Sensors

MTS introduces hydraulic cylinder position sensors

2006-10-23T12:21:00.000-05:00

Building on its Temposonics MH position sensor, MTS Sensors has now introduced what it calls a comprehensive line of mobile hydraulic position sensors.

Beginning with an enhanced version of the existing MH sensor, the M-Series sensors family will also include products designed for smaller diameter cylinders such as those less than 1.5 in., as well as a new sensor for applications requiring extended performance and features, such as programmable velocity outputs.

The M-Series sensors family will allow a broader array of on- and off-highway machinery to capitalize on the increased reliability and reduction in service costs realized from the use of Temposonics linear position sensors.

"By offering an entire family of sensors for mobile equipment applications, machine OEMs and cylinder suppliers now have additional options for position and velocity feedback, allowing them to further optimize the cost and performance of their next generation machines," said Drew Smedley, director of global marketing for MTS Sensors Division, Cary, N.C.

First in the fanny of mobile hydraulic position sensors, the MH sensor has been enhanced with a number of new features. Designed for 2 in. diameter cylinders (or larger), the MH sensor now provides a measuring range of 2 to 78 in., doubling the available stroke length while maintaining high levels of accuracy and repeatability, the company said.

The new MH sensor provides three position output options: 0-5 V, 4-20 mA, or PWM (16 recirculations). It is also available with a simultaneous velocity output for more precise closed loop control capability. The MH sensor operates from 104[degrees] to 219[degrees]F, and can be purchased with either individual wire or cable connection options that are compatible with typical mobile equipment electrical connector requirements, Smedley said.

The M-Series sensor family is designed for "embedded" application inside hydraulic cylinders, creating minimal impact on the cylinder installed envelope. Smedley added that the M-Series sensors are specifically designed and tested to the stringent shock, vibration and electromagnetic immunity specifications of the on- and off-highway machine industries and meet ISO 14982 standards for agricultural and forest machines, ISO 7637-0/1/2 standards for road vehicles, and are CE certified.

COPYRIGHT 2005 Diesel & Gas Turbine Publications
COPYRIGHT 2005 Gale Group

Engine controls: pressure sensors

2006-10-10T09:41:00.000-05:00

IN AUTOMOBILES, pressure sensors are used in the engine, transmission, air conditioner, some brake and suspension systems, and even inside the tires. There are several types of pressure sensors, but the most common is the strain gauge. A set of four resistors is mounted on a diaphragm and connected in a square series circuit known as a Wheastone bridge.

A constant input voltage is applied across two opposite sides of the bridge. Voltage output is measured across the other two sides using a differential amplifier, a device that emits an output signal only when the inputs are unequal. At rest, the resistance in the whole circuit balances the voltage, so output voltage is zero. When the diaphragm is distorted, resistance increases across one leg of the circuit and decreases across the other leg. This imbalance causes the output voltage to change in direct proportion to changes in circuit resistance.

There are several different types of strain gauge, but none have electronic resistors like those used on circuit boards. The traditional thick-film pressure sensor has tiny wires of specific length and cross-section that create an exact level of resistance.

These "calibrated resistance" wires are printed on a film that's often bonded to a ceramic substrate. In the center is a slight air bubble between the film and substrate. The film acts as the diaphragm and the supporting substrate limits the diaphragm's full-stroke deflection to prevent "blowouts." The bubble might be only a few square millimeters and total deflection might be only a few times the film's thickness. Still, it's fairly hardy and has enough resolution to read mid-range pressures.

Semiconductor pressure sensors are becoming more common, especially for reading very low pressures in harsh environments. They work the same as a film-type, but the diaphragm is a computer chip, which is really a multilayered silicon wafer. The Wheastone bridge is made by etching away layers of material to calibrate the chip's resistance to the correct levels and in specific "directions." Layers on the chip act as the diaphragm, and though only a few microns--hundred thousandths of an inch--thick with miniscule movement, its sensitivity and accuracy are better than film types, and it's smaller but far more durable. They are typically used in tire pressure monitors and manifold absolute pressure (MAP) sensors that are mounted directly on the manifold.

High-pressure applications, such as common rail fuel injection, require something more robust. Strain gauge sensors with spring steel diaphragms are common, but piezoelectric sensors are being developed that can withstand even higher pressures and extremely harsh environments. Piezoelectric sensors use a special crystal that emits its own voltage when pressure is exerted upon it. For more information, see the article about piezoelectric injectors in the August 2004 issue of Motor Age. Today they're more likely to be used as a switch rather than a sensor that reports an actual measured value, but amplifiers are being developed that can enhance the accuracy and resolution of their signals.

There are three different types of pressure measurement: gauge, absolute and differential. Gauge pressure is calibrated against atmospheric pressure, so it's a measure of pressure that's greater than atmospheric pressure. Absolute pressure is calibrated using a total vacuum as zero, such as a MAP sensor. When an engine is running and the throttle is closed, pressure in the manifold is below atmospheric but still above a total vacuum, so absolute pressure in the manifold is greater than zero. Differential pressure is nothing more than measuring the difference in pressure on either side of a sensor diaphragm.

Each of these measurements requires a slightly different sensor housing. In a MAP sensor, the space behind the diaphragm is evacuated and sealed, and atmospheric pressure pushes the diaphragm to its full deflection. Only reducing the pressure below atmospheric will cause the diaphragm to move. In a gauge pressure sensor, the back or non-pressure side of the diaphragm is open to the atmosphere. The diaphragm might be able to deflect in both directions, but it's usually only accurate in one direction.

A differential pressure sensor is connected to a pressure source on both sides of the diaphragm and is therefore calibrated to accurately measure pressure (diaphragm movement) in both directions. It's typically used to measure flow. For instance, Ford's Differential Pressure Feedback EGR (DPFE) sensor measures the flow through the EGR system by measuring pressure in the tube on both sides of an orifice. As gas flows through an orifice, pressure measured close to the downstream side will be lower than the upstream side. The faster the flow, the greater the pressure difference.

Most automotive applications involve harsh chemicals, big temperature changes and sometimes very small pressure changes which can be a challenge to measure accurately under severe conditions. For instance, a MAP sensor must withstand vibration and fuel vapors, operate reliably at -40[degrees]F and at 250[degrees]F, and it must accurately report a pressure change of only 1 inch of water, about 0.0036 psi.

Pressure sensors have come a long way since the steam gauge, but if you read about how they're used in robotic manufacturing, you'll see that their evolution is just beginning.

COPYRIGHT 2005 Advanstar Communications, Inc.
COPYRIGHT 2005 Gale Group

Color, high-resolution enhance vision sensors

2006-09-21T10:14:00.000-05:00

Two new sensors feature enhanced color vision and high-resolution capability. The In-Sight 5100C is designed to perform a range of color inspection tasks and can verify the color of packages. The In-Sight 5101 is a high-resolution (1024 x 768) version of the 5100 for high-accuracy gauging applications requiring increased resolution for inspecting small objects, or capturing images of larger parts.

Cognex Corp. 508-650-3000; www.cognex.com

COPYRIGHT 2004 Stagnito Communications
COPYRIGHT 2005 Gale Group

Burner-assisted DPF overcomes cold-temp, [NO.sub.2] limitations - diesel particulate filter

2006-09-13T13:06:00.000-05:00

San Diego--A fuel-burner-assisted system for regenerating a diesel particulate filter (DPF) not only overcomes problems with "too cold" duty cycles for "passive" DPF systems, but also avoids "[NO.sub.2] slip" problems with systems using nitrogen oxides (NOx) to regenerate catalyzed DPFs.

The system, first developed in the 1990's in Germany by ArvinMeritor partner Zeuna Staerker for low-temp/low-load applications such as garbage trucks and street sweepers, might enjoy a renaissance due to the growing need for DPFs in wider diesel applications. Both retrofit and original equipment maker (OEM) applications are seen.

Example: Euromot and Engine Manufacturers Association (EMA) just released a research report (see Diesel Fuel News 9/30/02, p7) that terms burner-assist as the "ideal" system universally applicable for non-road engines that can't be 100% assured of high-enough-temperature duty cycles for "passive" DPF regeneration.

Now, Zeuna Staerker and ArvinMeritor see potential for the burner-assisted DPF to compete with "passive" DPFs not only on total life-cycle system costs, but also for potential integration with NOx traps.

The system taps a small amount of compressed air typically found on heavy-duty diesel vehicles (for air brakes) to atomize diesel fuel for the burner. Additional air is injected via a pump to ensure soot-free, oxygen-rich combustion in a burner just upstream of a DPF.

A carefully programmed electronic control unit (ECU) and pulse-width modulation ensure the correct temperature window for DPF soot oxidation, while avoiding runaway exotherms that could crack or melt a DPF. This is achieved "irrespective of the exhaust gas temperature and the delivery rate" of exhaust through the DPF, the researchers explained in a paper (SAE 2002-01-2787) to Society of Automotive Engineers Powertrain & Fluids conference here.
This scheme also allows the use of a lower-cost cordierite DPF, described here as a "robust cordierite" variant that's "more exotherm-tolerant."

In tests for the "VERT" DPF certification process (see Diesel Fuel News 10/28/02, p15), the system developers put this new cordierite DPF under "worst-case" conditions at idle, when low exhaust flow minimizes heat transfer from a DPF undergoing soot oxidation.

The burner control program can be altered to dampen such exotherms by reducing fuel injection quantity.

The system also employs backpressure sensors to avoid soot over-loading. A fast heat-up rate allows DPF regenerations of only a few minutes, rather than hours as can occur with "passive" catalyzed soot filters. Resulting fuel penalty is typically less than 2%.

Recent initiatives to reduce total system cost include moving the ECU development work in-house, slashing the control-box size, and employing a relatively low-cost cordierite DPF substrate.

Fleet testing of the latest burner-DPF system is now in progress in Europe and further tests are now being planned for North America. VERT certification of the product is expected early in 2003.

Future research on possible combined burner-DPF/NOx trap systems are under investigation.

COPYRIGHT 2002 PBI Media, LLC
COPYRIGHT 2004 Gale Group

Temperature Sensors utilize thin film technology

2006-08-21T09:55:00.000-05:00

RoHS compliant, miniaturized Platinum RTD Series 700 is produced in Class 1000 clean room using vapor deposition, photolithography, and etching technologies. Featuring linear resistance, sensors come in leaded and SMT configurations in both DIN A and DIN B tolerances, and are suitable for use in HVAC, electronic assemblies, process control, appliances, automotive, and instrumentation.

********************

Thin-Film Sensor Technology Results in an Economical and Stable Miniaturized Sensor with Enhanced Accuracy

FREEPORT, Ill., October 21, 2005 - Honeywell [NYSE:HON] Sensing and Control announces the introduction of the 700 Series Platinum Resistance Temperature Detector (RTD) Temperature Sensors to its existing family of temperature sensors. Miniaturization is a key element to this series allowing quicker reactions and response times to temperature changes for many demanding applications. Thin-film technology increases the 700 Series' design flexibility by providing a high level of interchangeability as either a basic component or as custom-specific assemblies.

The sensors are produced in a Class 1000 clean room using state-of-the-art vapor deposition, photolithography and etching technologies that provides an optimized environment to manufacture a sensor with reliable performance and improved longevity. "With the 700 Series, Honeywell Sensing and Control can offer a leaded device that is more rugged and durable and can be handled more easily than RTDs with ribbon leads which are often fragile and easily damaged," said Chris Gauthier, senior product marketing manager.

700 Series sensors offer excellent stability and reliability featuring linear resistance, wide temperature ranges, leaded and SMT (Surface Mount Technology) configurations in both DIN A and DIN B tolerances and are potentially suitable for use in HVAC, electronic assemblies, process control, appliance, automotive and instrumentation applications.

The 700 Series is RoHS (Restriction of Hazardous Substances) compliant.

For more information, please contact us at www.honeywell.com/sensing/promo/pr700 or call us at 800-784-3011 (reference code 700).

Honeywell International is a $26 billion diversified technology and manufacturing leader, serving customers worldwide with aerospace products and services; control technologies for buildings, homes and industry; automotive products; turbochargers; and specialty materials. Based in Morris Township, N.J., Honeywell's shares are traded on the New York, London, Chicago and Pacific Stock Exchanges. It is one of the 30 stocks that make up the Dow Jones Industrial Average and is also a component of the Standard & Poor's 500 Index. For additional information, please visit www.honeywell.com

COPYRIGHT 2006 ThomasNet, Incorporated
COPYRIGHT 2006 Gale Group

A different view: accepted vision sensors have a new competitor: an inexpensive silicon-based 3D vision chip

2006-08-03T10:12:00.000-05:00

There is a basic reason most advanced safety systems appear in an OEM's most expensive vehicles first before migrating slowly through the rest of the lineup: Cost. Not only do new technologies cost a lot to develop, the technologies necessary to make them work as advertised don't begin to drop in price until volumes rise and less expensive alternatives are introduced.

This is true of automotive vision technologies, and is one major reason safety systems like Adaptive Cruise Control (ACC), Lane Departure Warning (LDW), Park Assist (PA), Lane Change Support (LCS), and others have been slow to make it from the lab to the road--or from the top of the line to the bottom. Especially since the systems, as currently configured, have sensing requirements just different enough to demand their own sensor array. That may be about to change.

The engineers at Canesta, Inc. (Sunny Vale, CA; www.canesta.com) think they have a solution to that problem, a 3D vision chip that can both identify objects and determine their range; one that will perform the functions of more expensive sensors, but add the additional functionality of being able to determine the closing rate of an object in its view. "The long-term vision," says Jim Spare, v.p, Marketing at Canesta, "is to have a sensor in the front, one in the back, and one on either side of the vehicle performing multiple functions for the vehicle's safety systems." The potential to cut cost by removing redundant hardware is seductive, especially since this module will cost somewhere between $5 and $50 each, versus as much as $300 for a single radar unit. This means an OEM or supplier could use up to six CanestaVision units for the price of one high-end radar sensor, thus greatly increasing the chance that advanced safety systems will proliferate.

The heart of the unit is a CMOS chip with a lens that focuses infrared (IR) light--from a light source located in the module or mounted remotely--onto it. The light source is turned on and off at a very high rate, and the distance traveled is measured at each pixel on the chip. This information is processed at a nominal 60 frames per second (full-motion video requires 24 frames per second), and the phase delay information is measured in picoseconds between pixels.

The ability to do the light demodulation/phase detection calculations in the hardware is the key innovation. "Each pixel has two gates," says Spare, "and we read the differential voltage between them, which allows us to create a 3D image with range information." Information that also can be used to create 3D images for security or navigation systems.

Spare claims each of the major automotive suppliers and a few OEMs already have bought development kits--a 2-in. by 4-in. module containing the CanestaVision chip and integral 3D camera--and the software that allows the developer to begin creating a 3D-enabled system. This device is the basis of the third-generation chip Canesta expects to supply for model year 2009 vehicles. Bumper-mounted ultrasonic parking sensors--which are easily damaged--are an early candidate for replacement, as are the radar units used in Adaptive Cruise Control and Lane Departure Warning systems. "From there," says Spare, "it's up to the imagination of the OEMs and suppliers."

 THE DATA FUSION ROADMAp

Passive Systems Active Systems Phase O: Restraint Enhancement Longitudinal Enhancement Front and Side Impact Airbags Traction Control (TCS) Automatic Cruise Control (ACC) Phase 1: Protection Enhancement Cornering Enhancement Rollover Protection Body Control Systems Occupant Sensing & Adjustment Roll Control Electronic Stability Control (ESC) Steering Assist Phase 2: Advanced Adaptive Approach Ride & Handling Enhancement Active Control Belt Retractor Parking Assist Advanced Occupant Sensing

Follow/Stop ACC Restraint Response Tailoring Rear Wheel Steer
Suspension Control
Integrated Vehicle Systems Phase 3: Enhanced Safety Systems
Highly Reactive Vehicle Control Anticipatory Crash Sensing
Lane Change Support Pedestrian Protection Lane Keeping
Collision Warning/Stop & Co ACC

RELATED ARTICLE: THE DATA FUSION REVOLUTION
Data Fusion is the next frontier for safety technology and a potential growth segment for suppliers who can supply the hardware and integration expertise that allows passive and active systems to work together. "Active and passive safety are converging as we interlink these systems to provide greater benefits than are possible if we deal with them as stand-alone products," says Phil Cunningham, director, Product Planning and Business Development, TRW Automotive (Livonia, MI; www.trw.com). The reasons are quite simple. First, as sensors proliferate around the vehicle, the data created can be used by other safety systems to prepare for, mitigate, or avoid a crash situation. Second, the limitations of passive safety systems are being reached and their cost-effectiveness is falling rapidly. Third, linking the systems reduces the societal cost of accidents, and may reduce insurance rates over time. Fourth, though the number of deaths per 100 million vehicle miles traveled continues to decline, the total number of traffic deaths remains stuck between 40,000 and 50,000 deaths per year. "The next level of value will come from systems that work together," says Cunningham. "The things that we can accomplish through data fusion--allowing sensors and systems to communicate with each other to provide the best response to a situation--are limited only by our imagination."

By Christopher A. Sawyer, Executive Editor

COPYRIGHT 2006 Gardner Publications, Inc.
COPYRIGHT 2006 Gale Group

Proximity Sensors offer sensing distance of 5 mm

2006-07-25T10:48:00.000-05:00

Offered in 4 mm and 5 mm unshielded versions, Mini Inductive Proximity Sensors are suited for small part detection where miniaturization is required for tight, difficult-to-install situations. Applications include robotic tooling and automated assembly systems in semiconductor, medical, and electronic industries.

********************

FLORENCE, KY (April 2006) - Balluff has expanded its line of long-range mini inductive proximity sensors to include 4mm and 5mm unshielded versions. These new sensors set a new world standard in sensing distance for their size - out to 5mm - the equivalent range of an M18 sensor three to four times larger. As extensions of a line that includes a 3mm sensor with unmatched 3mm range, these new sensors allow the use of significantly smaller sensors that save space, but do not sacrifice sensing range. This translates to a greater degree of functional reserve and greater reliability. Principal applications center on small part detection where a high level of miniaturization is required for tight, difficult-to-install situations, such as robotic tooling and automated assembly systems for the semiconductor, medical and electronic industries.

Balluff Inc., the U.S. subsidiary of Balluff GmbH & Co., Neuhausen, Germany, is a leading manufacturer of a wide range of inductive, optical, capacitive and magnetic sensors as well as linear position transducers and ID systems. Balluff products for OEM and factory floor solutions are used to control, regulate, automate, assemble, position, and monitor manufacturing, assembly, and packaging sequences for industries including metalworking, automotive, plastics, material handling, wood processing, aerospace, electrical, and electronics.

Editors: please contact Tom Draper, Manager, Marketing Programs (1 800 543-8390) for clarifications and additional information.

Direct reader service inquiries to:
Tom Draper
Marketing Programs Manager
Balluff Inc.
8125 Holton Drive
Florence, KY 41042

In Canada only, contact Norman J. Clarke, VP & Gen. Mgr., Balluff Canada, 2840 Argentia Road, Unit # 2, Mississauga, ON L5N 8G4, Phone 1-800-927-9654 or
Tel: 905-816-1494, 905-816-1411, E-mail: balluff.canada@balluff.ca

COPYRIGHT 2006 ThomasNet, Incorporated
COPYRIGHT 2006 Gale Group
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Artificial Intelligent Android Robotics and Potential Alloys

2006-07-18T11:17:00.000-05:00

Robotic engineers designing the next generation artificial intelligence androids will need to make use of new materials and potentially special alloys. These artificially intelligent androids will need to have an outer shell, which is strong but flexible. It must appear to be soft yet have the strength to protect its precious cargo inside; the brains and computer systems. Additionally the weight this saved all the exterior of the outer shell can help lower the weight overall, as the internal components such as batteries, motherboards, CPUs, transformers and power systems will indeed be heavy.

Further, the military will need agile, maneuverable and strong artificial intelligent android robots to complete its future mission to build a future fighting forces for the modern net-centric BattleSpace. Currently, systems are being devised which can supplement humans using exoskeletons, however the next generation will be fully robotic artificial intelligent android soldiers which will be deployed against the enemy. Robotic warfare is a future and it makes sense.

The money saved and training, hospitalization of casualties and salaries will be immense. Indeed, General Patton once said; Armies move on their stomachs. And thus the logistical supply chain for food, water and personal items the humans need is also very costly. All these things must be considered and this perhaps is the biggest reason for a robotic army. Even with the cost savings we must also understand that such artificially intelligent android robots will not be cheap to build or make and therefore we need to build the tough, durable and able to take rapid small arms fire. The strength of materials and the special alloys chosen are paramount. Please consider this in 2006.

Lance Winslow
Article Source: http://EzineArticles.com/?expert=Lance_Winslow

Using A Mass Air Flow Sensor

2006-07-13T09:48:00.000-05:00

USING A MASS AIR FLOW SENSOR

PURPOSE: To measure the speed of air using an automotive mass air flow sensor.

MATERIALS: Ford mass air flow sensor from newer vehicle, small fan, multimeter or computer with PSL DMM

PROCEDURE: Many newer automobiles use a mass air flow sensor for optimum fuel delivery.. A secondary school automotive shop, a wrecking yard, or your local mechanic can be a source for such a unit. We used a sensor from a 1996 Ford engine to measure the flow of air in a windtunnel.

The mass air flow sensor has 4 electrical terminals. We obtained the following data by connecting:

A - +12V
B - Ground
C - Not used
D - Signal

The DMM is connected between B and D. A car battery is connected between A and B.. A sensor has an output from approximately 0-3 V DC, depending on the flow of air through it. .

Doug Enns, KDHS 1996, borrowed a flow meter from a local company and calibrated the mass air flow sensor. The following results were obtained.

EXTENSIONS: The mass air flow sensor could be used in a small windtunnel to measure air speed.

Nanotubes make miniature gas sensors

2006-07-10T10:13:00.000-05:00

Researchers in the US have used carbon nanotubes to make a miniature gas ionization sensor. Pulickel Ajayan and colleagues at the Rensselaer Polytechnic Institute in New York state say that their detector offers a low-cost, more practical alternative to conventional ionization sensors (A Modi et al. 2003 Nature 424 171).

Every gas has a unique breakdown voltage – the electric field at which it is ionized – and ionization sensors identify gases by measuring these voltages. The concentration of the gas can be determined by measuring the current discharged in the device. However, existing sensors are bulky, consume lots of power and require “risky” high voltages to operate.

Nanotube sensor

Ajayan and colleagues made a simple discharge device in which the cathode is a thin-film array that contains billions of multiwall nanotubes. The anode is an aluminium sheet (see figure). Individual nanotubes in the film create very high electric fields near their tips, and the combined effect of all the nanotubes is to increase the overall field and so speed up the gas breakdown process. This means that the gases can be ionized at voltages that are up to 65% lower than in traditional sensors.

The researchers also found that the current discharged in the device was six times higher than in conventional electrodes, which makes the detector highly sensitive. It is able to detect concentrations of gas as low as 10-7 moles per litre. Moreover, it can distinguish between different gases in a mixture and is not affected by external factors such as temperature or humidity – unlike previous detectors.

The Rensselaer team says that its device could be incorporated into battery-operated portable sensors for use in environmental, industrial and even counter-terrorism applications. “We also intend to expand our technique to detect biomolecules, such as proteins, antibodies and DNA,” team member Nikhil Koratkar told PhysicsWeb.

About the author

Belle Dumé is Science Writer at PhysicsWeb

Image Sensor Bumping`

2006-07-06T14:17:00.000-05:00

Image Sensor Bumping

Factor 1 Inductive Proximity Sensors

2006-06-20T13:06:00.000-05:00

Standard inductive proximity sensors have already for several decades been used to detect metal, be it in a plant or on a machine. They are far from perfect, since the sensing distance varies with the kind of metal that needs to be detected.

The standard inductive proximity switches are designed for wear-free and non-contact detection of metal objects. Basically the sensing distance is related to the size, diameter and length of the sensor. When sensing different metals, ferrous and non-ferrous, the sensing distance changes. With non-ferrous metals, it is being reduced. Which causes an adjustment of the position of the sensor, in oder to be able to detect the non-ferrous metal. In other words, you have to put the sensor closer to the metal.

Factor 1 inductive proximity sensors on the other hand can detect all metals at the same distance without adjustment of their position. Fewer types can cover different applications, reducing inventory. There is also a reduction in maintenance, since you have more mounting flexibility, causing less failure.

Factor 1 sensors are inherently weld field immune. They are ideal for industries that need to sense multiple different metals in unique sensing environments, like car manufacturing plants. And last but not least factor 1 sensors are able to increase your bottom line.

Frank Heymans has been working with sensors for the last 18 years, starting in 1988. Since 1998 he has been advising sensor users on applications. Starting this 2006, he is willing to share his knowledge via his website http://askthesensorspecialist.hegatrading.com/e107/page.php?9

Fiber-Optic Ammonia Sensors

2006-06-12T10:18:00.000-05:00

John F. Kennedy Space Center, Florida

Reversible, colorimetric fiber-optic sensors are undergoing development for use in measuring concentrations of ammonia in air at levels relevant to human health [0 to 50 parts per million (ppm)]. A sensor of this type includes an optical fiber that has been modified by replacing a portion of its cladding with a polymer coat that contains a dye that reacts reversibly with ammonia and changes color when it does so. The change in color is measured as a change in the amount of light transmitted from one end of the fiber to the other. Responses are reversible and proportional to the concentration of ammonia over the range from 9 to 175 ppm and in some cases the range of reversibility extends up to 270 ppm. The characteristic time for the response of a sensor to rise from 10 to 90 percent of full scale is about 25 seconds. These sensors are fully operational in pure carbon dioxide and are not adversely affected by humidity.

This work was done by Michael T. Carter of Eltron Research, Inc., for Kennedy Space Center.

For further information, please contact:
Dr. Michael Carter
4600 Nautilus Court South
Boulder, CO 80301-3241
Tel. No.: (303) 530-0263 Ext. 113
E-mail: mtcarter@eltronresearch.com
KSC-12130

Automotive Sensors Market To Grow As OEMs Add More Electronic Features To Vehicles

2006-06-02T09:36:00.000-05:00

Automakers are installing more electronic systems to differentiate their cars from those of their competitors and to provide the comfortable driving experience consumers demand. Automotive sensors, which monitor and help control car functions, from powertrain operation to airbag deployment, will become increasingly important components in new automobiles.

New analysis by Frost & Sullivan "North American Automotive OE Sensor Market," reveals the total market reached $1.39 billion in 2000. Growth is expected to continue through the 2001-2007 forecast period. The total market comprises temperature, position, pressure, torque, motion and yaw-rate sensors. Revenues in 2007 are forecast to be $1.75 billion.

"Because of the price-sensitive nature of the original equipment automotive components market, suppliers must maximize the efficiency of their operations to remain competitive," says Frost & Sullivan Industry Analyst, Prince De. Production automation, employee training, inventory reduction, quality assurance and waste reduction programs are effective means to achieve this goal. "Finding new applications for existing technologies will help overcome price pressures," says Frost & Sullivan Industry Analyst Joerg Dittmer.

"Motion and yaw-rate sensors, which are used in stability systems, could be utilized in rollover detection and anti-theft systems. Meanwhile, sensor suppliers could find new automotive customers overseas."

Frost & Sullivan presents the 2001 Marketing Engineering Awards to companies that have worked diligently to make a positive contribution to the automotive sensor industry. These market specific awards are presented to: BI Technologies Corp., Breed Technologies Inc., Heraeus Sensor-Nite, MicroSensors Inc. and Schrader Electronics Division.

COPYRIGHT 2001 International Trade Services
COPYRIGHT 2001 Gale Group

Ultrasonic Sensors are suited for various applications

2006-05-30T11:50:00.000-05:00

Unaffected by dust, light, or color, 941-D sensors feature teach-in programming, which enables users to teach device desired position of switching outputs or limits of analog output. Products incorporate 2 switching or one analog output in limit switch-style housing with 5-pin standard M-12 connector. Additional features include epoxy heads with IP67 sealing for use in wet or difficult areas and optional hysteresis adjustment and Windows function.

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New Sensors are Easy to Install and Competitively Priced

FREEPORT, Ill., March 3, 2005 - Honeywell (NYSE:HON) today introduced the availability of the 941-D line of ultrasonic sensors. The sensors feature easy installation and teach-in programming and extend the capabilities of ultrasonic sensors into applications like level detection, PCB detection, wafer mapping, anti-collision and in general applications where space is at a premium.

The competitively priced, high-value 941-D series features longer scanning distances than inductive technology. Unlike photoelectric technology, these sensors are not affected by dust, light and color. The sensors' non-touch technology makes them generally more reliable than electromechanical sensors and more cost effective than laser technology. The 941-D teach-in properties mean the customer can "teach" the device the desired position of the switching outputs or the limits of the analog output.

"Previously, setting up an ultrasonic sensor could be technically challenging," said Honeywell product manager Adolfo Cano Munoz. "The 941-D series sensors can be easily installed and quickly set up using the new remote teach-in features. Generally speaking, using an ultrasonic sensor is no longer a specialist's job, because they are now very easy to install, similar to a proximity or photoelectric sensor."

Expected applications for the 941-D include use in tank level measurement, package filling control, metalworking, loop control, reel diameter measurement and in special machinery performing the winding, unwinding or slicing of various materials.

The 941-D series sensors feature two switching or one analog output in limit switch-style housing with a five-pin standard M-12 connector. They feature epoxy heads with high-sealing IP67 for use in many wet or difficult areas and applications with high chemical resistance. Hysteresis adjustment and Windows Function are available, often making the 941-D series sensors an excellent replacement for more expensive software programmable devices.
For more information, visit www.honeywell.com/sensing/promo/prultra or call 800-784-3011 (reference code ultra).

Honeywell International is a $26 billion diversified technology and manufacturing leader, serving customers worldwide with aerospace products and services; control technologies for buildings, homes and industry; automotive products; turbochargers; and specialty materials. Based in Morris Township, N.J., Honeywell's shares are traded on the New York, London, Chicago and Pacific Stock Exchanges. It is one of the 30 stocks that make up the Dow Jones Industrial Average and is also a component of the Standard & Poor's 500 Index. For additional information, please visit www.honeywell.com

COPYRIGHT 2005 ThomasNet, Incorporated
COPYRIGHT 2005 Gale Group

Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask

2006-05-24T09:30:00.000-05:00

Vibration of the mask against the wearer's nose warns of low oxygen pressure.
Lyndon B. Johnson Space Center, Houston, Texas

A device that generates an alarm when the partial pressure of oxygen decreases to less than a preset level has been developed to help prevent hypoxia in a pilot or other crewmember of a military or other high-performance aircraft. Loss of oxygen partial pressure can be caused by poor fit of the mask or failure of a hose or other component of an oxygen-distribution system. The deleterious physical and mental effects of hypoxia cause the loss of a military aircraft and crew every few years.

The device is installed in the crewmember's oxygen mask and is powered via communication wiring already present in all such oxygen masks. The device (see figure) includes an electrochemical sensor, the output potential of which is proportional to the partial pressure of oxygen. The output of the sensor is amplified and fed to the input of a comparator circuit. A reference potential that corresponds to the amplified sensor output at the alarm oxygen-partial-pressure level is fed to the second input of the comparator. When the sensed partial pressure of oxygen falls below the minimum acceptable level, the output of the comparator goes from the "low" state (a few millivolts) to the "high" state (near the supply potential, which is typically 6.8 V for microphone power).

The switching of the comparator output to the high state triggers a tactile alarm in the form of a vibration in the mask, generated by a small 1.3-Vdc pager motor spinning an eccentric mass at a rate between 8,000 and 10,000 rpm. The sensation of the mask vibrating against the crewmember's nose is very effective at alerting the crewmember, who may already be groggy from hypoxia and is immersed in an environment that is saturated with visual cues and sounds. Indeed, the sensation is one of rudeness, but such rudeness could be what is needed to stimulate the crewmember to take corrective action in a life-threatening situation.

The level chosen for triggering the alarm is the partial pressure of oxygen at an altitude of 11,000 ft ([asymptotically =]3.35 km). Because the response time of the electrochemical sensor is about 10 seconds, the device would ordinarily not respond to a sudden but temporary decrease in the partial pressure of oxygen. The device is equipped with a double-pole/double-throw pushbutton switch for turning on the motor temporarily so that the crewmember can verily that the device has power and the vibrations can be felt. When the alarm has been triggered by low oxygen partial pressure, cycling the same pushbutton switch causes the motor to be turned off for a short time (about 30 seconds). There is also a locking power switch that the crewmember can use to turn the device off in the event of a system failure that turns on the vibrator motor.

This work was done by Mark Kelly and Donald Pettit of Johnson Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Physical Sciences category.

Multi-Gas Detector features dual-channel sensor technology

2006-05-24T09:15:00.000-05:00

MultiPro provides real-time readings of up to 4 gases with one button operation. Backlit LCD display, mounted on front of unit, simultaneously shows readings for all gases being monitored, and both audible and visual alarms ensure safety. Unit includes O2 and LEL sensors, plus choice of either dedicated CO or H2S sensor, or Duo-Tox sensor that measures CO and H2S simultaneously. Event Logger stores max and average readings.

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-- Continues the high performance, miniature-sized and economically priced tradition of the "Pro" series.

Smithfield, RI -- The new MultiPro multi-gas detector from Biosystems provides real time readings of up to four gases with one button operation. An easy-to-read, backlit LCD display mounted on the front of the unit simultaneously shows readings for all gases being monitored, and both audible and visual alarms ensure optimum safety.

MultiPro's single "Mode" button controls all operations, including auto calibration. The unit features a Calibration Due reminder and Sensor Span Reserve indicators for predictive maintenance. For maximum convenience and efficiency, all sensors are field replaceable.

Unique dual-channel sensor technology allows the MultiPro to provide up to four channels of detection with just three sensors. The unit includes O2 and LEL sensors
The MultiPro detector offers visual and audible notification for Warning, Danger, STEL, and TWA alarms. A bright red LED alarm is visible from the top and sides of the instrument, and a two-tone audible alarm registers at 92 decibels at one foot. A vibrating alarm is included for use in high noise applications.

The MultiPro's Event Logger stores max and average readings, as well as time and duration for up to 20 events. A standard black box recorder provides over 40 hours of storage, automatically retaining the most recent calibration date and time, and can be upgraded to a full datalogger. The unit is equipped with a wireless IrDA port for communication with PCs, and is compatible with Biosystems' BioTrak(tm) software.

Constructed of a polycarbonate housing with a tough rubber overmold, the MultiPro gas detector is rugged enough to withstand harsh environments. It is resistant to Radio Frequency Interference (RFI), and complies with IEC 1000-4-3 for level 3 RFI test.

Also available with the MultiPro multiple gas confined space gas detector is an optional, software controlled, motorized sample draw pump. Powered by the MultiPro battery, the pump performs an automatic leak test before every use, and an automatic low flow alarm signals users if the pump becomes blocked.

The detector is available with interchangeable alkaline and rechargeable Lithium Ion (Li-Ion) battery packs. The alkaline battery offers 16 hours of run time, 12 hours when operating with the pump, while the Li-Ion battery runs 24 hours, 14 with pump. The Li-Ion battery recharges in less than 5 hours.

Biosystems' MultiPro gas detector comes standard with a calibration adapter and belt clip, as well as a reference manual, laminated quick reference card and training CD-ROM. The rechargeable Li-Ion version also includes a charger. Confined Space Kits and Value Packs are available.

Biosystems, LLC, a Bacou-Dalloz Company, is a leading supplier of gas detectors, respiratory maintenance equipment and other monitoring systems worldwide. Founded in 1981, Biosystems is headquartered in Middletown, CT. In 1997, Biosystems was acquired by Bacou USA, Inc. In 2001 Dalloz joined with Bacou to form the Bacou-Dalloz Group, the world leader in the design, manufacturing and sale of Personal Protective Equipment (PPE).

The company employs about 6,700 people and operates 48 production facilities. Bacou-Dalloz provides unmatched head-to-toe protection through three strategic business segments: head protection (eye, hearing and respiratory), body protection (gloves, clothes and shoes) and fall protection. Bacou-Dalloz offers a full product range aimed at the manufacturing, construction, telecommunications, medical, public services and other sectors. Its products are available from its distributor partners worldwide.

COPYRIGHT 2004 ThomasNet, Incorporated
COPYRIGHT 2004 Gale Group

Level Sensors operate in process temperatures up to 480F

2006-05-18T09:08:00.000-05:00

SHT-Series of vibrating rod level sensors are available in standard version that extends up to 7 in. and pipe-extended version that extends up to 160 in. Sensors provide point level detection in powdered, grained, or granular solids. When instrument's rod is uncovered, signal from sensor's electronic circuit excites rod that vibrates on resonance frequency of about 285 Hz. Vibration stops when rod is covered by material.

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(Lincoln, NE - February 17, 2006) A leading manufacturer of industrial level control products, BinMaster, today announced the release of the SHT-Series of vibrating rod level sensors for use in process temperatures as high as 480[degrees] degrees Fahrenheit. The sensors provide point level detection in powdered, grained or granular solids.

"This instrument allows industries with hot processing to enjoy the same reliability and precision measurement that BinMaster customers depend on for lower-temperature processes," said Todd Peterson, director of sales and marketing.

When the single rod of the instrument is not covered with product, a signal from the sensor's electronic circuit excites the rod, which vibrates on a resonance frequency of about 285Hz. When material covers the rod, the vibration stops. The electronic circuitry senses the absence of vibration and forces the output relay to switch. When product levels drop again and the rod is uncovered, the vibration restarts and the relay switches back.

BinMaster offers SHT-Series Vibrating Rod point level sensors in two versions. The standard version extends about seven inches into a vessel. The measuring rod of the pipe-extended version lengthens as far as 160 inches.

BinMaster offers a complete selection of reliable, top-quality industrial instrumentation, used worldwide for inventory management and control, including point level detection, dry flow/no flow detection, aeration, and indication of hazardous dust concentration. BinMaster instruments start or stop machinery instantly when product reaches a specified level or show whether product is flowing freely. For more information, visit BinMaster at www.binmaster.com.

BinMaster
7201 North 98th Street
Lincoln, NE 68507
Ph: 402-434-9100
Fax: 402-434-9133
www.binmaster.com

COPYRIGHT 2006 ThomasNet, Incorporated
COPYRIGHT 2006 Gale Group

Level Sensors feature output options

2006-05-16T10:06:00.000-05:00

Offered in 3A sanitary configurations, MTS Temposonics linear position sensors provide non-contact solutions with digitally based linear feedback and NEMA 4X- or IP68-rated housings. Magnetostrictive products, used for level and interface measurement, provide remote programming and diagnostic capabilities via serial communication over standard cabling. Output options include analog, digital pulse, SSI, and fieldbus outputs such as CANOpen, DeviceNet, and Profibus.

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Linear position expertise applied to liquid level installations....

CARY, N.C. (October 24, 2005) - MTS Systems Corp. Sensors Division has expanded its family of magnetostrictive level sensors by combining the MTS expertise in linear position measurement electronics with the application knowledge of thousands of liquid level installations around the world. These new level sensors provide faster response, a variety of output options, and the outer pipe and housing configurations of the company's standard liquid level M-Series.

"By marrying the functionality of both product areas, we can offer the benefits of various sensor families in one package," said Adrian Totten, MTS Liquid Level Marketing & Sales Manager. "Accuracy, repeatability, and reliability of the MTS magnetostrictive measurement, based on patented Temposonics technology, are the foundations of the new MTS level sensors."

Features of the new sensors include faster response for control, 3A (74-03) sanitary configurations, NEMA 4X- or IP68-rated housings, analog and digital output options, and level and interface measurement.

The new level sensors also provide remote programming and diagnostic capabilities, via serial communication over standard cabling, to simplify commissioning and trouble-shooting. Programming software is provided by MTS free of charge.

Compatibility with existing interface electronics is virtually guaranteed with the various outputs available including analog, digital pulse, high speed serial (SSI) and fieldbus outputs such as CANOpen, DeviceNet and Profibus.

The new level sensor is based on the proven technology behind popular MTS product lines. MTS Temposonics linear position sensors provide accurate, non-contact position sensing in a wide array of output configurations and application housing styles. Offering smart sensors with high resolution digitally based linear feedback, products with microprocessor intelligence, programming and diagnostics, as well as no-frills, low-cost sensing options, MTS' linear position sensors are ideal for today's advanced distributed control architectures.

For more information on the MTS Sensors Group and level sensing, please contact: Adrian Totten, MTS Sensors Division, 3001 Sheldon Drive, Cary, NC 27513. Phone: (919) 677-2332. E-mail: adrian.totten@mts.com or visit www.mtssensors.com.

MTS Sensors is the world leader in magnetostrictive technology. MTS Sensors is a global operation, with facilities in the U.S., Germany and Japan. In the U.S., the MTS Sensors Division has an ISO 9001/2000 facility manufacturing rugged and reliable magnetostrictive position sensors, level sensors, and mobile equipment sensors utilizing patented Temposonics[R] technology. With a strong commitment to research and development, product quality and customer service, the Sensors Division is constantly seeking ways to bring the highest value to customers.

COPYRIGHT 2005 ThomasNet, Incorporated
COPYRIGHT 2005 Gale Group

MTS introduces hydraulic cylinder position sensors

2006-05-11T09:30:00.000-05:00

Building on its Temposonics MH position sensor, MTS Sensors has now introduced what it calls a comprehensive line of mobile hydraulic position sensors.

Beginning with an enhanced version of the existing MH sensor, the M-Series sensors family will also include products designed for smaller diameter cylinders such as those less than 1.5 in., as well as a new sensor for applications requiring extended performance and features, such as programmable velocity outputs.

The M-Series sensors family will allow a broader array of on- and off-highway machinery to capitalize on the increased reliability and reduction in service costs realized from the use of Temposonics linear position sensors.

"By offering an entire family of sensors for mobile equipment applications, machine OEMs and cylinder suppliers now have additional options for position and velocity feedback, allowing them to further optimize the cost and performance of their next generation machines," said Drew Smedley, director of global marketing for MTS Sensors Division, Cary, N.C.

First in the fanny of mobile hydraulic position sensors, the MH sensor has been enhanced with a number of new features. Designed for 2 in. diameter cylinders (or larger), the MH sensor now provides a measuring range of 2 to 78 in., doubling the available stroke length while maintaining high levels of accuracy and repeatability, the company said.

The new MH sensor provides three position output options: 0-5 V, 4-20 mA, or PWM (16 recirculations). It is also available with a simultaneous velocity output for more precise closed loop control capability. The MH sensor operates from 104[degrees] to 219[degrees]F, and can be purchased with either individual wire or cable connection options that are compatible with typical mobile equipment electrical connector requirements, Smedley said.

The M-Series sensor family is designed for "embedded" application inside hydraulic cylinders, creating minimal impact on the cylinder installed envelope. Smedley added that the M-Series sensors are specifically designed and tested to the stringent shock, vibration and electromagnetic immunity specifications of the on- and off-highway machine industries and meet ISO 14982 standards for agricultural and forest machines, ISO 7637-0/1/2 standards for road vehicles, and are CE certified.

COPYRIGHT 2005 Diesel & Gas Turbine Publications
COPYRIGHT 2005 Gale Group

P&S DataCom Corp. Announces Alliance with Three Leading Manufacturers' Representative Firms in North America

2006-05-09T11:15:00.000-05:00

P&S DataCom Tuesday announced that they have formed alliances with Centaur Corp., Tech-Trek Ltd., and Electronic Sources Inc. for representation in North America.

"Centaur Corp. has a high standard in demand creation with our sales representation using a team oriented synergistic approach," said Kevin Cochran, general manager at Centaur Corp.

"This alliance will allow Centaur to provide a very effective, low-cost solution for companies that want to easily interface, monitor, and manage intelligent devices from around the world or in the next room."

Centaur Corp. is a high-technology manufacturers' representative firm serving the Los Angeles, Santa Barbara, Orange County, San Gabriel, San Bernardino and San Diego, Calif.; New Mexico and Arizona marketplaces. Centaur has earned the reputation of quality and distinction through highly technical and experienced sales personnel.

"There are so many uses for P&S' WebChip: automated maintenance and repair notification, equipment control in distance education, industrial automation, just to name a few applications," said Bill Ford, president of Tech-Trek.

"Monitoring the progress of long-distance projects and maintaining their resources is costing companies money in travel, stolen assets, and troubleshooting delays that could all be eliminated with the addition of the WebChip into their Intelligent Device's architecture."
Tech-Trek Ltd. is an electronic component sales representative company with sales coverage throughout the country of Canada. They exclusively represent some of the world's leading quality manufacturers of semiconductor and high-technology passive/electromechanical components.

"Many companies are looking for ways to increase their ROI on large equipment that they already own or lease. One way for them to reduce the cost of the equipment during downtimes or periods of low activity is to allow other companies remote usage to the equipment," said Joe Dragna of Electronic Sources.

"Other remote users could use and control the same equipment over the Internet from anywhere in the world. Thus, saving them the cost of buying their own."

Electronic Sources represents well-known companies such as Atmel, Invensys/Clarostat, General Semiconductor, United Chemi-Con and many more. Electronic Sources has offices in the two largest markets in the Northwest -- Bellevue and Beaverton, Ore. The company focuses on covering the following areas: Washington, Oregon, Idaho, Western Montana, Alaska, British Columbia, and Alberta, Canada.

"We are delighted to be represented by these three professional organizations in North America," said Yidong Zhao, vice president and managing director at P&S DataCom. "Our objective is to bring the WebChip solution to a worldwide audience through a range of traditional and unconventional vehicles that build heightened awareness for the WebChip total solution."
P&S' revolutionary technology can be widely used in building controls, security systems, computer products, communication products, factory automation, energy management, medical electronics, automotive electronics, and home appliances market segments.

Applications for the technology are virtually endless: any situation where it would be beneficial to manage and interact with an Intelligent Device (any device with at least one MCU) in a business, vehicle, or home from a worldwide remote location.

They vary from the simple time-saver, such as utility companies checking the status of remote sites and performing maintenance tests; to functions such as automobiles automatically reporting a malfunction or breakdown and being directed to a nearby repair shop; to even more critical functions such as health centers monitoring people's health conditions through a wrist watch-type device.

P&S DataCom has invented a simple, low-cost connectivity solution that allows any existing MCU-based Intelligent Device to be easily connected to the Internet through the WebChip(TM) Module and any Open System Gateway.

The solution includes WebChip(TM) firmware and hardware, MCUnet(TM) and MCUap(TM) protocols. The major functionality of the P&S WebChip(TM) is to turn data related to various intelligent device activities and tasks into objects and map them through different communication interfaces between the Intelligent Device and the Internet.

MCUnet(TM) works like the Rosetta stone to allow any Intelligent Device to seamlessly communicate with P&S' WebChip(TM) through industry standard SPI or I2C interface. MCUap(TM) is P&S' other protocol that allows the WebChip(TM) to talk to any Open System Gateway through nearly all physical links such as RS-232, RS-485, modem, USB, 900MHz, Bluetooth, Powerline, and CAN.

The WebChip(TM) Solution will provide users with an easy upgrade to any Intelligent Device, simple and fast to develop and install. The solution is also client application, operating systems, platform, communication protocol, and MCU independent.

Combining WebChip(TM) Development Kits with ProSyst software, MCU developers can now design Intelligent Device products for ubiquitous worldwide remote access, monitoring, and supervision with easy design, user friendly software.

COPYRIGHT 2001 Business WireCOPYRIGHT 2001 Gale Group

Sensors - O2 Sensors

2006-04-25T09:22:00.000-05:00

Sensors - O2 Sensors

Sensors - Current Sensors

2006-04-25T09:17:00.000-05:00

Sensors - Current Sensors

Sensors - Torque Sensor

2006-04-10T10:40:00.000-05:00

Sensors - Torque Sensor

Sensors - Inductive Proximity Sensors

2006-04-06T23:02:00.000-05:00

Sensors - Inductive Proximity Sensors

Sensors - Level Sensors

2006-04-04T21:40:00.000-05:00

Sensors - Level Sensors: "Level Sensors"

Combining low-cost inertial systems with GPS: applications for general aviation

2006-04-03T14:49:00.000-05:00

THANKS TO THE DEVELOPMENT OF MICROMACHINED SENSORS, the cost of some fairly sophisticated three-axis inertial navigation systems has dropped to a level where they can be seriously considered for use in a variety of demanding civil applications, including general aviation.

Inertial systems have been used on commercial and military aircraft as primary navigation instruments for many years but these systems are very expensive and out of reach of most of the general aviation community. Low-cost inertial systems coupled with GPS could benefit general aviation in a number of ways, including: their use in attitude and heading reference systems (AHRS) for advanced perspective displays; aiding of GPS receiver code- and/or carrier-tracking loops to increase interference margins; bridging over short-term GPS outages; and as a stand-alone navigation system after the loss of GPS. However, the errors produced by low-cost inertial systems need to be carefully assessed and contained if these applications are to see the light of day.

In this month's column, Drs. Andrey Soloviev and Frank van Graas of Ohio University's Avionics Engineering Center in Athens, Ohio, discuss the potential use of low-cost inertial systems by general aviation and, from a series of simulations and real-world tests, highlight the expected performance of the systems and the implementation challenges.--R.B.L.

Since November 2001, we have been carrying out a study to integrate GPS with an inertial navigation system (INS) with the aim of developing an autonomous navigation system for general aviation (GA). (General aviation is the term used to describe all aviation except government and scheduled-airline use. In addition to recreational flying, it includes flight training, shipping, surveying, agricultural applications, air taxis, charter passenger service, corporate flying, emergency transport, firefighting and more.)

The study also focuses on a U.S. Department of Transportation (DOT) action plan released on March 7, 2002, that seeks "to maintain the adequacy of backup systems for each area of operation in which the GPS is being used for critical transportation applications." This action plan follows the Volpe GPS vulnerability report that identifies susceptibility of GPS to unintentional interference caused by atmospheric effects, signal blockages from buildings, communication equipment, and potential intentional jamming.

The DOT action plan assumes two options for dealing with the GPS vulnerabilities. The first option consists of using adequate backup systems during GPS outages caused by interference. The second option is to increase the robustness of GPS to intentional or unintentional interference sources. Our work addresses both options through the evaluation of integrated low-cost GPS/INS, as well as the evaluation of accuracy and integrity performance following the loss of GPS for both low-cost and navigation-grade INS.

Our study explores the following potential GA applications of low-cost GPS/INS:

* attitude and heading reference system (AHRS) for advanced (perspective) navigation displays;

* aiding of GPS code- and/or carrier-tracking loops with INS to increase the GPS interference margin by approximately 20-30 dB to mitigate radio frequency interference (RFI);

* bridging over short-term GPS outages by using inertial navigation guidance;

* inertial coasting after the loss of GPS.

For these applications, a low-cost system is defined as an integrated system with a prospective total cost of $3,000-$5,000.

The remainder of this article evaluates the contributions of different error sources into output errors of low-cost inertial systems. We provide an error budget of a typical low-cost INS based on some evaluations we have performed. Next, we describe the enhancement of the low-cost INS accuracy performance by calibrating the INS in flight using GPS data. Finally, we consider the performance characteristics of a calibrated low-cost INS and address the feasibility of different options for the integration of low-cost INS and GPS for potential GA application areas.

Low-Cost System Performance

Our main goal in assessing the performance characteristics of low-cost inertial systems is to evaluate the influence of error sources that significantly contribute to output navigation errors.

The evaluation comprises an error sensitivity analysis for low-cost inertial sensors, analysis of sensitivity to errors in initial conditions, and consideration of sensor bandwidth requirements.

The error sensitivity analysis of low-cost inertial sensors evaluates the influence of components of sensor measurement errors for a particular inertial measurement unit (IMU). It is a solid-state, six degree-of-freedom inertial sensing system using three orthogonally mounted, micromachined quartz gyroscopes, and three high-performance linear servo accelerometers in a small, self-contained package. This IMU represents typical low-cost equipment with a projected cost suitable for GA applications (the current cost is approximately $10,000 per unit). In addition, this inertial sensor technology has been utilized in a commercial AHRS that has been certified for aviation use.

The IMU consists of two main sensor types: gyroscopes or "gyros" to measure angular rates and accelerometers to measure velocity rates. Our IMU sensitivity analysis first estimates the gyro and accelerometer measurement error components and then transforms the estimated error components into errors in navigation outputs.

Inertial sensor measurements were collected for a chosen set of motions and post-processed by initial IMU calibration procedures to estimate error components of the gyro and accelerometer measurements. Estimated sensor errors include gyro and accelerometer biases, scale factors, scale-factor non-linearities, misalignment of sensitive axes, noise, and gyro g-sensitive (that is, gravity-sensitive) bias. The IMU calibration platform developed at the Ohio University Avionics Engineering Center was used to generate motion trajectories. The IMU calibration platform provides pitch, roll, and yaw motions, with pitch and roll values varying in the range [+ or -]50 degrees, and yaw changes being continuous and bi-directional. In addition, the platform has freedom in plunge variations.

Transformations of estimated components of sensor measurement errors into navigation outputs were carried out analytically with the confirmation of analytical derivations obtained via simulation. Figure 2 exemplifies results of the gyro error analysis by representing components of gyro measurement errors (that include gyro bias, scale factor, misalignment of sensitive axes, noise, and g-sensitive bias) transformed into output position errors. The plots show standard deviation (1-sigma) position errors. Results of the gyro error analysis demonstrate that gyro biases provide the major contribution to inertial output errors. Efforts for enhancing existing low-cost gyro technologies should, therefore, focus on improving the gyro bias performance.

Figure 3 represents position errors caused by measurement errors of low-cost accelerometers. The results shown in Figure 3 demonstrate that accelerometer bias error dominates all other accelerometer error sources that include accelerometer scale factor, scale-factor non-linearities, misalignment of sensitive axes, and noise. However, accelerometer error sources are shown to be balanced; that is, the different error sources provide similar contributions to the total error.
INS output errors also are influenced by uncertainties in initial conditions (position, velocity, and attitude) as these influence the integration of gyro and accelerometer data to yield the navigation outputs. Specifically, initial tilt errors can significantly degrade INS velocity and position performance characteristics. Figure 4 shows position errors resulting from typical initial tilt errors of a low-cost INS.
[FIGURE 3 OMITTED]

In addition to sensor measurement errors and errors in initial conditions, restricted bandwidth of inertial sensors can significantly degrade performance characteristics of low-cost inertial systems. However, it is important to mention that limited bandwidth is not an important issue for low-cost accelerometers. The reason is high-frequency acceleration components are low-pass filtered by the integration of accelerometer measurements to provide velocity and position navigation outputs. Precise reconstruction of high-frequency accelerations in inertial algorithms is not required. Contrary to low-cost accelerometers, bandwidth limitations can be critical for processing outputs of low-cost gyros. Methods used to process gyro measurements need to be capable of reconstructing high-frequency coning motion components to ensure accurate computation of attitude.

Flight data. We collected flight data to assess bandwidth requirements of low-cost gyros. Figure 5 is a photograph of the Ohio University Avionics Engineering Center DC-3 test aircraft used for the data collection.

Inertial sensor data were collected with a sampling rate of 500 samples per second. The short-time Fourier transform (STFT) was employed to analyze frequency content of the flight motion. Figure 6 shows the results of the STFT-based time-frequency analysis of the angular rate from the x-axis gyro.

Results of the time-frequency analysis shown in Figure 6 indicate the presence of vibration motion components in the frequency region of 50-200 Hz. According to the Nyquist reconstruction criterion, a gyro bandwidth larger than 100-400 Hz is required to enable reconstruction and adequate processing of high-frequency vibrations in inertial algorithms. The bandwidth of low-cost gyros generally stays in the range of 50-70 Hz. The gyro bandwidth requirement to accommodate these frequencies could be reduced through the use of vibration absorbers. Care must be taken that these absorbers do not worsen other error contributions, such as cross-axis sensitivities. We will consider the detailed investigation of vibration reduction in future research. Once the installation vibrations have been mitigated, low-cost gyros need to have bandwidths in the range of 50-70 Hz for adequate processing of high-frequency components of flight angular motion.
[FIGURE 4 OMITTED]

Table 1 summarizes the significant error sources of a typical low-cost INS based on the results presented in this section. Contributions of significant error sources into INS outputs are evaluated for different durations of INS stand-alone operations.

Calibration. Performance characteristics of a low-cost INS can improve significantly if the INS is calibrated in-flight using GPS reference data. The most effective INS calibration approach applies position changes derived from GPS carrier-phase measurements to construct precise calibration reference trajectories. Precise position changes can be derived from carrier-phase measurements of differential GPS, as well as stand-alone GPS.
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]

We simulated a particular calibration case study to assess performance characteristics of a low-cost INS, which is calibrated in-flight. The analysis of INS error sources discussed in the previous section indicates that initial tilt errors, gyro biases, and accelerometer biases provide the major contribution to INS output errors. The set of INS parameters to be calibrated in-flight includes tilt, gyro biases, and accelerometer biases. For the motion-platform simulation, the characteristics of the low-cost inertial sensor mentioned earlier were applied as follows:

* accelerometer biases were modeled as first-order Gauss-Markov processes with a standard deviation of 0.01 meters per second squared and 300 seconds correlation time;

* gyro biases were modeled as a first-order Gauss-Markov processes with a standard deviation of 0.1 degrees per second and 300 seconds correlation time;
[FIGURE 7 OMITTED]

* gyro angular noise: [F.sub.gyro] = 0.008 degrees per square-root Hz;

* gyro bandwidth: B = 70 Hz.

An initial tilt error of 1 degree was assumed. The following GPS characteristics were simulated:
* carrier-phase position changes;
* GPS update rate: 10 samples per second;
* Standard deviation of noise in GPS position changes: [F.sub.GPS] = 5 millimeters, which stays in a close agreement with results of flight tests for the estimation of position changes using stand-alone GPS.

Simulated flight trajectories incorporated circular turns in the xy-plane with a turn rate of 3 degrees per second. The inertial calibration was performed utilizing frequency domain calibration techniques.

We used the calibration case-study results to evaluate the performance of low-cost INS calibrated in-flight using GPS carrier-phase measurements. Inertial error sources mitigated by implementations of the INS calibration procedure were propagated into INS attitude, velocity, and position errors. Figures 7 through 9 show the corresponding error curves.

Evaluations indicate that without GPS calibration, gyro bias, initial tilt and accelerometer bias errors dominate the navigation performance, while after in-flight calibration with GPS carrier phase, the INS error sources are balanced. In other words, to improve low-cost INS performance beyond the results presented in Figures 7 through 9, all error sources must be improved. These error sources include calibrated tilt, gyro and accelerometer biases, gyro and accelerometer scale factors, misalignment of sensitive axes, noise, accelerometer scale-factor non-linearities, and gyro g-sensitive biases.
[FIGURE 8 OMITTED]

Integration Options
Based on the low-cost GPS/INS performance characteristics presented in the previous section, the following GA applications of integrated GPS/INS were identified: AHRS for advanced (perspective) displays; aiding of GPS code- and/or carrier-tracking loops with INS to increase the GPS tracking margin by approximately 20-30 dB to mitigate RFI; short-term continuity through INS aiding during demanding operations such as precision approach and landing; and coasting after the loss of GPS.

Integration for AHRS. Stand-alone INS for AHRS applications is an existing technology. Currently available AHRS cost $30,000 to $50,000, which exceeds feasible cost figures for GA applications. Integration with GPS could lower the cost of the AHRS through the use of less expensive sensors that are calibrated by GPS data using in-flight calibration techniques as described in the previous section. Integration of current low-cost sensor technologies with GPS could reduce the cost of AHRS applications. This integration would require GPS to be available nearly continuously. Specifically, an AHRS is generally required to maintain angular accuracy in the range of 0.1-1 degrees. For advanced displays, velocity errors should not exceed 1 meter per second. Figures 7 and 8 represent the growth of errors in attitude and velocity of low-cost INS after in-flight calibration using GPS carrier-phase measurements. The error plots demonstrate that the attitude and velocity accuracies required can be maintained if the time interval of a GPS outage does not exceed 30 seconds. If longer GPS outages are anticipated, then the AHRS would need to satisfy all requirements by itself and no cost benefits are obtained.
[FIGURE 9 OMITTED]

Inertial Aiding. Aiding of GPS code- and/or carrier-tracking loops allows for longer integration of the GPS signals, thus increasing the GPS signal energy relative to the interference source. An unaided GPS receiver typically integrates the signals for 10 to 20 milliseconds. Inertial aiding provides the reference trajectory for GPS signal integration up to a few seconds, which has the potential to increase the GPS signal energy by approximately 20-30 dB. While the GPS signals are being integrated, the inertial outputs are used for realtime guidance. For a 1-second integration of the GPS carrier signal, the frequency reference must be accurate to within approximately 0.5 Hz, which corresponds to a velocity error of less than 9 centimeters per second. As a result, the inertial reference should be designed to be accurate at the centimeter-level for 1-second coasting. With low-cost IMUs that exhibit drift performance up to several hundreds of degrees per hour, this level of performance is feasible if the IMU is calibrated using GPS carrier phase. Particularly, velocity and position error plots presented in Figures 8 and 9 demonstrate that a calibrated low-cost inertial unit is capable of maintaining the accuracy required for aiding during time intervals from 2 to 3 seconds. Note that the error plots presented correspond to 1-sigma performance characteristics. Further investigation is required to assess the integrity of inertial aiding of GPS receiver tracking loops.

Short-term Inertial Coasting. Once an INS has been calibrated using GPS carrier-phase measurements, brief GPS outages can be bridged by the INS to maintain the continuity of the GPS positioning service. Table 2 summarizes performance characteristics of short-term inertial coasting during one minute of GPS outage. The summary provided is based on inertial error growth plots represented in Figures 7 through 9.

It is noted that the performance in Table 2 is expressed in terms of 1-sigma displacement noise. Further work is required to investigate the integrity of short-term coasting applications.
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Long-term Inertial Coasting. Long-term coasting after loss of GPS is the most demanding integration application. If an aircraft operation is scheduled into an area with a known GPS outage, the inertial coasting solution must satisfy the same integrity requirements as those provided by existing navigation systems. This is an important application. In response to a Federal Aviation Administration (FAA) request, Working Group 2C of RTCA Special Committee 159 has been addressing post-GPS-calibration INS coasting performance.

The INS performance parameters used for the coasting analysis are listed in Table 3. Clearly, the parameter values presented in the table are not within the capabilities of low-cost devices either now or in the near future. Moreover, some of these values can be considered optimistic even for existing navigation-grade inertial systems. Our study provides some insight into the feasibility of coasting operations.

We have analyzed inertial coasting for terminal and non-precision approach operations. The horizontal alert limit (HAL)--the lateral position error tolerance--is 1 nautical mile for terminal navigation and 0.3 nautical miles for the non-precision approach. We analyzed two coasting scenarios. The first case study considers straight flight for which the aircraft speed is conservatively set at 180 knots. The second case study incorporates a flight profile which was developed by the RTCA Working Group with input from the FAA.
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Figure 10 illustrates the RTCA coasting profile and specifies the aircraft speed for different legs of the flight profile. The INS coasting performance must remain below the HAL at the end point of the profile.
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Three levels of integrity were considered: [10.sup.-3] (emergency applications--per event), [10.sup.-5] (per hour) and [10.sup.-7] (per hour). The coasting integrity level is defined as the probability of exceeding HAL while using inertial coasting.

The case studies assume that the inertial solution is calibrated with stand-alone GPS pseudoranges during a one-hour straight and level flight segment. A pseudorange bias of 10 meters and pseudorange noise with a standard deviation of 2 meters represent the error sources of the GPS measurements. A 15-state Kalman filter was used to estimate INS horizontal position and velocity, barometric altitude, receiver clock bias and frequency offset, attitude, gyro biases, and accelerometer biases. Figures 11 and 12 show results of coasting analysis for the case of straight and level flight. Results of coasting analysis for the RTCA coasting profile are similar to the inertial coasting performance for straight flight.

Table 4 summarizes the inertial coasting performance.
Based on the results in Table 4, it appears that INS coasting has limited application for demanding operations such as terminal navigation and non-precision approach. INS coasting could be applied to other operations, such as the guided missed approach, where coasting durations are limited to about 10 minutes. Also, if HAL requirements are at the level of 10-50 nautical miles, INS coasting also can be used, as is currently the case for primary means oceanic navigation. For GA applications in the continental United States, INS coasting applications mostly have potential for emergency procedures, but it is not feasible for scheduled operations where integrity requirements must be satisfied.

Since it was assumed that GPS only contributes pseudorange bias and noise during the calibration time interval, further work is under way to address INS calibration during GPS malfunctions.

To improve the coasting performance observed, we recommend investigations of the following options:

* reduction in errors of gravity models;

* improving the quality of the INS inflight calibration;

* enhancing characteristics of inertial sensors used for coasting.

For the particular coasting scenarios considered, the coasting performance is mainly limited by the gravity model--the description of the spatial variations in gravity. In this case, better accelerometers and gyros would not significantly improve the coasting performance. Once the reduction of gravity errors is investigated, improvements in inertial sensors should be explored. The sensor performance also can be improved by optimizing sensor in-flight calibration. Potential optimization approaches include extensive flight maneuvers to separate INS error states and implementations of advanced calibration techniques (e.g. frequency-domain calibration) to improve the calibration quality. Lastly, we recommend that a study of the feasibility of increasing the coasting duration by improving the sensor manufacturing technology be carried out.

Summary

In this article, we have evaluated the feasibility of integrated low-cost GPS/INS for several potential GA applications. We found that such a system could be used for an AHRS for advanced (perspective) navigation displays; aiding of GPS code- and/or carrier-tracking loops with INS to increase the GPS interference margin by approximately 20-30 dB to mitigate RFI; and bridging over short-term GPS outages by using inertial navigation guidance. We also investigated inertial coasting after the loss of GPS but found that long-term inertial coasting has limited applications for GA, even if navigation-grade inertial performance is assumed.
We recommend additional investigations in the areas of integrity for integrated systems, especially during coasting operations, and in the general area of certification.