WO2001084096A1 - Co2 gas measurement system for a laboratory incubator - Google Patents

Co2 gas measurement system for a laboratory incubator Download PDF

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Publication number
WO2001084096A1
WO2001084096A1 PCT/US2000/011487 US0011487W WO0184096A1 WO 2001084096 A1 WO2001084096 A1 WO 2001084096A1 US 0011487 W US0011487 W US 0011487W WO 0184096 A1 WO0184096 A1 WO 0184096A1
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WO
WIPO (PCT)
Prior art keywords
gas
energy
measurement system
detector
concentration
Prior art date
Application number
PCT/US2000/011487
Other languages
French (fr)
Inventor
Charles G. Butts
Timothy R. Runion
Original Assignee
Spx Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Spx Corporation filed Critical Spx Corporation
Priority to PCT/US2000/011487 priority Critical patent/WO2001084096A1/en
Priority to AU2000248069A priority patent/AU2000248069A1/en
Publication of WO2001084096A1 publication Critical patent/WO2001084096A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
    • C12M41/30—Means for regulation, monitoring, measurement or control, e.g. flow regulation of concentration
    • C12M41/34—Means for regulation, monitoring, measurement or control, e.g. flow regulation of concentration of gas
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N2021/1748—Comparative step being essential in the method
    • G01N2021/1751—Constructive features therefore, e.g. using two measurement cells

Definitions

  • the present invention relates to a CO 2 gas measurement system for use in a laboratory incubator. More particularly, the invention relates to a gas measurement system that more accurately measures the amount of CO 2 gas in an incubator as the components of the system degrade over time.
  • CO 2 gas is commonly introduced into laboratory incubators to facilitate cell growth and testing. Because CO 2 levels must be kept within a desired range, laboratory incubators typically include CO 2 detector assemblies for detecting the concentration of CO 2 therein.
  • CO 2 detector assembly includes a sensing cell containing the same environment as its incubator, an infrared (IR) source that radiates energy within the sensing cell at the absorption band of CO 2 , and a detector positioned to receive the radiated energy from the source and operable to generate an output signal representative of the intensity of the received energy in the absorption band of the CO 2 .
  • IR infrared
  • the CO 2 in the sensing cell partially absorbs the energy that is within the absorption band of CO 2 ; therefore, the amount of energy that reaches the detector corresponds to the amount of CO 2 in the cell.
  • the output of the detector accurately corresponds to the concentration of CO 2 in the cell.
  • temperature changes can affect the operation of both the source and the detector.
  • the present invention solves the above-described problems and provides a distinct advance in the art of incubator CO 2 measurement systems. More particularly, the present invention provides a CO 2 gas measurement system that continuously calibrates itself before each measurement to account for degradation of both its source and detector.
  • the gas measurement system of the present invention broadly includes a radiation source for radiating energy; a reference detector operable to receive the radiated energy, to detect a spectral range of the radiated energy outside of an absorption band of the gas, and to generate a signal representative thereof; a sample detector operable to receive the radiated energy, to detect a spectral range of the radiated energy within the absorption band of the gas, and to generate a signal representative thereof; and a control assembly for comparing the signals generated by the detectors to determine the concentration of the gas in the enclosed area.
  • the radiation source, reference detector, and sample detector are preferably positioned in a sensing cell that contains the same CO 2 gas concentration as its corresponding incubator.
  • the output signal of the sample detector is sensitive to the amount of CO 2 gas in the sensing cell in a similar manner as prior art detectors.
  • the reference detector is only sensitive to energy that is outside the absorption band of CO 2 , it generates a signal that is independent of the amount of CO 2 in the sensing cell. Therefore, the difference between the output signals of the two detectors corresponds to the amount of CO 2 in the sensing cell and is independent of the degradation of the source and the detectors. This allows the control assembly to continuously calibrate the system by comparing the signals generated by the two detectors.
  • Fig. 1 is a schematic diagram of a CO 2 gas measurement system constructed in accordance with a preferred embodiment of the invention and shown coupled with a laboratory incubator.
  • CO 2 gas measurement system broadly referred to by the numeral 10 and constructed in accordance with a preferred embodiment of the invention is illustrated.
  • the preferred measurement system is shown coupled with an incubator 12 and is operable for detecting and measuring the concentration of CO 2 gas therein; however, those skilled in the art will appreciate that the measurement system can be configured to measure the concentration of any gas in any enclosed area.
  • the preferred gas measurement system 10 broadly includes a gas detector assembly referred to by the numeral 14 and a control assembly referred to by the numeral 16.
  • the gas detector assembly 14 includes a sensing cell 18, a radiation source 20, a reference detector assembly 22, and a sample detector assembly 24.
  • the sensing cell must contain the same environment as the incubator 12 and therefore may simply be an area within the incubator. Alternately, the sensing cell may be remote from the incubator and coupled therewith with piping or tubing so that the environment from the incubator can be pumped or otherwise introduced into the sensing cell.
  • the source 20 is positioned within the sensing cell 18 and is operable to radiate energy through the environment of the cell.
  • the source is preferably an incandescent lamp that radiates infrared (IR) energy in the absorption band of CO 2 .
  • the source, as well as the other components of the gas detector assembly, are preferably manufactured by Digital Control Systems, Inc., of Portland, Oregon.
  • the present invention takes advantage of the principle that CO 2 gas is invisible to radiation at wave lengths outside of a narrow CO 2 absorption band. Therefore, radiation outside the absorption band of CO 2 passes unimpeded through CO 2 . Conversely, radiation within a narrow absorption band of CO 2 is partially absorbed by CO 2 gas. Therefore, radiation within the absorption band of CO 2 is at least partially blocked by the presence of CO 2 within the sensing cell.
  • the reference detector assembly 22 is positioned within the sensing cell 18 so that it at least some of the energy emitted from the source 20 impinges thereon.
  • the reference detector assembly includes a conventional IRdetector and a filter coupled therewith that passes a spectral range of the energy emitted from the source that is outside of the absorption band of the CO 2 gas present in the sensing cell. Thus, the energy in this spectral range passes unimpeded to the reference detector regardless of the amount of CO 2 gas present in the sensing cell.
  • the reference detector's output is therefore independent of the CO 2 gas concentration in the sensing cell, but is dependent upon the brightness or intensity of the energy emitted from the source.
  • the sample detector assembly 24 is also positioned with the sensing cell 18 so that at least some of the energy emitted from source 20 impinges thereon.
  • the sample detector assembly preferably includes a conventional lR detector and a filter coupled therewith that passes a spectral range of the radiated energy that is within the absorption band of CO 2 . Therefore, the amount of radiated energy that reaches the sample detector is dependent upon the concentration of CO 2 gas within the sensing cell so that the output of the sample detector changes with the CO 2 gas concentration in the cell.
  • the control assembly 16 is coupled with the gas detector assembly 14 and is operable for analyzing the signals generated by the sample and reference detectors 22,24 to determine the concentration of CO 2 within the sensing cell 18.
  • the control assembly includes a comparator 26, a multiplexer 28, and a microprocessor 30, all powered by a conventional power source 32.
  • the comparator 26 receives the output signals from both the reference detector 22 and the sample detector 24 and determines the difference therebetween. The difference between these signals corresponds to the amount of CO 2 in the sensing cell and is independent of other factors such as the degradation of the source and the detectors.
  • the multiplexer 28 is coupled with the comparator 26 for receiving signals therefrom, multiplexing the signals, and passing them to the microprocessor 30.
  • the ' microprocessor analyzes the signals to determine the concentration of CO 2 within the sensing cell 18 as described below.
  • the microprocessor may be coupled with other components such as a CO 2 valve for regulating the delivery of CO 2 to the sensing cell in accordance with the measured value of the CO 2 in the cell.
  • the gas detector assembly 14 is placed in our coupled with the incubator 12 or other enclosed area having a concentration of CO 2 or other gas therein.
  • the source 20 is then turned on so that radiation emitting therefrom impinges upon the reference and sample detector assemblies 22,24.
  • the reference and sample detectors generate output signals as described above which are in turn received by the comparator 26.
  • the comparator first reads the output from the reference detector 22 and stores it in memory. The comparator then reads the output from the reference detector again and compares it to the stored output signal to determine if there is a difference. If there is a difference, the comparator and multiplexor 28 multiplex the difference with the output signal of the sample detector and pass the multiplexed signal to the microprocessor 30. The microprocessor then determines the CO 2 gas concentration in the sensing cell by analyzing the signals from the comparator and multiplexer.
  • the CO 2 gas measurement system 10 of the present invention continuously calibrates itself prior to each CO 2 measurement to compensate for degradation of the source 20 and the reference and sample detectors 22,24. This enables the system to accurately and quickly determine the CO 2 gas concentration in the sensing cell 18 without first evacuating the cell of all CO 2 gas.

Abstract

A gas measurement system (10) for measuring the concentration of CO2 gas in an incubator (12) includes a radiation source (20) for radiating energy; a reference detector (22) operable to receive a portion of the radiated energy, to detect a spectral range of the energy outside of an absorption band of the gas, and to generate a signal representative thereof; a sample detector (24) to detect the spectral range of the energy within the absorption band of the gas, and to generate a signal representative thereof; and a control assembly for comparing the signals generated by the reference and sample detectors to determine the concentration of the gas in the enclosed area.

Description

CO2 GAS MEASUREMENT SYSTEM FOR A LABORATORY INCUBATOR
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to a CO2 gas measurement system for use in a laboratory incubator. More particularly, the invention relates to a gas measurement system that more accurately measures the amount of CO2 gas in an incubator as the components of the system degrade over time.
2. DESCRIPTION OF THE PRIOR ART
CO2 gas is commonly introduced into laboratory incubators to facilitate cell growth and testing. Because CO2 levels must be kept within a desired range, laboratory incubators typically include CO2 detector assemblies for detecting the concentration of CO2 therein. One such prior art CO2 detector assembly includes a sensing cell containing the same environment as its incubator, an infrared (IR) source that radiates energy within the sensing cell at the absorption band of CO2, and a detector positioned to receive the radiated energy from the source and operable to generate an output signal representative of the intensity of the received energy in the absorption band of the CO2. The CO2 in the sensing cell partially absorbs the energy that is within the absorption band of CO2 ; therefore, the amount of energy that reaches the detector corresponds to the amount of CO2 in the cell. As long as the energy emitted from the source and the sensitivity of the detector remain constant, the output of the detector accurately corresponds to the concentration of CO2 in the cell. However, overtime, the amount of energy emitted from the source decreases and the sensitivity of the detector changes. Also, temperature changes can affect the operation of both the source and the detector. These changes, commonly referred to as source and detector "drift", cause inaccurate CO2 measurements and therefore inaccurate control of CO2 introduced into the incubator. One prior solution to this problem is to periodically calibrate the detector assembly by evacuating the sensing cell of all CO2 and then measuring the intensity of the radiation received by the detector. This reading is then compared to a reading taken when the assembly was first used to determine the degradation of both the source and the detector. Although this solution is effective, it is time consuming and therefore impractical.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention solves the above-described problems and provides a distinct advance in the art of incubator CO2 measurement systems. More particularly, the present invention provides a CO2 gas measurement system that continuously calibrates itself before each measurement to account for degradation of both its source and detector.
The gas measurement system of the present invention broadly includes a radiation source for radiating energy; a reference detector operable to receive the radiated energy, to detect a spectral range of the radiated energy outside of an absorption band of the gas, and to generate a signal representative thereof; a sample detector operable to receive the radiated energy, to detect a spectral range of the radiated energy within the absorption band of the gas, and to generate a signal representative thereof; and a control assembly for comparing the signals generated by the detectors to determine the concentration of the gas in the enclosed area. The radiation source, reference detector, and sample detector are preferably positioned in a sensing cell that contains the same CO2 gas concentration as its corresponding incubator.
The output signal of the sample detector is sensitive to the amount of CO2 gas in the sensing cell in a similar manner as prior art detectors. However, because the reference detector is only sensitive to energy that is outside the absorption band of CO2, it generates a signal that is independent of the amount of CO2 in the sensing cell. Therefore, the difference between the output signals of the two detectors corresponds to the amount of CO2 in the sensing cell and is independent of the degradation of the source and the detectors. This allows the control assembly to continuously calibrate the system by comparing the signals generated by the two detectors. BRIEF DESCRIPTION OF THE DRAWING FIGURES
A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein:
Fig. 1 is a schematic diagram of a CO2 gas measurement system constructed in accordance with a preferred embodiment of the invention and shown coupled with a laboratory incubator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawing figure, a CO2 gas measurement system broadly referred to by the numeral 10 and constructed in accordance with a preferred embodiment of the invention is illustrated. The preferred measurement system is shown coupled with an incubator 12 and is operable for detecting and measuring the concentration of CO2 gas therein; however, those skilled in the art will appreciate that the measurement system can be configured to measure the concentration of any gas in any enclosed area. The preferred gas measurement system 10 broadly includes a gas detector assembly referred to by the numeral 14 and a control assembly referred to by the numeral 16.
In more detail, the gas detector assembly 14 includes a sensing cell 18, a radiation source 20, a reference detector assembly 22, and a sample detector assembly 24. The sensing cell must contain the same environment as the incubator 12 and therefore may simply be an area within the incubator. Alternately, the sensing cell may be remote from the incubator and coupled therewith with piping or tubing so that the environment from the incubator can be pumped or otherwise introduced into the sensing cell. The source 20 is positioned within the sensing cell 18 and is operable to radiate energy through the environment of the cell. The source is preferably an incandescent lamp that radiates infrared (IR) energy in the absorption band of CO2. The source, as well as the other components of the gas detector assembly, are preferably manufactured by Digital Control Systems, Inc., of Portland, Oregon. The present invention takes advantage of the principle that CO2 gas is invisible to radiation at wave lengths outside of a narrow CO2 absorption band. Therefore, radiation outside the absorption band of CO2 passes unimpeded through CO2. Conversely, radiation within a narrow absorption band of CO2 is partially absorbed by CO2 gas. Therefore, radiation within the absorption band of CO2 is at least partially blocked by the presence of CO2 within the sensing cell.
The reference detector assembly 22 is positioned within the sensing cell 18 so that it at least some of the energy emitted from the source 20 impinges thereon. The reference detector assembly includes a conventional IRdetector and a filter coupled therewith that passes a spectral range of the energy emitted from the source that is outside of the absorption band of the CO2 gas present in the sensing cell. Thus, the energy in this spectral range passes unimpeded to the reference detector regardless of the amount of CO2 gas present in the sensing cell. The reference detector's output is therefore independent of the CO2 gas concentration in the sensing cell, but is dependent upon the brightness or intensity of the energy emitted from the source.
The sample detector assembly 24 is also positioned with the sensing cell 18 so that at least some of the energy emitted from source 20 impinges thereon. The sample detector assembly preferably includes a conventional lR detector and a filter coupled therewith that passes a spectral range of the radiated energy that is within the absorption band of CO2. Therefore, the amount of radiated energy that reaches the sample detector is dependent upon the concentration of CO2 gas within the sensing cell so that the output of the sample detector changes with the CO2 gas concentration in the cell. The control assembly 16 is coupled with the gas detector assembly 14 and is operable for analyzing the signals generated by the sample and reference detectors 22,24 to determine the concentration of CO2 within the sensing cell 18. The control assembly includes a comparator 26, a multiplexer 28, and a microprocessor 30, all powered by a conventional power source 32. The comparator 26 receives the output signals from both the reference detector 22 and the sample detector 24 and determines the difference therebetween. The difference between these signals corresponds to the amount of CO2 in the sensing cell and is independent of other factors such as the degradation of the source and the detectors. The multiplexer 28 is coupled with the comparator 26 for receiving signals therefrom, multiplexing the signals, and passing them to the microprocessor 30. The' microprocessor then analyzes the signals to determine the concentration of CO2 within the sensing cell 18 as described below. The microprocessor may be coupled with other components such as a CO2 valve for regulating the delivery of CO2 to the sensing cell in accordance with the measured value of the CO2 in the cell.
In operation, the gas detector assembly 14 is placed in our coupled with the incubator 12 or other enclosed area having a concentration of CO2 or other gas therein. The source 20 is then turned on so that radiation emitting therefrom impinges upon the reference and sample detector assemblies 22,24. The reference and sample detectors generate output signals as described above which are in turn received by the comparator 26.
In one embodiment, the comparator first reads the output from the reference detector 22 and stores it in memory. The comparator then reads the output from the reference detector again and compares it to the stored output signal to determine if there is a difference. If there is a difference, the comparator and multiplexor 28 multiplex the difference with the output signal of the sample detector and pass the multiplexed signal to the microprocessor 30. The microprocessor then determines the CO2 gas concentration in the sensing cell by analyzing the signals from the comparator and multiplexer.
As evident from the foregoing description, the CO2 gas measurement system 10 of the present invention continuously calibrates itself prior to each CO2 measurement to compensate for degradation of the source 20 and the reference and sample detectors 22,24. This enables the system to accurately and quickly determine the CO2 gas concentration in the sensing cell 18 without first evacuating the cell of all CO2 gas.
Although the invention has been described with reference to the preferred embodiment illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, although the invention is particularly useful for measuring the concentration of CO2 gas in an incubator, it may also be used to measure the concentration of other gases in other enclosed areas.
Having thus described the preferred embodiment of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following:

Claims

CLAIMS:
1. A gas measurement system for measuring the concentration of a gas in an enclosed area comprising: a radiation source for radiating energy; a reference detector operable to receive a portion of the radiated energy, to detect a spectral range of the energy outside of an absorption band of the gas, and to generate a signal representative thereof; a sample detector operable to receive a portion of the radiated energy, to detect a spectral range of the energy within the absorption band of the gas, and to generate a signal representative thereof; and a control assembly for comparing the signals generated by the detectors to determine the concentration of the gas in the enclosed area.
2. The gas measurement system as set forth in claim 1 , wherein the gas is CO,
3. The gas measurement system as set forth in claim 1 , the enclosed area including a laboratory incubator.
4. The gas measurement system as set forth in claim 1 , wherein the radiation source is an infrared lamp.
5. The gas measurement system as set forth in claim 1 , the control assembly including- a comparator for comparing the signals generated by the reference and sample detectors, a multiplexer coupled with the comparator for multiplexing the signals, and a controller coupled with the multiplexer for receiving the multiplexed signals and for determining the concentration of the gas in the enclosed area as a function thereof.
PCT/US2000/011487 2000-04-28 2000-04-28 Co2 gas measurement system for a laboratory incubator WO2001084096A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/US2000/011487 WO2001084096A1 (en) 2000-04-28 2000-04-28 Co2 gas measurement system for a laboratory incubator
AU2000248069A AU2000248069A1 (en) 2000-04-28 2000-04-28 Co2 gas measurement system for a laboratory incubator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2000/011487 WO2001084096A1 (en) 2000-04-28 2000-04-28 Co2 gas measurement system for a laboratory incubator

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1403363A1 (en) * 2002-09-27 2004-03-31 SANYO ELECTRIC Co., Ltd. CO2 incubator
DE102005047326B3 (en) * 2005-09-30 2006-11-02 Binder Gmbh Climate-controlled test cupboard for long-term storage stability tests on prescription medicines has spherical light detectors
CN104777126A (en) * 2015-02-13 2015-07-15 中国科学院合肥物质科学研究院 High-detection-precision sounding apparatus and method for vertical profile of atmospheric CO2

Citations (4)

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Publication number Priority date Publication date Assignee Title
US3860818A (en) * 1972-04-27 1975-01-14 Texas Instruments Inc Atmospheric pollution monitor
US4692621A (en) * 1985-10-11 1987-09-08 Andros Anlayzers Incorporated Digital anesthetic agent analyzer
JPH0577A (en) * 1991-06-24 1993-01-08 Sanyo Electric Co Ltd Culture device
US5444249A (en) * 1994-02-14 1995-08-22 Telaire Systems, Inc. NDIR gas sensor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3860818A (en) * 1972-04-27 1975-01-14 Texas Instruments Inc Atmospheric pollution monitor
US4692621A (en) * 1985-10-11 1987-09-08 Andros Anlayzers Incorporated Digital anesthetic agent analyzer
JPH0577A (en) * 1991-06-24 1993-01-08 Sanyo Electric Co Ltd Culture device
US5444249A (en) * 1994-02-14 1995-08-22 Telaire Systems, Inc. NDIR gas sensor

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1403363A1 (en) * 2002-09-27 2004-03-31 SANYO ELECTRIC Co., Ltd. CO2 incubator
KR101059291B1 (en) * 2002-09-27 2011-08-24 산요덴키 바이오메디칼 가부시키가이샤 Carbon dioxide incubator
DE102005047326B3 (en) * 2005-09-30 2006-11-02 Binder Gmbh Climate-controlled test cupboard for long-term storage stability tests on prescription medicines has spherical light detectors
CN104777126A (en) * 2015-02-13 2015-07-15 中国科学院合肥物质科学研究院 High-detection-precision sounding apparatus and method for vertical profile of atmospheric CO2

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