Patent Publication Number: US-2015063408-A1

Title: Gaseous concentration measurement apparatus

Description:
INCORPORATION OF RELATED PATENT APPLICATIONS 
     The entire contents of the following documents are incorporated by reference herein: U.S. Pat. No. 6,639,678, titled “Apparatus and Method for Nondestructive Monitoring of Gases in Sealed Containers,” issued on 28 Oct. 2003. In the event of a conflict, the subject matter explicitly recited or shown herein controls over any subject matter incorporated by reference. For example, the incorporated subject matter should not be used to limit or narrow the scope of the explicitly recited or depicted subject matter. 
     BACKGROUND 
     Tunable diode laser absorption spectroscopy (TDLAS) is a technique that can be used to measure the concentration of a gas species such as water vapor, methane, and more, in a gaseous mixture. As the name suggests, the technique relies on a tunable diode laser (TDL) and laser absorption spectrometry (LAS) to perform the measurement. 
     One of the advantages of TDLAS over other techniques for concentration measurement is its ability to measure very low concentrations, on the order of parts per billion (ppb). Another advantage is that TDLAS is capable of distinguishing between species that are relatively closely related such as a mixture of water and ethanol. Also, it is capable of measuring other parameters of the gas under investigation such as temperature, pressure, velocity and mass flux. 
     These advantages stem largely from the ability of the TDL to be finely tuned in respect to its frequency to the specific absorption band of the target species. The energy absorbed at this tuned frequency is proportional to the concentration of the target species. For example, the TDL can be tuned to measure the water vapor concentration in a mixture of water vapor and ethanol vapor without measurement interference from the ethanol when other measurement devices such as broad-band optical sensors cannot distinguish between the two vapors. One application for which TDLAS is particularly well suited is measuring water activity of samples containing interfering volatiles such as the water/ethanol mixture mentioned. This is a very challenging problem in the food industry as well as many others. 
     In one application, TDLAS is used to measure the water activity of a sample. The sample is enclosed in a transparent container and placed in a temperature controlled device that includes a tunable diode laser and a detector. The temperature is held constant to allow the water vapor in the headspace of the container to equilibrate with the sample. 
     The laser radiation source and the corresponding detector are positioned on opposite sides of the sealed container. The laser radiation passes through the outside air, the container wall, the headspace of the container, the opposite container wall, and the outside air, until it finally reaches the detector. The outside air and the container wall introduce measurement noise and errors that must be accounted for to get an accurate reading. 
     The outside air has a different mixture of gases than that in the headspace of the sealed container. One way to minimize errors caused by the outside air is to purge the area around the container with dry nitrogen while the measurement is taken. This purging requires seals and enclosures. The purging gas also increases the measurement cost. 
     The optical characteristics of the container wall can also adversely affect the measurement. The optical characteristics can vary from one container to the next and can be influenced by foreign matter present on the exterior or interior surface such as dirt, smudges, and the like. The container material could also skew the measurement accuracy. There have been attempts to reduce this measurement error using complicated approaches such as spinning the containers during testing. Despite these attempts, the container wall still presents a significant source of measurement error. 
     Another problem associated with conventional water activity measurement devices stems from the way the temperature is measured. The water activity of the sample is assumed to be the vapor pressure in the head space, as measured by the TDL, divided by the saturation vapor pressure at the temperature of gases in the head space. This works when the temperature of the gases and the sample are the same. Unfortunately, they usually are not and even small differences can cause significant measurement errors. For example, a temperature difference of 0.1° C. between the sample and the gases in the head space can result in a water activity error of 0.006. 
     Conventional systems for measuring water activity and water content tend to be single input systems that require operator oversight. The operator typically must manually position each sample container in the device, take the measurement, record the measurement, and remove the sample container. Opportunities exist to improve this process. 
     Current practice of sample testing utilizes opening the container which allows the test sample to be subjected to environmental conditions. These conditions could alter the sample makeup as compared to the sample makeup of interest. 
     Elevated temperatures and humidity conditions can contaminate many humidity sensors and reduce sample reading accuracy. Therefore, a state of constant calibration is needed to maintain accuracy. 
     The TDL system should be less prone to sensor contamination compared to other methods. For example, certain gases such as ethylene glycol tends to skew chilled mirror accuracy as well as what was aforementioned regarding typical humidity sensors. 
     SUMMARY 
     A number of representative embodiments are provided to illustrate various features, characteristics, and advantages of the disclosed subject matter. The embodiments are provided in the context of water activity measurement apparatus. It should be understood, however, that the concepts may be used in a variety of other settings, situations, and configurations such as other types of measurement devices. Also, the features, characteristics, advantages, etc., of one embodiment may be used alone or in various combinations and sub-combinations with one another. 
     A measurement apparatus includes a sample container and a tunable diode laser. The measurement apparatus may be used to measure any of a variety of parameters associated with a gaseous mixture such as the concentration of a gaseous species in the mixture, temperature of the gaseous mixture, pressure of the gaseous mixture, velocity of the gaseous mixture, and/or mass flux of the gaseous mixture. 
     In one embodiment, the measurement apparatus is a water activity measurement apparatus. In this embodiment, the measurement apparatus is configured to at least measure the concentration of water vapor in a gaseous mixture. This can be used to determine the water activity of a sample in the sample container. 
     The sample container includes a sample chamber that holds the sample under investigation. The sample can be any material but is typically a non-gaseous material such as a liquid, solid, powder, and so forth. The sample chamber is sealed from outside air to prevent the outside air from contaminating the gaseous mixture in the sample chamber and causing measurement errors. 
     The tunable diode laser includes a laser radiation source and a laser radiation detector. The laser radiation source emits laser radiation that passes through the gaseous mixture in the sample chamber and is received by the laser radiation detector. The sample chamber can be located in the sample container. 
     The sample container includes a sealing member that closes an opening into the sample chamber. The measurement apparatus moves the sealing member from over the opening to allow the tunable diode laser access to the sample chamber without allowing outside air to enter the sample chamber. The tunable diode laser can emit laser radiation into the sample chamber without having it pass through the wall of the sample container, with the chamber remaining sealed from the outside air. 
     The water activity measurement apparatus may include a temperature sensor that directly measures the temperature of the sample. This may provide a more accurate measurement of the water activity of the sample in comparison to methods that, for example, measure the temperature of the gaseous mixture and assume that the sample is the same temperature. 
     Any suitable temperature sensor can be used and it can be positioned at any suitable location in the water activity measurement apparatus. For example, the water activity measurement apparatus may include an infrared temperature sensor positioned inside and at the top of the sample chamber. The temperature sensor may be used to measure the temperature of the sample at the same time the tunable diode laser is measuring the concentration of water vapor. 
     The measurement apparatus may also be automated to allow multiple samples to be analyzed with little or no operator input. Sample containers may be added to a feeder, tested, and ejected without any operator input. The sample containers may include electronics that store, transmit, and/or receive information about the sample in the container. This information may be analyzed later by the operator. 
     The system can also have the ability to control the sample to a set temperature determined by an operator. It can also be capable of changing the temperature of the sample from one temperature to a more preferred one. 
     The Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. The Summary and the Background are not intended to identify key concepts or essential aspects of the disclosed subject matter, nor should they be used to constrict or limit the scope of the claims. For example, the scope of the claims should not be limited based on whether the recited subject matter includes any or all aspects noted in the Summary and/or addresses any of the issues noted in the Background. 
    
    
     
       DRAWINGS 
       The embodiments are disclosed in association with the accompanying drawings in which: 
         FIG. 1  is a perspective view of one embodiment of a measurement apparatus. 
         FIG. 2  is a perspective view of one embodiment of a sample container. 
         FIGS. 3 and 4  are exploded perspective views of the sample container shown in  FIG. 2 . 
         FIG. 5  is a bottom perspective view of the top housing of the sample container shown in  FIG. 2 . 
         FIG. 6  is a cross-sectional perspective view of the sample container shown in  FIG. 2 . 
         FIG. 7  is a perspective view of the measurement apparatus shown in  FIG. 1  with the sensor unit positioned over the sample container and in position to measure one or more parameters associated with the sample in the sample container. 
         FIG. 8  is a cross-sectional perspective view of the sensor assembly positioned over the sample container shown in  FIG. 7 . 
         FIG. 9  is a perspective view of a portion of the feeding assembly for the measurement apparatus shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a perspective view of one embodiment of a measurement apparatus  10  configured to measure the water activity of a sample. Those skilled in the art will appreciate that although the remainder of the description focuses on measuring water activity, the measurement apparatus  10  may be used to measure a variety of parameters such as the temperature, pressure, velocity, and/or mass flux of a gaseous mixture. 
     By way of background, the water activity is defined as: 
     
       
         
           
             
               a 
               w 
             
             = 
             
               
                 p 
                 a 
               
               
                 p 
                 s 
               
             
           
         
       
     
     where a w  is the water activity, p a  is the water vapor pressure, and p s  is the saturation water vapor pressure at the temperature of the sample. The measurement apparatus  10  measures p a  directly. The measurement apparatus  10  also measures the temperature of the sample. Once these parameters are known, it is a straightforward calculation to obtain the water activity since p s  is determined by sample temperature. 
     The measurement apparatus  10  includes a base  12 , a feeding assembly  14 , a sensor assembly  16  including a tunable diode laser  74  ( FIG. 8 ), and a plurality of sample containers  18 . The measurement apparatus  10  uses the tunable diode laser  74  to measure various parameters of the gaseous mixture inside the sample containers  18 . Each sample container  18  includes a sample of material  30  ( FIG. 6 ) ready to be analyzed. The measurement apparatus  10  feeds the sample containers  18  through a measurement station  20  where the water activity of each sample is measured. 
       FIGS. 2-6  show the sample container  18  in greater detail.  FIG. 2  shows the sample container  18  fully assembled and  FIGS. 3-4  show exploded perspective views of the sample container  18  from the top and bottom, respectively. The sample container  18  includes a top housing  22 , bottom housing  24 , sealing member  26 , sample cup  28 , and electronics  32 . The sample container  18  also includes a sample chamber  40  ( FIG. 6 ) that is sealed from the outside air. 
     The top housing  22  is open on the bottom and the bottom housing  24  is open on the top. The top housing  22  is sized and shaped to receive the bottom housing  24  as shown in  FIGS. 2-6 . The bottom housing  24  includes a seal  34  that sits in a groove  36  around the outer circumference of the top of the bottom housing  24 . When the top and bottom housings  22 ,  24  are coupled together, the seal  34  contacts an inner wall or surface  38  of the top housing  22  to seal the interior sample chamber  40  from the outside air. 
     It should be noted that for purposes of this disclosure, the term “coupled” means the joining of two members directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining can be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate member being attached to one another. Such joining can be permanent in nature or alternatively can be removable or releasable in nature. 
     The top housing  22  includes a notch or gap  54  that is used to align properly the sample container as it moves to the measuring station  20 . The notch  54  also allows the operator to disassemble easily the sample container  18  for cleaning and sample actuation. A further description of the notch  54  and how it is used is provided below in connection with the description of the operation of the measurement apparatus  10 . 
     Those skilled in the art will appreciate that the design of the housing of the sample container  18  may be modified in a number of ways. For example, the separate housings  22 ,  24  may be replaced by a single unitary housing with a fill hole. The fill hole may be closed to seal the sample chamber  40  from the outside air. Also, the shape of the housing may be something other than cylindrical, e.g., square, hexagonal, etc. 
     The top housing  22  includes a first opening  42  and a second opening  43  positioned opposite the first opening. The openings  42 ,  43  extend through the wall of the top housing  22  and into the sample chamber  40 . The openings  42 ,  43  are provided to allow unimpeded access to the interior of the sample chamber  40  when the sample  30  is being analyzed. 
     The openings  42 ,  43  are positioned above the area occupied by the sample  30  to allow laser radiation to pass from one opening through the gaseous mixture in the head space, and on to the other opening. It should be appreciated that the openings  42 ,  43  may have any suitable configuration. For example, the top housing  22  may include a single opening or more than two openings. The tunable diode laser  74  could also be mounted permanently to the top housing  22 . 
     The sealing member  26  is a rigid ring-shaped component that encircles the top portion of the top housing  22  and covers the openings  42 ,  43 . The sealing member  26  seals the sample chamber  40  closing it from the outside air. 
     Those skilled in the art will appreciate that the sealing member  26  may have any of a number of configurations. For example, the sealing member  26  can have a different shape than a ring. Also, the sample container  18  can include multiple sealing members  26  where each sealing member  26  covers one of the respective openings  42 ,  43 . 
     The top housing  22  includes an upper seal  44  and a lower seal  46  which are positioned in corresponding grooves  48 ,  50  in the outer surface of the top housing  22 . The inner surface of the sealing member  26  contacts the seals  44 ,  46  to prevent the gaseous mixture inside the sample container  18  from escaping or mixing with the outside air. 
     The seals  34 ,  44 ,  46  may have any suitable configuration and be made of any suitable material. In one embodiment, the seals  34 ,  44 ,  46  are o-rings made of an elastomeric material such as buna. Those skilled in the art will appreciate that the housings  22 ,  24  and the sealing member  26  may be sealed using a variety of other sealing techniques. 
     The sealing member  26  moves between a closed position where the sealing member  26  covers the openings  42 ,  43  ( FIGS. 2 and 6 ) and an open position where the sealing member  26  does not cover the openings  42 ,  43 . (FIG.  1 —the sealing container that has already passed through the measurement station  20 ). The sealing member  26  does this by sliding downward along the outside of the top housing  22 . 
     Those skilled in the art will appreciate that the sealing member  26  may be configured in a variety of ways to cover and close the openings  42 ,  43 . For example, the sealing member  26  may be configured to slide upward along the outside of the top housing  22 . 
     The sample cup  28  holds the sample  30  being analyzed and prevents the sample material from contacting the housings  22 ,  24 . The sample cup  28  can be reused multiple times, or it can be disposed after each use. In general, the sample cup  28  can be disposed of after each use to minimize the possibility of contamination from one sample to the next. 
     The sample container  18  also includes a temperature sensor  52  located at the top of the sample chamber  40 . The temperature sensor  52  is connected to the electronics  32  and extends through the top wall of the top housing  22 . The temperature sensor  52  is positioned at the top of the sample chamber  40  to allow it to directly measure the temperature of the sample  30 . 
     Those skilled in the art will appreciate that the temperature sensor  52  may be any suitable temperature sensor. In one embodiment, the temperature sensor  52  includes an infrared temperature sensor or infrared thermometer that measures a portion of the infrared thermal radiation (i.e., blackbody radiation) emitted by the sample  30  and uses that to determine the sample&#39;s temperature. The infrared temperature sensor may include a lens that focuses the infrared thermal radiation on a detector, which converts the radiant power to an electrical signal that is transmitted to the electronics  32 . A suitable temperature sensor is GE ZTP-315 sensor. 
     The electronics  32  may include a variety of electrical hardware and/or software. In one embodiment, the electronics include a processor, memory, and a wireless or wired communication component. The electronics  32  may be used to allow the sample container  18  to process, store, transmit, and/or receive data regarding the sample  30 . 
     For example, the electronics  32  may be configured to receive an electrical signal from the temperature sensor  52 , convert it into a temperature reading, and transmit the temperature to a remote computer where the temperature is used to calculate the water activity of the sample. In another embodiment, the electronics  32  may receive information regarding the concentration of water vapor in the sample and use the processor to calculate the water activity. The measured water activity is stored in the electronics  32  until needed later. 
     The sample container  18  and any of its subcomponents may be made of any suitable material. Examples of suitable materials include metals, plastics, and composites. In one embodiment, the housings  22 ,  24  and/or the sealing member  26  may be made of aluminum. Aluminum may be desirable because it is easy to machine, has high thermal conductivity (allows the sample  30  to equilibrate with the environment faster), and it can be coated with a coating or anodized to seal any pores. 
     Referring back to  FIG. 1 , the feeding assembly  14  includes a magazine  56  that holds a vertical stack of sample containers  18 . The sample containers  18  move downward through the magazine  56  as each sample container  18  is taken from the bottom of the stack and analyzed. The residence time of the sample containers  18  in the stack allows the samples  30  to equilibrate at measurement temperature. 
     The feeding assembly  14  also includes an actuator  58  that moves the sample containers  18  from the magazine  56  to the measurement station  20 . In one embodiment, the actuator  58  is a linear actuator that pushes the bottom sample container  18  to the measurement station  20 . 
       FIG. 9  shows the actuator  58  in greater detail. The actuator  58  includes a motor  60  that extends and retracts a drive cylinder  62  to move the sample container  18 . A drive block  64  is positioned at the distal end of the drive cylinder  62 . The drive block  64  moves between a retracted position where the drive block  64  is not in contact with the sample containers  18  to an extended position where drive block  64  pushes a sample container  18  to the measurement station  20 . 
     The drive block  64  is elongated so that as it moves to the extended position, the top surface  66  of the drive block  64  holds the sample containers  18  in the magazine  56  in place. The drive block  64  also has a sloped face  68  so that as it moves from the extended position to the retracted position, the drive block  64  allows the next sample container  18  to slowly lower into position. 
     The sloped face  68  of the drive block  64  includes a wedge member  70  that is configured to continue the slope of face  68  thereby lowering the sample container  18  to its lowest position. Wedge member  70  retracts as the sample container  18  is pushed forward. Notch  54  in the sample container  18  aligns properly as the sample container  18  passes spring ball  81  while it moves to the measurement station  20 . The openings  42 ,  43  should be in a certain position to facilitate measurement of the water activity of the sample  30  when the sample container  18  is at the measurement station  20 . 
     The actuator  58  and drive block  64  may be configured in a variety of different ways from that shown in the Figs. Any of a variety of components and methods may be used to move the sample container  18  to the measurement station  20 . 
     The base  12  includes a downward sloping ramp  72  that receives the sample container  18  after it has been analyzed at the measurement station  20 . The spent sample container  18  is pushed down the ramp  72  by the next sample container  18  as it is pushed to the measurement station  20  by the actuator  58 . A spent sample container  18  is shown on the far end of the ramp  72  in  FIGS. 1 ,  7 , and  9 . 
     The sensor assembly  16  includes an actuator  76  coupled to a sensor unit  78 . The actuator  76  moves the sensor unit  78  toward and away from the measurement station  20 .  FIG. 1  shows the sensor unit  78  in the retracted or raised position away from the sample container  18 .  FIG. 7  shows the sensor unit  78  in the extended or lowered position adjacent to the sample container  18  and ready to take the measurement. 
       FIG. 8  shows the sensor unit  78  positioned over the sample container  18 . The sensor unit  78  includes a housing  80  that slides along the outside surface of the top housing  22  of the sample container  18 . The housing  80  pushes the sealing member  26  downward away from the openings  42 ,  43 . The housing  80  and the sealing member  26  fit closely together so that as the sealing member  26  moves downward, the housing  80  immediately covers the openings  42 ,  43 . In this way, the gases in the sample chamber  40  are not exposed to or contaminated with outside air. 
     The sensor unit  78  is surrounded by a heat sink  90  when the sensor unit  78  is in the extended position. The heat sink  90  helps to maintain the temperature of the sensor unit  78  and the sample container  18  constant during the measurement process. 
     It should be appreciated that the sensor unit  78  and its housing  80  can have any suitable configuration as long as the sensor unit  78  is capable of moving the sealing member  26  to provide access to the openings  42 ,  43 . In one embodiment, a seal can be provided between the housing  80  and the sealing member  26  to further prevent outside air from entering the sample chamber  40 . 
     The sensor unit  78  includes openings or holes  82 ,  83  that align with the openings  42 ,  43 , respectively, in the sample container  18 . The tunable diode laser  74  emits laser radiation through the openings  42 ,  43 ,  82  and into the interior of the sample chamber  40  where it passes through the gaseous mixture in the head space of the sample container  18 . 
     The tunable diode laser  74  includes a laser radiation source  84  that emits the laser radiation and a laser radiation detector  86  that receives the emitted laser radiation. The concentration of a gas species in the sample chamber  40 , as well as other parameters, may be measured by comparing the emitted laser radiation to the detected laser radiation. The tunable diode laser  74  may also include other components such as optics to facilitate transmission and detection of the laser radiation. 
     Any suitable tunable diode laser  74  may be used. For example, the laser radiation may be generated by a temperature controlled diode and transmitted through a fiber optic cable to the interior of the sample chamber  40 . Examples of suitable tunable diode lasers may be found in U.S. Pat. Nos. 6,639,678, 7,616,316, 7,230,711, 7,126,685, 7,092,852, 7,003,436, 6,940,599, 6,615,142, all of which are incorporated herein by this reference in their entireties. 
     The laser radiation source  84  may be positioned on one side of the sample container  18  and the laser radiation detector  86  may be positioned on the opposite side of the sample container  18 . For example, the laser radiation source  84  may be positioned to emit laser radiation through the openings  42 ,  82 , and the laser radiation detector  86  may be positioned to receive the laser radiation through openings  43 ,  83 . 
     In one embodiment, the laser radiation source  84  and the laser radiation detector  86  are coupled to and part of the sensor unit  78 . For example, the laser radiation source  84  and the laser radiation detector  86  can be coupled to the side of the housing  80  over the openings  82 ,  83 . In another embodiment, the laser radiation source  84  and the laser radiation detector  86  are separate from the sensor unit  78 . 
     The measurement apparatus  10  may be operated in the following manner. The sample  30  is positioned in the sample cup  28  and put into the sample container  18 . The sample  30  is allowed to equilibrate inside the sample chamber  40  at control temperature. This may happen while the sample container  18  is in the magazine  56  or at some other location. Once the sample  30  has reached equilibrium, the amount of water vapor in the sample chamber  40  should reflect the activity of the water in the sample  30 . The sample container  18  is sealed during the equilibration process. 
     Information about each sample  30  may be added to the electronics  32 . This may be done manually or wirelessly. When the sample  30  is evaluated, the data generated is added to the electronics  32  or to a main processor for the apparatus. 
     The actuator moves the sample container  18  to the measurement station  20  where it is ready to be analyzed with the sensor unit  78 . The actuator  76  moves the sensor unit  78  downward over the sample container  18 . The housing  80  of the sensor unit  78  contacts the sealing member  26  and pushes it downward until the openings  82 ,  83  in the housing  80  are aligned with the openings  42 ,  43 , respectively, in the top housing  22 . During this process, the sample chamber  40  remains sealed from outside air. 
     At this position, the tunable diode laser  74  is aligned with the openings  42 ,  43 ,  82 ,  83 . The tunable diode laser  74  emits laser radiation through the gaseous mixture in the head space of the sample chamber  40 . At the same time, the temperature of the sample  30  is measured with the temperature sensor  52 . The raw data obtained are then processed to calculate the water activity of the sample  30 . 
     After the measurement has been made, the sensor unit  78  is raised and the sample container  18  is pushed on to the ramp  72  by the next sample container  18 . The sealing member  26  remains in the lowered position because once the measurement has been made it no longer matters if outside air enters the sample chamber  40 . 
     Illustrative Embodiments 
     Reference is made in the following to a number of illustrative embodiments of the disclosed subject matter. The following embodiments illustrate only a few selected embodiments that may include one or more of the various features, characteristics, and advantages of the disclosed subject matter. Accordingly, the following embodiments should not be considered as being comprehensive of all of the possible embodiments. 
     The concepts and aspects of one embodiment may apply equally to one or more other embodiments or may be used in combination with any of the concepts and aspects from the other embodiments. Any combination of any of the disclosed subject matter is contemplated. 
     In one embodiment, a measurement apparatus comprises: a sample chamber enclosing a gaseous mixture and a tunable diode laser configured to emit laser radiation through the gaseous mixture in the sample chamber without passing through a wall of the sample chamber. The sample chamber may be sealed from the air or atmosphere outside the sample chamber. 
     The tunable diode laser may be configured to emit the laser radiation through the gaseous mixture in the sample chamber without passing through the air outside the sample chamber. The tunable diode laser may include a laser radiation source and a laser radiation detector. The laser radiation may be emitted from the laser radiation source and received by the laser radiation detector without passing through a wall of the sample chamber. 
     The measurement apparatus may include a laser radiation source and a laser radiation detector. The laser radiation is emitted from the laser radiation source and received by the laser radiation detector without passing through the air outside the sample chamber. The laser radiation source and the laser radiation detector may both be in fluid communication with the gaseous mixture in the sample chamber. 
     The measurement apparatus may comprise a sample container that includes the sample chamber. The tunable diode laser may include a laser radiation source and a laser radiation detector both of which are separate from the sample container. The laser radiation source and the laser radiation detector may be exposed to the gaseous mixture in the sample chamber. 
     The measurement apparatus may comprise a sample container including a sealing member that moves between a closed position where the sealing member covers an opening into the sample chamber and an open position where the sealing member does not cover the opening into the sample chamber. The measurement apparatus may move the sealing member from the closed position to the open position while keeping the sample chamber sealed from the air outside the sample chamber. 
     The measurement may comprise a magazine configured to hold multiple sample containers each of which includes a sample chamber enclosing a gaseous mixture. The measurement apparatus may also comprise a plurality of sample containers positioned in the magazine, each of which includes a sealed sample chamber enclosing a gaseous mixture. The measurement apparatus may be configured to successively move, without operator input, the plurality of sample containers to a measurement station where the tunable diode laser emits the laser radiation through the gaseous mixture without passing through a wall of the sample chamber. 
     The measurement apparatus may be configured to measure the water activity of a sample in the sample chamber. The measurement apparatus may comprise a temperature sensor configured to measure the temperature of a sample in the sample chamber. 
     In another embodiment, the measurement apparatus comprises: a sample chamber enclosing a gaseous mixture, a tunable diode laser configured to emit laser radiation through the gaseous mixture in the sample chamber, and a temperature sensor configured to measure the temperature of a sample in the sample chamber. The sample chamber is sealed from the air outside the sample chamber. 
     The temperature sensor may be positioned inside the sample chamber and/or at the top of the sample chamber. The temperature sensor may be an infrared temperature sensor. 
     The tunable diode laser may be configured to emit the laser radiation through the gaseous mixture in the sample chamber without passing through the air outside the sample chamber. The tunable diode laser may include a laser radiation source and a laser radiation detector. The laser radiation is emitted from the laser radiation source and received by the laser radiation detector without passing through a wall of the sample chamber. 
     The measurement apparatus may comprise a sample container including a sealing member that moves between a closed position where the sealing member covers an opening into the sample chamber and an open position where the sealing member does not cover the opening into the sample chamber. The measurement apparatus may move the sealing member from the closed position to the open position while keeping the sample chamber sealed from the air outside the sample chamber. 
     The measurement apparatus may comprise a plurality of sample containers each of which includes a sealed sample chamber enclosing a gaseous mixture. The measurement apparatus may be configured to successively move, without operator input, the plurality of sample containers to a measurement station where the tunable diode laser emits the laser radiation through the gaseous mixture without passing through a wall of the sample chamber. 
     The measurement apparatus may be configured to measure the water activity of a sample in the sample chamber. 
     In another embodiment, a sample container comprises: a sample chamber enclosing a gaseous mixture and a sealing member that moves between a closed position where the sealing member covers an opening into the sample chamber and an open position where the sealing member does not cover the opening into the sample chamber. The sample chamber is sealed from the air outside the sample chamber. The sample chamber may be configured to cooperate with a tunable diode laser measurement apparatus that moves the sealing member from the closed position to the open position while keeping the sample chamber sealed from the air outside the sample chamber. 
     The sample container may comprise a temperature sensor configured to measure the temperature of a sample of non-gaseous material in the sample chamber. The temperature sensor may be positioned at the top of the sample chamber. The temperature sensor may be an infrared temperature sensor. The temperature sensor may be positioned inside the sample chamber. 
     The opening may be a first opening and the sample container may comprise a second opening into the sample chamber positioned opposite the first opening. The sample container may comprise one or more sealing members that move between a closed position where the one or more sealing members cover the first opening and the second opening and an open position where the one or more sealing members do not cover the first opening and the second opening. 
     The sample container may comprise a housing component having a cylindrical shape and forming at least part of the sample chamber. The sealing member may include a sealing ring that slides along the housing component to move the sealing member between the closed position and the open position. The sample container may comprise a top housing open at the bottom and a bottom housing open at the top. The top housing and the bottom housing fit together to form the sample chamber and enclose the gaseous mixture. 
     The sample container may comprise a sample cup positioned in the bottom housing. The sample cup is separable from the top housing and the bottom housing and configured to hold a sample of non-gaseous material. 
     The sample container may comprise electronics that store, transmit, and/or receive information about a sample of non-aqueous material in the sample container. 
     The terms recited in the claims should be given their ordinary and customary meaning as determined by reference to relevant entries in widely used general dictionaries and/or relevant technical dictionaries, commonly understood meanings by those in the art, etc., with the understanding that the broadest meaning imparted by any one or combination of these sources should be given to the claim terms (e.g., two or more relevant dictionary entries should be combined to provide the broadest meaning of the combination of entries, etc.) subject only to the following exceptions: (a) if a term is used in a manner that is more expansive than its ordinary and customary meaning, the term should be given its ordinary and customary meaning plus the additional expansive meaning, or (b) if a term has been explicitly defined to have a different meaning by reciting the term followed by the phrase “as used herein shall mean” or similar language (e.g., “herein this term means,” “as defined herein,” “for the purposes of this disclosure the term shall mean,” etc.). 
     References to specific examples, use of “i.e.,” use of the word “invention,” etc., are not meant to invoke exception (b) or otherwise restrict the scope of the recited claim terms. Other than situations where exception (b) applies, nothing contained herein should be considered a disclaimer or disavowal of claim scope. 
     The subject matter recited in the claims is not coextensive with and should not be interpreted to be coextensive with any particular embodiment, feature, or combination of features shown herein. This is true even if only a single embodiment of the particular feature or combination of features is illustrated and described herein. Thus, the appended claims should be given their broadest interpretation in view of the prior art and the meaning of the claim terms. 
     As used herein, spatial or directional terms, such as “left,” “right,” “front,” “back,” and the like, relate to the subject matter as it is shown in the drawings. However, it is to be understood that the described subject matter may assume various alternative orientations and, accordingly, such terms are not to be considered as limiting. 
     Articles such as “the,” “a,” and “an” can connote the singular or plural. Also, the word “or” when used without a preceding “either” (or other similar language indicating that “or” is unequivocally meant to be exclusive—e.g., only one of x or y, etc.) shall be interpreted to be inclusive (e.g., “x or y” means one or both x or y). 
     The term “and/or” shall also be interpreted to be inclusive (e.g., “x and/or y” means one or both x or y). In situations where “and/or” or “or” are used as a conjunction for a group of three or more items, the group should be interpreted to include one item alone, all of the items together, or any combination or number of the items. Moreover, terms used in the specification and claims such as have, having, include, and including should be construed to be synonymous with the terms comprise and comprising. 
     Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, etc. used in the specification (other than the claims) are understood as modified in all instances by the term “approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should at least be construed in light of the number of recited significant digits and by applying ordinary rounding techniques. 
     All ranges disclosed herein are to be understood to encompass and provide support for claims that recite any and all subranges or any and all individual values subsumed therein. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all subranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).