gas analyzer

Abstract

An infrared gas analyzer and a detector assembly for the infrared gas analyzer. In one example, the infrared gas analyzer includes a measurement module and a detector assembly coupled to the measurement module. The measurement module includes an infrared light source configured to emit an infrared light signal. The detector assembly includes an infrared sensing element and a hermetically sealed detector housing having an optical window transparent to the infrared light signal and an internal volume under vacuum. The infrared sensing element is disposed within the internal volume of the detector housing and configured to detect the infrared light signal via the optical window.

Description

[0001] Government Rights Statement

[0002] This invention was completed with the assistance of the U.S. government, pursuant to National Science Foundation license number 1737184. The U.S. government holds certain rights to this invention.

[0003] Cross-references to related applications

[0004] This application claims priority to co-pending U.S. Provisional Application No. 63 / 498,429, filed April 26, 2023, entitled “GAS ANALYZER,” which is incorporated herein by reference in its entirety for all purposes. Background Technology

[0005] Accurate observation of atmospheric composition and greenhouse gas exchange between ecosystems and the atmosphere is crucial for constraining climate models and predicting future climate characteristics. Infrared gas analyzers, which can be implemented using broadband nondispersive or narrowband tunable laser technology, are widely used to obtain atmospheric measurements. Infrared gas analyzers use infrared (IR) detectors to measure the amount of infrared radiation emitted by an IR source and absorbed by the gas as radiation passes through an optical sensing path. By comparing the infrared radiation before and after passing through the optical path, the average gas concentration between the source and detector can be inferred. However, studies have found that IR gas analyzers deployed on mobile platforms (such as buoys or ships) have errors in gas concentration determination due to the analyzer's motion and orientation relative to gravity. These errors limit the performance of gas analyzers and necessitate the development of specialized correction methods. Summary of the Invention

[0006] Various aspects and embodiments relate to gas analyzers with improved performance on mobile platforms. According to certain examples, techniques for eliminating or reducing carbon dioxide measurement errors caused by platform movement in open-circuit and closed-circuit infrared carbon dioxide (CO2) and / or water vapor (H2O) gas analyzers are disclosed.

[0007] According to one example, a closed-circuit infrared gas analyzer includes a housing and an infrared detector having an internal volume under vacuum.

[0008] According to another example, an infrared gas analyzer includes a measurement module comprising an infrared light source; and a detector assembly coupled to the measurement module. The detector assembly includes a hermetically sealed detector housing, a sensing element, a temperature sensor, and a thermoelectric cooler. The hermetically sealed detector housing has an internal volume under vacuum, wherein the sensing element, temperature sensor, and thermoelectric cooler are disposed within the internal volume of the detector housing, and wherein the sensing element and temperature sensor are coupled to the thermoelectric cooler.

[0009] Another example relates to a detector assembly for an infrared gas analyzer. In one example, the detector assembly includes: a hermetically sealed detector housing having an internal volume under vacuum, the hermetically sealed detector housing including an optical window transparent to infrared radiation; an infrared sensing element disposed within the internal volume of the hermetically sealed detector housing and positioned to detect infrared light signals via the optical window; a thermoelectric cooler disposed within the internal volume of the hermetically sealed detector housing and configured to cool the infrared sensing element; and a temperature sensor coupled to the thermoelectric cooler and configured to provide a temperature measurement, wherein the thermoelectric cooler is configured to adjust the temperature of the infrared sensing element to a selected temperature based on the temperature measurement.

[0010] According to another example, a closed-loop infrared gas analyzer includes a measurement module and a detector assembly coupled to the measurement module. The measurement module includes a housing having a first optical window transparent to infrared radiation; and an infrared light source configured to emit an infrared light signal, disposed within the housing and positioned to guide the infrared light signal through the first optical window. The detector assembly includes: a sealed detector housing having an internal volume under vacuum, the sealed detector housing including a second optical window transparent to infrared radiation; an infrared sensing element disposed within the internal volume of the sealed detector housing and positioned to detect the infrared light signal via the second optical window; a thermoelectric cooler disposed within the internal volume of the sealed detector housing and configured to cool the infrared sensing element; and a temperature sensor coupled to the thermoelectric cooler and configured to provide a temperature measurement, wherein the thermoelectric cooler is configured to adjust the temperature of the infrared sensing element to a selected temperature based on the temperature measurement. Attached Figure Description

[0011] The following discussion of at least one example's aspects with reference to the accompanying drawings, which are not intended to be drawn to scale. The drawings are included to provide an illustration of the aspects and further understanding, and are incorporated in and constitute a part of this disclosure. However, the drawings are not intended to be limiting of any particular example. The drawings, along with the remainder of this disclosure, serve to explain the principles and operation of the described and claimed aspects. In the drawings, identical or similar components shown are indicated by the same reference numerals. For clarity, each component is not labeled in every drawing. In the drawings:

[0012] Figure 1 This is a block diagram of an example of an infrared gas analyzer system according to aspects of this disclosure;

[0013] Figure 2 It is applicable to aspects of this disclosure. Figure 1 A block diagram of an example of an infrared detector in a system;

[0014] Figure 3 The figure illustrates an example of the variation in the detector's spectral sensitivity as a function of temperature, according to aspects of this disclosure.

[0015] Figure 4 The figure shows an example of co-spectral data of CO2 concentration and IRGA detector cooler voltage obtained from individual tests, according to aspects of this disclosure, illustrating results from a moving platform versus a fixed platform;

[0016] Figure 5A This is a cross-sectional view of an example of a detector housing (vertical direction) according to certain aspects of this disclosure, showing the temperature gradient between the cold sensing element and the hot housing and heat sink;

[0017] Figure 5B Based on the aspects of this disclosure Figure 5A A cross-sectional view of the detector housing, with the detector oriented at a 90-degree angle to the vertical, showing the temperature gradient between the cold sensing element and the hot housing and heat sink;

[0018] Figure 6A The figure is a diagram of laboratory motion table test data according to aspects of this disclosure, showing the change of the standard EC155 CO2 molar mixture ratio over time when the platform pitch is adjusted;

[0019] Figure 6B The figure is a diagram of laboratory motion table test data according to aspects of this disclosure, showing the change of the standard EC155 H2O molar mixing ratio over time when the platform pitch is adjusted;

[0020] Figure 6CThe figure shown is a graph of low-pass CO2 mixing ratio data and instantaneously tilted scatter plots, according to aspects of this disclosure;

[0021] Figure 6D The figure shown is a graph of low-pass H2O mixing ratio data versus a scatter plot with instantaneous tilt, according to aspects of this disclosure;

[0022] Figure 7A The figure is a diagram of laboratory motion table test data according to aspects of this disclosure, showing the change of the standard EC155 CO2 molar mixture ratio over time when the platform yaw is adjusted;

[0023] Figure 7B The figure is a diagram of laboratory motion table test data according to aspects of this disclosure, showing the change of the standard EC155 H2O molar mixture ratio over time when the platform yaw is adjusted;

[0024] Figure 7C The figure shown is a graph of low-pass CO2 mixing ratio data and instantaneously tilted scatter plots, according to aspects of this disclosure;

[0025] Figure 7D The figure shown is a graph of low-pass H2O mixing ratio data versus a scatter plot with instantaneous tilt, according to aspects of this disclosure;

[0026] Figure 8A Similar to those shown in this disclosure Figure 6A and 7A The plot shows the standard EC155 time series data, but only shows CO2 IRGA data with pitch motion only, and adds the time variation of EC155 detector temperature after subtracting its average level;

[0027] Figure 8B Similar to those shown in this disclosure Figure 6A and 7A The plot shows the standard EC155 time series data, but only shows CO2 IRGA data with only roll motion, and adds the time variation of EC155 detector temperature after subtracting its average level;

[0028] Figure 9A The diagram illustrates time-series pitch test data of the standard EC155 and exemplary EC155P, according to aspects of this disclosure, showing examples of bandpass filter variations in CO2 and detector temperature data after subtracting the average level.

[0029] Figure 9BThe diagram illustrates time-series roll test data of the standard EC155 and exemplary EC155P, according to aspects of this disclosure, showing examples of bandpass filter variations in CO2 and detector temperature data after subtracting the average level.

[0030] Figure 10 The diagram illustrates an automated spectrum of CO2 measurements during both static platform and mixed ocean motion tests, according to aspects of this disclosure.

[0031] Figure 11A The figure illustrates an example of motion-induced error (MIE) on a moving buoy, according to aspects of this disclosure, showing the results of pitch and roll CO2 tests.

[0032] Figure 11B The diagram illustrates an example of MIE on a moving buoy, according to aspects of this disclosure, showing the results of mixed ocean current CO2.

[0033] Figure 12A The diagram illustrates an example of a MIE on a moving buoy, according to aspects of this disclosure, showing the H2O test results for pitch and roll motions; and

[0034] Figure 12B The figure shown is based on an aspect of this disclosure and illustrates an example of MIE on a moving buoy, which shows the results of mixed oceanic motion H2O. Detailed Implementation

[0035] Infrared gas analyzers (IRGAs) are used to perform atmospheric measurements to determine the concentrations of certain gases, such as CO2. Typically, these analyzers are mounted on fixed weather towers on land; however, an increasing number of systems are being deployed on mobile platforms and buoys to extend spatial coverage and include measurements at sea. For example, eddy covariance (EC) flux is one of the few field measurement methods that can be used to directly validate and improve gas transport models used in global estimates of CO2 exchange between the ocean and atmosphere. High-speed, nondispersive IRGAs are a suitable CO2 sensor for these measurements. Due to demand, ocean-atmosphere EC mass flux systems are often used for marine expeditions conducted on research vessels. However, there are several technical challenges in using gas analyzers on mobile platforms.

[0036] Accurate EC CO2 flux measurement at sea requires IRGA CO2 mixture ratio measurement accuracy at or below 0.2 ppm. However, a long-standing technical problem affecting the accuracy of vortex-related air-sea CO2 flux estimation is motion contamination in CO2 concentration measurement. Several research reports on field experiments of gas transfer using mobile platforms have reported on IRGA motion contamination issues. These errors limit system performance. For example, this problem has been found to cause high-frequency CO2 mixture ratio artifacts at the 0.5–1.5 ppm level. The causes of IRGA motion sensitivity have been speculated in the literature, and various correction methods have been attempted, but the problem remains largely unresolved. For example, empirical correction methods can be used, but their generality is limited because the sources and underlying mechanisms of these sensor-related effects are not understood. Therefore, many important issues remain regarding the development and use of gas analyzers on mobile platforms.

[0037] The examples disclosed in this paper identify the causes of motion-induced errors and provide improved IRGA architectures to reduce such errors. As further described below, a significant portion of motion sensitivity is associated with the detection methods common in most conventional closed-loop and open-loop IRGAs used for H2O and CO2 measurements. The examples provide solutions to this problem and demonstrate sensor architectures with significant improvements.

[0038] According to certain aspects, the primary source of error has been identified as the orientation-dependent temperature stability of the thermoelectrically cooled infrared detector used in IRGA. As described in more detail below, the temperature difference between the cooled sensing element and the surrounding detector housing results in a density gradient, which, combined with the gravitational field, generates natural free convection within the detector housing. These cyclical patterns affect the actual temperature of the infrared sensing element and are highly dependent on the orientation of the detector assembly. Therefore, platform motion that alters the orientation of the detector assembly as the gas analyzer rotates relative to the gravitational field introduces gas concentration measurement errors. Furthermore, changes in gas acceleration can cause similar effects, suggesting that linear displacement, in addition to rotational motion, can also introduce gas concentration errors.

[0039] To address these issues, the examples disclosed herein provide an IRGA (e.g., a closed-loop IRGA) with an improved infrared detector having an internal volume under vacuum. The use of a vacuum-sealed enclosure reduces convective circulation associated with acceleration and gravity, and minimizes convective heat exchange. This allows for more precise temperature control and eliminates temperature dependence on direction. As further described below, laboratory and deep-water tank tests of IRGAs according to certain embodiments show a 4-10 fold reduction in CO2 error under typical marine buoy pitch and roll conditions compared to conventional IRGA systems. Similar noise reduction factors of 2-8 were observed in water vapor measurements. Examples demonstrate the ability to achieve improved flux measurements using embodiments of the IRGA disclosed herein on mobile ocean observation and aircraft platforms.

[0040] The present invention relates to an infrared gas analyzer for measuring atmospheric gases on a mobile platform, including the use of a vacuum-sealed detector to improve performance. According to one example, the infrared gas analyzer includes a measurement module and a detector assembly coupled to the measurement module. The measurement module includes an infrared light source configured to emit infrared light signals. The detector assembly includes an infrared sensing element and a hermetically sealed detector housing having an optical window transparent to the infrared light signals and an internal volume under vacuum. The infrared sensing element is disposed within the internal volume of the detector housing and configured to detect the infrared light signals via the optical window.

[0041] These and other features, along with examples, will be described in more detail below.

[0042] refer to Figure 1 This diagram illustrates a block diagram of an example of an IRGA 100 according to certain embodiments. The IRGA 100 includes an electronics module 110 (also referred to as a measurement module) coupled to an infrared detector 120 (also referred to as a detector assembly). In some embodiments, the electronics module 110 includes a housing 112 that houses an infrared (IR) light source 114 and various other components generally identified as electronics 116. In some embodiments, the electronics module 110 and the infrared detector 120 are housed together within a common housing 102. The IRGA 100 includes at least one I / O port 104 to allow gas to enter and exit the IRGA 100. In some embodiments, electronics 116 includes a pump to draw a gas sample into the IRGA 100. The IRGA 100 may further include one or more power and / or data ports 106, which are coupled to electronics 116 and configured to allow measurement data (e.g., via one or more wired or wireless, analog or digital connections) and / or power and / or configuration data to be provided to the IRGA 100.

[0043] In some instances, the IR light source 114 is a broadband infrared source. Light from the IR light source 114 is transmitted towards the detector 120 through the gas sample volume. The detector 120 may include various components, some of which are... Figure 2 As shown, these various components are housed within a sealed detector housing 122 with an optical window 124 to allow infrared light from the IR source 114 to enter. In some instances, the IRGA 100 uses the IR detector 120 to measure the amount of infrared radiation emitted by the IR source 114 and absorbed by the gas sample as radiation passes through the optical sensing path. By comparing the infrared radiation before and after passing through the optical path, the average concentration of the gas between the IR source 114 and the IR detector 120 can be inferred.

[0044] In some instances, the electronics 116 includes a rotary chopper controller through which light is transmitted, modulating the light at a high rate, alternating between signal and dark (zero or reference) source levels. In other instances, other types of modulation can be applied to the light (source signal) from the IR source 114. An IR detector 120, which can be positioned at the receiving end of a volume, is aligned to measure changes in IR radiation at repeating source and dark reference levels, where the detected IR level varies with gas absorptivity due to volumetric variations in carbon dioxide and water vapor concentrations within the sample cell. Measurements by the lowest (raw) level detector within several individual IR bands can provide demodulated bright and dark reference data, which can be used to calculate the mixing ratio of the two gases.

[0045] refer to Figure 2 In some instances, the IR detector 120 includes an IR sensing element (SE) 202. The SE 202 may be coupled to a temperature sensor 204, such as a thermistor. To improve the responsivity of the IR detector 120 and reduce measurement noise, the IR sensing element 202 is cooled to below ambient temperature by a thermoelectric cooling (TEC) device 206. In some instances, the sensing element 202 and the thermistor 204 are mounted on the TEC 206. To protect the environment, the SE 202 and the TEC assembly 206 are enclosed in a sealed detector housing 122. In some instances, the sealed detector housing 122 is filled with a dry, non-IR-absorbing inert gas, such as nitrogen or xenon. In other instances, as further described below, the sealed detector housing 122 is maintained under vacuum conditions. The TEC 206 converts electrical energy into heat energy and transfers heat from one side of the TEC to the other, and the detector SE 202 on the cold side is coupled to a heat sink (502) on the hot side. Figure 5A and 5BA temperature difference is created between the SE and SE 202. Heat sink 502 dissipates heat and keeps the hot side of the TEC close to ambient temperature. A temperature sensor (e.g., a thermistor) 204 is mounted next to SE 202 and is used to measure and control the temperature of SE to a constant value, typically -40 degrees Celsius. This is important for the performance of the IRGA 100 because the spectral response of the IR detector 120 depends on the temperature of SE 202, and any variation can lead to errors in gas concentration measurements.

[0046] Figure 3 This is a graph showing an example of the change in detector spectral sensitivity as a function of the temperature of sensing element 202.

[0047] Refer again Figure 1 and 2 In some instances, the coupling 108 between the electronics module 110 and the detector 120 may include one or more mechanical supports (such as struts) to hold the detector 120 in place relative to the electronics module 110, such that the IR light source 114 is aligned with the sensing element 202. In some instances, the detector 120 is configured to receive light from the IR light source 114 via an optical window 124. Therefore, the sensing element 202 can be centrally positioned below the optical window 124. Furthermore, although in Figure 1 Not shown, but the housing 112 of the electronic module 110 may include another optical window positioned to allow light from the IR light source 114 to travel toward the detector 120. The coupler 108 may further include any electrical coupling paths required to connect the electrical components of the electronic module 110 and the detector 120.

[0048] Based on certain aspects, and contrary to some other recommendations, it has been determined that motion-induced errors in gas concentration measurements are primarily present in detector 120. The examples and experimental results described below demonstrate the identified cause of motion sensitivity in the IRGA 100, and the improvements obtained using examples of the IRGA 100 configured to address the cause of motion sensitivity.

[0049] According to certain aspects, field test data obtained from an EC system using a closed-circuit IRGA for EC CO2 mass flow measurement were analyzed to assess motion sensitivity. The field test data were obtained from an EC system comprising a dried sample line and a closed-circuit LI-7200 sensor (available from LI-COR biosciences, Inc.). The field test data revealed that the motion of the discus buoy (typically larger and more unstable than that encountered on large research vessels) caused the IRGA CO2 mixing ratio error to be larger than previously reported, and these errors could not be corrected using some existing empirical post-processing methods. Further investigation following deployment of the sensor itself and the available open-circuit LI-7500 unit (available from LI-COR Biosciences, Inc.) led to the observation that most of the CO2 motion contamination signal was correlated with the detector temperature control voltage associated with the sensor's receiver.

[0050] Figure 4 This is a graph showing the frequency cospectral density of CO2 molar density and the receiver (Rx) control voltage measurements, derived from fixed and mobile 20 Hz time series measurements collected in similar wind and sea-air CO2 environments. Trace 402 (C CO2_Rx Pier-固定的 This indicates data obtained from a test in which the buoy was positioned on the dock of the UNH Coastal Marine Laboratory and remained stationary. Track 404 (C CO2_Rx 浮标 The data () represents data obtained from a test in which the buoy was moored 6 miles offshore from the dock under the influence of wind and waves. Data sets corresponding to traces 402 and 404 were collected in the coastal Gulf of Maine using an off-the-shelf closed-circuit IRGA (LI-7200). For both cases, the wind speed was 7 rpm, and the cospectral data were derived using 10-minute data segments. Figure 4 The diagram also shows the buoy roll (track 406; S) for moving conditions. 横摇 浮标 ) and pitch (track 408; S 俯仰 浮标 The motion spectrum. In these examples, the sample line entering the LI-7200 sensor was dried to limit water vapor contamination. Under these 7 rpm wind conditions, the buoy's average pitch and roll angles were 8.5 degrees, and Figure 1 The tilt spectrum shows that the buoy's nominal motion band is between 0.2 and 0.7 Hz. The CO2-Rx voltage covariance during motion within this band is significant and at least 7 times that outside the motion passband, while measurements on a stationary platform under similar wind conditions show no significant correlation with the detector control signal.

[0051] As described above, aspects and instances provide IRGA with improved performance on mobile platforms. As mentioned above, for... Figure 4 The evaluation of the measurement data presented has led to the determination that the key factor causing the noise driving the IRGA motion is not at the transmitter end of the device (e.g., IR light source 114), but exists in the detector 120. As stated above, according to certain aspects, the main source of error has been identified as the orientation-dependent temperature stability of the thermoelectrically cooled sensing element 202 of the IRGA 100. Due to the temperature difference between the sensing element 202 and the detector housing 122, the gas cloud closer to the cooled sensing element 202 has a higher density compared to the gas cloud closer to the detector housing 122. When the detector housing 122 is filled with gas, these density gradients, combined with the gravitational field, generate natural free convection within the detector housing 122, such as... Figure 5A and 5B As shown in the document.

[0052] Figure 5A This is a cross-sectional view of an example of the detector housing 122 shown in a vertical orientation, illustrating the temperature gradient between the cold sensing element 202 and the hot detector housing 122 and the heat sink 502. Arrows indicate free convection circulation of cold air descending near the sensing element 202 and warmer gas rising near the bottom flange 504 of the detector housing 122 (coupled to the heat sink 502). These circulations are symmetrical about the vertical axis 506.

[0053] Figure 5B This is a cross-sectional view of the detector housing 122, with the detector 120 oriented at 90 degrees to the vertical. This cross-sectional view shows the temperature gradient between the cold sensing element 202 and the hot detector housing 122 and the heat sink 502.

[0054] The cycling pattern occurring within the detector housing 122 is highly dependent on the orientation of the detector 120 and affects the actual temperature of the temperature sensor 204, and thus the actual temperature of the sensing element 202. For example, refer to Figure 5B In this configuration, the space above sensing element 202 exhibits stable stratification and limited free convection, while the space below sensing element 202 exhibits unstable density stratification and enhanced free convection. Consequently, the upper and lower portions of sensing element 202 have different temperatures. Therefore, depending on the position of the thermistor 204, sensing element 202 can be controlled to different temperatures, leading to errors in gas concentration measurement. Thus, the platform movement that alters the orientation of detector 120 introduces gas concentration measurement errors because the movement changes the circulating airflow and consequently alters the actual temperature of sensing element 202.

[0055] Therefore, to address this issue, in some instances, detector 120 can be configured such that the internal volume of detector housing 122 is evacuated rather than filled with gas. In some instances, the internal volume of detector housing 122 can be evacuated to less than 2E9 Torr. This prevents any convective circulation related to acceleration and gravity and minimizes convective heat exchange, thereby allowing for more precise temperature control of sensing element 202 and eliminating or reducing temperature dependence on the orientation of detector 120.

[0056] Depending on certain aspects, an open-circuit or closed-circuit IRGA 100 can be constructed using a vacuum-sealed detector housing 122. Other mechanical and / or electrical components and configurations of the IRGA 100 can remain unchanged. Various experiments were conducted to demonstrate the temperature and orientation dependence of motion sensitivity and the improvements obtained using an IRGA with a vacuum-sealed detector housing 120, and the results are presented below. In particular, experimental data demonstrating the performance of an exemplary closed-circuit IRGA with an infrared detector housing with a vacuum-sealed detector housing are described below and compared to a standard model of a commercially available IRGA for measuring CO2 and H2O. Tilt experiments were conducted on a controlled laboratory platform with independent pitch and roll axes, with side-by-side IRGAs mounted at tilt. Within a range of ±30-degree angular positions, the orientation-related errors in the exemplary IRGA were reduced by 4 to 10 times for CO2 and by 2 to 8 times for H2O compared to the standard IRGA. Additional tests were conducted in a deep-water tank to replicate real buoy motion with typical marine combined pitch and roll motions, as described below. In these tests, the improvement in measurement error was similar to that in laboratory experiments.

[0057] To demonstrate the improved performance of the IRGA based on certain examples, including detectors with vacuum pumping, the motion-induced error was established. This metric is used to accurately quantify the level of CO2 or H2O error caused by motion. It is defined by the ratio of the signal change during motion to the measurement collected in the absence of motion (i.e., in a static condition). As shown in equation (1) below. In some instances, calculations are performed in the spectral domain across the motion frequency passband encountered under given conditions (e.g., frequencies between fHi and fLo). This explains the inherent noise of each individual sensor when the platform is fixed. Approaching one Horizontal means that the motion has no effect on the given measurement.

[0058] (1)

[0059] In equation (1), This refers to the CO2 or H2O concentration spectral density for a given motion test segment. It is calculated for each test segment out of many 60-120 s measurement test segments. Each test segment has a specified duration (e.g., in the range of 60–120 seconds), wherein the standard deviation of platform tilt for each segment is calculated according to the following equation (2).

[0060] (2)

[0062] As further described below, MIE calculations performed using experimental test data demonstrate that the exemplary IRGA according to certain embodiments exhibits significantly improved performance compared to a standard IRGA with a similar configuration.

[0063] Therefore, aspects and embodiments provide an IRGA in which improved measurement accuracy can be achieved for measurements based on a mobile platform. As described above, in some instances, the IRGA includes a detector assembly having a thermoelectrically cooled sensing element disposed together with a temperature sensor in a sealed, vacuum-sealed housing. By achieving a cooled sensing element under vacuum, orientation-dependent (e.g., motion-induced) temperature-based errors can be reduced or eliminated, thereby providing an IRGA with improved performance on a mobile platform.

[0064] Experimental results

[0065] Based on certain examples disclosed herein, various comparative measurements are obtained using a standard, commercially available IRGA and a modified IRGA with a vacuum-sealed detector chamber (referred to herein as “exemplary IRGA” or EC155P). The standard IRGA is the EC155 unit available from Campbell Scientific Inc. (CSI), referred to herein as EC155 or standard IRGA.

[0066] The EC155 is a closed-loop IRGA system with sensors configured to provide high-rate and high-accuracy measurements of the CO2 and H2O mixing ratio, requiring a data sampling rate of 5-20 Hz and specifying CO2 and H2O measurement accuracies of 0.15 Hz each. -1 and 0.006 -1. The EC155 also provides high-precision temperature and pressure measurements within a closed-loop sample cell to adjust for environmental effects on flow rates when converting from raw molar concentration measurements to mixing ratios. While the commercially available EC155 field sample air collector employs a vortex inlet, this inlet was bypassed in the tests that generated the measurements presented herein to allow focus only on noise caused by motion associated with the analyzer itself. EC155 control, transducer sampling, and data conversion were performed using the CSI EC100 electronics unit, and the CSI CR6 data acquisition system was used to collect measurements from all experiments.

[0067] In the operation of the EC155 analyzer, light from a broadband infrared source is transmitted through the gas sample volume via a rotary chopper controller that modulates the source signal at a high rate, alternating between signal and dark (zero or reference) source levels. As in some examples described above, IR detectors at the receiving end of the volume are aligned to measure repeated IR radiation changes at source and dark reference levels, where the detected IR level varies with gas absorptivity due to volumetric variations in carbon dioxide and water vapor concentrations within the sample cell. Measurements by the lowest (raw) level detector in several independent IR bands provide demodulated bright and dark reference data for calculating the mixing ratio of the two gases.

[0068] The exemplary IRGA presented herein for acquiring measurement data is a modified version of the EC155 analyzer with an improved detector thermal performance. Specifically, the modified EC155 analyzer includes a detector with an internal volume under vacuum. This modification was achieved without further alterations to the established EC155 mechanical and optoelectronic design, data processing and output, and sensor control. In this disclosure, this exemplary unit is referred to as EC155P. The limited scope of modification means that side-by-side evaluation of the exemplary EC155P with the standard EC155 unit is very straightforward, simplifying the quantification of sensor performance differences.

[0069] In these tests, one of two inertial motion measurement packages (Parker Lord Microstrain 3DM-GX3 or 3DM-GX5) was used to record platform motion data. Both provided dynamic attitude data consistent with IRGA measurements at a sampling rate of 20 Hz. The motion sensors were calibrated and mounted on a rigid IRGA test plate near the analyzer. All platform pitch, roll, and acceleration estimates were derived using standard post-processing methods employed at sea. All recorded datasets included continuous high-rate measurements of all standard EC155 output variables, including pool temperature and pressure, additional low-level EC155 engineering outputs, and motion sensor outputs, including triaxial acceleration and angular rotation rates. Most presented data were recorded at a sampling rate of 20 Hz. The EC155 and EC155P CO2 and H2O mixing ratio outputs were low-pass filtered using the recommended 10 Hz EC155 bandwidth prior to data recording. Sensor error assessment involves a simple method of measuring a continuous flow of nearly pure (dry) CO2 reference gas through the system, typically at a controlled flow rate of 0.7–1.5 lpm.

[0070] The assessment of the differences from the prototype of the standard EC155 sensor was primarily conducted through direct comparison of time-series measurements or by deriving the noise variance from CO2 and H2O mixing ratio data observed from synchronously recorded motion sensors in the frequency range associated with platform motion.

[0071] Simple biaxial and dynamic triaxial motion stage tests were employed to diagnose, improve, and evaluate EC155 measurement noise associated with platform tilting motions of expected amplitude and frequency at sea. In all tests, sensor CO2 and H2O mixing ratio errors were assessed by sampling an intake gas with a known and fixed CO2 concentration, drawn through an IRGA measurement sample cell at a flow rate typical for field measurements. The CO2 reference gas was dry (virtually free of water vapor) and the CO2 concentration was 500 or 520 ppm. Biaxial motion tests were performed first to evaluate the effects of rotation (pitch or roll) separately. The laboratory motion stage consisted of a rigid 1.2 x 1.2 m plate with a free axis of rotation around its center, in which both EC155 and EC155P were mounted side-by-side, centered at the top of this axis of rotation, and in the same horizontal orientation as the motion sensors. To evaluate the effects of orthogonal tilting (i.e., roll rather than pitch) motion, the motion stage was physically rotated 90 degrees on its support. The sample gas input to the sensor is connected in series, flows through the EC155P and then through the EC155. All measurements are recorded simultaneously using a CSI CR6 data logger.

[0072] A series of rotational tests were conducted at different pitch and roll levels using an average rotational rate of 0.33 Hz to assemble an IRGA measurement dataset spanning the expected range of field tilt amplitudes (0–20 deg. in typical pitch and roll for a discus buoy platform). This average rotational rate is close to the fundamental resonant frequency of our specific air-sea flux buoy. Each EC155 has a rectangular footprint (7 x 43 cm), and within the test framework, roll impact measurements are defined as rotation about the long axis and pitch about the short axis. This two-axis (2D) test was developed following L. Bariteau's assessment of the motion effects of the LI-COR IRGA cell in 2010 at NOAA's Earth System Research Laboratories.

[0073] Figures 6A-6D This demonstrates the performance of CO2 ( ) in these 2D stage tests when using the standard EC155. Figure 6A and 6C ) and water vapor ( Figure 6B and 6D The error caused by pitch observed in both cases. Figure 6A and 6B The changes in the molar mixing ratio of CO2 and H2O over time were displayed, while the platform pitch (by...) Figure 6A Trajectory 606 and Figure 6B The trace 612 in the text indicates that it is being adjusted. Figure 6A and 6B A short test segment is shown, in which some plateau oscillations are observed. Figure 6A In the diagram, trace 602 (CO2mr) represents the CO2 mixing ratio data at the original 20 Hz rate, and trace 604 (CO2mr LP) represents the CO2 mixing ratio data after low-pass filtering. Figure 6B In the diagram, trace 608 (H2Omr) represents the H2O mixing ratio data at the original 20 Hz rate, and trace 610 (H2Omr LP) represents the H2O mixing ratio data after low-pass filtering. Figure 6A and 6B In both cases, the average CO2 and H2O levels have been subtracted to focus on relevant small-scale signal variations. The platform rotation rate is approximately 0.35 Hz.

[0074] Figure 6C and 6D Scatter plots of low-pass mixing ratio data for CO2 (Figure 5C) and H2O (Figure 5D) measurements relative to the instantaneous tilt angle are provided. Pitch variation is + / - 15 degrees.

[0075] Figures 6A-6D The results presented clearly demonstrate the high correlation between platform tilt and mixture ratio measurements. This test was performed for repeated pitch motions of + / - 14 degrees. Higher frequency (> 1 Hz) CO2 sensor noise is evident, with a measured root mean square (rms) noise level of 0.047 ppm. The results were estimated using a smoothed curve. Figure 6A The pitch-induced signal amplitude is close to 0.12 ppm peak-to-peak, at least twice that of the noise. The signal induced by EC155 motion is clear. The variation is also consistent with the 0.5–2.0 ppm signals recorded in some previous field studies, but smaller in this case. Figure 6B As shown, for H2O, a similar increase in tilt correlation above the noise level was observed. The high correlation between motion and IRGA error suggests linearity; however, Figure 6C and 6D A significant system hysteresis was observed, which was more pronounced in CO2 than in water vapor.

[0076] Figures 7A-7D Similar data is shown, but for roll rotation (tilting the EC155 left and right). Figure 7A and 7B The changes in the molar mixing ratio of CO2 and H2O over time were shown, while the platform rocked (by...). Figure 7A Traces 706 and Figure 7B The trace 712 in the diagram is modulated. Figure 7A and 7B The data for both raw 20 Hz (trace 702, CO2 mr; and 708, H2O mr) and low-pass filtered (trace 704, CO2 mr LP; and 710, H2O mr LP) are shown for CO2 and H2O, respectively. Figure 7A and 7B The average levels of CO2 and H2O have already been subtracted from the data.

[0077] Figure 7C and 7D Provides support for CO2 ( Figure 7C ) and H2O ( Figure 7D A scatter plot of the measured low-pass mixing ratio data and the instantaneous roll angle. The roll variation is + / - 15 degrees.

[0078] In this situation, the CO2 signal amplitudes caused by roll are similar, but the hysteresis varies depending on the CO2 error and the pitch result. For example, in Figure 7C As observed, the change in CO2 with roll is more linear. Under both pitch and roll conditions, it is clear that the errors caused by the movement of water vapor and CO2 in the EC155 do not track the resulting motion in the same way.

[0079] It was observed that once 3D motion and more varied platform motion frequencies were allowed, the hysteresis between the mixture ratio and tilt angle time series data became increasingly nonlinear. This means that simple tilt-related data correction methods would be problematic even on platforms with lower dynamics, such as those primarily affected by pitch motion, like gliders, ships, or aircraft with roll motion.

[0080] A similar mounting configuration was used for triaxial motion testing, designed to more closely simulate field measurement conditions. Two sensor test plates were mounted directly to the center of a 2-m discus buoy platform. A CO2 reference gas tank was attached to the buoy, and the entire platform was then floated in an 8-m deep ocean instrumentation test tank located at the Chase Engineering Laboratory at the University of New Hampshire. Both periodic and irregular platform motions were induced by coordinated manipulation of the buoy from multiple sides, with the buoy positioned at the center of the large tank. This method allows for simulated time-series data collection at platform pitch and roll rates near the nominal buoy resonant frequency (f = 0.33 Hz), as well as variations in the mean tilt level. Tests were conducted with mean pitch and roll variations ranging from 3 to 15 degrees, reflecting low to high wind conditions measured in recent buoy deployments, with a root mean square (rms) tilt angle of 8 degrees. This is the nominal value for a wind speed of 9 m / s. By forcing the platform more randomly, this setup also achieves mixed (or chaotic) ocean conditions more typical of real-world adverse field situations. Typically, for a given motion test (e.g., in roll...), = 5 degrees), collect two to three minutes of continuous data. This allows for characterization of motion-induced noise at different average tilt angles.

[0081] The EC155 provides high-rate temperature measurements associated with thermoelectrically cooled (TEC) IR sensor detectors. Figure 8A and 8B This shows the independent buoy pitch in the deep water tank. Figure 8A ) and roll ( Figure 8B Standard model EC155 data from a short 20-second measurement segment during motion testing (f ≈ 0.35Hz). Figure 8A and 8B The time series data presented in the middle is similar to Figure 6A , 6B 7A and 7B are shown, but only CO2 IRGA data are presented, and the time variation of EC155 detector temperature is added after subtracting its average level. The average pitch and roll variations are + / - 10 to 12 degrees. Figure 8A Corresponding to only pitch motion, and Figure 8B This corresponds to only lateral movement. Figure 8A In the diagram, trace 802 (CO2mr) represents the CO2 mixing ratio data at the original 20 Hz rate, trace 804 (CO2mr LP) represents the CO2 mixing ratio data after low-pass filtering, trace 806 (detector temperature) represents the detector temperature, and trace 808 (pitch) represents the pitch. Figure 8B In the diagram, trace 810 (CO2 mr) represents the CO2 mixing ratio data at the original 20 Hz rate, trace 812 (CO2 mr LP) represents the CO2 mixing ratio data after low-pass filtering, trace 814 (detector temperature) represents the detector temperature, and trace 814 (roll) represents the roll.

[0082] Both tests showed that the EC155 detector temperature data (traces 806 and 810) had an amplitude of 0.1–0.2°C. The frequency of change is significantly increased in the roll test. Figure 8B These changes are inversely correlated with tilt, but slightly out of phase with motion. There is also a significant detector temperature correlation, but a phase shift relative to changes in CO2 measurements, most pronounced in smooth CO2 signals.

[0083] In all platform tilting and acceleration tests, this motion-related variation in CO2 and H2O data was observed in relation to detector temperature, but the amplitude and phase shift differed. Empirically, it is clear that there is a considerably high nonlinearity between control temperature, motion, and trace gas measurements. This may be related to... Figure 6C , 6D The observed hysteresis between the mixing ratio and platform tilt changes shown in 7C and 7D is related to the hysteresis.

[0084] Improvements were made to the EC155P to address this issue. Figure 9A and 9B The results of parallel tests on the performance of EC155P and EC155 are shown. Figure 9A and 9B The time-series data for both EC155 and EC155P are presented, showing the bandpass filter changes in CO2 and detector temperature data after subtracting the average level. Figure 9A Pitch test data is shown in Figure 1, and roll test data is shown in Figure 9B. The variation is + / - 10 to 12 degrees. Figure 9AIn the diagram, trace 902 (CO2_EC155) represents the CO2 mixing ratio data for EC155, trace 904 (CO2_EC155P) represents the CO2 mixing ratio data for EC155P, trace 906 (DetT_EC155) represents the detector temperature of the EC155 detector, and trace 908 (DetT_EC155P) represents the detector temperature of the EC155P detector. Similarly, in... Figure 9B In the diagram, trace 910 (CO2_EC155) represents the CO2 mixing ratio data of EC155, trace 912 (CO2_EC155P) represents the CO2 mixing ratio data of EC155P, trace 914 (DetT_EC155) represents the detector temperature of EC155 detector, and trace 916 (DetT_EC155P) represents the detector temperature of EC155P detector.

[0085] Compared to the EC155, the EC155P exhibits a significantly reduced TEC temperature change. In fact, the EC155P appears to have a TEC change of 0.0, as there is virtually no measurable high-rate TEC change in the exemplary cell, while the EC155 again shows 0.1. Changes. The test data also demonstrates an improvement in the motion-dependent CO2 mixing ratio signal of the EC155P. While not completely eliminated, the CO2 signal variation at the tilt frequency is reduced by at least 4 to 5 times. A significant phase shift in the motion-induced CO2 effect between the EC155 and EC155P also indicates a fundamental change between the two sensors. An additional observation is that a larger EC155 TEC and CO2 variation is observed during pitch motion compared to that observed for roll, which is consistent with... Figure 8A and 8B Consistent. A similar effect was observed in the H2O channel data (not shown). This complete attenuation of the TEC temperature change associated with sensor motion was observed throughout the entire range of the tilt motion tests conducted.

[0086] The EC155P results confirm the findings published in this paper that improved detector stability leads to a reduction in motion contamination in IRGA CO2 and H2O measurements.

[0087] To further illustrate the performance variation of the EC155P relative to the standard EC155 unit, MIE calculations were performed using the above equations (1) and (2). In some instances, the MIE calculation was performed in the spectral domain within the motion frequency passband encountered in the buoy wave trough test described herein. = 0.2 to = 0.6 Executed in ). Figure 10 An exemplary spectrum for a mixed ocean motion test group is shown in the figure. Figure 10 The automated spectrum of CO2 measurements was demonstrated during both static platform and mixed ocean motion tests. (Platform for this segment) It is 10 degrees. (Regarding...) The calculated frequency passband limit is shown as a dashed line. Figure 10 In the middle, trace 1002 (EC155P) 运动 This represents the automated spectrum of CO2 measurements performed using an exemplary EC155P unit during mixed ocean motion testing. Trace 1004 (EC155P) 静态 This represents the automated spectrum of a CO2 measurement performed during static platform testing using an exemplary EC155P unit. Trace 1006 (EC155) 运动 ) represents the automatic spectrum of CO2 measurements performed using a standard EC155 unit during mixed ocean motion testing, and trace 1008 (EC155) 静态 The figure represents the automatic spectrum of CO2 measurements performed using the standard EC155 unit during static platform testing. The significant increase in the EC155 CO2 signal in the passband compared to the static case is evident, while the exemplary IRGA (EC155P) level is closer to its noise floor. It should be noted that even within the passband, the EC155P noise level in the static case is slightly higher than that of the EC155. As a measure of the difference, the rms CO2 noise level above 1 Hz is 0.047 for the EC155 and 0.068 ppm for the EC155P. This is a known limitation of the exemplary unit, unrelated to motion improvement goals, and can be improved in the future.

[0088] exist Figure 11A , 11B Summary of side-by-side sensor measurements under different motions is provided in 12A and 12B, including individual pitch, roll, and mixed ocean segments. Figure 11A and 11B This section presents a summary of the errors caused by CO2 movement during tank measurements. Each test segment has a different average tilt amplitude. For both EC155 and EC155P, in Figure 11A The results of pitch or roll motion tests are shown in the figure. Figure 11B The results of mixed ocean motion are shown with increasing tilt. The error factor related to effective motion above the noise floor is also presented. Defined in equation (1) above. The buoy tilting motion is always present, and therefore the platform will not provide less than 3-4 degrees. level.

[0089] refer to Figure 11A and 11BThe largest sensor error was observed for pitch motion in the EC155, specifically for tilt amplitudes of 5-15 degrees. The error increases from 4 to 11. This is 3 to 4 times the error observed for the EC155's roll motion error. The EC155 error shows a quasi-linear increase with the tilt amplitude of pitch, roll, or mixed motion. In all cases, the difference between the EC155 and EC155P is significant. The EC155P has a much lower error. It never exceeded 1.1, and did not increase with... The increase was significant. Hybrid ocean test data Figure 11B This represents the net effect of the expected buoy tilt on the field CO2 error. An improvement to the exemplary IRGA is the ratio of the EC155 to EC155P signals for a given motion test segment, i.e., 𝑀𝐼𝐸 𝐸𝐶155 / 𝑀𝐼𝐸 𝐸𝐶155𝑃 Using this, the observed improvement of EC155P over EC155 is observed for temperatures below 8 degrees Celsius. The improvement factor is 3.6-6.2 times, and 10.4 times for the highest tilt. The average improvement factor is 5.2.

[0090] exist Figure 12A and 12B The text shows the relationship with... Figure 11A and 11B The data presented are from the same test series of water vapor channel data. Figure 12A The results of pitch and roll motion tests for both the EC155 and EC155P are shown. Figure 12B The results of mixed ocean motion are shown with increasing tilt. Figure 12A and 12B The data presented indicate that the overall EC155P increased by 2-8 times, but the results differ somewhat from the CO2 data. For example... Figure 12A As shown, the H2O response caused by EC155 pitch is similar to Figure 11A The CO2 data is shown. However, compared to CO2, the signal is significantly enhanced due to the rocking motion. Second, the H2O measurement error in the exemplary IRGA is also significant and increases with... The pitch test MIE range of the EC155P increases with the increase, although the overall level is much lower than that of the EC155. Slightly above 1.3 to above 14 degrees At 3.2, the EC155P's roll error is approximately three times smaller than its pitch error. Figure 12BThe mixed ocean test results shown further quantify the overall H2O improvement of the exemplary IRGA relative to EC155. These results indicate an average EC155P improvement level of 3.5, ranging from 1.6 to 8.5 across various motion amplitude tests.

[0091] Therefore, aspects and examples demonstrate that detector modifications to chopper-type IRGAs (e.g., replacing the standard infrared detector assembly with an infrared detector assembly having a vacuum-equipped internal volume) reduce motion-induced errors due to platform tilt by 3.6 to 10.4 times in the CO2 channel and by 1.6 to 8.5 times in the water vapor channel. The EC155P unit also shows no measurable increase in CO2 error with increasing platform tilt amplitude or when the orientation of the applied rotation is changed. This significant level of improvement suggests that closed-loop IRGA methods for trace gas measurements may still achieve near-cavity ring-down spectrometer CO2 field measurement accuracy and allow for accurate CO2 mass flux measurements at IRGA EC flux baseline levels where the ocean-atmosphere pCO2 imbalance is well below the currently assumed 40–50 K Atm level. The data presented in this paper indicate that the effect of platform motion on measurement errors of the standard IRGA (EC155) has several distinct characteristics. The error increases with the platform tilt angle, varies with the tilt direction relative to the sensor mounting direction, changes non-linearly with platform tilt, and is correlated with sensor detector temperature control data.

[0092] While most of the data presented in this paper focuses on CO2 measurements, these four characteristics are similarly observed in H2O data. Each of the first three characteristics has been mentioned or implied in previous literature discussing platform motion effects. In particular, the data presented in this paper show that the significantly increased error magnitude under pitch compared to roll rotation is consistent with the understanding that sensor mounting orientation should be optimized to limit errors for any particular platform or field deployment. The exemplary EC155P unit discussed in this paper eliminates or significantly reduces almost all of these error-related characteristics.

[0093] Additional instances

[0094] The following examples relate to further embodiments, whereby many permutations and configurations will be apparent.

[0095] Example 1 is an infrared gas analyzer comprising: a measurement module; and a detector assembly coupled to the measurement module. The measurement module includes an infrared light source configured to emit an infrared light signal. The detector assembly includes an infrared sensing element and a hermetically sealed detector housing having an optical window transparent to the infrared light signal and an internal volume under vacuum. The infrared sensing element is disposed within the internal volume of the detector housing and configured to detect the infrared light signal via the optical window.

[0096] Example 2 is an infrared gas analyzer comprising: a measurement module including an infrared light source; and a detector assembly coupled to the measurement module. The detector assembly includes a sealed detector housing, a sensing element, a temperature sensor, and a thermoelectric cooler. The sealed detector housing has an internal volume under vacuum, wherein the sensing element, the temperature sensor, and the thermoelectric cooler are disposed within the internal volume of the detector housing, and wherein the sensing element and the temperature sensor are coupled to the thermoelectric cooler.

[0097] Example 3 includes the infrared gas analyzer according to Example 2, wherein the infrared gas analyzer is a closed-circuit infrared gas analyzer.

[0098] Example 4 includes an infrared gas analyzer according to one of Examples 2 or 3, wherein the measurement module includes a housing having a first optical window, wherein the detector housing has a second optical window, and wherein the detector assembly is positioned relative to the measurement module, the infrared light source is positioned within the housing and relative to the first optical window, and the sensing element is positioned relative to the second optical window such that light emitted from the infrared light source is directed toward the sensing element via the first optical window and the second optical window.

[0099] Example 5 includes the infrared gas analyzer according to Example 4, further including a coupling mechanism that couples the detector assembly to the measurement module, wherein the coupling mechanism includes one or more mechanical coupling elements configured to hold the detector assembly in place relative to the measurement module.

[0100] Example 6 includes an infrared gas analyzer according to Example 4 or 5, wherein the sensing element is centered relative to the second optical window.

[0101] Example 7 includes an infrared gas analyzer according to any one of Examples 2-6, wherein the internal volume of the detector housing is evacuated to less than 2E9 Torr.

[0102] Example 8 includes an infrared gas analyzer according to any one of Examples 2-7, wherein the thermoelectric cooler is configured to cool the sensing element to a temperature of approximately -40 degrees Celsius.

[0103] Example 9 includes an infrared gas analyzer according to any one of Examples 2-8, wherein the temperature sensor is a thermistor.

[0104] Example 10 includes an infrared gas analyzer according to any one of Examples 2-9, further comprising a component housing having at least one gas inlet port, wherein the measurement module and the detector assembly are disposed within the component housing.

[0105] Example 11 is a detector assembly for an infrared gas analyzer, the detector assembly comprising: a sealed detector housing having an internal volume under vacuum, the sealed detector housing including an optical window transparent to infrared radiation; an infrared sensing element disposed within the internal volume of the sealed detector housing and positioned to detect infrared light signals via the optical window; a thermoelectric cooler disposed within the internal volume of the sealed detector housing and configured to cool the infrared sensing element; and a temperature sensor coupled to the thermoelectric cooler and configured to provide a temperature measurement, wherein the thermoelectric cooler is configured to adjust the temperature of the infrared sensing element to a selected temperature based on the temperature measurement.

[0106] Example 12 includes the detector assembly according to Example 11, wherein the internal volume of the sealed detector housing is evacuated to less than 2E9 Torr.

[0107] Example 13 includes a detector assembly according to one of Examples 11 or 12, wherein the selected temperature is -40 degrees Celsius.

[0108] Example 14 includes a detector assembly according to any one of Examples 11-13, wherein the sensing element and the temperature sensor are mounted to the thermoelectric cooler.

[0109] Example 15 includes a detector assembly according to any one of Examples 11-14, wherein the temperature sensor is a thermistor.

[0110] Example 16 includes a detector assembly according to any one of Examples 11-15, wherein the sensing element is centered relative to the optical window.

[0111] Example 17 is a closed-loop infrared gas analyzer comprising: a measurement module; and a detector assembly coupled to the measurement module. The measurement module includes a housing having a first optical window transparent to infrared radiation; and an infrared light source configured to emit an infrared light signal, the light source being disposed within the housing and positioned to guide the infrared light signal through the first optical window. The detector assembly includes: a sealed detector housing having an internal volume under vacuum, the sealed detector housing including a second optical window transparent to infrared radiation; an infrared sensing element disposed within the internal volume of the sealed detector housing and positioned to detect the infrared light signal via the second optical window; a thermoelectric cooler disposed within the internal volume of the sealed detector housing and configured to cool the infrared sensing element; and a temperature sensor coupled to the thermoelectric cooler and configured to provide a temperature measurement, wherein the thermoelectric cooler is configured to adjust the temperature of the infrared sensing element to a selected temperature based on the temperature measurement.

[0112] Example 18 includes the closed-circuit infrared gas analyzer according to Example 17, further including a component housing having at least one gas inlet port, wherein the measurement module includes a pump configured to draw a gas sample into the component housing via the at least one gas inlet port, and wherein the measurement module and the detector assembly are disposed within the component housing and arranged such that the infrared light source directs the infrared light signal to the sensing element through the gas sample.

[0113] Example 19 includes a closed-circuit infrared gas analyzer according to Example 18, wherein the gas sample includes at least one of CO2 or H2O.

[0114] Example 20 includes a closed-circuit infrared gas analyzer according to any one of Examples 17-19, further including one or more mechanical coupling elements configured to couple the detector assembly to the measurement module and keep the detector assembly aligned relative to the measurement module.

[0115] Example 21 includes a closed-circuit infrared gas analyzer according to any one of Examples 17-20, wherein the internal volume of the sealed detector housing is evacuated to less than 2E9 Torr.

[0116] Example 22 includes a closed-circuit infrared gas analyzer according to any one of Examples 17-21, wherein the sensing element and the temperature sensor are mounted to the thermoelectric cooler.

[0117] Example 23 includes a closed-circuit infrared gas analyzer according to any one of Examples 17-22, wherein the infrared light source is a broadband infrared source.

[0118] Example 24 includes a closed-circuit infrared gas analyzer according to any one of Examples 17-23, wherein the temperature sensor is a thermistor.

[0119] Example 25 includes a closed-circuit infrared gas analyzer according to any one of Examples 17-24, wherein the selected temperature is -40 degrees Celsius.

[0120] After describing several aspects of at least one embodiment herein, various changes, modifications, and improvements will readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to be part of this disclosure and are intended to fall within the scope of this disclosure. Therefore, the descriptions and drawings of various embodiments are presented by way of example only. These examples are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Methods and apparatus can be implemented in other embodiments and can be practiced or performed in various ways. Furthermore, the wording and terminology used herein are for descriptive purposes and should not be considered limiting. Any reference to an instance, component, element, or action of a system or method cited herein in the singular may also cover instances including multiple instances, components, elements, or actions, and any reference herein in the plural may also cover instances containing only a single instance, component, element, or action. References in the singular or plural form are not intended to limit the currently disclosed system or method, its components, actions, or elements. The use of “comprising,” “including,” “having,” “containing,” “involving,” and variations thereof herein means to cover the items listed thereafter and their equivalents, as well as additional items. A reference to “or” can be interpreted as inclusive, such that any term described using “or” can refer to any one, more than one, or all of the terms described.

Claims

1. An infrared gas analyzer, comprising: The measurement module includes an infrared light source; and A detector assembly coupled to the measurement module, the detector assembly comprising: a sealed detector housing having an internal volume under vacuum; a sensing element; a temperature sensor and a thermoelectric cooler, wherein the sensing element, the temperature sensor and the thermoelectric cooler are disposed within the internal volume of the detector housing, and wherein the sensing element and the temperature sensor are coupled to the thermoelectric cooler.

2. The infrared gas analyzer according to claim 1, wherein the infrared gas analyzer is a closed-circuit infrared gas analyzer.

3. The infrared gas analyzer according to claim 1, wherein the measurement module includes a housing having a first optical window; The detector housing has a second optical window; The detector assembly is positioned relative to the measurement module, the infrared light source is positioned within the housing and relative to the first optical window, and the sensing element is positioned relative to the second optical window, such that light emitted from the infrared light source is directed toward the sensing element via the first and second optical windows.

4. The infrared gas analyzer of claim 3, further comprising a coupling mechanism that couples the detector assembly to the measurement module, wherein the coupling mechanism includes one or more mechanical coupling elements configured to hold the detector assembly in place relative to the measurement module.

5. The infrared gas analyzer according to claim 3, wherein the sensing element is centered relative to the second optical window.

6. The infrared gas analyzer according to claim 1, wherein the internal volume of the detector housing is evacuated to less than 2E9 Torr.

7. The infrared gas analyzer of claim 1, wherein the thermoelectric cooler is configured to cool the sensing element to a temperature of approximately -40 degrees Celsius.

8. The infrared gas analyzer according to claim 1, wherein the temperature sensor is a thermistor.

9. The infrared gas analyzer according to claim 1, further comprising a component housing having at least one gas inlet port; The measurement module and the detector assembly are housed within the assembly housing.

10. A detector assembly for an infrared gas analyzer, the detector assembly comprising: A sealed detector housing having an internal volume under vacuum, the sealed detector housing including an optical window that is transparent to infrared radiation; An infrared sensing element is disposed within the internal volume of the sealed detector housing and positioned to detect infrared light signals via the optical window; A thermoelectric cooler is disposed within the internal volume of the sealed detector housing and configured to cool the infrared sensing element; and A temperature sensor, coupled to the thermoelectric cooler and configured to provide temperature measurement, wherein the thermoelectric cooler is configured to adjust the temperature of the infrared sensing element to a selected temperature based on the temperature measurement.

11. The detector assembly of claim 10, wherein the internal volume of the sealed detector housing is evacuated to less than 2E9 Torr.

12. The detector assembly of claim 10, wherein the selected temperature is -40 degrees Celsius.

13. The detector assembly of claim 10, wherein the sensing element and the temperature sensor are mounted to the thermoelectric cooler.

14. The detector assembly of claim 10, wherein the temperature sensor is a thermistor.

15. A closed-circuit infrared gas analyzer, comprising: Measurement module, which includes: The housing has a first optical window that is transparent to infrared radiation. An infrared light source configured to emit an infrared light signal is disposed within the housing and positioned to guide the infrared light signal through the first optical window; and A detector assembly, coupled to the measurement module, includes: A sealed detector housing having an internal volume under vacuum, the sealed detector housing including a second optical window transparent to the infrared radiation. An infrared sensing element is disposed within the internal volume of the sealed detector housing and positioned to detect the infrared light signal via the second optical window. A thermoelectric cooler, disposed within the internal volume of the sealed detector housing and configured to cool the infrared sensing element, and A temperature sensor, coupled to the thermoelectric cooler and configured to provide temperature measurement, wherein the thermoelectric cooler is configured to adjust the temperature of the infrared sensing element to a selected temperature based on the temperature measurement.

16. The closed-circuit infrared gas analyzer according to claim 15, further comprising: The component housing has at least one gas inlet port; The measurement module includes a pump configured to draw a gas sample into the component housing via the at least one gas inlet port; and The measurement module and the detector assembly are disposed within the assembly housing and arranged such that the infrared light source guides the infrared light signal to the sensing element through the gas sample.

17. The closed-circuit infrared gas analyzer according to claim 15, further comprising: One or more mechanical coupling elements configured to couple the detector assembly to the measurement module and keep the detector assembly aligned with respect to the measurement module.

18. The closed-circuit infrared gas analyzer of claim 15, wherein the internal volume of the sealed detector housing is evacuated to less than 2E9 Torr.

19. The closed-circuit infrared gas analyzer of claim 15, wherein the sensing element and the temperature sensor are mounted to the thermoelectric cooler.

20. The closed-circuit infrared gas analyzer according to claim 15, wherein the infrared light source is a broadband infrared source.

Images