's range, and designers can usually reduce it electronically. After designers remove any offset error, a gain error may remain. It represents a difference between the slope of an ideal ADC's measurement steps and those in a real ADC. As with offset error, designers can reduce gain error through circuit trimming. The use of matched components and circuit designs that minimize the effect of temperature changes help overcome problems of thermal drift.


Noise Helps: Adding a bit of controlled noise to an ADC's input can force a signal above or below each step.

After designers remove offset, thermal, and gain errors, they still may face nonlinearity errors. Differential nonlinearity (DNL) occurs at the transitions between each step and DNL values specify the difference between an actual step width and the ideal value of 1 LSB. DNL errors vary from step to step.

Integral nonlinearity (INL) relates all the DNL errors to the ideal performance of an ADC, and ADC suppliers can represent INL in two ways. The first technique plots the best straight-line fit for all the DNL errors and relates this to the straight line produced by a perfect ADC. The second technique draws a straight line between the DNL value at the start and end of the measurement range. Manufacturers of analog-measurement cards strive to find ADCs that minimize any effects of DNL and INL. Specification sheets should list the values for these types of errors, and a DNL of plus or minus 1/2 LSB and an INL of plus or minus 1 to plus or minus 2 LSB are reasonable for a high-accuracy measuring instrument.

Simplify the Specs

These error specifications can get confusing and users often wonder why manufacturers can't specify performance in simpler terms. Actually, some do; they specify a signal-to-noise ratio (SNR) that can simplify comparisons. Every measuring device has a noise floor, below which it can't make accurate measurements. The ratio of the maximum measurable signal to the noise floor provides the signal-to-noise ratio in units of decibels (dB).

Given a measuring instrument's SNR-also called its dynamic range-you can calculate a quantity called the effective number of bits (ENOB). This value tells you how many of the bits in a given system provide accurate information. Here's an example that compares two hypothetical data-acquisition systems:

System ADC Bits Theoretical SNR (dB) Actual SNR (dB)
A 16 96 92
B 18 108 90

At first glance it might appear the 18-bit system has an advantage-two more bits and only a slightly smaller SNR than the 16-bit system. You can use the formula below to relate a system's SNR to its number of effective bits, n:

n = (SNR - 1.76 dB)/6.02 dB

So for the two systems, the 16-bit ADC yields 15 effective bits and the 18-bit system can provide only 14.7 effective bits. It looks like the 16-bit system will perform slightly better than the 18-bit system, and probably at lower cost. Real ADC accuracy is usually lower, and never higher, than the number of bits produced by an ADC.

Engineers make realistic comparisons based on signal-to-noise ratios because manufacturers make these measurements on an entire system, from the analog signal inputs through a multiplexer and amplifier to an ADC. And the SNR measurements account for any noise generated by the surrounding circuits. Thus the SNR most accurately represents how equipment will operate in actual use.

For a Few Bits More

After taking great pains to reduce errors and noise, some manufacturers actually add a small amount of noise to incoming signals to better resolve them. This technique, called dithering, sounds counterintuitive, but in some situations, it can work well.

Say an incoming dc signal with slight fluctuations exists between two adjacent ADC steps. The ADC produces only one output value, x, because the signal never crosses the threshold for the ADC's next highest step, x + 1 LSB. Adding 1/2 LSBrms of Gaussian white noise to the signal may at times force it above the ADC's next level. Thus a series of measurements will include some values for x and some for x + 1 LSB. Averaging these values can help resolve an unknown signal with better accuracy. But keep in mind that the ADC did not instantaneously measure just one value. Instead, software applied a statistical technique to several acquired values to derive information about the original dc input.

Electronics

Electronics

Monitor backlighting

Low cost, maximum efficiency

SolidState(TM) CCFL backlight assembly for 15-inch desktop thin film transistor (TFT) LCD monitors uses the company's MicroLens(TM) technology, which precision molds light extraction features into the panel. The technology also reduces the number of light management films required, while increasing brightness by as much as 25%. The backlighting assembly can be supplied in high volumes ranging from 120k/month to 450k/month. Global Lighting Technologies, www.glthome.com Enter 615

Firewire device

Fast and far

With the 1394b (FireWire) Device, consumer, computing and audio/video applications can, according to the company, reach higher speeds and greater distances. Capable of speeds up to 800 Mbps, the TSB81BA3 three-port bilingual physical layer device is compliant with the approved version of the IEEE 1394b specification. It reportedly not only doubles the speed, but increases communication distances up to 100m for high speed data transfers and multimedia networking. Applications include computers, server networks, au-dio/visual hard disk drives, musical instrument controllers, and home networking for audio/visual distribution. Texas Instruments Inc., www.ti.com Enter 626

Precision micro-ohmmeter

For measuring resistance and voltage

Including thermal emf compensation and temperature compensation, the HHM518 Precision Micro-Ohmmeter is used for four-wire resistance measurement from low values up to 50 kV, with reportedly excellent accuracy. It also measures dc and ac voltages and ambient temperatures. It is battery-powered, but is fitted with a removable stand and powered by an external ac charger. OMEGA Engineering www.omega.com Enter 627

Exhaust pressure sensor

Helps meet EPA emission standards

This pressure sensor, with reportedly high accuracy (1%), monitors and controls pressure with a ceramic capacitive sensing technology. The sensor utilizes a number of internal features engineered to withstand high temperatures and pressure pulses along with tolerance for high- soot and acid-rich media found in engine exhaust. Available in a pressure range of 6.5 to 90 psi. the sensor has standard features including over-voltage, reverse polarity, short circuit, and EMI/RFI protection. Kavlico www.kavlico.com Enter 628

Neutral density filters

Varied light intensity

These 12 neutral density filters are designed to vary light intensity uniformly through a broad spectrum range, for use in color imaging, astronomy, and microscopy. Filters achieve density ranges between 0.01 and 2.5, or transmission of 0.32 to 97.5%, via thin-film metal coatings with 0.01 to 2 density values. Rolyn Optics Co. www.rolyn.com Enter 629

VF Converters

Rugged drop-in replacements

A new series of compact dc to ac/dc converters, used to power vacuum fluorescent displays in security access terminals, gaming machines, appliances, consumer electronics, and automotive displays, provides rugged, US-made drop-in replacements for imported converters. The E2598VF converter, part of the new series, measures 1.25 inches x .93 inches with a low profile of 0.545 inches. It offers an input voltage range of 4.5 to 5.5V dc and two negative dc output voltage ranges of 21.6 to 26.4V dc (-V1) and 27.9 to 34.1V dc (-V2). Endicott Research Group, www.ergpower.com Enter 630

Power amplifier

For use in 802.11b/g applications

Designed for high-performance WLAN applications in the 2.4 to 2.5 GHZ frequency band, the RMPA2453-251 power amplifier is optimized for 802.11b and g applications. With internal matching on both input and output to 50 ohms, the low-profile 16-pin, 3 x 3 x 1-mm package minimizes external component count and next-level PCB space. The RMPA2453-2512 requires a single positive-supply operation and has an integrated power detector with 20 dB dynamic range. Raytheon www.raytheon.com Enter 631

Transmissive LCD modules

Wide operating temperature range

The F-51553 series 128 x 64 dot COG (chip-on-glass) monochrome STN transmissive LCD modules feature a 2.8-inch diagonal area that can display text and graphics together. The modules provide a wider temperature range (-20 to +70C) and greater temperature stability through use of a liquid crystal fluid with a flat voltage vs. operation temperature. Designers can reportedly specify the desired interface type since the module supports serial as well as parallel interfaces. Optrex America Inc., www.optrex.com Enter 632

Latching relay output module

Provides fail-safe control

By latching the last output contact state before power is lost, the G-1AMPx-LTCH Latching Relay Output Module provides fail-safe control. It is reportedly compatible with industry standard I/O mounting racks for G-Series, G4, G5, and C4 type modules and is available for 5V, 12V, 15V, and 24V logic operation. Special features include Power to the Set/Reset Relay coil(s) only applied for 3 msec when changing the output state. The LED indicator operates from an auxillary set of relay contacts internally to give the "real-time" indication of the output state. Brentek International Inc., www.brentek.com Enter 633

BCF sensors

Superior noise immunity

The new ac version Noise Immune Capacitive Sensor features a fixed oscillator frequency combined with a rectifier filter reportedly providing superior noise immunity over the competition. Regardless of sensitivity adjustment, the fixed oscillator allows the sensor to maintain a constant frequency. The sensors are available in 18- and 30-mm plastic barrel housings for dc and a 30-mm plastic housing for ac. TURCK Inc., www.turck.com Enter 634

Heater assemblies

Fits in tight locations

Providing moderate, controllable heat in economical and low-profile designs, the expanded element heater assemblies reportedly lower costs and simplify installation. With aluminum, copper, or stainless steel plates, plate dimensions up to 22 x 72 inches are possible. Applications for these heater assemblies include warming electrical enclosures in harsh environments, warming vehicle batteries in cold weather, and warming trays for the food service industry. Minco Products Inc., www.minco.com Enter 635

Wiper/washer control

L-series combines reliability and performance

The Wiper/Washer Control, keeping in step with the needs of the transportation industry, has reportedly sleek aesthetics to integrate into most any dashboard design. Features include robust packaging that protects critical components and flexibility to meet a variety of customer requirements, while controlling several functions through the use of one single control product. Carling Technologies, www.carlingtech.com Enter 636

Registration mark sensor

Detect any color

The Mark-Eye(TM), a pulse-modulated photoelectric registration mark sensor, detects color marks on most transparent and translucent packing materials on a continuous web. The sensor is useful on form, fill, and seal machines. Features include easy setup and adjustment with the push of a button, operation on 10 to 30V dc, and mark detection as small as 1/32 inch wide by .25 inch long. Tri-Tronics Inc., www.ttco.com Enter 637

Pluggable circuit breaker

Re-settable circuit protection

A pluggable thermal circuit breaker, for the Series 282 DIN rail mount Cage Clamp terminal blocks, is suited for protection of power distribution systems, automation systems, and process control applications. Combining the circuit breaker with the terminal blocks reportedly ensures the reliability of a secure, maintenance-free, corrosion-resistant connection. It reduces wiring time, which saves money. For rapid trouble-shooting, the plug-in circuit breaker features a push-button reset. WAGO Corp., www.wago.com Enter 638

Pressure switch

Powerful, compact

The Series 7000 pressure switch measures, controls, and switches pressures up to 3,000 psi. It is available in corrosion-resistant thermoplastic or stainless steel, and incorporates standard 1/8 inch MNPT or .25 inch MNPT process connections, and optional 7/16-20, G1/4, or .25 BSP threads. Applica-tions include food and beverage. Barksdale, www.barksdale.com Enter 639

Mini sensors

Compact and compatible

CSM 1 / KT 3/LUT 2 Mini Sensors, the new mini series of color, contrast, and luminescence sensors meet color and design demands with their identical housings and connection technology. The sensor identifies, sorts, and checks objects based on their color. For reflective target objects, the sensor has an easy-to-use 2-point teach-in on marks and backgrounds, high contrast resolution, and integrated switching threshold adaptation. SICK Inc., www.sickoptic.com Enter 640

Subminiature oscillators

Breaks size versus frequency barrier

Optimized for optical network interface cards (NICs), the SEL381x Series of extended frequency LVPECL crystal clock oscillators features an extensive frequency range of 25 to 670 MHz and stability as tight as plus or minus 20 ppm. The oscillators offer a space-saving solution with compact size, comprehensive frequency range, and variety of stability options for Gbit and 10 Gbit Ethernet. According to the company, the 10 Gbit Ethernet devices also benefit from the optimized performance at 156.25 and 312.5 MHz. Saronix, www.saronix.com Enter 641

Eight-slot chassis

Delivers precision timing

The PXI-1042 chassis, with eight slots, is used for automated test and data acquisition applications. It offers a low-jitter internal clock and external clock connectors for precision timing and synchronization. An eight-slot backplane with high output power supply, integrated cooling, and compact structural design suits it for bench-top or rack-mounted test and control systems. National Instruments, www.ni.com Enter 642

Ac inverter

For harsh weather

Resisting dust and forced water or chemicals, the MV-4X AC inverter's NEMA 4X/12 and IP66 ratings make it suitable for tough washdown or dust-tight environments. The user operates the inverter by using the front panel with a quick-start keypad, and viewing the LED display for easy setup and programming. Available in 230V ac, 3-phase from 1/2 to 10 hp, and in 460V ac, 3-phase from 1/2 to 15 hp, it is made for the food and beverage industry, mixers, machine tools, and pumps. Omron Electronics LLC, www.omron.com Enter 643

Data acquisition and recording

For SIGNATEC PDA500 Wafeform Digitizer

The GIGAMEM2-500-500-MHz 8 bit scope card with 256 Mbytes to 8 Gbytes-is reportedly the highest capacity 500-MHz data acquisition and recording solution. It digitizes and records one or several channels simultaneously in real-time. Application areas include digital oscilloscopy with deep acquisition memory, test benches for signal acquisition/recording and playback, telecommunications, defense, electronics intelligence, radar, ultrasound, cryptography, video recording, and arbitrary function generation. Horizon Technologies, www.horizon-tech.fr Enter 644

Illuminated pushbuttons

Brighter LEDs

Designed for use in YB, LB, and KB series of illuminated pushbuttons, the cost-effective LEDs offer a reportedly brighter light source and good energy efficiency. LEDs with built-in resistors are available in 5V, 12V, and 24V ratings. Available in red, green, or amber, the LEDs allow light to radiate further and illuminate the full face of the pushbutton cover. Various models feature PC adapters in single-pole or double-pole configurations, with straight-PC or right-angle mount for single-pole options. NKK Switches, www.nkkswitches.com Enter 645

MEMS Sensors Rev Their Engines

MEMS Sensors Rev Their Engines


Fast Lane: Delphi ENgineer Bruce Natvig led the team that developed an earpiece sensor that measures dynamic forces impacting a race car driver's head when a crash occurs. The data will help engineers design better restraint systems.

Drivers in the Indy Racing League have a new piece of gear this year, and it isn't under the hood, but in their ears. Embedded in the drivers' radio earpieces is a tiny MEMS sensor system developed by engineers at Delphi (www.delphi.com) that measures the dynamic forces applied to the driver's head during an accident. The g-force data collected will provide researchers a clearer picture of what happens in that split-second of time that it takes for a crash to occur, leading to better design of driver restraint systems and safety devices.

Size mattered, since the sensing system-consisting of 3 accelerometers, one for each axis, and two circuit boards-had to fit inside the earpiece alongside the transducer for the radio receiver. "Engineers first tried putting the sensors into the helmet, but discovered that the helmet moves relative to the head. It did not produce an accurate reading of head forces," says Bruce Natvig, an engineer at Delphi who headed up the development project.


Small Stuff: The small size of MEMS accelerometers enables them to fit inany application.

Fortunately, the tiny 4.5 x 4.5 x 2-mm sensor system fit comfortably inside an earpiece, sized even for the smallest ear because of the technology of microelectromechanical systems (MEMS), which has made sensors very small. That size opens up a host of new applications.

MEMS devices are essentially mechanical systems in extreme miniature. In their packages, they look like ordinary integrated circuits, but inside they're mechanical systems with extremely small masses, beams, and springs that move. The proof mass in Analog Devices' MEMS gyroscopes, for example, weighs only eight millionths of a gram. It's suspended only two microns (two millionths of a meter) over the device's electronic circuitry. The proof mass in accelerometers from MEMSIC beats even that. It's nothing but a gas that moves in a sealed chamber, and because gas is the only thing that moves, there are no parts that can break. MEMSIC claims its devices can withstand shocks of up to 50,000 g's.

The credit for enabling such small mechanical systems goes to semiconductor manufacturing technology. The same photolithographic processes that create super small transistors are just as capable of creating super small beams, springs, and other mechanical structures. In fact, these mechanical structures, tiny as they are, loom huge in comparison with electronic circuit components. That means that MEMS devices can be produced on trailing-edge semiconductor fabrication equipment, a financial bonus for semiconductor manufacturers. In addition, semiconductor manufacturing processes create hundreds or thousands of MEMS chips at a time on a single silicon wafer, bringing about enormous per-unit cost savings that will only increase as semiconductor manufacturing technology continues to improve.

Two Paths to Production

Two different approaches-bulk micromachining and surface micromachining-create different kinds of MEMS devices. The bulk micromachining process, normally used to make pressure sensors, creates mechanical structures by etching away material from both sides of a silicon slab that's relatively thick (typically 400 microns). The other approach, surface micromachining, adds the common IC-fabrication steps of depositing and then selectively etching multiple silicon layers that are very thin (typically 2 to 4 microns). Surface-micromachined MEMS devices are typically 20 times smaller, by volume, than bulk-micromachined devices, which are tiny themselves. Surface micromachining is the process used to make accelerometers, but Motorola also turned to surface micromachining to make the pressure sensor in its new tire-pressure monitoring system.





How it works: In a MEMS accelerometer, a moving proof mass shifts capacitive sensing fingers that are attached to it. The resulitng change in the capacitance provides a measure of acceleration. In MEMs accelerometers from MEMSIC below, a heated gas changes position as the device moves. Temperature sensors measure the gas's shift to determine acceleration.

Both bulk micromachining and surface micromachining capitalize on silicon's physical strength to make microscopic mechanical structures. According to Dave Monk, development engineering manager for Motorola's Sensor Products Division, a typical diaphragm thickness in a MEMS pressure sensor is 12 to 25 microns, compared to 75 microns for the thickness of a human hair. "This is silicon, but it can flex," Monk says. "You can flex it with a pencil and see it with the naked eye."

In surface-micromachined MEMS devices, mechanical structures are indeed microscopic. For example, the sensor in the ADXRS150 and ADXRS300 MEMS gyroscopes from Analog Devices measures only 1 x 0.5 mm and yet includes, among other things, 5,000 interleaved capacitive-sensing fingers (beams) that move. In a MEMS accelerometer, says Chris Lemaire, business development engineer at Analog Devices, the device's proof mass moves by mere Angstroms.

How do such small devices work? "Picture a trampoline," says Motorola's Monk. A MEMS accelerometer's proof mass, Monk says, is like the trampoline's surface. Silicon springs connect the proof mass to anchor points. The springs aren't coils, but serpentine cantilever beams, and even though they're made of silicon, they can stretch enough to do their intended job. When the proof mass moves, with control provided by the springs, interleaving capacitive-sensing fingers detect minuscule changes in capacitance, which then get converted electronically to an acceleration reading. In a MEMS gyroscope, or angular rate sensor, a vibrating mass replaces the spinning mass of a traditional gyroscope.

The changes in capacitance that a MEMS device detects are just as tiny as MEMS mechanical components. "We're measuring zeptofarads," says Paul Ganci, product line director for the Inertial MEMS Group at Analog Devices. A zeptofarad is 10-21 farads, Ganci notes-so small that having on-chip circuitry to measure it and process the reading is preferable to off-chip circuitry, which can affect readings. Analog Devices and MEMSIC both have such on-chip circuitry. Other MEMS manufacturers put two chips-one with MEMS mechanical components and one with circuitry-in each MEMS package.

Small Size, Big Market

MEMS applications may be growing, but the technology isn't exactly new. Motorola has sold over 300 million MEMS pressure sensors since 1980. Analog Devices has shipped over 100 million MEMS accelerometers since introducing them in 1991.

And now, MEMS devices are getting set to become even more numerous. Automotive applications, for example, already the largest market for MEMS devices, will use more of them-9.1 per vehicle in 2007, according to market research firm In-Stat/MDR (www.instat.com), up from 5.0 in 2002. MEMS pressure sensors are useful for engine management, braking, fuel measurement, suspension control, tire-pressure monitoring, and more. MEMS accelerometers and angular rate sensors are finding use in active suspensions, rollover detection, and automatic headlight leveling.

Falling prices are even pushing MEMS devices into consumer applications. MEMS accelerometers have recently become available for around $2.50 from Analog Devices and startup MEMSIC (www.memsic.com), an Analog Devices spinoff. STMicroelectronics (www.st.com), a big player in components for consumer electronics, is also getting into MEMS. It plans-along with other MEMS manufacturers-to put them into cell phones and PDAs to give engineers functions they never even knew they needed. Says Benedetto Vigna, manager of MEMS development for ST, "I believe this will be the decade of MEMS inertial sensors for consumer applications."


The Skinny: The silicon diaphragm, left, in a mems snesor is typically 12-25 microns thick.

Part of the impetus of new MEMS applications comes from increasingly sophisticated features. Low-g MEMS accelerometers, for example, now have measurement ranges as small as 1g (the acceleration of gravity), with resolution as fine as 0.001 of full scale. Performing as very sensitive motion and tilt sensors, they're starting to provide one-handed, keyless scrolling of displays on cell phones and PDAs. To scroll a mobile phone's tiny display, you just tilt the phone in the appropriate direction. Three-axis accelerometers are even adding zoom capabilities to the displays. To zoom in, you raise the phone or PDA a bit; to zoom out, you lower it. MEMS gyroscopes-more accurately described as angular rate sensors-are also recently available. One of their uses will be in cars for rollover detection.

MEMS sensors are also prized for their reliability and low-power consumption. The accelerometers from Analog Devices (www.analog.com) that deploy airbags in car crashes exhibit less than one failure per billion hours of operation. Motorola's tire-pressure monitor, including MEMS device and additional circuitry for remote wireless operation, will operate for seven to 10 years on a single, tiny button battery.

And then, there are the really esoteric MEMS devices. Researchers have created microscopic MEMS motors, for example, and minuscule mechanical manipulators that can grasp a single red blood cell. On a more practical level, fluidic MEMS actuators by the millions are serving as printheads in inkjet printers. They accurately dispense ink in amounts as small as four picoliters (four trillionths of a liter).

What's not small about MEMS is the growth potential. As automotive applications for MEMS devices increase, and as consumer applications get ready to take off, other areas also show promise. MEMS optical components, such as those in LCD projectors, are one promising area; another is healthcare, where MEMS blood pressure sensors are already widely used. Some observers even view MEMS as being positioned now where microelectronics was in the 1970s and early 1980s, with nowhere to go but up. If that's true, we may see another instance of something very small becoming very big.

New and Notable Product Design

New and Notable Product Design

Ergo mus

Xerox Ergonomic Mouse. Take two engineers, who are guitarists, add a case of tendonitis the next day at work, and the result is an ergonomic mouse to mitigate Mouse-Arm Syndrome. One, Jim Reid, is also a chiropractor and the other, Dale Boudreau, is using the device. By using ergonomic engineering, "The design puts the finger into a more relaxed curled position and the mouse "floats" under the hand rather than being gripped by it," notes Reid. A less stressful finger curling motion, as opposed to pressing down, activates the switch clicks and a "fin" between the fingers provides tracking (positioning) cues. Xerox is looking to license the technology. Lead Engineer: Jim Reid, (www.xeroxtechnology.com) Enter 690

You'll get a charge out of this

iSun(TM) Portable Solar Charger. Engineers at ICP Global Technologies thought they had a bright idea for a new solar device to charge the batteries in cell phones. But before they put mouse to screen they asked potential customers if they'd use it. You bet, they said, but make it work for PDAs and laptops too. Good thing the engineers checked. They revised their SolidWorks and AutoCAD models and produced the iSun, which connects to any cell phone, PDA, or GPS device directly or using optional product-specific cables. To charge a laptop, daisy-chain several iSuns together. What separates this device from similar products, says Chief Technology Officer Po K. Lau, is the way engineers encapsulated the solar cells to keep them from oxidizing. They use a special, clear epoxy from a Japanese supplier and cure it slowly in a proprietary process. Lau says the 7.2 x 4.5 x 1.25-inch device puts out about 2 watts of power, 50% more than competitive chargers. Lead engineer: Po K. Lau ([email protected]) Enter 691

No tip lift

Jungheinrich Lift Truck EFG-DF. A Curve Speed Reduction System prevents the Electric Three-wheel Counterbalance Fork Lift Truck (EFG-DF) from tipping. President Dirk von Holt notes that, "Sensors tailer the centrifugal force on the operator and load to keep it at a safe level." Based on sensor input that also includes steering angle, load height, and speed, the microprocessor-based system will adjust speed or activate an electronic brake to safely negotiate a turn. The truck can handle loads up to 4,000 lbs at speeds of 10 mph. There are five operating modes that allow operators to adjust acceleration, braking, travel, and lift, and lower speeds to the task. The tip prevention system functions independently of the selected mode. President Dirk von Holt (www.jungheinrich.com) Enter 692

3d in your hand

Sharp 3D Phone. Imagine seeing in 3D, without the glasses-and on your cell phone no less. The Sharp camera phone uses a 3D display to provide a sense of depth and presence. The phone features an occlusion filter - for no-glasses 3D. "The display works by generating right eye and left eye information to alternative columns of a TFT LCD [display matrix]," says Joel Pollack, vice president of the display business unit, Sharp. "The brain combines these two images to give the impression of a 3D object." VP: Joel Pollack (www.sle.sharp.co.uk/research/3d/3dprimer.htm) Enter 693

tank doesn't fuel around

TI Automotive PERMBLOK(R)AS6 Gas Tank. Made from six layers of materials, including barrier materials ethylene vinyl alcohol copolymer (EVOH) and chemical company ATOFINA's ORGALLOY(R) FT104 nylon-based alloy, this tank meets California's stringent Partial Zero Emission Vehicle (PZEV) requirements. Incorporating the barriers was key to meeting limits covering fuel permeation (emissions from the tank), according to Pierre Delbarre, global director of materials and innovations. In addition, the tank structure had to meet crash-test safety standards. The tank is built like a ship in a bottle, enclosing pumps, sensors, and other components, to reduce possible vapor exit points. The non-corroding plastic can hold different types of fuels, including alcohols. Director: Pierre Delbarre, (www.tiautomotive.com) Enter 694

Tame TV volume

TERK Technologies TV Volume Regulator (VR-1). Set and forget the volume of your TV set and kill the excessive volume of commercials. It's made possible by Octiv's Volume Logic software, which applies only the appropriate amount of processing to any audio source material. TERK's Program Manager, John Francia says, "Volume Logic enables digital re-mastering in real-time by sampling thousands of times a second to produce consistent loudness and sound quality." So no matter what you're watching, you'll hear a uniform, quality audio level for more intelligible dialog and reduced sound effects without having to adjust the volume-a great asset for the hearing impaired. Program Manager: John Francia (www.terk.com) Enter 695

Tune Up At Jaguar

Tune Up At Jaguar

Consider this: Jaguar Racing has had a less than stellar performance record in its brief three-year history of Formula One (F1) racing. It was formed in 1999 when Ford bought the team from Stewart Grand Prix, re-branded it, and painted the cars green, and debuted in the mother of all motor racing, F1, in the 2002 racing season. The team scored just nine points in its first season, a mere four in its second, and lagged behind in 2002 when design flaws made its car slow. But just when some thought Ford would pull Jaguar out of the running, the company dug its heels into the tarmac and sent in Richard Parry-Jones, the head of Ford's product development program, to shake things up. The move marked the dawn of a new culture at Jaguar Racing, one led not by racecar drivers but technical gurus. More importantly, it shows the value of strong engineering management, and the process and product improvements that can come from wise use of software tools.

The Shake Up

Parry-Jones's first move in his new position was to conduct an extensive three-month evaluation of Jaguar Racing. As a result of the review, he reduced head count by one sixth and sacked three-time F1 champion Niki Lauda as CEO of the Premier Performance Division, which encompasses Jaguar Racing, Cosworth Engines, and Pi Research. Lauda's replacement was Tony Purnell, a quiet fellow with a background in aerodynamics. Purnell founded Pi Research, the company that supplies wind-tunnel controls and electronic instrumentation for F1 cars. He started Pi in his basement 20 years ago with a circuit board and wire. In an industry dominated by present and former racecar drivers who have achieved hero status, Purnell is no brand name but rather a "horrifyingly clever engineer," as Jaguar Spokesperson Nav Sidhu describes him. And his talents lie in picking other good people. "Tony is the one who identified the new talent to take the company forward," Sidhu says.

As the new brains for the Premier Performance Division, Purnell set to work installing a new senior management team to attempt a turnaround at Jaguar Racing. The recruits also were not household names, but hard core engineers with a nose for technology. Today, in fact, every senior manager from Parry-Jones on down has a highly technical background.

But Jaguar Racing is more than a bunch of techies. The company culture has morphed completely. "It's different from what people here have experienced-but not different from blue chip companies," says Purnell. "We're trying to slow things down a bit and get people to take a systems approach to everything."

With its procedure manuals and scientific manner, some wonder if such a structured environment doesn't stifle creativity. "People ask me that all the time," says Purnell. "And it completely baffles me because it implies that being sloppy encourages creativity. What fosters creativity is good management and an environment where people can contribute." What's more, he adds, a system of checks and balances curbs bad work.

Testing, Testing, and More Testing

Whether because of a lack of thorough testing or a miscalculation in the wind tunnel, somehow Jaguar's 2002 racing car, the R3, slipped out of the box flawed. The car suffered from poor aerodynamics and too much flex in the chassis. The errors weren't spotted until the car hit the race tracks. But by then, the best solution-a new car-wouldn't be available until 2003.

Purnell attributes the oversight to a lack of a "test-first culture" at Jaguar. The R3 was designed in an old school way, he says. Disciplines at the company tended to work independently without a system for crosschecking and comparing notes. So, Purnell instilled a philosophy of systematic and methodical engineering that relies heavily on the dissemination of data.

"Now we're testing extensively and measuring the car to death before it gets to the track," says Steve Nevey, engineering technology business manager for Jaguar Racing. "Any tools that we use, whether for vehicle dynamic simulation using ADAMS software, or the shaker rig, or wind-tunnel testing are measured against each other to make sure the results are absolutely valid, and therefore much more useful."

Before the group began work on the 2003 model, the R4, Managing Director David Pitch formulated 80-pages worth of specifications for the car. The goal was to identify, in one fell swoop, everyone's requirements for the car-from the stiffness of the chassis to aerodynamics loads and suspension geometry. The strategy was to get everyone thinking as a unit.

"Rather than people having to discuss all the interfaces between different disciplines as the design progressed, all those decisions took place upfront," says Nevey. Some changes were made while designing, but those compromises were kept to a minimum.

Race to the Finish

Racecar design is fast work, aided by software coordination. Scattered throughout the 8,500-ft2 Milton Keynes Jaguar Racing headquarters in England are 60 or so Hewlett-Packard workstations humming with EDS software-Unigraphics for integrated computer-aided design, manufacturing, and engineering and TeamCenter for product lifecycle management. Jaguar designs the chassis and gets it engines from Cosworth Engines, which also uses EDS software. With TeamCenter, Jaguar can give Cosworth remote access to its database.

At Jaguar, there is a hard push to build a race car in six months. Aerodynamic concepts take shape in March, construction begins in September and the car begins track testing in January. During the concept meeting, designers first identify an efficient aerodynamic shape, taking into consideration F1 regulations, cooling, weight distribution, and packaging of the engine. Coordination is essential as work begins on the many subsystems.

Design meetings are regular and generally take place during a live CAD session. All design teams members are present, and the CAD model is projected onto the wall. Designers take turns in the "hot seat," says Nevey. "The hydraulics designer will sit at the keyboard and drive the CAD session for a while as he talks about his part, and then the guy who's doing the cooling installation takes his turn."

Jaguar manufactures 100% of its chassis in house. Unigraphics updates tool paths automatically when there's a change in the CAD model. The manufacturing group can get to work on machine tools while the designer squeezes in last-minute iterations. The designer may run another structural analysis and realize he can make a pocket bigger to reduce the weight of the part. "The more iterations you can consider, the more optimized the component is going to be and the faster the car will be," Nevey says.


Brains before brawn: Fronting Jaguar Racing's new engineering-led philosophy is Tony Purnell, head of Ford's Premier Performance Division, the group that includes Jaguar Racing, Cosworth Engines and Pi Research.

Winds of Change

For its first two years in F1, Jaguar relied on the Ford-owned Swift wind tunnel in far-away California. On top of the time difference and the logistical nightmare of having to ship engineers and parts halfway around the world, testing was limited to only two weeks a month. Last year, Jaguar opened its own wind tunnel facility in Bicester, England, only 30 miles from the Milton Keynes factory. Now, the team tests 16 hours a day, six days a week, with plans to move to full 24-hour-a-day operation. Controls for the tunnel are supplied by Pi Research. The R4 is the first car designed using the Bicester wind tunnel.

Among other purposes, windtunnels are used to identify aerodynamic factors in the battle between downforce and drag. To test components, Jaguar uses a 50% model of its racecar. It will produce eight or ten variations of parts and sequentially test each to acquire data on the most aerodynamically efficient. To vary ride height conditions, the car is suspended by a pillar from the ceiling.

"Wind tunnel testing is an interactive process," stresses Nevey. It's not uncommon that in the midst of testing, an engineer will get a light-bulb idea for a new configuration, which he'll want to test immediately. With the wind tunnel nearby, he can have the part in his hands the next day.

Realizing it has to keep pace with the increased demand for prototypes at the tunnel, Jaguar purchased two stereolithography machines from 3D Systems. To keep up with the prototyping machines, designers produce a generic version of a part in Unigraphics and update thickness, trim, or angle, parametrically to create the variations.

And to complement wind tunnel analysis and give engineers a head start on physical prototypes, Jaguar uses Fluent CFD analysis software.





Building a WInner: engineering tools are useless unless you correlate them with measurements directly from the car, says Steve Nevey, computer-aided engineering guru for Jaguar Racing, shown here at his desk. Below is a CAD image of a Formula One rear suspension.

Whole Lotta Shakin'

Racecars can bounce about violently during a race and even become airborne if they hit the right curve or a bump. With the wheels in the air, control is lost and the engine can't do its job of moving the car forward. To set the spring and shocks properly and get the best grip for the tires, the physical dynamics team hoists the car on a Servotest (www.servotest.com) seven-post shaker rig. One hydraulic ram goes onto each wheel, simulating bumps along the course, and three others go underneath the car to simulate aerodynamic down force. The shaker rig can simulate the surface profile of any track on the F1 circuit.

Complementing the 7-post shaker, the team also uses ADAMS software for virtual physical dynamic simulation of the CAD model.

Keeping the wheels "planted" and pointing in the same direction is another concern. Too much flex or bend in the chassis can prevent that. To compensate for elasticity in the car, engineers put the car on a compliance and kinematics testing rig to test the stiffness of the chassis and movement of the suspension. The machine applies pressure to the wheel hub to simulate loads under race conditions. With the car stationary on the test rig, engineers can measure the deflection of suspension parts and adjust them accordingly.

"Everything on the car has an inherent compliance and will twist or bend, maybe only minimally, but ultimately, it will affect the way the car handles," says Nevey.

Testing doesn't stop when the race begins. In the two weeks between races, the team takes the car to the track to determine the best set up. These include wing balances, tire pressures, brake coolant-the carbon fiber brakes only operate in a certain temperature range-and suspension configuration. Engineers can modify the suspension in all sorts of ways, according to Nevey, making it stiff or soft, letting the car roll side to side or not.

On the track, the car becomes a rolling source of data, with 250 different sensors. Along with engine functions, the sensors monitor fluid temperature and pressure, suspension movement, and stresses. Lasers measure ride height and strain gauges measure the compliance of suspension components. An onboard computer system collects the information and transmits vital signs by radio signal back to the garage. Engineers use MatLab for data analysis.

During the March 23, 2003 Malaysian Grand Prix, radioed sensor readings indicated that the engine oil pressure of driver Mark Webber's car had dropped dangerously low. The car was pulled out of the race before the engine expired, ultimately saving Jaguar a costly engine rebuild.

Jaguar doesn't expect to find glory overnight. It acknowledges that the R4 is unlikely to be a race-winning car. But then again, Nevey doesn't see the racecar as Jaguar's real end product. "It's more like a prototype that we develop for twelve months. If we do have an end product, it's knowledge and intellect. We develop that week by week, month by month, year by year. That's what allows us to move forward and, really, the racecar is just a manifestation."

RPN users take note

RPN users take note

Concerned that you'll never be able to replace your HP 41C when it finally craps out? We were, too. Until we found out about calculator emulators for the PC. As one engineer says, "I just pop the 41CX up on the screen, load my old program files written in the standard HP language, and voila!" Check it out at www.hpcalc.org/hp48/pc/emulators/.

Open door policy stays open

Open door policy stays open

Southco (www.southco.com) has come out with a hands-free way to keep open doors in place. Its new constant-torque friction hinge, developed in partnership with Reell Precision Manufacturing (www.reell.com), provides constant torque through a 270 degrees range of motion. This single component avoids the need for separate door positioning devices. The hinge is available in two standard sizes with four constant-torque options each. Each hinge comes in two standard finish options: black powder coat or brushed zinc.

Two-in-One Special

Two-in-One Special

Maybe they should call themselves The "A" Team.

While adopting that moniker is not really in their plans, CAD developer Alibre (www.alibre.com) and FEA developer ALGOR (www.algor.com) are billing their recently announced software-bundling agreement as a major offensive. They say they want to expose as many engineers as possible to 3D design.

But just as important, the partnership is giving birth to a support system that promises to give users of both companies' products guidance on how to use the software to improve their flexibility, better visualize concepts, solve problems, and optimize designs.

As new partners, the two companies are bundling their software to give Alibre users an opportunity to perform first-pass analyses on their designs, and to give ALGOR customers 3D solid modeling, data sharing and management, and real-time design.

As part of the relationship, the Alibre Design Professional product will include ALGOR DesignCheck as an add-on. ALGOR, for its part, will bundle Alibre Design Basic with all core software licenses. ALGOR customers can also purchase Alibre Design and Alibre Design Professional directly from ALGOR.

That part of their new relationship puts them in line with a trend toward cooperative agreements that's been common in engineering software for several years. For example, analysis-software provider MSC.Software (www.mscsoftware.com) has launched a line of embedded simulation products for IBM/Dassault Systemes' (www.3ds.com) CATIA Version 5i software platform. SolidWorks' (www.solidworks.com) close working relationship with SRAC, developer of COSMOS analysis software, led to the acquisition of SRAC. And PTC (www.ptc.com) recently announced it is integrating Adobe Acrobat into Windchill Product View, its visualition tool for product lifecycle management.

But the extra dimension in the Alibre/ALGOR partnership is in the support, the companies say. Any user of Alibre Design Professional can directly contact live representatives of either company for support and technical guidance through the Alibre Assistant feature or the ALGOR Assistant feature. Both are totally integrated into Alibre Design Professional. The capability is also available to engineers who have not yet purchased the software so they can ask questions before the sale.

Regular communication

"This is more than a simple partnership," says ALGOR Engineer Bob Williams. "Our development teams will communicate with each other as we develop additional features for each product. While we each will look for additional partners, we won't be working with the other's competitors."

"This relationship changes the market," says Alibre President J. Paul Grayson. "Until now, most designers have been unable to justify purchasing FEA software, and most analysts couldn't afford to pay for 3D solid modeling software that wasn't their primary tool."