Fiber optic sensors enable new MRI applications

Fiber optic sensors have become a critical technology enabler behind the latest functional MRI (magnetic resonance imaging) suite upgrades and new MRI equipment designs. It is increasingly desirable to synchronize certain patient activity with the MRI imaging system. The incredible high magnetic field strengths are increasing with each generation (3.0 Tesla being the top of the line norm today) so that the electromagnetic transparency of components become more important with each succeeding generation and new application. The intrinsic passiveness and electromagnetic immunity of optical sensors plus the all-dielectric nature of optical fiber is ideal for both sensor design and optical signal transmission in and out of Zone 4 (MRI Scanner location) of the MRI suite.
Designing equipment that can operate within the extreme electromagnetic fields present in an MRI suite is extremely challenging. The MRI suite precludes the use of conventional components and structures fabricated from ferrous-based materials, nickel alloys and most stainless steel materials – including electronics, electric motors and other electrical and electromechanical devices commonly used in the industrial world. Magnetically attracted metals – small or large - can become harmful projectiles and either damage the machine or affect patient/operator safety. Also improper materials can create undesirable artifacts or distortions which affect the quality of the imaging results.
Our central focus is the development and application of MRI compatible fiber optic sensors necessary for closing the loop - specifically for measuring position, speed and limits. In this article we present three MRI-based motion control applications which demonstrate the operation and use of recently developed, commercially available MRI safe fiber optic-based feedback sensors.
Mythbuster - fiber optics is not fragile
Although made of glass, fiber optics is not fragile! Optical fiber and cabling is designed to be strong and resistant to physical abuse – especially excess bending and high tensile loads. The military uses optical fiber in the harshest applications , including aircraft, missiles, satellites and the most hostile environments - from the desert to the arctic, from undersea to space.
It’s essentially just another type of wire – a glass wire.
What is a fiber optic sensor?
As shown in Figure 1, a fiber optic sensor is a device that alters the properties of the light passing through the device based on a physical quantity imparted on the device. In this sense, the fiber optic sensor is not a true transducer - it does not convert one form of energy into another - but is instead a “sensing element” which changes a characteristic parameter of the light injected into the sensor. Hence, a typical fiber optic sensor system consists of three parts – the fiber coupled “passive” optical sensor, the “active” interrogator or system interface, and the fiber optic light path or link that connects them. Because of its low loss and ability to transmit interference-free over long distances, the fiber optic link provides the means of locating the active interrogator/system interface outside the MRI Scanner (Zone 4) Area. Figure 1. Block diagram of a fiber optic sensor systemHow does a fiber optic position sensor work?
Typically optical power (light) is sent to the sensor where the light is being altered or changed in amplitude, wavelength, polarization, etc. Other sensors measure the time of flight of the light while the physical property changes the optical path length.
The simplest form of a fiber optic sensor is an optic limit switch where the presence or absence of an object in the light path must be determined. In this case evaluating the ON-OFF state of light is sufficient and works reliably. To the fiber optic designer it is an unfortunate reality that optical amplitude within a fiber optic link is not stable and cannot be relied on for making absolute measurements. Long term source degradation, fiber bending and fiber optic connector non-repeatability all affect optical transmission over time and environmental factors severely affect measurement accuracy. Fiber optic communication links are reliable because they transmit digital information and all receivers incorporate an automatic gain control (AGC) amplifier.
Thus, position sensors that depend on light amplitude modulation have proven to be unstable, inaccurate and unreliable. Spectral-based techniques are much more reliable because they are not affected by light intensity. Whether the light level is low or high, the spectral light distribution in the fiber remains the same. For instance, Fiber Bragg Gratings are one such technology which alter the spectral behavior but are affected by temperature – making for a poor position sensor. The key optical innovation of the Micronor MR330 series MRI position sensor is that the position information is embedded into the optical spectrum and provides accurate, high resolution position information unaffected by varying losses or degradation in the fiber optic link. Utilizing the optical spectrum as the information carrier rather than amplitude assures reliable accuracy, even when the fiber link installation is degraded.
Figure 2. Diagram of the MR338 MRI safe fiber optic absolute position sensor
As shown in Figure 3, the interrogator/controller transmits a broadband light pulse to the sensor via the input fiber. Based on the position of the rotary code wheel, the internal optics passively convert this light pulse source into a return signal transmitted over the output fiber, in which the spectral pattern is essentially a unique binary representation of the rotary encoder’s angular position. Internally, the interrogator functions like a spectral analysis system in which the optical return signal is imaged onto a CCD and the resultant spectral signature analyzed and converted to an angular position code.
Figure 3. How the MR338 fiber optic position sensor works
The second innovation of the MR338 MRI Safe Position Sensor is its fabrication from non-metallic materials so to be completely RF transparent. This was not a simple substitution of non-metallic materials versus the original MR332 “Metallic” industrial sensor design. Due to the accuracy required, the materials must be extremely stable over temperature, humidity and time. Internally the sensor accurately resolves down to 4µm thus any shift of the material introduces an error in position reading. There are numerous plastic materials that have a suitable low temperature coefficient, however, as is typical for plastics, they exhibit hygroscopic property which means they change size based on moisture content. A suitable ceramic-like material is used for alignment of the dimensionally critical optics. This part is fabricated using high precision stereo lithographic fabrication technology.
The resulting MR338 MRI position sensor system offers 13-bit (8192 counts or 0.044°) single turn resolution and 12-bit (4096 count) multiturn tracking. The same optical technique is also applied to a fiber optic linear position sensing system.

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Showcase of world's first self-powered CO2 sensor at ISH 2011

Gas Sensing Solutions (GSS) will showcase the world's lowest power CO2 gas sensor enabled by revolutionary EnOcean self-powered wireless technology at ISH 2011 - the leading international trade fair for innovative bathroom design, energy efficient heating and air-conditioning technology and renewable energies - taking place in Frankfurt, 15-19 March.

Scottish-based GSS recently joined the EnOcean Alliance as a member and will demonstrate its innovative COZIR sensor product to the building services industry for the first time on the Alliance Booth (D10, Hall 10.2). Since becoming a member, GSS has been working closely with the EnOcean Alliance and its other member companies to integrate the EnOcean Standard in its product portfolio.

Enabled by EnOcean self-powered wireless technology, the COZIR CO2 sensor works entirely without batteries and is absolutely maintenance-free. It also has very low power consumption and a fast warm-up time of less than two seconds, making it ideal for applications such as Indoor Air Quality (IAQ) monitoring, Heating, Ventilation and Air Conditioning (HVAC) systems, Horticultural and Building Control. COZIR utilises EnOcean's energy harvesting technology in which the sensor draws ambient energy from motion, light or temperature differences in its surroundings.

Using available room light to power the CO2 sensor, three readings are taken every 10 minutes and the values are sent wirelessly to a receiver, which sets an alarm to open a ventilation system, for example. When no room light is available the sensor operates on stored energy in energy storage mode, taking fewer measurements or only sending signals when critical values are measured. In this way EnOcean-enabled devices can work fully autonomously, at low cost.

The COZIR CO2 sensor incorporates a non-dispersive infra-red (NDIR) configuration based on GSS patented technology, combined with low loss compact injection moulded optics and low noise electronics. It consumes only 3.3mW in continuous operation, with two CO2 measurements per second, which is typically 50 times lower power than standard NDIR sensors. The sensor is available in three ranges: 0 to 2000ppm, 0-1 percent or 0-2 percent.

The COZIR low power consumption sensor offers many benefits compared to conventional NDIR CO2 gas sensors. Key product features include: Average current is less than 1.1mA Operating voltage 3.3V Short warm up time ( < 2secs) Power consumption = 3.3mW (continuous operation) Compatibility with EnOcean Standard wireless communications

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More Microwave Sensors To Keep Midtown Traffic "In Motion"

 The DOT's "Midtown in Motion" congestion management system will double in size, growing from a 110-block zone to a 270-block service area. The innovative system launched last July, and the DOT says it's resulted in an overall 10% improvement in travel times on the avenues. Using 100 microwave sensors, 32 traffic video cameras and E-ZPass readers at 23 intersections to measure traffic speeds, engineers in the DOT’s Traffic Management Center (TMC) have been able to spot congestion as it occurs and use "networked Advanced Solid State Traffic Controllers (ATSC) to remotely adjust Midtown traffic signal patterns" and unplug bottlenecks.

The expansion will include an additional 110 microwave sensors, 24 traffic video cameras, and 36 E-ZPass readers, and will become fully operational this September. According to an announcement from the DOT, the service area will more than double in size to include Midtown, from 1st to 9th avenues and from 42nd to 57th streets. The expansion will cost $2.9 million, with $580,000 coming from the city, and the rest from New York State. Another $2 million is being invested in 200 new ASTCs, $1.6 million of that from the Federal Highway Administration and the remainder from the city taxpayers.

The data from the sensors and cameras is transmitted wirelessly in real time to the TMC in Long Island City, where engineers make constant adjustments to traffic signals. The real-time Midtown in Motion traffic information is also available on DOT’s website, on smartphones and tablets (and is also accessible to app developers).

Midtown's bike network is also getting an upgrade as part of the DOT's bike lane expansion. The DOT plans to install four new pairs of crosstown bike lanes through Midtown; if approved, the lanes would be tightly spaced, located on 39th and 40th Streets, 43rd and 44th, 48th and 51st, and 54th and 55th. Head on over to Streetsblog for a closer look at the lanes' "odd" design.

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iPhone 7 photo sensor and less noticeable antennas?

Contrary to his habits, Apple may not be would review in depth the design of the iPhone for the next generation. In any case it indicated MacRumors citing a source who ” gave accurate information in the past .” According to her, the iPhone 7 overall resume the appearance of current models with two main differences.

The iPhone 7 would ultimately not much different from the iPhone 6 / 6S from an aesthetic point of view. The new smartphones resume the line of current models with some minor modifications. iPhone 7 photo sensor.

The first: Apple has managed to completely return the photo sensor in the chassis. The object would be perfectly flat, as the good old days of 5S and iPhone earlier. The second: Plastic covers for antennas would be less conspicuous, some would be removed to retain bands than at the border. The first involves the rear camera, which protrudes slightly on the iPhone 6 and 6s. On the iPhone 7, the camera is said to sit flush with the rear casing, enabled by a thinner camera module. Recent rumors have indicated Apple is considering equipping the iPhone 7 Plus with a dual-lens rear camera, but the smaller iPhone 7 is expected to include a more traditional camera.

iPhone 7 photo sensor? The supposed result is shown below to get an idea and frankly. We do not believe too. With iPhone sales stalled , it is hard Apple settle for that. The firm must offer something new to clients to get them to purchase. It also goes against the habits of the firm. The strategy is so well oiled, and worked so well so far it seems very difficult to change. Take your tweezers; no, your pliers. iPhone 7 photo sensor



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Combined-structure semiconductor gas sensor based on butane gas

A new combined-structure semiconductor gas sensor based on butane gas is reported in this paper. The combined structure sensor is a gas sensor that is based on the complementary feedback principle.

The sensor is composed of two sensitive materials A and B whose conductive types are the same. The materials A and B are all n-type materials. The results analysed from a theoretical viewpoint showed that the sensor had higher selectivity and better thermal stability when materials A and B satisfied certain conditions.

According to the sensor's structure and meeting conditions, we prepared the combined-structure gas sensor for butane gas. The experimental results showed that they are consistent with theoretical analysis and can be applied to monitor and control leakage of butane gas.

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A Review of Industrial Microwave Sensors

This paper reviews the field of microwave sensors. The field is broad and the applications numerous. This review will therefore only be able to present the broad outlines.

Firstly the historical perspective and the physical background are briefly described, and the general advantages and disadvantages are listed.

An overview of the various working principles of microwave sensors is given with a few examples of the applications mentioned. Important fields of applications and interesting examples are treated separately, starting with the measurement of moisture, which is the single most important field of applications in microwave sensors.

Applications in the petroleum industry are also mentioned, because they are relatively new, they play an exceptionally important economical role, and represent the field in which the author is currently working. Followed by some trends for the future.

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Characteristics of semiconductor gas sensors II. transient response to temperature change

Temperature-stimulated transient responses of the conductance of SnO₂ gas sensors, as exemplified by the Taguchi Gas Sensor (TGS), are comprehensively studied. These responses are determined at many temperatures for sensors exposed to several fixed concentrations of oxygen in nitrogen. The dynamic response of conductance exhibits complex kinetics characterized by time constants which range, depending on ambient conditions, from seconds to days.

Measurement results are analyzed in the light of a proposed model of device behavior. This heuristic model is constructed by combining some fundamental experimental observations with kinetic predictions of the barrier layer theory of adsorption. The analyses result in identification of the physical mechanisms responsible for the complex kinetics and long time constants. We find that sensor conductance is controlled by an intergranular potental barrier consequent to oxygen adsorption.

The barrier potential exhibits an Elovich-type rate kinetic and its functional dependences on sensor temperature for several oxygen partial pressures are determined. In addition, the long-term drift of the TGS results from the diffusion of a native non-stoichiometric defect, an oxygen vacancy, evoked by changes in temperature or ambient oxygen pressure.

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Microwave Sensor Applications in Industry

Microwave measuring methods can be applied to determine the properties of materials and hence it is possible to develop microwave sensorsfor processing industry. The first applications were in moisture measurement but lately many new sensor applications have appeared.

Microwave sensors especially suitable in forest industry (wood, paper), in chemical industry (plastics, chemicals), in food industry (tobacco, butter) etc. In developing sensors several problems must be solved. The dielectric properties of the material in question must be known. They can be measured or in some cases determined theoretically by applying mixing theories.

The sensor is often some kind of a resonator. Its structure must be such that the electric field penetrates the material as required, and allows free flow of material. Displacements occurring normally in the material flow or dirt in the sensor must not cause measuring errors. Several examples of lately developed sensors are given.

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Legal challenges mount against controversial breath-alcohol tester

Doubts about the reliability of a breath-alcohol tester  have undermined drunken driving prosecutions in Ohio and other states, four years after Ohio bought hundreds of the machines on the recommendation of a state official who later went to work for the manufacturer.
Several Ohio courts in the past two years have ruled that breath-test readings from the machine, called the Intoxilyzer 8000, were not admissible because of questions about accuracy or other vulnerabilities.
One such ruling in Painesville Municipal Court last summer prompted law enforcement agencies in the court's jurisdiction to stop using the device to test blood alcohol content of suspected drunken drivers. Cincinnati police last year stopped using the machine because of the high number of court challenges.
"These machines are judge and jury," Painesville Municipal Judge Michael Cicconetti said in an interview. "If you're going to do that to any defendant, that person has a basic right, a constitutional right, to have a machine that's reliable."
The Intoxilyzer 8000 is a new generation machine that uses infrared technology to measure the amount of alcohol in a breath sample. It won approval in Ohio under a cloud of controversy. The State Controlling Board in 2008 agreed to spend $6.4 million for 700 of the machines, despite the breath tester being under scrutiny in several other states because of questions about its accuracy and reliability.
The Plain Dealer reported at the time that Dean Ward, the Ohio Department of Health official who drew up specifications and recommended the purchase, was friends with the head of CMI Inc., an Owensboro, Ky., company that makes the device. Ward's specifications fit only the Intoxilyzer 8000 among 17 companies invited to bid for the contract, the newspaper reported.
Ward, the chief of alcohol and drug testing at the Health Department, said at the time that his friendships at the company had nothing to do with his recommendation.
Ward has since gone to work for CMI as a technical sales manager.
Reached by the newspaper, he declined to discuss the mounting number of court challenges.
"I can't comment on things that happened after I left," Ward said. He referred questions to CMI lawyer Alan Triggs.
Triggs said in an interview the Intoxilyzer 8000 is scientifically sound.
"It's very reliable," he said. "No one has ever proven that it's given a false reading. It's all speculation."
But judges in Ohio municipal courts, which hear drunken-driving cases, have cited several issues with the Intoxilyzer 8000. An Athens County Municipal judge said in a 2011 ruling that the device could be vulnerable to interference from smart phones. Though the judge ruled test results were admissible, he raised a number of doubts about the tester's precision. He noted expert testimony in two Florida courts that a high volume of breath blown into the device can give a false reading.
A Circleville court ruling that same year said the machine's accuracy has not been proven. The judge said an Ohio Department of Health witness failed to explain why the agency believes the machine is reliable. He ruled test results inadmissible until the Health Department can show scientific principles that support its reliability.
CMI lawyer Triggs and the state Health Department said smart phone interference is not an issue. The machine will detect cell phone interference and abort the breath test if necessary, Health Department spokesman Robert Jennings said. Triggs also dismissed claims that the test score can be inflated by the duration of the breath a person blows into the device.
Jennings said the department does not have to prove scientific reliability in court. He cited a 1984 Ohio Supreme Court ruling that said once the state sanctions an alcohol-detection machine, its general reliability is presumed. "However, upon request, ODH has provided scientific proof of the instrument's general reliability," Jennings wrote in an e-mail.
Some courts have validated the presumed reliability of the test, and said test results should not be suppressed. The 11th District Ohio Court of Appeals in Portage County last year rejected a number of challenges, and sent the cases back to the municipal court. In the case of a Rocky River woman charged with drunken driving and aggravated vehicular assault, Cuyahoga County Common Pleas Judge Brendan Sheehan in June rejected arguments that the equipment is unreliable and the test was not performed according to regulations.
Yet judges disagree on whether the 1984 Supreme Court ruling prohibits challenges of the instrument. In light of the controversy surrounding the Intoxilyzer 8000, some believe the matter is likely to wind up again before the Ohio Supreme Court.
The Health Department said its has distributed 396 machines to Ohio police agencies. Forty-three departments in Cuyahoga County have them, while some agencies use an older machine called the BAC Datamaster. The Ohio Highway Patrol uses both machines, depending on the jurisdiction, a spokeswoman said.
The Westlake Police Department is training on an Intoxilyzer 8000 it received from the state, and plans to start using it later this year, said Capt. Guy Turner. Turner questioned challenges from defense lawyers.
"Some of the things you're hearing might be sort of a smokescreen, or a red herring," he said.
Asked about court rulings that question the credibility of test results, he said Westlake and other departments are depending on Judge Sheehan's ruling in June.
"A number of agencies found that to be very comforting, that a judge found it reliable," he said.

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Recalibration technique for NDIR gas sensors without the need for gas standards

The output of nearly all non-dispersive infrared NDIR gas sensors deployed in the heating, ventilation, and air conditioning (HVAC) industry today cannot maintain their accuracy specifications within six months to a year. Consequently, all installed NDIR gas sensors must be re-checked for accuracy over time at great costs. The purpose of this paper is to advance a novel technique for expeditiously recalibrating such installed NDIR gas sensors without the need for using any gas standards.

Design/methodology/approach
By recognizing the fact that the calibration curve for absorption biased designed NDIR gas sensors comprises two distinct domains, namely an invariant NDIR absorption physics domain and a variant sensor components characteristics domain. By formulating a novel recalibration procedure which corrects only changes that have taken place in the variant sensor components characteristics domain over time, it is possible to recalibrate the sensor very rapidly and remotely via wireless or infrared means using only the gas concentration level surrounding the sensor as a reasonably accurate gas standard.

Findings
Implementation of the currently described recalibration technique to a large number of absorption biased designed NDIR gas sensors has been carried out for over a year in the laboratory. Results of these experiments have unambiguously confirmed the capability and the accuracy of this novel recalibration technique.

Originality/value
The currently presented recalibration technique for absorption biased designed NDIR gas sensors is original and has never been published elsewhere. This technique significantly reduces the maintenance costs, inclusive of labor and material, for installed NDIR gas sensors that require periodic and mandatory accuracy commissioning over time.

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Photosensors: Technology and Major Trends

Daylighting is going mainstream and daylight harvesting, the energy-saving lighting control strategy that actually makes daylighting “sustainable,” is beginning to catch up. Of particular interest is the fact that daylight harvesting is transitioning from being something encouraged by energy programs to something required by energy codes and standards—not just California’s Title 24, but IECC 2009 and, likely, ASHRAE 90-1.2010 as well. It is likely, in fact, that in the future, most commercial buildings that have windows and skylights will be required to have some type of daylight harvesting control in the adjacent area.

Daylight harvesting’s value proposition is fairly simple: As daylight levels increase in a space, electric light levels can be automatically reduced to maintain a target task light level and save energy. All automatic daylight harvesting control systems need a device that can measure light levels and signal a controller to dim or switch the lights in response to daylight contribution. This device is called a photosensor.

The photosensor is a small device that can include a light-sensitive photocell, input optics and an electronic circuit used to convert the photocell signal into an output control signal, all within a housing and with mounting hardware.

Photosensors may be mounted on walls, ceilings and even as a part of light fixtures. Fixture-integrated sensors may be installed as part of the original fixture or installed later in the field by attaching to a lamp via a clip and being wired directly to the ballast. The visible size of a photosensor ranges from a golf ball to a standard wall switch.

As daylight harvesting grows in importance, photosensors are becoming more sophisticated. But buyer beware: There is no standard defining how photosensors should operate. When selecting a photosensor, important questions to ask about a given product include: Is it compatible with the given controller? What control method does the system use? What is the sensor’s spatial response? What range of light levels can it “see”? How accurate is its signal? Is it photopic-corrected? How far is it to be installed from its controller? How is it commissioned? How many zones can it support? What are the configuration options? Is it capable of operating reliably within the given environment—heat, cold, moisture? Are there listing or compliance requirements such as UL or ROHS?

“Studies have shown the importance of using daylight harvesting strategies in commercial spaces, particularly with the growing emphasis on architectural daylighting design, but have also illustrated the importance of choosing the right product for the application,” says Daniel Trevino, LEED-AP, Daylighting Product Manager for WattStopper. “This helps maximize energy savings while avoiding user complaints.”

“Using the correct photosensor for a particular application is one of the most critical design aspects,” says Bob Freshman, Marketing Manager for Leviton Lighting Management Systems. “The sensor that is used should be appropriate for the size of the space and the environment in which the sensor is located.”

Control algorithm
Daylight harvesting controls may be “open loop” or “closed loop” systems. Each measures the daylight contribution on the task surface differently. Dual loop is now emerging as a potentially significant technology.

Closed-loop systems measure the combined contribution to light level from both daylight and the electric lighting system. Because the photosensor measures the electric lighting system’s light output, it “sees” the results of the controller’s adjustment and may make signal further adjustments based on this feedback—creating a closed loop.

With closed loop, the photosensor measures actual light levels, so it is sometimes considered more accurate than open loop, Closed loop is considered preferable by some for applications where a specific target light level must be maintained, such as small offices. But control is limited to a single zone and the system must be properly set so that transient light level changes (e.g., white sheets of paper shuffled on and off a dark desk). do not cause overly frequent dimming or switching.

Open-loop systems measure only the incoming daylight, not the contribution from the electric lighting. The photosensor should not see any electric light and therefore it is mounted outside the building or inside near a daylight aperture facing away from the controlled lighting. Because there is no feedback, it is an open loop.

With open loop, the sensor is not affected by transient light level changes but it does not measure actual light levels. This means that a sensor placed outside a window would not know that the blinds were closed, and dim the lights inside anyway. As a result, open loop is often preferable for applications where accuracy is less important, such as hallways and atria.

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Microwave Sensors vs Infrared Sensors

 Automatic lighting controls work by sensing when an area is occupied, the level of daylight or both. They then switch lighting on or off or dim the level.
There are two main ways for sensors to detect when an area is occupied:
Microwave sensors transmit an inaudible microwave and monitor reflections from walls or objects in the room irrespective of heat or light. Line of sight issues do not affect microwave sensors as any movement of solid objects changes the pattern of the reflections and activates the sensor.
Key points:
• Activated by motion – speed and size not heat and light
• Unaffected by background temperature
• Completely enclosed within the lighting fixture as microwave operation can safely penetrate non-metallic objects such as glass and plastic
• Very stable performance which is suitable for any climate
• In line with the fittings IP rating, the units are dust and smoke proof as they are inside the fitting
• Very long life span of 100,000 hours plus
Passive infrared (PIR) sensors relate to the movement of objects by detecting their heat and light, but only in their field of view. As these products rely on line of sight their performance is affected when inanimate objects obstruct their field of view.
Key points:
• Activated by infrared – heat and light
• Do not function well in temperatures >35 degrees Celsius
• Cannot penetrate plastic or glass, so the detector has to be positioned externally to a light fitting, therefore they can become vulnerable to smoke and dust
• Lenses can age due to exposure to the atmosphere, which results in reduced performance over time
• Short life span of around 20,000 hours
The cutting edge microwave sensors used by Netlec.co.uk in a new generation of light fittings, such as the Lunar 2D wIth Microwave Sensor have numerous benefits:
• Purpose made for use in intelligent light fittings to suit energy saving applications
• Turn on when presence is detected, then dim down for a pre-set time to a lower percentage of brightness once the presence has passed
• The sensor is unobtrusive as it is located inside the light fitting, so there is no compromise to decoration or room design
• Extremely low transmission power equivalent to only 2% of that of a typical mobile phone
• Multi-operational settings which are variable to suit the user
• Wide operating temperature range of between -35 deg to +70 deg Celsius
• Replaceable rim trims with a range of colour options to suit the decor of the room
The Lunar 2D wIth Microwave Sensor is an Energy saving surface mounted flight fitting complete with a cutting edge integral microwave occupancy/light sensor. The fitting has been designed for Netlec.co.uk specifically to enhance their offering of energy saving products.
Fittings with microwave sensors are ideally suited to areas which only need to be illuminated when occupied and daylight diminishes below the required level. They are perfect for use in a wide variety of environments, where energy efficiency is of prime importance, for instance corridors, stairways, storage areas, toilets etc. Popular in schools and commercial premises, the Lunar 2D wIth Microwave Sensor is aesthetically pleasing enough to be used in almost any setting, especially when used in conjunction with one of the replaceable coloured rims which give the product increased diversity in its interior design applications.
As well as reducing energy costs, there are other benefits too through the use of a light fitting such as the Lunar 2D wIth Microwave Sensor. Organisations and business could reduce their lighting maintenance costs, create a better workplace and show, in a really visible way, that their organisation cares about the environment.

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PARC Secures ARPA-E Funding to Develop Printed Methane Sensor Array

PARC, a Xerox company, has secured funding with the U.S. Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E) under the Methane Observation Networks with Innovative Technology to Obtain Reductions (MONITOR) program.
PARC will deliver very low cost printed sensor arrays to quantify and locate methane leaks, using a variety of modified carbon nanotube (CNT) sensors. The combined response of the sensors will provide "fingerprints" for methane sensor and other gases. The novel approach offers a solution to identify, quantify and locate natural gas leaks at a cost point compatible with widespread deployment. Methane, a major component of natural gas, is a significant greenhouse gas, with many times the heat-trapping effect of carbon dioxide.
"We are very excited about this project," said David Schwartz, project lead and Manager of Energy Devices and Systems at PARC. "It's a perfect example of how printed sensor systems can provide new capabilities and enable applications with real positive impact in the energy sector and beyond."
The ARPA-E funded System of Printed Hybrid Intelligent Nano-Chemical Sensors (SPHINCS) will be delivered in partnership with BP and NASA Ames Research Center. BP will provide gas composition data, access to production sites and other facilities, and will help develop a market strategy to address upstream and downstream applications. The system will build upon NASA Ames' delivered and successful demonstration of both best-in-class electrochemical methane sensors and selective gas sensor arrays.
PARC's methane detection system is based on sensor arrays fabricated on polymer substrates. Each substrate contains functional printed CNT sensor elements and supporting electronics. The CNTs are modified with dopants, coatings, or nanoparticles, allowing them to respond differently to different gases. Pattern matching supported by machine learning techniques allows specific gas "fingerprints" to be discerned from the combined sensor data. PARC's history of successfully enabling ultra-low-cost, high-performance deployable electronic systems for commercial applications will accelerate the development cycle for this technology. The system will have broad applicability beyond gas wells to pipelines, industrial and residential gas-sensing applications.
This SPHINCS project is part of a broad portfolio within the PARC Energy Technology Program aimed at developing practical solutions to make clean and abundant energy available across a wide range of applications. This includes a focus on improving chemical energy storage for EVs, consumer electronics, and electric grid support; advanced energy conversion devices, including medium temperature fuel cells; harsh-environment wireless sensors to improve the efficiency of coal gasification plants; and advanced analytics to maximize energy utilization.

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What’s NDIR gas sensor?

A miniaturized NDIR gas sensor is manufactured using semiconductor micromachining techniques from a semiconductor material such as Si or GaAs. The NDIR gas sensor comprises an optical waveguide, a light source at one end of the waveguide, at least one light detector at the end of the waveguide opposite the light source, a diffusion type gas sample chamber formed within the waveguide and interposed in the optical path between the light source and light detector so that the light source and light detector are thermally isolated from the gas sample, and a separate bandpass filter interposed between the light source and each light detector. Because the NDIR sensor is fabricated out of a semiconductor material, the source driver and signal processing electronics may be added directly to the sensor using integrated circuit fabrication techniques. Particles and smoke and dust may be kept out of the sample chamber by application of a gas permeable membrane over apertures in the sample chamber walls.

Description
This is a continuation of co-pending application Ser. No. 08/195,523, filed on Feb. 14, 1994, now abandoned.

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the field of gas sensing devices and, more particularly, to NDIR gas analyzers.
2. Description of the Prior Art
Nondispersive infrared (NDIR) gas analyzers are used for detecting the presence and concentration of various gases. The NDIR technique has long been considered one of the best methods for gas measurement. In addition to being highly specific, the NDIR gas analyzers are also very sensitive, stable and easy to maintain.

In contrast to NDIR gas sensors, which are by definition noninteractive, interactive optical gas sensors are less reliable, are generally nonspecific, and in some cases can be poisoned into a nonfunctional state.

Interactive gas sensors are generally nonspecific because the reagent being used to determine the concentration of the desired gas may react with other gases that are present. This will naturally result in false readings. Further, if the equilibrium of the reaction between the nonspecific gas and the reagent is such that the gas and reagent remain reacted even after the partial pressure of the gas drops in the environment being monitored, the sensor will no longer function properly and is poisoned.
The response time for NDIR gas sensors is also typically shorter than that for interactive gas sensors. The reason being that the kinetics of the reaction between the sample gas and reagent controls how quickly the sensor detects a change in the concentration of the gas in the environment being monitored.

Despite the fact that interactive gas sensors are unreliable and that the NDIR gas measurement technique is one of the best, NDIR gas analyzers have not enjoyed wide spread application because of their complexity and high cost of implementation.

In the past, NDIR gas analyzers typically included an infrared source, a motor-driven mechanical chopper to modulate the source, a pump to push or pull gas through a sample chamber, a narrow bandpass interference filter, a sensitive infrared detector plus expensive infrared optics and windows to focus the infrared energy from the source onto the detector.

In an attempt to reduce the cost and simplify the implementation of the NDIR technique, a low-cost NDIR gas sensor technique was developed. The low-cost NDIR technique employs a diffusion-type gas sample chamber of the type disclosed in U.S. Pat. No. 5,163,332, issued Nov. 17, 1992, to the present applicant, and hereby incorporated by reference. This diffusion-type gas sample chamber eliminates the need for: expensive optics, mechanical choppers, and a pump for pushing or pulling the gas into the sample chamber. As a result, a number of applications for the NDIR technique, which were previously considered impractical because of cost and complexity, have been opened.

The diffusion-type gas sample chamber of U.S. Pat. No. 5,163,332 uses an elongated hollow tube having an inwardly-facing specularly-reflective surface that permits the tube to function as a light-pipe for transmitting radiation from a source to a detector through the sample gas. A plurality of filtering apertures in the wall of the non-porous hollow tube permit the sample gas to enter and exit freely under ambient pressure. Particles of smoke and dust of a size greater than 0.1 micron are kept out of the chamber by use of a semi-permeable membrane that spans the apertures in the hollow tube, and condensation of the sample gas is prevented by heating the sample chamber electrically to a temperature above the dew point of the gas.

Although the low-cost NDIR gas sensor technique opened a wide variety of new applications, the gas sample chamber and the corresponding gas sensor of the low-cost NDIR technique are still too large for many potential gas sensor applications. As a result, applications in which low-cost NDIR gas sensors may be used remain limited. Furthermore, while the cost of gas sensors employing the gas sample chamber of U.S. Pat. No. 5,163,332 is less than previous NDIR gas sensors requiring expensive optics, pumps, and choppers, a further reduction in the cost of NDIR gas sensors would further increase the number of applications in which such sensors are used and the frequency of their use.
Therefore, while a need exists for a compact, inexpensive NDIR gas sensor, this need has gone unfilled. Accordingly, a goal of the present invention is to further advance the NDIR technique by providing a miniaturized, reliable, and low cost NDIR gas sensor.

SUMMARY OF THE INVENTION
The present invention is directed to an NDIR gas sensor for detecting the concentration of a predetermined gas. To this end, an optical waveguide is provided having a light source at one end and a light detector at the other end. A bandpass filter is interposed in the optical path between the light source and detector, so that the detector primarily receives radiation of a wavelength that is strongly absorbed by the gas whose concentration is to be determined. The waveguide is formed from two or more substrates of a semiconductor material, at least one of which has been micromachined. In addition, the light source and detector are directly manufactured on at least one of the semiconductor substrates used to form the optical waveguide. A pair of windows are also optically disposed between the light source and detector so as to define therebetween a sample chamber within the optical waveguide. The windows thermally isolate the light source and light detector from the sample gas, thus preventing the sample gas from cooling these elements. The gas whose concentration is to be determined diffuses into and out of the sample chamber in the optical waveguide through apertures or slots in the semiconductor substrates.

Because the walls of the optical waveguide are reflective, radiation is transmitted from the light source to the light detector through the sample gas without the need for expensive optics. Furthermore, because gas sensors according to the present invention employ a diffusion-type gas sample chamber, no pump is required to push or pull the sample gas into the sample chamber.

In a preferred embodiment, a gas permeable dielectric layer is deposited over the apertures to act as a filter and prevent dust or smoke particles from entering the optical waveguide sample chamber. Preferably, the gas permeable layer prevents particles larger than about 0.1 μm from entering.
In another preferred embodiment, at least a portion of the optical waveguide is metallized thereby improving its internal reflectivity and the overall efficiency of the NDIR gas sensor according to the present invention.

In yet another preferred aspect of the present invention, an NDIR gas sensor is provided that prevents condensation of gases or vapors on the walls of the sample chamber. To accomplish this object, means are provided for heating the gas sample chamber so that its temperature remains above the dew point of any gas or vapor that might have a tendency to condense on an inner surface of the sample chamber.

Other integrated circuit semiconductor devices can also be added wherever needed to further enhance the performance of the NDIR gas sensor according to the present invention. For example, temperature sensors, pressure transducers, and humidity sensors may be added. In addition, a micro-flow sensor may be added to detect the flow rate of the sample gas through the sample chamber.

In a particularly preferred embodiment of the present invention, an NDIR gas sensor is provided which can be used to simultaneously determine the concentration of a plurality of gases in the gas sample. The NDIR gas sensor according to this embodiment is comprised of a plurality of detectors and a plurality of bandpass filters. Each bandpass filter is interposed in the optical path between the light source and one of the plurality of detectors. The number of gases whose concentration is desired to be determined dictates the specific number of detectors and bandpass filters that are required. Each bandpass filter, therefore, is designed so that the detector it is associated with primarily receives radiation of a wavelength that is strongly absorbed by the gas whose concentration that detector is to determine.

Alternatively, in this embodiment, at least one of the detectors may be used as a reference detector. In this situation, the bandpass filter interposed in the optical path between the light source and the reference detector must be designed to pass a neutral wavelength. In other words, the bandpass filter must pass a wavelength of light that is not absorbed by the gas sample.

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Presence Detectors (PIR sensors and Microwave sensors)

Our wide range of PIR sensors and microwave presence detectors are designed to reduce the amount of time lighting is left on unnecessarily, for example if an area is unoccupied or if there is sufficient natural light.

A presence detector monitors the detection zone for occupancy; if a person is sensed then the detector will automatically turn the lighting on. When the area is vacated, the lighting will turn off after a preset time delay. Most of our PIR sensors and microwave sensors have a built in light level (lux) sensor which will keep the lighting off if there is enough natural light available.

Controlling lighting with a presence detector can save up to 60% of lighting energy costs dependent on occupancy behaviour and the amount of natural light available; our PIR switches and microwave sensors can also be used to control heating and ventilation.

Presence and Absence Detection Explained

The choice between presence and absence detection for different spaces can make a big difference in user-friendliness and the amount of energy saved.

Presence Detection

Detectors will switch on lighting automatically when a person enters the room, and switches off lighting automatically when no movement is detected.

Absence Detection

Upon entering the room the person switches on the light as normal, but on leaving the detector switches off the lighting automatically. Lights can also be switched off manually.

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Liquid Level Sensors

Monitoring the level of liquid can be accomplished through the use of a pressure transducer. The density of the liquid and its height create pressure on the diaphragm of the pressure transducer to generate an accurate and cost effective level measurement. Generally, pressure transducers can be used for level measurement from 10 inches of water column, up to 10,000 PSI (700 bar).

Pressure transducers can either be submerged in the liquid or mounted externally. Submersible pressure transducers can be installed freely or with a rigid conduit to monitor the hydrostatic liquid above it. As the liquid level decreases, the output decreases. Submersible sensors are commonly used in vented tanks such as diesel tanks or for water and waste water level.
 
Pressure transducers can also be mounted to the side or bottom of the tank through a separate line, feed line or drain line. This design can cost less, as it doesn't require a special cable, and installation is quick. Differential pressure transducers can be used on vented or sealed tanks, measuring the difference in pressure between the top and bottom of the tank.

Custom Liquid Level Sensors
AST manufactures a variety of custom liquid level sensors and solutions for OEM applications. If you find a product that is close to a solution, but not exactly what you hoped for, please contact us and an engineer will follow up with you regarding our custom capabilities for pressure ranges, outputs, sizes and materials.

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Sensor in Android Tutorial: Barometer Sensor

 One of the most interesting topics in my opinion is how to use Sensor in Android. Nowadays our smartphone are full of sensors and we can use it to control somehow our app.

The most common sensors are:
• GPS
• Proximity sensor
• Light sensor
• Temperature sensor
• Barometer sensor
• NFC
just to mention some of them. In this post we will explain how to obtain a list of sensor and how we can use one of them (i.e Barometer sensor).

Using sensor in android
When we develop an android app and we need a specific sensor so that our app can run we have two different choices:
• Specify it the sensor in the AndroidManifest.xml
• Detect the sensor list and check if the one we are interested on is available

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Sensing Carbon Dioxide for Total Organic Carbon Monitoring (NDR Gas Sensor)

Organic carbon compounds are often specified in terms of carbon mass. Recent developments in TOC (total organic carbon) analysis have resulted in considerable improvements, which allow for complete and direct measurement of the quantity of carbon with a biological source. Where there are fluctuations and differences, the cause and effect on biological processes in waste water study can be identified.

The TIC (total inorganic carbon) is usually removed from a sample by means of purging prior to oxidizing the residual organic carbon in the water sample to carbon dioxide (CO2) and then quantifying the amount of CO2 generated (Figure 1).

Figure 1. Typical TOC process
A number of techniques are available which can be used to oxidize the organic carbon, such as oxygen, UV radiation, wet chemistry, or heat to generate CO2. Regardless of the method, the resulting CO2 is dissolved in a carrier gas, such as oxygen. This carrier gas is passed via the TOC level will also be higher and the water sample will be more contaminated.

Based on the cleanliness of the water being analyzed and the methods utilized, different concentrations of CO2 can be anticipated in the carrier gas, from wastewater to drinking water. Edinburgh Sensors’ Gascard® NG is a high performance OEM gas detector that provides real-time measurement of CO2 0-500ppm to 0- 3%.

OEM Gascard® NG
A suitable OEM solution for TOC monitoring, Gascard NG can be easily integrated into a range of gas detection solutions where lasting stability, high quality, superior repeatability and reliable measurement of carbon , CO2 and methane gas concentrations are needed. These features are due to Edinburgh Sensors’ proprietary dual wavelength fail to safe InfraRed NDIR gas sensor technology. The Gascard NG range offers ideal solutions for measuring and testing industrial as well as environmental gases. Table 1 shows the Gascard NG models for gas measurement range of CO2.
The Gascard NG from Edinburgh Sensors comes with different interface options, such as true RS232 communication, analogue 4-20 mA/0-20 mA/0-5 v, serial interface for interfacing relay alarms and optional on board LANsupport. The on-board firmware is capable of supporting a modern graphical display or a conventional 4 segment LCD.

In addition, the Gascard NG series needs only minimum maintenance and thus eliminates significant amount of costs. Automatic pressure and temperature correction features allow real-time environmental condition measurements and thus provide consistent measurement and exact concentration readings of target gases.

The sensor head and electronics of the Gascard NG series are positioned on a Eurocard PCB with several bit-switches, which allow users to control different aspects of the sensors behaviour such as filter type and analogue output selection.

The Gascard NG is backward compatible with outputs from current generations of Gascard series and includes onboard true RS232 communications with the option of TCP/iP communications protocol and on-board data logging. With built-in features for multi-sensor and multigas operation, the Gascard NG can integrate additional gas detection technologies.

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UV Sensors Information

UV sensors measure the power or intensity of incident ultraviolet (UV) radiation. This form of electromagnetic radiation has shorter wavelengths than visible radiation, but is still longer than x-rays. UV sensors are used for determining exposure to ultraviolet radiation in laboratory or environmental settings. They are transmitters which respond to one type of energy signal by producing energy signals of a different type. Generally, these output signals are electrical signals that are routed directly to an electrical meter for observation and recording. The generated electrical signals from UV sensors can also be sent to an analog-to-digital converter (ADC), and then to a computer with software for generating graphs and reports.
Types of UV Sensors
There are many types of UV sensors. Examples include UV phototubes, light sensors, and UV spectrum sensors. UV phototubes are radiation-sensitive sensors that are used for monitoring UV air treatments, UV water treatments, and solar irradiance. Light sensors are general-purpose devices for measuring the intensity of incident light. UV spectrum sensors are charged coupled devices (CCD) that are used in scientific photography. These UV sensors are also used for measuring the portion of the UV spectrum which sunburns human skin. Ultraviolet light detectors, germicidal UV detectors, and photostability sensors are also commonly available.
UV Sensor Specifications
Selecting UV sensors requires an analysis of specifications such as wavelength range, accuracy, power range, weight, and operating temperature. Wavelength range is the range of wavelengths, in nanometers (nm), that UV sensors can detect. UVA radiation ranges over wavelengths from 315 nm to 400 nm. UVB radiation covers wavelengths from 280 nm to 315 nm. UVC radiation is defined as between 100 nm and 280 nm. Because UVC radiation is more energetic, it is also the most harmful. Accuracy is a measure of how effectively UV sensors measure ultraviolet radiation. Power range and weight are also important parameters to consider, especially for UV sensors that are used in the field. Operating temperature is defined as a full-required range.
Applications for UV Sensors
UV sensors are used in many different applications. Examples include pharmaceuticals, automobiles, and robotics. UV sensors are also used in the printing industry for solvent handling and dyeing processes. In addition, UV sensors are also used in the chemical industry for the production, storage, and transportation of chemicals.

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Feasibility of novel four degrees of freedom capacitive force sensor for skin interface force

 The objective of our study was to develop a novel capacitive force sensor that enables simultaneous measurements of yaw torque around the pressure axis and normal force and shear forces at a single point for the purpose of elucidating pressure ulcer pathogenesis and establishing criteria for selection of cushions and mattresses.
Methods
Two newly developed sensors (approximately 10 mm×10 mm×5 mm (10) and 20 mm×20 mm×5 mm (20)) were constructed from silicone gel and four upper and lower electrodes. The upper and lower electrodes had sixteen combinations that had the function as capacitors of parallel plate type. The full scale (FS) ranges of force/torque were defined as 0–1.5 N, –0.5-0.5 N and −1.5-1.5 N mm (10) and 0–8.7 N, –2.9-2.9 N and −16.8-16.8 N mm (20) in normal force, shear forces and yaw torque, respectively. The capacitances of sixteen capacitors were measured by an LCR meter (AC1V, 100 kHz) when displacements corresponding to four degrees of freedom (DOF) forces within FS ranges were applied to the sensor. The measurement was repeated three times in each displacement condition (10 only). Force/torque were calculated by corrected capacitance and were evaluated by comparison to theoretical values and standard normal force measured by an universal tester.
Results
In measurements of capacitance, the coefficient of variation was 3.23% (10). The Maximum FS errors of estimated force/torque were less than or equal to 10.1 (10) and 16.4% (20), respectively. The standard normal forces were approximately 1.5 (10) and 9.4 N (20) when pressure displacements were 3 (10) and 2 mm (20), respectively. The estimated normal forces were approximately 1.5 (10) and 8.6 N (10) in the same condition.
Conclusions
In this study, we developed a new four DOF force sensor for measurement of force/torque that occur between the skin and a mattress. In measurement of capacitance, the repeatability was good and it was confirmed that the sensor had characteristics that enabled the correction by linear approximation for adjustment of gain and offset. In estimation of forces/torque, we considered accuracy to be within an acceptable range.


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