This webinar will provide pesticides residue analysts with valuable information on the development and optimization of gas chromatographic separations and mass spectrometry methods for the analysis of pesticide residues in food. The expert speakers will share their knowledge in understanding the critical points of the method, assisting analysts in modifying existing methods, and understanding instrumental and software technologies with the goal of improving laboratory productivity and reducing the overall cost per sample. The results of experiments for both screening and quantification workflows, using the latest technology, will be presented.
This webinar will provide pesticides residue analysts with valuable information on the development and optimization of gas chromatographic separations and mass spectrometry methods for the analysis of pesticide residues in food. The expert speakers will share their knowledge in understanding the critical points of the method, assisting analysts in modifying existing methods, and understanding instrumental and software technologies with the goal of improving laboratory productivity and reducing the overall cost per sample. The results of experiments for both screening and quantification workflows, using the latest technology, will be presented.
تقنية سهلة الإستخدام، آمنة بيئياً، سريعة، توفر الجهد والوقت والكلفة وذات إنتقائية عالية يتم من خلالها تنقية وزيادة تركيز مركب يُراد تحليلهُ Analyte، والذي يكون ذائب أو عالق في مزيج سائل و فصله عن المتداخلات الأخرى Interferences في مزيج النموذج إعتماداً على خواصه الفيزيائية والكيميائية.
mercury analysis in AAS, by fayaz hussain chandio, Introduction of Atomic Absorption Spectroscopy
Mercury-Element information, properties and uses
Mercury contamination and Human health
Analytical methods for mercury analysis
Determination of mercury by Cold-vapor Atomic absorption spectroscopy
Conclusion
Acknowledgment
Atomic Spectroscopy
Atomic-absorption (AA) spectroscopy uses the absorption of light to measure the concentration of gas-phase atoms.
samples are usually liquids or solids
Analyte atoms or ions must be vaporized in a flame or graphite furnace
The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels.
Discovered approximately 1500 BC
Group 12, Period 6, Block d, Atomic number 80, Boiling point 356.619 ℃.
Mercury is an element and a transition metal that is found in air, water, and soil.
It is liquid at room temperature
Mercury has long been known as quicksilver.
Elemental mercury is liquid at room temperature. (Hg)
Inorganic mercury compounds are formed when mercury combines with other elements, such as sulfur or oxygen, to form compounds or salts. inorganic Hg (Hg2+).
Organic mercury compounds are formed when mercury combines with carbon. (MMHg, CH3Hg+), (DMHg, CH3HgCH3).
Mercury is also used in dental applications.
Coatings for mirrors.
The most important use of mercury is in the preparation of chlorine.
Mercury thermometers
and barometers.
Mercuric arsenate used
as waterproofing paints.
Mercuric chloride, or
mercury bichloride, or corrosive sublimate (HgCl ):disinfectant, insecticide.
Vapors pass through the skin into the blood stream. Can also be inhaled, can also be swallowed.
Mercury chloride known as calomel was sometimes used as a poison to kill people.
Depression, nervousness, and personality changes.
Damage to the kidneys and muscles.
Most exposure to mercury comes from the ingestion of certain foods, such as fish, in which the mercury has accumulated at high levels.
According to US EPA, list of many of the regulatory methods that are available for use with today’s technologies.
Cold Vapour Atomic Absorption Spectroscopy (CVAAS):
Cold Vapour At omic Fluorescence Spectroscopy (CVAFS):
Direct Analysis by Thermal Decomposition:
ICP or ICP-MS:
SCOPE AND APPLICATION METHOD:
This procedure measures total mercury (organic + inorganic) in drinking, surface, ground, sea, brackish waters, industrial and domestic wastewater, fish and coal.
The range of the method is 0.2-10 μg Hg/L.
most modern CVAAS instruments are more sensitive, automated, smaller, faster, and less expensive than generic flame spectrometers with cold vapor devices attached.
Heating the sample in the presence of different combinations of mineral acids such as nitric, hydrochloric, sulfuric and per chloric acids and also other oxidizing agents such as hydrogen peroxide.
INTip SPE utilizes a patented technology known as Dispersive Pipette XTRaction. This device is unique from all other SPE devices because sorbent is loosely contained within a pipette tip.
This technology enables INTip solid phase extraction for easy sample preparation. The disperser helps to perturb the sample solution and loose sorbent during aspirate and dispense steps. This mixing provides a highly efficient interaction of the sorbent with the analyte of interest resulting in ideal analyte recoveries.
What's the right quaternary LC system for your analysis? Waters Corporation
Waters' portfolio of liquid chromatography (LC) systems is designed to meet your laboratory's requirements for analytical reliability, robustness, and repeatability. HPLC, UHPLC, UPLC ... Waters has your lab covered.
Elemental analysis does not just start by inserting the sample into the combustion tube! Sample preparation is an essential part of elemental analysis and influences analysis results directly. This webinar addresses all users of elemental analysis and communicates important basics of sample preparation – from homogenization of the sample to wrapping it.
The Rydberg formula helps to determine the wavenumber or wavelengths of hydrogen spectral lines obtained in the hydrogen spectrum. Previously, Johann Jakob Balmer discovered an empirical formula to determine the wavelengths of hydrogen spectral lines obtained in the visible region of the hydrogen spectrum. As we all know, the hydrogen spectrum is not limited to the visible zone only. It occupies the ultraviolet and infrared parts of the electromagnetic spectrum also. Hence, the scientists' quests to determine the spectral positions of various spectral lines of the hydrogen spectrum finally came to an end with the Rydberg formula.
Incepted in 1988 by Dr. Lalit Kumar, Laser Science is India's premier distributor of Lasers and Spectroscopy instruments. Our range of products covers scientific and industrial laser systems, spectroscopy, microscopy & imaging systems. We distribute major brands that are reputable global market leaders in their respective fields. These names include Coherent Inc (USA), Femtolasers (Austria), Optronis GmbH, PCO AG (Germany), Beneq (Finland) and many others.
تقنية سهلة الإستخدام، آمنة بيئياً، سريعة، توفر الجهد والوقت والكلفة وذات إنتقائية عالية يتم من خلالها تنقية وزيادة تركيز مركب يُراد تحليلهُ Analyte، والذي يكون ذائب أو عالق في مزيج سائل و فصله عن المتداخلات الأخرى Interferences في مزيج النموذج إعتماداً على خواصه الفيزيائية والكيميائية.
mercury analysis in AAS, by fayaz hussain chandio, Introduction of Atomic Absorption Spectroscopy
Mercury-Element information, properties and uses
Mercury contamination and Human health
Analytical methods for mercury analysis
Determination of mercury by Cold-vapor Atomic absorption spectroscopy
Conclusion
Acknowledgment
Atomic Spectroscopy
Atomic-absorption (AA) spectroscopy uses the absorption of light to measure the concentration of gas-phase atoms.
samples are usually liquids or solids
Analyte atoms or ions must be vaporized in a flame or graphite furnace
The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels.
Discovered approximately 1500 BC
Group 12, Period 6, Block d, Atomic number 80, Boiling point 356.619 ℃.
Mercury is an element and a transition metal that is found in air, water, and soil.
It is liquid at room temperature
Mercury has long been known as quicksilver.
Elemental mercury is liquid at room temperature. (Hg)
Inorganic mercury compounds are formed when mercury combines with other elements, such as sulfur or oxygen, to form compounds or salts. inorganic Hg (Hg2+).
Organic mercury compounds are formed when mercury combines with carbon. (MMHg, CH3Hg+), (DMHg, CH3HgCH3).
Mercury is also used in dental applications.
Coatings for mirrors.
The most important use of mercury is in the preparation of chlorine.
Mercury thermometers
and barometers.
Mercuric arsenate used
as waterproofing paints.
Mercuric chloride, or
mercury bichloride, or corrosive sublimate (HgCl ):disinfectant, insecticide.
Vapors pass through the skin into the blood stream. Can also be inhaled, can also be swallowed.
Mercury chloride known as calomel was sometimes used as a poison to kill people.
Depression, nervousness, and personality changes.
Damage to the kidneys and muscles.
Most exposure to mercury comes from the ingestion of certain foods, such as fish, in which the mercury has accumulated at high levels.
According to US EPA, list of many of the regulatory methods that are available for use with today’s technologies.
Cold Vapour Atomic Absorption Spectroscopy (CVAAS):
Cold Vapour At omic Fluorescence Spectroscopy (CVAFS):
Direct Analysis by Thermal Decomposition:
ICP or ICP-MS:
SCOPE AND APPLICATION METHOD:
This procedure measures total mercury (organic + inorganic) in drinking, surface, ground, sea, brackish waters, industrial and domestic wastewater, fish and coal.
The range of the method is 0.2-10 μg Hg/L.
most modern CVAAS instruments are more sensitive, automated, smaller, faster, and less expensive than generic flame spectrometers with cold vapor devices attached.
Heating the sample in the presence of different combinations of mineral acids such as nitric, hydrochloric, sulfuric and per chloric acids and also other oxidizing agents such as hydrogen peroxide.
INTip SPE utilizes a patented technology known as Dispersive Pipette XTRaction. This device is unique from all other SPE devices because sorbent is loosely contained within a pipette tip.
This technology enables INTip solid phase extraction for easy sample preparation. The disperser helps to perturb the sample solution and loose sorbent during aspirate and dispense steps. This mixing provides a highly efficient interaction of the sorbent with the analyte of interest resulting in ideal analyte recoveries.
What's the right quaternary LC system for your analysis? Waters Corporation
Waters' portfolio of liquid chromatography (LC) systems is designed to meet your laboratory's requirements for analytical reliability, robustness, and repeatability. HPLC, UHPLC, UPLC ... Waters has your lab covered.
Elemental analysis does not just start by inserting the sample into the combustion tube! Sample preparation is an essential part of elemental analysis and influences analysis results directly. This webinar addresses all users of elemental analysis and communicates important basics of sample preparation – from homogenization of the sample to wrapping it.
The Rydberg formula helps to determine the wavenumber or wavelengths of hydrogen spectral lines obtained in the hydrogen spectrum. Previously, Johann Jakob Balmer discovered an empirical formula to determine the wavelengths of hydrogen spectral lines obtained in the visible region of the hydrogen spectrum. As we all know, the hydrogen spectrum is not limited to the visible zone only. It occupies the ultraviolet and infrared parts of the electromagnetic spectrum also. Hence, the scientists' quests to determine the spectral positions of various spectral lines of the hydrogen spectrum finally came to an end with the Rydberg formula.
Incepted in 1988 by Dr. Lalit Kumar, Laser Science is India's premier distributor of Lasers and Spectroscopy instruments. Our range of products covers scientific and industrial laser systems, spectroscopy, microscopy & imaging systems. We distribute major brands that are reputable global market leaders in their respective fields. These names include Coherent Inc (USA), Femtolasers (Austria), Optronis GmbH, PCO AG (Germany), Beneq (Finland) and many others.
Laser-Based Standoff Methane Sensors for Enhancing Coal Miner SafetyClinton Smith
This presentation shows a demonstration of the PSI & Heath Consultants Remote Methane Leak Detector (RMLD) being applied to remote detection of methane within coal mines to supplement existing technology to further enhance coal miner safety.
High-accuracy laser spectrometers for wireless trace-gas sensor networksClinton Smith
The subject of this dissertation is the development of a wireless sensor network composed of instruments which employ both VCSELs and QCLs for accurate, highly sensitive, and reliable long-term monitoring of environmental trace-gases. The dissertation focuses on the development of low-power instruments and calibration methods that ensure the reliability of long-term measurements.
First the field deployment of a low-power, portable, wireless laser spectroscopic sensor node for atmospheric CO2 monitoring is demonstrated. The sensor node shows 0.14 ppmv Hz^-1/2 1 sigma measurement sensitivity of CO2 concentration changes. It was first used to measure top-soil respiration rates in the laboratory and on forest floors in the field.
Then after a long-term field deployment to further assess instrument performance, new design solutions were implemented to improve fringe-limited precision of the nodes to 4-7 ppmv against a 400 ppmv CO2 background, making their performance comparable to higher power consuming commercial trace-gas analyzers. Three optimized nodes were then deployed into mixed landscapes as part of a solar powered CO2 monitoring wireless network. The three node network monitored CO2 in a grassy/woody courtyard, on top of the roof of an engineering building, and next to a road in the Princeton area. These works show that ultra-low powered VCSEL based sensor nodes can be placed in off-the-grid environments for autonomous distributed geographic monitoring of trace-gases in a manner which is impossible with current commercial techniques.
Next, this dissertation covers two techniques that were developed for the real-time calibration of laser-based trace-gas measurements. The first technique used an in-line reference gas cell and employed wavelength modulation spectroscopy (WMS) at higher harmonics to simultaneously probe the sample and reference spectra. The second technique used a revolving in-line reference cell to suppress background and other non-spectroscopic signals. These techniques were designed for eventual inclusion as a real-time calibration source for field deployable trace-gas sensors and wireless sensor networks.
Finally, this dissertation demonstrates the use of the CW injection current into a VCSEL in an external cavity configuration to tune the cavity emission's self-oscillation frequency and show through simulation and experiment that the tuning is dependent on VCSEL birefringence change.
Dissertation PDF at www.clintonjsmith.com
Group III nitride semiconductors are recognized as having great potential for short wave length emission (LEDs, LDs, UV detectors) and high-temperature electronics devices. The field of III-N semiconductors has shown an intensive patenting activity since early 1990s, with a substantial increase during the past decade. Today, there are more than 27,000 patent families filed all over the world. The most active companies are Panasonic, Toshiba, Samsung, Sumitomo and Hitachi. The patents related to LED technology account for more than 40% of filings, followed by those related to GaN substrates (5%) and RF & Advanced Electronics (<5%).
More than 1,570 new patent families were published between early April 2012 and late March 2013. They were filed by about 350 patent applicants mainly located in Japan, Korea, USA and China. The main patent applicants are Sumitomo, Toshiba, Samsung, Sharp and Mitsubishi which represent together almost 25% of the patents published the last 12 months. The academic organisms account for almost 15% of new patent filings and they are mainly located in China. The data set was segmented by type of application (Substrates, Epi-wafers, LED & Laser, Power Devices, RF & Advanced Electronics, Photovoltaics, Sensors-Detectors-MEMS). About 45% of new patent families published the last 12 months are related to LED technology.
They were mainly filed by Toshiba, LG and Samsung, while Chinese companies are increasing their patent activity (Tongfang, Sanan Optoelectronics). The patents claiming an invention related to III-N Substrates and Power Devices represent 20% and 14% of new filings respectively. The patents dedicated to Substrate technology were mainly filed by Sumitomo, Hitachi and Mitsubishi, while University of California and Soitec filed 15 and 8 new patents respectively. The patents dedicated to Power Devices were mainly filed by Advanced Power Device Research Association, Samsung and Sumitomo and the patent filings remain dominated by Japanese companies. Numerous patent applications published this year are offered for sale or for license. This year, the most relevant offers are the ones from the University of California (e.g. Ammonothermal growth technique, CAVET for High Power Application, Defect reduction of semi-polar III-N, GaN substrates, III-N tandem solar cells .
It is a powerpoint presentation which can be presented as a seminar topic in engineering. It is for branches like Computer Science, Electronics as well as Electrical. Hope you like it!!!
Solid state lighting, GaN LEDs and lasersGerhard Fasol
Gallium Nitride LEDs are on the way to replace light-bulbs and fluorescent tubes, and GaN lasers have many applications including Blue-Ray storage. This presentation introduces the basic technologies
Cameron's CamCor™ PRO Series Coriolis flow meter features high-accuracy, shallow bow-shaped dual sensor tubes and is ideal for oilfield production applications. This industrial process-grade Coriolis flow meter offers high performance for accuracy, repeatability, wide flow range, low pressure loss, and safe design.
Liquid Sensing: Visible light absorption spectroscopy and colorimetry are two fundamental tools used in chemical analysis. Most of these light-based systems use photodiodes as the light sensor, and require similar high input impedance signal chains. This session examines the different components of a photodiode amplifier signal chain, including a programmable gain transimpedance amplifier, a hardware lock-in amplifier, and a Σ-Δ ADC that can measure a sample and reference channel to greatly reduce any measurement error due to variations in intensity of the light source.
Gas Sensing: Many industrial processes involve toxic compounds, and it is important to know when dangerous concentrations exist. Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of toxic gases. This session will describe a portable toxic gas detector using an electrochemical sensor. The system presented here includes a potentiostat circuit to drive the sensor, as well as a transimpedance amplifier to take the very small output current from the sensor and translate it to a voltage that can take advantage of the full-scale input of an ADC.
KwikSense smart digital gas transmitter is a field mountable device suitable for the detection and continuous monitoring of hazardous gases at industrial plant locations. Apart from providing RS-485 MODBUS-RTU digital output signal, that can be connected to a suitable control system, such as a Uniphos controller, DCS, PLC, etc, it also provides an industry standard 4-20 mA analog output. KwikSense is available for a large number of gases which include Oxygen, toxic gases, combustible gases & VOC.
The EC900 offers unsurpassed accuracy, reliability and flexibility
under the most demanding on-line operating conditions. Systech Illinois has long been recognised worldwide as a leader in oxygen analysis. Utilising a variety of specially engineered electrochemical fuel cells, the EC900 Oxygen Analysers are designed to monitor oxygen within most industrial gases and atmospheres.
The ZR800 Oxygen Analysers offer unsurpassed accuracy,
reliability and flexibility under the most demanding on-line
operating conditions. All ZR800 Oxygen Analysers utilise
precision Zirconia Oxide sensors for accurate detection of oxygen.
35. Enhanced Laser Diode Spectroscopy “ Fulfilling the promise of open path gas detection”
Editor's Notes
Presenter Mr. Ian Mackay is the Area Sales Manager (EAME) for Senscient Ltd. He is based in the UK and manages a network of technical-sales support partners across Europe, Asia, Africa and the Middle East. During his career Mr. Mackay has worked for several gas analyser manufacturers in sales, marketing and technical roles and has lived in Asia, America and Europe. Mr Mackay has worked at Senscient since early 2009. Information for Senscient and contact information for Mr Mackay as follows; Website: http://www.senscient.com Email: [email_address] Mobile: +44 7769 652003 (UK) LinkedIn: http://uk.linkedin.com/in/ianmackay007
History Open Path Gas Detectors (OPGD) utilizing NDIR detection techniques have been in use since the late 1980’s and are widely accepted for many Oil & Gas, Petrochemical and other industry’s combustible gas detection applications. OPGD systems are currently used to monitor hydrocarbon gas leaks at offshore and onshore oil and gas production facilities, refineries, petrochemical plants, gas transmission stations and many other industrial facilities. The earliest NDIR OPGD systems were plagued with environmental interferences and failed to provide consistent performance when exposed to direct sunlight or weather conditions such as rain, snow and fog. In order to cope with these environmental challenges, designers of OPGDs pushed NDIR technology to its limits, but this has left little room for further improvement. Consequently, there are many demanding flammable gas detection requirements which cannot be adequately met using NDIR-based equipment. HVAC ducts and turbine acoustic enclosures are examples of applications where NDIR-based systems cannot meet the needs of many customers. In order to address the most demanding flammable gas detection requirements and to provide the first reliable open path toxic gas detector, Senscient developed Enhanced Laser Diode Spectroscopy (ELDS™) . The technology that Senscient has invented is called Enhanced Laser Diode Spectroscopy (ELDS for short). ELDS is the first laser based gas detection technology that is both highly sensitive AND highly robust. Earlier, conventional laser based gas detection technologies are sensitive, but they are not robust, which means that they can’t be used in critical applications such as for safety, or in harsh environments such as those commonly encountered at Oil & Gas facilities. Conventional LDS simply gives too many false alarms, and stops working when the weather gets bad. ELDS was specifically invented to make laser based gas detection suitable for critical applications and harsh environments, and the techniques that make ELDS sensitive and robust are patented.
Enhanced Laser Diode Spectroscopy (ELDS) Enhanced Laser Diode Spectroscopy is a revolutionary gas detection technology, specifically developed for safety related applications in industry. ELDS provides the following unique benefits and advantages: ELDS based OPGD systems provide reliable, sensitive detection of both flammable and toxic gases at low ppm concentrations. Toxic gases of primary interest include hydrogen sulfide, hydrogen fluoride and ammonia. ELDS-based OPGD systems offer three orders of magnitude in increased sensitivity for hydrocarbons, greatly increasing the probability of detecting a flammable gas leak before it reaches catastrophic proportions. Current NDIR methodology fails to provide warnings early enough, or reliably enough to facilitate any significant remedial action. ELDS based OPGD units can be produced for combinations of toxic and / or flammable gas hazards, significantly reducing the cost for a comprehensive gas detection system. Unique SimuGas™ feature provides the long sought-after ability to accomplish automatic or on-demand functional testing of open path gas detectors. The full list of ELDS benefits is available on the Senscient website: http://www.senscient.com/downloads/2238Senscient-Top-10-Reasons.pdf
Theory of Operation Concept In an ELDS system a beam of carefully modulated laser diode radiation is sent from a transmitter to a receiver along an open path. When target gas enters the beam, it introduces a highly characteristic ‘harmonic fingerprint’ onto the beam, and the receiver measures the size of the ‘harmonic fingerprint’ to determine how much target gas is in the beam. Using a separate transmitter / receiver configuration, ELDS systems detect and measure gas concentrations at specific target gas absorption wavelengths over distances of up to 200 meters. The detector measures absorbance changes along the line-of-sight path when a combustible or toxic gas passes through the beam. Enhanced Laser Diode Spectroscopy (ELDS) utilizes highly reliable, solid-state laser diode sources similar to those used in demanding telecommunications applications. Innovative signal processing methods significantly increase sensitivity, enabling reliable detection down to fractions of a % LEL meter of combustible gases, and low ppm meter levels of toxic gases. ELDS addresses problems experienced by traditional laser diode systems including laser Relative Intensity Noise (RIN), absorption by atmospheric gases, and coherence / fringe effects. ELDS uses a combination of techniques which significantly enhance the ability of an OPGD to detect small fractional absorbances with an extremely low false alarm rate. ELDS techniques allow our customers to finally meet stringent regulatory and safety integrity requirements with a false-alarm free system for low level combustible and toxic gas detection.
Multiple Measurement Wavelengths: It is widely understood that measuring gases with a single wavelength can be limiting to the sensitivity and accuracy of the measurement. Multiple wavelength measurement and detection, employed by scanning spectroscopy systems, has long been the technique of choice for analyzers providing low level, selective analyses of gas concentrations in the lab and on the process floor. But for ambient gas detection systems, multiple-wavelength scanning has been too complicated and too expensive to employ in the majority of applications. The Vertical Cavity Surface Emitting Lasers (VCSELs) employed in Senscient’s ELDS-based gas detectors provide economic scanning of wavelength ranges of 2-3nm, enabling multiple wavelength or multiple species measurements.
Wave Modulation Spectroscopy (WMS): ELDS technique employs Wave Modulation Spectroscopy. The laser diode is driven by a current as shown. The laser’s wavelength is alternately scanned across the chosen absorption line for a designated time interval. The use of WMS generates multiple harmonic overtones that are compared to generate a highly stable gas detection.
Multiple Modulation Frequencies: To successfully address system noise and the associated unacceptable false alarm rates, the ELDS technique employs Multiple Modulation Frequencies. The laser diode is driven by a current as shown, comprising two components, a bias component and a sinusoidal wavelength modulation component. The bias component is chosen to operate the laser diode at a wavelength close to a chosen optical absorption line of the target gas. The sinusoidal component alternates between two, non-harmonically related electrical frequencies f and f’. At each of the chosen frequencies, the laser’s wavelength is alternately scanned across the chosen absorption line for a designated time interval.
Multiple Modulation Frequencies: To successfully address system noise and the associated unacceptable false alarm rates, the ELDS technique employs Multiple Modulation Frequencies. The laser diode is driven by a current as shown, comprising two components, a bias component and a sinusoidal wavelength modulation component. The bias component is chosen to operate the laser diode at a wavelength close to a chosen optical absorption line of the target gas. The sinusoidal component alternates between two, non-harmonically related electrical frequencies f and f’. At each of the chosen frequencies, the laser’s wavelength is alternately scanned across the chosen absorption line for a designated time interval. When there is no gas present in the measurement path, the combined Fourier transform of the detector zero signal will look like the figure on the right, with just two frequency components f and f’.
Harmonic Fingerprints: Although conventional Laser Diode Spectroscopy (LDS) methods of measuring gases have been in use for several years in process control and environmental monitoring applications, such systems have not been popular in safety related applications due to their high false alarm rates when detecting low levels of hazardous gases. Conventional LDS systems suffer from the combined effects of system noise, absorption by atmospheric gases and coherent interference effects, all of which can produce spurious readings and false alarms. ELDS overcomes the false alarm problems experienced by conventional LDS systems by the use of Harmonic Fingerprints . Using a small retained sample of target gas inside the transmitter, the temperature and wavelength modulation currents applied to the transmitter’s laser diodes are actively controlled to lock the lasers such that absorption by target gas produces specific Harmonic Fingerprints. The relative amplitudes and phases of the harmonic components in a Harmonic Fingerprint are so specific that only absorption by target gas produces a signal with the desired Harmonic Fingerprint. Noise, absorption by atmospheric gases and coherent interference effects never produce signals with the Harmonic Fingerprint, enabling an ELDS-based gas detector to effectively eliminate false alarms from these causes. When there is a substantial quantity of target gas in the monitored space, the combined Fourier transform of the detector signal will look like the diagram, with multiple sets of harmonics of both f and f’. The probability of both measurements simultaneously suffering noise induced deviations above the alarm threshold is extremely small, lower than the targeted 1 in 100 years false alarm rate probability. The benefits of modulation and measurement at multiple, non-harmonically related electrical frequencies are not limited to reducing the impact of inherent system noise. The use of modulation at a number of non-harmonically related frequencies also reduces the likelihood that electromagnetic interference and/or thermal noise will affect all measurement frequencies simultaneously, again enabling false alarm rates to be significantly reduced.
Multiple Laser Diodes: Even though it is not possible to completely eliminate coherence / fringe effects from a laser diode system it is possible to reduce the rate of false alarms arising from such effects by using an ELDS system that contains two laser diodes, operating at two different wavelengths corresponding to two different absorption lines of one or more target gases. The use of multiple laser diodes and multiple measurement wavelengths is an effective way of addressing problems with coherent interference / fringe effects, a common problem experienced by conventional LDS systems. Two and even three VCSEL laser diodes can easily be mounted on a common temperature stabilized mount, sharing all of the associated optics and detectors; whilst keeping system costs reasonable. The electrical signal from at the detector contains two sets of independent frequency components proportional to the amount of target gas present in the measurement path. These effectively independent measurements of the quantity of target gas in the monitored space can then be compared and used to confidently determine the quantity of target gas present in the monitored space, if any. Multi-Gas Capability: The use of two lasers, scanning different wavelengths at different electrical frequencies makes it possible to treat each measurement as being completely independent of the other. Consequently, ELDS provides the opportunity to monitor two or more different target gases simultaneously in the same transmitter/receiver system. Combinations of gases that are likely to be of interest include methane + hydrogen sulfide (solution gas), butadiene + hydrogen fluoride (alkylation) and methane + methanol (methanol injection). Increased system reliability, virtually false-alarm free low level gas detection, and even simultaneous multiple gas detection capability is now possible.
Reference Channel (Retained Sample) & SimuGas ™ The Reference channel produces the Harmonic Fingerprint by directing part of the Laser energy through the retained gas sample(s) in the cuvette. The ability to continuously Lock on to this fingerprint means Gas Specificity plus the capability to copy the gas signal and simulate gas presence in the laser beam for operational validation using SimuGas™
Reference Channel (Retained Sample) & Laser Lock The retained sample of target gas in an ELDS transmitter is the key to maintaining Harmonic Fingerprint lock. The microprocessors in an ELDS transmitter actively maintain the operating conditions of the laser diode(s) to achieve continuous Harmonic Fingerprint lock. Achieving and maintaining Harmonic Fingerprint lock is not dependent upon the amount of target gas in the retained sample. Under conditions of Harmonic Fingerprint lock, the size of Harmonic Fingerprint components produced by a given quantity of gas is a known constant.
SimuGas: Senscient uses SimuGas™ as the simplest and most reliable gas detector functionality test available. In an ELDS system with SimuGas the transmitter’s microprocessor has direct control of the synthesis of the laser diode drive waveforms, and access to the Harmonic Fingerprints being produced by absorption of laser diode radiation by the retained sample of target gases. Upon receiving a command instruction from an operator or automatically each day, the transmitter’s microprocessor adds Harmonic Fingerprint components to the laser diode drive waveforms to simulate the presence of a given quantity of target gas in the monitored space. The optical radiation leaving the transmitter then faithfully simulates the presence of target gas in the monitored path. When the receiver processes the signal that it is receiving from the transmitter, it sees the Harmonic Fingerprint components and calculates and outputs the corresponding quantity of target gas. By simply comparing the gas reading output by the receiver to the quantity of target gas that the transmitter was instructed to simulate, it is possible to verify the correct operation of the gas detector.
SimuGas ™ The laser diode drive waveforms used in an ELDS transmitter are digitally synthesised Upon command, it is possible for an ELDS transmitter to digitally synthesise laser diode drive waveforms which include Harmonic Fingerprint components When an ELDS transmitter’s laser diode(s) are driven with waveforms including Harmonic Fingerprint components, the resulting optical output is indistinguishable from that produced when target gas is present in the monitored path Simulated Gas – SimuGas ™ can be used to functionally test an ELDS-based gas detector
SimuGas: Compared to the conventional techniques currently used to test gas detectors, SimuGas testing has the following advantages: Functional testing can be performed remotely, without operators needing to gain access to difficult-to-reach gas detectors. No more scaffolding or abseiling! Gas detectors can be functionally tested much more frequently, providing greater safety integrity. SimuGas enables SIL 2 or SIL 3 gas detection systems to be easily realised. There is no need for operators to carry cylinders of hazardous gases around facilities in order to test gas detectors. The results of detector functionality testing can be gathered and logged automatically. The operation and maintenance costs for a gas detection system are greatly reduced. With the innovative SimuGas technique the Cost of Ownership effectively reduces to zero as SimuGas permits gas detector functionality to be confirmed on command, locally or remotely under any condition.
Enhanced Laser Diode Spectroscopy (ELDS) Enhanced Laser Diode Spectroscopy is a revolutionary gas detection technology, specifically developed for safety related applications in industry. ELDS provides the following unique benefits and advantages: ELDS based OPGD systems provide reliable, sensitive detection of both flammable and toxic gases at low ppm concentrations. Toxic gases of primary interest include hydrogen sulfide, hydrogen fluoride and ammonia. ELDS-based OPGD systems offer three orders of magnitude in increased sensitivity for hydrocarbons, greatly increasing the probability of detecting a flammable gas leak before it reaches catastrophic proportions. Current NDIR methodology fails to provide warnings early enough, or reliably enough to facilitate any significant remedial action. ELDS based OPGD units can be produced for combinations of toxic and / or flammable gas hazards, significantly reducing the cost for a comprehensive gas detection system. Unique SimuGas™ feature provides the long sought-after ability to accomplish automatic or on-demand functional testing of open path gas detectors. The full list of ELDS benefits is available on the Senscient website: http://www.senscient.com/downloads/2238Senscient-Top-10-Reasons.pdf