RamanFlex School of Engineering Science Burnaby, BC V5A 1S6
Contents
1. Nonetheless the functional specifications provided for the phase 1 prototype are rigorous Should we be unable to achieve them a thorough explanation of the failings of our methods or equipment is required to constitute any success in our endeavour We are confident that the market for this device exists We are also confident that the project is technically feasible Both of these statements are supported by the fact that Raman spectrometers are used in a number of biomedical applications What remains to be seen is whether a Raman gas analyzer can be constructed on a thin budget in an extremely limited amount of time and targeted for larger production scales 22. RN 36 23 Under normal use the system shall not require regular servicing more frequently than once per month RN 37 23 The gas sample cavity which may require cleaning or inspection shall be con veniently accessible RN 38 2 The system maintenance shall be able to be accomplished by a serviceperson at the location of end use 5 3 2 Operational Lifetime RN 39 2 The system shall have an expected operational lifetime of no less than 22000 Hrs of continuous operation 5 3 3 Repairability RN 40 2 The system shall be field repairable by a trained repairperson RN 41 2 The system shall be modularized so as to be repairable without full component replacement 5 4 USER INTERFACE REQUIREMENTS We envision a number of possible user interfaces for the device The gas analyzer unit itself will only have a power switch rudimentary status lights and a RS 232 port therefore no real user interface is provided with the analyzer itself Primarily a user will attach the gas analyzer to a PC running companion software However there are situations in which a user might not wish to place a full PC near the analyzer Large charter boats or small dive shops for instance might not have spare room or power for a PC Therefore we could also supply a small companion unit with a LCD display 17 6 RamanFlex Functional Specification October 17 2002 and some rudimentary controls This device when attached to the analyzer s RS 232 port c
3. and applies to firefighters etc T S RamanFlex Functional Specification October 17 2002 5 5 3 User Warnings RN 51 3 The device shall contain a laser warning label RN 52 3 Where appropriate the device shall feature a label indicating that there are no serviceable parts inside 5 6 SAFETY FEATURES RN 53 23 The device contains a chassis interlock so that it will not operate while open RN 54 23 System failure modes should be clearly indicated and not be confusable with valid readings No invalid readings should be presented should the system enter a common failure mode 5 7 MARKET AND MANUFACTURING REQUIREMENTS RN 55 23 The product shall be manufactured for a production cost not exceeding 2 000 5 8 DOCUMENTATION AND TRAINING MATERIALS RN 56 3 A training video will be provided in English French and Spanish RN 57 3 A technical user s manual will be provided in English French and Spanish RN 58 3 A service manual will be provided in English French and Spanish for repair technicians 6 TEST PLAN As the initial design phase will serve as a proof of concept the following requirements must be met for the device to be considered a success at phase I and design work to continue to phase II The device completed for ENSC 340 only has one function it measures the gaseous contents of laboratory air Furthermore the output consists of a strip of pixels interpretable as a waveform which contains the measured
4. connection or disconnection of air couplings RN 4 23 The unit shall have an under clearance sufficient for any required cooling air intakes RN 5 23 All connections of hoses power and data cables as well as the cooling exhaust vents shall be on the top of the unit to ensure that the cooling air exhausts are not obstructed by the placing of items on top of the unit RN 6 23 All connections of hoses and power and data cables must be fastenable so that they cannot be dislodged easily if the unit is jarred 5 1 2 Robustness RN 7 23 The device shall be sufficiently mounted e g by the use of rubber feet to ensure isolation from the vibration generated by a large air compressor nearby 14 6 RamanFlex Functional Specification October 17 2002 RN 8 23 The outer casing of the device should be sufficiently strong to withstand an acci dental impact by a large wrench or other device typically used in the freeing of stuck gas valves on air tanks RN 9 23 The device shall be constructed in such a way to withstand the connection of the sampling intake to a high pressure 3000 PSI nominally plus a safety margin air tank RN 10 23 The device should rest stably on an appropriate surface and should not slide 5 1 3 Required Connections RN 11 23 The device shall include a fully contained power supply unit capable of operating on 120 or 240 VAC at either 50 or 60 cycles RN 12 23 The gas input connection should accept the standard hi
5. 2 3 5 FEASIBILITY CONCLUSIONS There is no doubt that it will be extremely difficult for us to construct an apparatus which measures the Raman effect It is feasible barely using reasonable assumptions however we are aware that the failure of a number of assumptions should they prove too optimistic could make it impossible to measure the Raman effect The solution to these problems is invariably money and time With a more powerful laser the intensity of the Raman effect becomes larger With a better CCD sensitivity and noise immunity improve However these sensors cost money and we do not have an unlimited budget or the luxury of time to wait for replacements to ship At a higher level the goal of this project is to establish whether or not it is economically possible to construct a Raman gas analyzer We will see 4 REQUIREMENTS AND LIMITATIONS The above section digressed into some design details While any mention of for example part numbers does not strictly belong in a functional specification some device characteristics were vital in order to establish whether or not it is possible for us to measure the Raman effect The following sections detail the restrictions and functions that a gas analyzer using the above principle should or must adhere to Most of the functions meet user requirements While some of the restrictions are imposed by theoretical limitations of a Raman analyzer the greatest portion of them re
6. Raman data T RamanFlex Functional Specification October 17 2002 We do not anticipate the completion of an automated analysis tool Therefore evaluating the success of this device consists of determining how closely the measured Raman spectrum matches the ideal Raman spectrum Therefore a brief explanation of how to derive the ideal Raman spectrum is neccessary 6 1 DERIVING RAMAN WAVELENGTHS Table 1 specifies Raman shift data for a number of gases Schr tter 1982 Molecule Raman Shift cm Relative Intensity Na 2331 1 O2 1555 1 04 CO 1388 1 13 CO 1285 0 75 Table 1 Raman shifts for gases of interest 1 Raman lines in units of cm may be converted to wavelengths via the following formula 1 fa 11004 fi where fa is the Raman frequency A is the Raman shift in cm units and f is the wavelength of the laser light in meters For example N gives a Raman frequency of 766nm from a laser at 650nm 6 2 CALIBRATING THE DEVICE We hope to be able to calibrate the device simply by ensuring that stray laser light i e not Raman shifted falls onto the sensor With this light as a reference and using the diffraction grating equation we should be able to determine approximately which pixel cooresponds to a particular wavelength This calibration data is not provided simply since it is not yet available For testing the device we will provide calibration data g S RamanFlex Function
7. RamanF lex School of Engineering Science Burnaby BC V5A 156 October 17 2002 Dr Andrew Rawicz School of Engineering Science Simon Fraser University Burnaby British Columbia V5A 156 Dear Dr Rawicz Enclosed are the functional specifications for a Gas Analyzer based on measurements of the Raman effect This document details both our goals for the remainder of this semester and some product requirements which we do not anticipate meeting but which would be important for a production quality product These specifications also contain a high level description of the Raman effect with the intent to convince you that it is possible for us to construct such a device I must stress again that we are planning the completion of a lab bench prototype We intend to spend our time exploring the process of measuring the Raman spectrum of a gas We do not expect to have time to perfect or even investigate large portions of the surrounding infrastructure that a gas analyzer requires for example we expect to measure the Raman spectrum of laboratory air rather than a sample gas from another source There are still a large number of requirements which a commercial product would have to meet these requirements are also explored in this document To neglect them now would result in a product which meets a small portion of requirements but perhaps precludes others required for the device s commercial viability due to oversight Therefore we h
8. al Specification October 17 2002 6 3 TAKING A SAMPLE We will provide a means to extract a sample from our microcontroller This sample will be read onto a PC 6 4 EVALUATING A SAMPLE The process of evaluating a sample consists of visually lining up the measured and the oretical spectral graphs We cannot provide a reference graph simply because we have not yet finalized the operating frequency of our laser Such a graph will be provided at testing time Determining the relative concentrations of a gas require integration of the area underneath spikes on the spectral graph A method manual or automated for accomplishing this will be provided at testing time 7 CONCLUSION In the preceding functional specifications we presented a large number of requirements Very few of these requirements apply to phase 1 of the project which is to be completed at the end of the Fall 2002 semester The unit itself has very little user interaction we strongly desire that this device be as functionally transparent as possible Therefore the large proportion of the above functional requirements apply to the commercialization process The process of actually obtaining and evaluating a Raman profile of a gas is daunting For this reason we have placed an appropriately large emphasis on completing this stage of the project Many of the remaining specifications are incremental refinements on a process the possibility of which we intend to demonstrate
9. ave tried to be both comprehensive and realistic in our analysis If there are any questions concerns or comments do not hestitate to contact any member of the design team Our contact information has been included in the first page of our proposal Sincerely Graeme Smecher Project Lead RamanF lex RamanfFlex Functional Specifications Jon Jolivet Graeme Smecher Bernard Smit RamanF lex Functional Specification October 17 2002 THE FINE PRINT This document reflects the plan for a four month project and is accurate to the best of our abilities The project is however a moving target Therefore this document is subject to revision The RamanFlex team may be contacted en masse at lensc340 napiformOsfu ca Al ternately our individual contact information is as follows name e mail home cel pager 604 942 9935 604 444 3431 604 473 1367 604 324 5055 604 945 7155 604 837 9468 Simon Laalo Jon Jolivet Graeme Smecher Bernard Smit This is Version 1 of this document prepared on October 17 2002 Please check for newer versions with one of the above contacts RamanFlex Functional Specification October 17 2002 ABSTRACT This functional specification details the investigation and prototyping of a gas analyzer based on the Raman effect Because it is a functional specification it focuses on the bound aries and interfaces between such a device its operator and its environmen
10. ber of situations in which we expect to encounter limitations All of these situations directly result from the physics behind the Raman effect which will allow our analyzer to measure sample concentrations Because many of our functional requirements and restrictions are intimately tied to these results we present a brief description of the Raman effect Also since the Raman effect is extremely difficult to measure we provide a high level calculation in an attempt to demon strate that measuring the Raman effect is within our grasp Unfortunately the feasibility study requires some order of magnitude figures that require us to draw design details such as some IC characteristics into this document Due to the roughness of the following calculations however we expect that part substitutions will not greatly effect the results of the following sections 8 6 RamanFlex Functional Specification October 17 2002 3 1 THE RAMAN EFFECT When a light beam passes through a gaseous sample the photons that make up the light beam pass the particles that make up the sample Sometimes photons and molecules interact resulting in a measureable change in the properties of the light beam Most of the time these interactions simply changes the direction of the light beam This effect is not unlike a flashlight beam passing through fog the light scatters in many different directions However a very small proportion of photon particle interactio
11. ctober 17 2002 1 INTRODUCTION The purpose of a functional specification is to outline the boundaries between a device its user and its environment It may be viewed in essence as a contract which such a device must meet in order to achieve its designers goals This contract entails far more than the user interface itself All constraints that apply to a product power consumption operating conditions safety requirements and so forth are fodder for this functional specification Because there is so much ground to cover we have tried to maintain a consistent level of detail Some considerations will be omitted because they would require a level of detail which belongs in the design specifications they may after such a document is completed be introduced to successive revisions of this document The device outlined in these specifications though it has applications ranging beyond SCUBA diving is primarily intended to afford divers and compressor operators some im mediate feedback on the quality of their air mixtures The device is designed to provide an in situ analysis of breathing gas for compressor operators at the time of tank filling Additionally the contents of a previously filled cylinder could be verified The device specified will provide concentration information for a wide variety of gases including nitrogen and helium which are currently inaccessible using existing technology outside of a laboratory environm
12. e s oa 0 6 2 he ia a ES SS 9 3 2 The Strength of the Raman Effect 0a aaa aa lt lt 9 3 3 Detecting the Raman Effect oaa 4 a ee 5 0 eee 10 O O we ee 11 uate te per Stands oe A Erte Ge de oe a as i 12 12 Sees Bae ote wee Cee Esa aa eee 12 4 2 Acronyms and Definitions 2 4 4 4 e248 64 68 2 Spee wae ee 13 4 3 CONVERSA AA ee ee AA AAA 13 14 Sk et a oe ee o a eee 14 pe General s s secs Bee Re BS EAE ena a Ow Oe E OO 14 5 1 2 RODUSIES os z sa sce KORE aw Od aw oe Oe eee eS 14 Bat hk eH Be bk oe A EDS BBE 15 Be ater OR eke BOS nS Sek bo ere 15 ee ee Ra re ee ee 15 oe SA et ee a ei ee A 16 5 3 Reliability and Servicability o o 17 5 3 1 Required Maintenance scx bao de ARA 17 ss Gh etn So A E II 17 5 3 3 REPARA s s p ole ke D e ee OS AA A 17 a ee e ee ee Oe a we ee 17 ote eee amp bee a eee ee Se eee a A A 18 bee ee bee ee a ee 18 Cs peg Ow og eae oe e 18 a eee eee ee ee eee eee eee eee 18 AR PST ods ee ek ee ae ee ee Pe a hoe ae oe oS 18 ee bo ck be ees te ee eee See EE 19 Fe pane eA Bre eA Sra oe Soe a aed A Bee ou 19 RamanFlex Functional Specification October 17 2002 5 7 Market and Manufacturing Requirements 5 8 Documentation and Training Materials 6 Test Plan aos BK Beat inten Ao A Beer cree LIST OF FIGURES 1 A general block diagram LIST OF TABLES 1 Raman shifts for gases of interest RamanFlex Functional Specification O
13. ent We will provide continuous rapid feedback on gas contents The development of our laboratory prototype should proceed with the goal of producing a commercial product costing between 1 000 and 3 000 The device prototype will be developed in several phases the initial phase completion targeted for Dec 2002 consists of a lab bench prototype device to provide a proof of concept for the technology and components to be used We intend to demonstrate that a commercial gas analyzer based on the Raman effect is both possible and economically viable for breathing gas analysis The remainder of this document is laid out in several sections We will provide e a brief explanation of the need which we are attempting to address e an introduction to the Raman effect and an exploration of the feasibility of measuring it and e a list of constraints and requirements for the project to be considered a success 6 6 RamanFlex Functional Specification October 17 2002 1 1 REFERENCES Two ICs are referenced in a feasability study included below e The datasheet for the Atmel TH7834C may be found at http www atmel com atmel acrobat doc1997 pdf e The datasheet for the National Semiconductor LM9823 may be found at national com ds LM LM9823 pdf In addition the following printed materials are referenced Schrotter H W 1982 Linear Raman Spectroscopy A State of the Art Report Non Linear Raman Spectroscopy and Its C
14. flect the limited amount of time that we have to develop our laboratory prototype 4 1 SCOPE As mentioned above we have included functional specifications for both our laboratory prototype and a commercial prototype We do not anticipate completion of many functional requirements beyond those which are required for the laboratory prototype The remainder are included for completion it would be negligent of us to consider only those which we can achieve over the short term r S RamanFlex Functional Specification October 17 2002 4 2 ACRONYMS AND DEFINITIONS PADI The Professional Association of Dive Instructors This association is the largest body which certifies SCUBA divers PADI also certifies instructors and dive shops CSA The Canadian Standards Association This body certifies that products are safe under certain circumstances 4 3 CONVENTIONS The design of our Phase I prototype will be driven by the requirements listed below Subsequent design documents will retain the Requirement Number RN references given below The final phase 1 post mortem will address each of the requirements by number and detail the success or failure of the system to meet the requirement Any requirement changes deletions or additions to phase I will be made using sequential Requirement Change Numbers RC and this document shall be updated accordingly For example RN 14 P123 Requirement Number RC 15 P12 Requirement Change Number In the ab
15. gh pressure whips used for SCUBA diving RN 13 123 The device shall have an IEEE 1284 RS 232 serial connection via a 9 pin DB port MALE RN 14 123 The RS 232 port shall provide sufficient driving voltage and current as per the IEEE 1284 standard RN 15 123 The RS 232 port shall be isolated and protected from the rest of the device circuitry RN 16 23 The device power supply shall accept a standard north American 3 pin 120 V power outlet or a standard 3 pole 220V twist lock outlet RN 17 23 The device shall have an outlet port for depressurization and flushing of the gas sample chamber with an easily operated open closed butterfly valve RN 18 123 The device shall draw under 100W of power from the power outlet 5 2 SYSTEM PERFORMANCE REQUIREMENTS 5 2 1 Analysis Specifications RN 19 1 The device shall provide percentage composition data to an accuracy of not less than 10 i 8 RamanFlex Functional Specification October 17 2002 RN 20 23 The device shall provide percentage composition data to an accuracy of not more than 1 RN 21 123 The sampling time required by the device shall be under 30 seconds RN 22 1 The device shall provide digital intensity values for the spectral lines of the raman shifted light for both Nz and O gases RN 23 23 The device shall provide digital intensity values for the spectral lines of the raman shifted light for O2 No CO2 CO NO and detect for the presence of some hydrocarbon comp
16. harge for five seconds at room temperature This integration time is how long a CCD can collect charge before it is full of noise this noise doubles every 6 degrees or so Therefore if we assume a 5 second integration time maximum at 25 degrees we can integrate for 5 x 2 x 2 x 2 40s at 25 6 6 6 7 degrees A 40 second integration time will provide 40 x 3 x 1078J 1 2uJ which implies that our signal will be 1 2uV 3 4 DIGITIZING THE RAMAN DATA A signal of 1 2u4V is measurable however there are some difficulties in converting it to a digital value Most CCDs consider a voltage spread of about 1 5V to be the total difference between a black pixel and a white pixel A digitization accuracy of 16 bits is provided by chips such as National s LM9823 CCD controller This IC performs the read out function and digitization of a signal from a CCD sensor such as the Atmel part mentioned above However on a voltage spread of 1 5V 16 bits only results in an accuracy AV yin of 1 5 23uV is about 20 times larger than the signal we re trying to measure in other words to even get a single bit of accuracy neglecting noise the signal we measure would have to be magnified by an order of magnitude However the LM9823 has an offset function by subtracting a DC offset from the mea sured signal we can reclaim the signal and disregard the large useless DC offset that results from noise T S RamanFlex Functional Specification October 17 200
17. hemical Applications p 19 1 2 INTENDED AUDIENCE This document is intended as a design guideline for engineers to track the design require ments and any requirement changes The project and company management will use this document to ensure that the pro posed design meets all of the requirements and that any changes to the requirements are properly tracked and mutually agreed upon by both the design team and management prior to impacting the design specifications Marketing and Sales will use this document to plan sales strategies and to contribute to the design process via requirements change requests when applicable 2 PROJECT OVERVIEW Without an understanding of the market space we are attempting to meet with this project as well as the technical foundations of our solution it is difficult to motivate the requirements we intend to meet The following material attempts to briefly explain our reasons for embarking on this project Afterwards we provide an explanation of the technical foundations of this project SCUBA divers breathe compressed gas Because of the expense and expertise required to safely operate a compressor very few divers fill their own tanks Instead they buy air from dive shops charter operators and sometimes even gas stations RamanFlex Functional Specification October 17 2002 The operators of these shops are generally knowledgeable and trustworthy However sometimes the compressor s ope
18. ns cause the photon to be absorbed and re emitted by the particle In these interactions the energy of the photon manifested in its colour changes in a way that is unique for the gas particle The result is that by shining a very intense beam containing only a single colour of light we can detect a fingerprint that contains enough information to determine what s in the sample gas Lasers provide a suitably high intensity monochromatic beam Almost all materials have a Raman spectrum However monoatomic gases such as He lium do not Since Helium is used in mixed gas diving measurement of its concentration is important for a commercial device However by including a pressure sensor the combina tion of pressure data and the concentrations of the other gases can be used to derive Helium concentration Such a pressure sensor can also be used to provide an overpressure warning and calibration data Figure I shows the basic configuration of our device 3 2 THE STRENGTH OF THE RAMAN EFFECT The reason that we don t see the Raman effect in everyday circumstances is that is is extremely faint A related but slightly stronger process known as Raleigh scattering is what provides the sky with its blue tint Scattering theory indicates that we can expect the Raman scattering to have an intensity of about 107 times the intensity of the laser beam We are anticipating a laser intensity of on the order of 300mW 0 300J s therefore
19. of development can begin In the second phase we will design a production grade prototype model which will meet several additional requirements The production prototype will 1 Produce a Raman Spectrum of a gas mixture contained in a closed sampling chamber 2 Detect the Raman signatures for a wide array of gases including O2 No CO2 CO NO and others 3 Produce a digital output value for each of the above signatures which is proportional to the intensity of each wavelength RamanFlex Functional Specification October 17 2002 4 Calculate the percent composition of each of the gases in the sample within the accu racy level required for commercial dive shop use 5 Provide a pass fail grade for a particular sample compared against a standard air rating such as CSA Grade E 6 Be self contained reliable easily used and meet all necessary CSA and PADI standards for commercial dive shop use 7 Be manufactured for a cost in line with the market sale price for such a device in a commercial non laboratory environment 8 Be inexpensive to operate continuously both in terms of electrical consumption and maintenance schedule We will finish the first of the above phases in December 2002 RamanFlex Functional Specification October 17 2002 CONTENTS 6 1 1 References 4 ee 8 Boke eke oe ee Ee ee ee eR ES be OES Bx T 1 2 Intended Audiencel ooa a es T 7 3 Technical Foundations 8 31 The Raman Effect ss
20. ould function as a display for the gas analyzer By dividing the analysis and interface portions of the device users may place the gas analyzer where it is convenient to attach gas sample hoses Then they may place the interface near controls or wherever it is convenient 5 4 1 PC GUI requirements RN 42 1 The PC software shall display the data on screen as it is received from the device RN 43 23 The PC software shall display a graphical representation of the percent compo sition of the sample via a pie chart with actual values for each gas listed on a separate table RN 44 23 The PC software shall control the starting and ending times for each sample integration RN 45 23 The PC software shall provide a user friendly graphical interface and contain diagnostic routines which inform the user should the device fall out of calibration RN 46 23 The PC software shall verify that the device is properly connected to the PC serial port and inform the user of any problems encountered 5 4 2 On System Indicators and Controls RN 47 23 The device shall feature a power switch RN 48 23 The device shall feature indicator LEDs for power error and calibration status 5 5 SAFETY amp REGULATORY REQUIREMENTS 5 5 1 CGA RN 49 23 The device will determine gas adherence to CGA gas standards 5 5 2 CSA UL RN 50 23 The device will adhere to the CSA breathing air standard CAN CSA Z180 1 00 This standard applies to the quality of SCBA gas
21. ounds RN 24 23 The device shall provide a percentage composition of He 5 2 2 Operational Specifications RN 25 23 The system power supply shall provide accurate voltages to the device within a range of 20 of the nominal AC input voltages 115 230 VAC RN 26 23 The system power supply shall have a protection circuit designed to cut power in over voltage over current or ground fault situations RN 27 23 The system power supply shall be designed for 100 duty cycle operation RN 28 23 The system shall adhere to OSHA Occupational noise standard 1910 95 RN 29 23 The system shall produce noise levels under 40 dB when operating RN 30 23 The system shall operate correctly in temperatures ranging from OdegC to 50 deg C RN 31 23 The system shall operate correctly in ambient humidity levels from 0 to 100 humidity RN 32 23 The system shall operate correctly at altitudes from sea level 0 m to not less than 1000m RN 33 23 The system shall contain appropriate sensors to alert the user when it is outside of its reliable operating temperature or pressure RN 34 123 The device shall communicate with the PC at a data rate of not less than 9600 bps E RamanFlex Functional Specification October 17 2002 5 3 RELIABILITY AND SERVICABILITY 5 3 1 Required Maintenance RN 35 23 The system shall detect contaminant build up and alert the user to such a condition before the system accuracy falls outside of tolerance levels
22. ove the requirement numbers 14 15 are sequential tracking numbers Numbers following the dash represent the phases to which the requirement or change should be applied as follows e P 1 Applies to the proof of concept device e P 2 Applies to the commercial prototype e P 3 Applies to production units Note that in addition to the two phases described elsewhere in the project a third phase P 3 has been added This phase cooresponds to the completion of a production unit complete with documentation and training materials r RamanFlex Functional Specification October 17 2002 5 SYSTEM REQUIREMENTS The following sections list functional requirements that must be met They are split among the three development stages as described above 5 1 PHYSICAL REQUIREMENTS The gas analyzer is designed to be used in conjunction with a tank filling compressor Standard AC power is assumed to be readily available The device should be able to be carried in appropriate protective crating by a single individual however it is not designed to be moved during use The initial phase I prototype is designed to be implemented on a lab bench and is not designed to be mobile at any point 5 1 1 General RN 1 23 The unit shall be under 100 lbs when packed in protective crating RN 2 23 The unit shall have no dimension over 1 meter in size RN 3 23 The unit shall be of sufficient mass to rest firmly in place and not be moved about by
23. rating or maintainence schedules or a lack of expertise of the staff lead to unsafe situations It is extremely easy for a poorly maintained or installed compressor to introduce toxins to the air it produces Additionally an increasingly large number of technical divers use mixed gas Mixed gas is created when divers change the concentrations of the major components in air or introduce other gases such as Helium Divers use mixed gases because it is absorbed differently by their bodies which allows them to dive in more demanding situations Often mixed gases allow longer or deeper dives than would be possible using regular air The problem with mixing gas is simple divers need to know the concentration of each gas in their mixture in order to dive safely with it There are commercially available devices to measure the concentration of several of these gases but they cannot measure at least two of the constituent gases of clean air We are attempting to prototype a gas analyzer that will determine some of the con stituents of a breathing gas sample We do not anticipate having the accuracy to determine all of the constituents Before explaining our goals for the semester an explanation of the physical basis of our analyzer helps to provide an understanding of the strengths and limitations which we expect to encounter 3 TECHNICAL FOUNDATIONS There are a number of situations in which we expect our gas analyzer will excel and a num
24. t Because of the long exploratory phase involved with developing a project as technically involved as this gas analyzer the RamanFlex team has divided our functional goals and constraints into several categories We are careful to distinguish between the limited set of goals which we intend to complete during the Fall 2002 semester and either the required or wish list goals to which a production quality device would be subject Even though we cannot hope to achieve many of the second set of goals within the time constraints facing us we intend to remain careful not to reduce our commercial viability by precluding a particular function or goal by accident For this reason we have attempted to provide a complete analysis which reaches beyond our short term goals for the remainder of this semester We will construct the gas analyzer in two phases The initial phase concludes with the completion of a proof of concept This laboratory prototype will 1 Produce a Raman Spectrum of the air in the lab 2 Detect the Raman signatures for Oz and Na in the above spectrum through manual calibration 3 Produce a digital output value for each of the above signatures which is proportional to the intensity of each wavelength 4 Provide a system of equations which can be used with the above digital values to provide the percent composition of the gases Oz and Na in the laboratory air Once the above requirements have been met the second phase
25. the Raman fingerprint signal will have a strength of about 3 x 108 J s 9 6 RamanFlex Functional Specification October 17 2002 Laser Module Controller Module Laser beam Sample Chamber Digitized Raman signal scattered light Sensor Figure 1 A general block diagram 3 3 DETECTING THE RAMAN EFFECT CCD sensors such as the camera elements used in digital cameras have the ability to collect energy from a sensor for long periods of time CCDs behave as charge integrators that is they can detect an extremely faint signal if they are allowed to collect it for a long period of time The sensitivity of CCD sensors is typically measured in V uJ cm A nominal value for one device the Atmel TH7834C is about 5V pJ cem To simplify calculations we must make several assumptions First assume that the above signal strength 3 x 1078 J s is the strength of a single Raman fingerprint These fingerprints are measured on the CCD as pixels let us assume that the entire Raman signal for a single fingerprint falls on a single sensor element or pixel y S RamanFlex Functional Specification October 17 2002 Therefore for the Atmel TH7834C which has pixel sizes of 6 5 x 6 5um 4 225 x 10 7cm we have a sensitivity of x 4x 107cm 20 x 10 V pJ uJ x en In other words a single pixel will measure 1 volt per joule of energy CCD devices such as the one mentioned above can easily collect c
Download Pdf Manuals
Related Search