Gas Chamber Research Articles

Employing the pyroelectric effect in LiTaO3 thin film for infrared detection of complex gases

Abstract In this paper, the lithium tantalite ( LiTaO 3 ) thin film has been employed as the highly sensitive element for infrared detection of compound (refrigerant) gases such as 1,1,1,2-Tetrafluoroethane ( C 2 H 2 F 4 ) and 1,1,1,2,3,3,3-Heptafluoropropane ( C 3 F 7 H ). The LiTaO 3 thin film was subjected to the mid-infrared light from output transmission spectra of C 2 H 2 F 4 as well as C 3 F 7 H molecules used as sources. The technology for preparation of LiTaO 3 thin film as well as detector design and manufacturing are presented. Particular attention was paid to production of conductive electrodes, including a very thin semitransparent Au layer evaporated on the top surface of LiTaO 3 pyroelectric material. Important characteristics of the LiTaO 3 based pyroelectric system are briefly discussed. Additionally, the design, construction, and performance of the gas chamber operating as a channel for gas sensor testing is briefly described. The pyroelectric open-circuit voltage generated in LiTaO 3 was boosted with a signal processing circuit for selective high-sensitivity detection of compound gases at room temperature. The infrared (IR) filters such as titanium dioxide ( TiO 2 ) and zinc oxide ZnO having narrow bandwidth and working at a normal incidence were integrated into a compact and portable pyroelectric micro-sensor before the LiTaO 3 pyroelectric element in the same package for cleaning background in a broad IR spectrum of both refrigerant gases. The performance, stability, and accuracy of fabricated LiTaO 3 -based IR gas sensors operating on the pyroelectric open-circuit voltage were tested and improved. IR gas sensors designed and prepared in this study can be utilized for non-contact, sensitive, and selective detection of highly hazardous and explosive gases.

Study of atomic sputtering and transport dynamics by Monte Carlo simulation

Magnetron sputtering vacuum coating technology is widely used in Accident Tolerant Fuel (ATF) cladding materials. The growth of thin films is a crucial step in the magnetron sputtering process, closely linked to the energy and angular distribution of atoms sputtered from the target to the substrate. However, experimental investigations of atomic sputtering are challenging due to the difficulty of accurately detecting electron distributions, incident ion distributions, and quantities, especially collisions between sputtered and vacuum chamber gas atoms. In this study, the SRIM/SIMTRA programs based on the Monte Carlo method have been carried out to predict the energy and angular distributions of sputtered atoms from the target surface and to calculate the energy, angle, and number distributions of supering atoms arriving on the substrate after traversing the vacuum chamber. The results of SRIM indicate the sputtered atom distribution in the low-energy region, with the scattering angles exhibiting a ‘heart-shaped’ profile. Additionally, SIMTRA simulation results show that increasing the target-substrate distance (TSD) and vacuum chamber gas pressure leads to significant attenuation of the energy of atoms arriving on the substrate and a tendency for larger incidence angles. These simulation outcomes provide crucial theoretical guidance for optimizing magnetron sputtering coating performance for ATF cladding.

Suspension height tune-up with constant stiffness properties through motor-driving double-gas-chamber hydro-pneumatic strut: Experimental study and modeling.

In vehicle suspension, it is important to achieve continuous height adjustment to reduce the possibility of unstable and off-tracking caused by uneven postures. It is usually solved by air suspension, in which the dynamic properties will change under the adjusting process and these changes are not conducive to control. Considering the above, in this paper a double-gas-chamber hydro-pneumatic strut (DHPS) with the constant and/or predicted stiffness during continuous height adjustment, as masses (oil and gas) conversation are guaranteed in the whole system, which is achieved by volume variation of auxiliary gas chamber through motor-driving piston, is proposed. The dynamic properties and mathematic model of the proposed DHPS are investigated and established through bench test applying to the designed prototype. The system response speed has been evaluated through experimental data that for harmonic test the system can reach the stable condition in 1 (2) cycle subjected to 50mm/s (25mm/s) motor-driving piston moving speed. Finally, a typical quarter-car model is utilized to evaluate the performance of the proposed DHPS. It has been shown that the system takes 0.40s and 0.50s (200mm/s moving speed), and 0.76s and 1.36s (40mm/s moving speed) subjected to step test (25 and 50 mm), respectively.

Pore accessibility matters in CO2 electrolysis: Preventing H2 formation and boosting triple-phase boundary on microtubular gas-diffusion electrodes

The availability of CO2 near the active sites is crucial for suppressing hydrogen evolution reaction (HER) and improving the kinetics of electrochemical reduction of CO2 (CO2RR) in aqueous electrolytes at high current density. The hollow fiber gas-diffusion electrodes (HFGDEs) configuration can deliver CO2 continuously to catalyst/electrolyte interfaces without requiring a separate gas chamber, contrasting with planar gas-diffusion electrodes (GDEs). However, the relatively inhomogeneous pore geometry on the surface of HFGDEs leads to poor CO2 distribution, resulting in an increasing number of flooded pores and parasitic HER, especially at high current densities. This work presents a facile strategy to enhance CO2 distribution and optimize triple-phase boundary formation by manipulating the surface wettability of HFGDEs. The infiltration and melting of hydrophobic agents (e.g., polytetrafluoroethylene (PTFE)) have been carried out on the Zn nanosheet-deposited Cu hollow fiber. The fluorescent residue area (water surface coverage) with a ∼66.7 % decrease and the observation of CO2 bubbling enhancement confirmed the improvement of CO2 distribution on HFGDE, and the resulting HFGDE achieved around ∼39 % increase in terms of industrial-scale CO partial current density and 4 times higher stability compared to the pristine HFGDE. This research highlights the use of HFGDEs to achieve gas flow-through, further combining with a versatile strategy to enhance CO2 distribution which can be applied for other gas-phase electrolysis reactions through creating improved triple-phase interfaces and maximizing reaction activity.

Development of National Emission Factor for Rice Production System in Malaysia: A Step Toward Achieving Sustainable Development Goals

Objective: Currently, methane (CH4) emissions from rice cultivation in Malaysia are calculated using the regional’s methane emission factor (EF) of 1.60 kg CH₄ ha⁻¹ day⁻¹, as Malaysia has not yet developed a national emission factor. The objective of this study is to generate a country-specific EF of CH4 emission from rice cultivation in Malaysian rice fields. The EF generated would then be used in future emission estimates and the country’s greenhouse gas (GHG) inventory reports to the United Nations Framework Convention on Climate Change (UNFCCC). Theoretical Framework: The establishment of a national GHG emission factor for rice cultivation in Malaysia is critical for accurate GHG inventory reporting and effective climate change mitigation. This study utilizes the Intergovernmental Panel on Climate Change (IPCC) guidelines to derive a country-specific emission factor, enhancing Malaysia’s compliance with international climate obligations and promoting sustainable agricultural practices. Method: A new national EF was developed from eleven rice planting seasons in rice granary areas (IADA Pulau Pinang, IADA Barat Laut Selangor, MADA and KADA) and non-granary area (Sik, Kedah). The EF was calculated from methane emissions from the new data sets, published journals and unpublished data from MARDI. For the new data set, methane gas (CH4) was measured using a static chamber method (Minamikawa et al., 2015). Sampling of GHG from the gas chamber is carried out in the field every 2 weeks and gas was analysed by a GC System Agilent 7890A gas chromatography. The daily methane flux and methane emission follow the methods by Habib et al. (2007), Fauzi et al. (2023) and the Guidelines for National Greenhouse Gas Inventories for Cropland (IPCC, 2006a). Results and Discussion: The national EF calculated from CH4 gas emissions over eleven rice planting seasons in Malaysia between 2012-2024 was 1.80 kg CH4 ha-1 day-1, which is higher than the current regional EF used (1.60 kg CH4 ha-1 day-1). However, the value is within the range of the default value of 1.30 kg CH4 ha-1 day-1 by the Intergovernmental Panel on Climate Change (IPCC) 2006 and 2.00 kg CH4 ha-1 day-1 (IPCC, 1996). Research Implications: The use of this new EF resulted in 12.49% increase in the national GHG inventory from the rice cultivation sub-sector as compared to using the current regional EF. This initiative is part of a comprehensive plan to enhance and strengthen GHG inventory reporting for Malaysia's agriculture sector, aiming to meet IPCC requirements and progress to Tier 2 status.

Tunable diode laser absorption spectroscopy for gas detection with a negative curvature anti-resonant hollow-core fiber

In this study, an all-fiber gas sensing technology was proposed, which is based on tunable diode laser absorption spectroscopy in the near infrared. A negative curvature anti-resonant hollow-core fiber was used as the gas chamber and optical channel, and an opto-gas coupling miniature tee was used in the configuration. Down to ppb (parts-per-billion) level noise-equivalent concentration was achieved with a fast-response capability of less than 6 s. The results demonstrated strong long-term stability, with a relative standard deviation of approximately 2.1% over a 12-h period. This approach demonstrates a simple, robust, fast response and compact sensor configuration that contributes to better management of greenhouse gas emissions and environmental pollution.

Design and Experimental Analysis of an Air-Suction Wheat Precision Hill-Seed Metering Device

The uniformity of the wheat distribution within and between rows has a significant effect on crop population structure, leading to decreased yield as nonuniformity increases. Traditional drills are influenced by soil porosity and flatness in the field, making accurate control of sowing depth and amount challenging and resulting in an uneven spatial distribution of gramineous seedlings. Precision cave-sowing technology effectively enhances wheat population distribution uniformity. However, owing to limitations in existing mechanical precision cave planters, their operational speed is lower than that of drill planters. To address these issues, this study designed an air-suction precision wheat seed dispenser, described its basic structure and working principle, and developed a seed mechanical model. A theoretical analysis was conducted on the working process and key components of the seed feeder. A suitable mould hole diameter was determined to be 1.6~2.0 mm, and the rotation speed range for the seed plate was found to be 65~85 r·min−1. Fluent simulations were used to determine the influence of orifice type on gas chamber flow fields; DEM-CFD-coupled simulation identified an appropriate negative pressure range of 2.6~3.4 kPa for optimal performance during seeding operations. Orthogonal experiments were carried out with mould hole diameter, negative pressure size, and seed plate speed as test factors alongside a qualification index, multiple sowing index, and missed sowing index as response indicators—leading to regression equation establishment, which yielded the optimal parameter combination: mould hole diameter at 1.8 mm; gas chamber negative pressure at 3.2 kPa; and a seed plate speed of 74 r·min−1, with the corresponding forwards speed of the machine being 7 km·h−1—resulting in a qualification index of 91.66%, multiple sowing index of 5.98%, and missed sowing index of 2.36%. This pneumatic suction type wheat precision seeder achieves equivalent operational speeds as traditional drills while enabling precision seeding.

Ultra-compact dual-channel integrated CO2 infrared gas sensor

Expiratory CO2 concentrations can directly reflect human physiological conditions, and their detection is highly important in the treatment and rehabilitation of critically ill patients. Existing respiratory gas analyzers suffer from large sizes and high power consumption due to the limitations of the internal CO2 sensors, which prevent them from being wearable to track active people. The internal and external interference and sensitivity limitations must be overcome to realize wearable respiratory monitoring applications for CO2 sensors. In this work, an ultra-compact CO2 sensor was developed by integrating a microelectromechanical system emitter and thermopile detectors with an optical gas chamber; the power consumption of the light source and ambient temperature of the thermally sensitive devices were reduced by heat transfer control; the time to reach stabilization of the sensor was shortened; the humidity resistance of the sensor was improved by a dual-channel design; the light loss of the sensor was compensated by improving the optical coupling efficiency, which was combined with the amplitude trimming network to equivalently improve the sensitivity of the sensor. The minimum size of the developed sensor was 12 mm × 6 mm × 4 mm, and the reading error was <4% of the reading from −20 °C to 50 °C. The minimum power consumption of the sensor was ~33 mW, and the response time and recovery time were 10 s (@1 Hz), and the sensor had good humidity resistance, stability, and repeatability. These results indicate that the CO2 sensor developed using this strategy has great potential for wearable respiratory monitoring applications.

Research on adaptive damper based on cone-slide valve combination regulation principle

In the wet process of semiconductor manufacturing, the high reliability and safety of the liquid supply system are crucial. The pulsation of liquid output from bellows pumps can cause pipeline vibrations, leading to reduced system lifespan and reliability, potential component damage, and ultimately decreased process yield. To address this issue, this paper proposes an adaptive damper based on a combination of cone-slide valve regulation, specifically designed to mitigate pulsations in the liquid supply system. By establishing a mathematical model of the damper, we investigated the parameters affecting its pulsation absorption rate and response characteristics, and developed a prototype. Experimental results indicate that increasing the gas chamber volume and reducing the stiffness of the bellows significantly enhance the damper pulsation absorption rate. The effective flow area of the control valve influences the response characteristics of the system. The damper demonstrates excellent pulsation suppression performance with varied system pressure and input flow rates. The proposed design method and damper model are experimentally validated, providing a theoretical foundation and technical support for optimizing liquid supply systems in semiconductor wet processes.

Modeling and analysis of a novel CPSC/CI combined profile for scroll compressors

The scroll profile design has become a research hotspot and plays a decisive role in scroll machines. However, the modeling process is complicated due to different expressions of peripheral and central profiles in most full meshing profile (FMPs). Moreover, systematic modeling and in-depth property investigation of scroll profile are still insufficient. Herein, this study simplifies scroll profile modeling by constructing a novel FMP that combines a cubic power series curve (CPSC) with a circular involute (CI) to improve the properties of scroll compressors. An analytical model of CPSC/CI scroll wraps is proposed using the orthogonal components approach and validated by numerical examples. Geometric models to calculate chamber volume and gas load action length, and gas load models, are established. The effects of the CPSC/CI on the scroll wrap tip, built-in volume ratio and gas load are investigated. The proposed CPSC/CI enhances scroll compressor's properties by providing favorable properties not only with wider range of variation in scroll wrap tip and built-in volume ratio but also smaller gas load vibrations due to its superior flexibility, compared to circular arc/CI. This study provides new possibilities for enhancing scroll compressor performance through the design of scroll wrap profile.

Integrative approach to fluorescence-based oxygen sensing in polymer optical fibers with surface plasmon resonance

This study demonstrates a technique to enhance oxygen (O2) concentration measurement by combining surface plasmon resonance (SPR) and fluorescence-based sensor on polymer optical fiber (POF). The SPR was generated using silver (Ag) and the fluorescence was generated by organic dye. Three fluorescence dyes were used, Tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II) dichloride ([Ru(dpp)3]2+), platinum octaethylporphyrin (PtOEP) and 5,10,15,20-tetrakis (pentafluorophenyl) 21 H,23H-porphine palladium (II) (PdTFPP). The sensor was tested in a gas chamber with different concentration level of O2. Sensitivity values for the fluorescence dyes for [Ru(dpp)₃]²⁺, PtOEP, and PdTFPP were 0.0099 a.u/%, 0.0343 a.u/% and 0.05 a.u/% respectively. When SPR was implemented, the sensitivity values for Ag/[Ru(dpp)₃]²⁺, Ag/PtOEP, and Ag/PdTFPP were 0.0589 nm/%, 0.0345 nm/%, and 0.118 nm/% respectively. PdTFPP and Ag/PdTFPP exhibit highest sensitivity in each experiment. Therefore, the further analysis for the sensing performance of PdTFPP and Ag/PdTFPP were held. As a result, Ag/PdTFPP exhibits lower limit of detection (LOD), and limit of quantification (LOQ) with 3.054 % and 9.254 %, respectively, with higher R2 of 0.9971 and lower mean standard deviation of 0.174, compared to PdTFPP 16.496 % and 49.988 % respectively, with R2 of 0.9211 and higher mean standard deviation of 2.003. This improvement can benefit researchers and professionals in medical diagnostics, environmental monitoring, and industrial process control by providing a more sensitive and accurate method for measuring O2 levels.

Growth chamber gas dynamics in Cz silicon single crystal growth process

Mathematical simulation results for inert gas (argon) dynamics in the rarefied atmosphere of Redmet-10 Cz single crystal silicon growth furnace chamber have been reported. Gas flows in cold (room temperature) and hot (growth process) chambers have been analyzed. Convective gas flows have been considered for two growth chamber gas supply options: basic supply, i.e., through the top central inlet hole only, and combined, i.e., with additional gas supply through the lateral inlet hole. Gas outlet is through the growth chamber bottom outlet hole for both options. For the cold chamber option, forced convection has been studied using the incompressible ideal gas model. For hot chamber, both the nonisothermal compressible ideal gas model and the weakly compressible gas model in the Boussinesq approximation have been used for studying the vortex structure produced by a joint action of forced and thermal-gravitational convection. The effect of different gas inlet methods on the convective transport of silicon monoxide evaporating from the free melt surface has been discussed.

Underestimation of global soil CO2 flux measurements caused by near-surface winds

Soil respiration (Rs) is the largest source of atmospheric CO2, and an accurate understanding of the relationship between near-surface winds, CO2 release from the soil surface, and measurement methods is critical for predicting future atmospheric CO2 concentrations. In this study, the relationship between wind speed and soil CO2 fluxes is elucidated on a global scale through meta-analysis, and the flux measurement methodology is further explored in conjunction with the results of a controlled trial to clarify the uncertainty of the measurement results. The results indicate that near-surface wind speed is positively correlated with soil CO2 release and that near-surface winds result in increased soil CO2 gas release. Wind disturbance affects both the concentration gradient and gas chamber measurements, and the lower calculated soil CO2 release conflicts with the notion that the wind pump effect and Bernoulli effect of negative pressure cause a greater surface gas exchange. The results of the log-response ratios indicate that near-surface winds lead to an underestimation of 12.19–19.75% in widely-used gas chamber method measurements. The results of this study imply that some of the current Rs measurements are biased and that the influence of near-surface winds on Rs measurements needs to be urgently addressed to assess the terrestrial carbon cycle more accurately and develop climate change response strategies.

The influence of non-starch polysaccharides on the formation mechanism of wheat dough

The study examined the effects of oat β-glucan (OβG), chitosan (CTS), araboxylan (AX), and fructosan (FOS) on wheat dough formation. Adding 0–7 % OβG, AX, and FOS increased SS content, enhancing gluten stability. D-AX and D-FOS showed higher β-sheet structures, higher air retention and gluten network, smaller pores and denser structures, higher elastic and viscosity moduli. Excessive OβG and CTS could reduce the dough stability, and β-turn and β-sheet ratios, respectively. Therefore, B-7AX and B-7FOS exhibited lower hardness indices during storage, leading to a smoother appearance and more orderly gas chamber distribution. The study provides a theoretical foundation for using non-starch polysaccharides in flour-based products.

Ground test modeling of cylindrical aero-engine casing under high-temperature and high-pressure aerodynamic load

The aero-engine casing is subjected to high-temperature and high-pressure aerodynamic loads during operation. It is essential to perform the ground strength tests for the casing. To optimize the ground strength test and to improve the accuracy of temperature and pressure loading during the test, a mathematical model of high-temperature and high-pressure aerodynamic loading system for simulating the ground strength test of typical aero-engine casing is established to study the actual temperature and pressure loads on casing during ground test. The temperature and pressure results calculated by the mathematical model under typical loads matched well with the experimental measurements. The verification results show that under the test conditions, the thermal inertia of the heater, the radiation heating of the gas in the test chamber by the heater, and the heat transfer of gas mixing in the pressure process can be ignored. The sensitivity analysis of the parameters affecting the accuracy of pressure and temperature loading is carried out. We show that the pressure can be controlled quantitatively by adjusting the inlet and exhaust pipe parameters, and accurate temperature control can be achieved by designing reasonable heater power and selecting appropriate heating control parameters.

Investigation on growth rate and quality of diamond materials in MPCVD system

Abstract In the paper, experiments of diamond growth with varied parameters are conducted in the microwave plasma chemical vapor deposition system. The growth mechanism of the diamond is analysed based on the phase diagram. The results show that the growth rate and the crystalline quality of the diamond are influenced by the gas phase and chamber pressure. The oxygen can help to improve the crystalline quality of the diamond, while to decrease the growth rate. The methane concentration and the chamber pressure are also key parameters to influence the quality and the growth rate of the diamond. The nitrogen concentration can contribute to the growth of the diamond, and the thermal conductivity is influenced at the same time. The grown diamond substrate can be used as thermal conductor in power devices with promising thermal conductivity.

Impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate

This study combines the experimental and numerical simulation methods to deeply analyze the impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate. Experiments were conducted to examine the influence of momentum flux ratio and theoretical momentum flux ratio on the discharge coefficient under various crossflow Reynolds numbers. It was found that the variation of the discharge coefficient with the theoretical momentum flux ratio clearly reflects the impact of the crossflow boundary layer velocity profile on the discharge coefficient. The rapid growth of velocity in the boundary layer near the wall in the direction normal to the wall surface, or the decrease in the thickness of the boundary layer, both enhance the shearing effect of the crossflow, leading to a decrease in the discharge coefficient. Analysis of the cavity morphology at the hole exit captured by high-speed camera revealed that the averaged profile of the gas–liquid boundary on the symmetrical plane of the jet below the hole can be approximated as a straight line within the scale of the hole diameter, and the sine of the angle between this line and the upper wall surface is roughly equivalent to the normalized discharge coefficient. This relationship was physically interpreted through the analysis of effective and equivalent flow cross-sectional shapes derived from numerical simulation at different crossflow Reynolds numbers and theoretical momentum flux ratios. Additionally, this paper introduces an innovative method for predicting jet flow rate based on image processing technology. A notable feature of this method is that it does not require the measurement of the pressure inside the gas chamber.

Design and construction of the cylindrical drift chamber for the COMET Phase-I experiment

COMET is an experiment at J-PARC that searches for the charged lepton flavor violating process of neutrino-less muon-to-electron conversion (μ→e conversion) in a muonic atom. The COMET Phase-I experiment, which represents the first stage of its staged approach, utilizes the cylindrical drift chamber (CDC) as the main detector to measure the momentum of electrons emitted from μ→e conversion in a 1 T magnetic field. The CDC is designed for optimal performance to achieve the best momentum resolution and effectively separate the μ→e conversion electron signal from background signals. This design entails adapting He:i-C4H10 (90:10) as its chamber gas and employing an all-stereo wire configuration. This document provides a comprehensive overview of the CDC detector, encompassing design considerations, mechanical structure, construction methodologies, and results of performance evaluations conducted using cosmic-rays.

Improving used Lubricant Oil Burner Performance: Effect of Swirled Flow of Internally Distributor Type on the Combustion and Flue Gas Temperature and Emission

This study aimed to experimentally investigate the combustion characteristics of used lubricant oil (ULO). A simple cylindrical burner of the natural draft vaporizing type, equipped with an internal air distributor, was designed and fabricated to achieve this objective. The burner’s efficiency was evaluated based on combustion temperature, flue gas temperature, and concentration levels. The key feature of this burner lies in the swirled flow of air combustion and ULO vapor within the combustion chamber, facilitated by the swirled flow air distributor type. Various air-fuel ratios (ϕ), ranging from 0.5 to 4, were considered in characterizing the burner’s performance. The results revealed increased combustion and flue gas temperatures in the radial airflow types. The highest temperatures achieved using the radial flow type are 930 oC and 410 oC for combustion and exhaust gas temperature, respectively. In contrast, the combustion chamber and exhaust gas temperatures are 980 oC and 465 oC for the swirled flow type, respectively. It was found that there is a decrease in the emission of CO and CO2 by volume under optimum conditions. This decrement was attributed to the swirled flow effects, which promoted a better mixture of air combustion and ULO vapor during combustion.

Development of a Compact NDIR CO2 Gas Sensor for a Portable Gas Analyzer

A carbon dioxide (CO2) gas sensor based on non-dispersive infrared (NDIR) technology has been developed and is suitable for use in portable devices for high-precision CO2 detection. The NDIR gas sensor comprises a MEMS infrared emitter, a MEMS thermopile detector with an integrated optical filter, and a compact gas cell with high optical coupling efficiency. A dual-ellipsoid mirror optical system was designed, and based on optical simulation analysis, the structure of the dual-ellipsoid reflective gas chamber was designed and optimized, achieving a coupling efficiency of up to 54%. Optical and thermal simulations were conducted to design the sensor structure, considering thermal management and light analysis. By optimizing the gas cell structure and conditioning circuit, we effectively reduced the sensor’s baseline noise, enhancing the overall reliability and stability of the system. The sensor’s dimensions were 20 mm × 10 mm × 4 mm (L × W × H), only 15% of the size of traditional NDIR gas sensors with equivalent detection resolution. The developed sensor offers high sensitivity and low noise, with a sensitivity of 15 μV/ppm, a detection limit of 90 ppm, and a resolution of 30 ppm. The total power consumption of the whole sensor system is 6.5 mW, with a maximum power consumption of only 90 mW.