A new method for membrane-based gas measurements

Lazik, Detlef; Geistlinger, Helmut

doi:10.1016/j.sna.2004.06.015

Cited by 21 publications

(23 citation statements)

References 6 publications

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“…The maximum or limiting current density is attained only when the diffusion limited condition is reached. To reduce the flow-rate dependence of sensors, activities such as covering the working electrode with a gaspermeable membrane has been investigated [25]. In future work, we will also study how the modifying the gas flow path leading up to and around the sensor element impact the flow rate dependence on sensitivity.…”

Section: Resultsmentioning

confidence: 99%

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensor

Sekhar

Brosha

2015

IEEE Sensors J.

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In this paper, selective and sensitive detection of trace amounts of 2, 4, 6-trinitrotoluene is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors with integrated heaters were used to capture the signature of the explosive. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (down to 250 ng). The sensitivity was found to depend on the flow rate and sensor orientation. The sensitivity was found to increase with increasing flow rate. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner.Index Terms-Explosives, TNT, mixed potential, and electrochemical sensor.

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Section: Resultsmentioning

confidence: 99%

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensor

Sekhar

Brosha

2015

IEEE Sensors J.

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“…As shown in [27], the steady-state diffusive flows (dynamic equilibrium) of gas molecules between an outer (index “ a ”) and an inner face (index “ i ”) of a gas-selective membrane result in a pressure change

a_{1}

(mbar/s):

\frac{d p^{i}}{d t} = a_{1} = p^{a} g P_{x} \sum_{j} f_{j x} (χ_{j}^{a} - β χ_{j}^{i})

within a measurement chamber, covered with that membrane. Considering a linear gas sensor with a tubular membrane, the geometric factor g (m −2 ) in Equation (1) is

g = 2 π \cdot L / (V_{0} \ln (R_{a} / R_{i}))

, (

L

(m)—length of tube,

V_{0}

(m 3 )—gas volume in the tube,

R_{a}, R_{i}

(m)—outer and inner radius of tube),

P_{x}

(m 2 /s) is the permeability of gas component “ x ” in the membrane,

f_{j x} = P_{j} / P_{x}

is the permeation selectivity (referred to as selectivity) of gas component “ j ” with respect to gas component “ x ”, the ratio of gas pressures inside and outside the tube is described by

β = p^{i} / p^{a}

, and

χ_{j}^{i}, χ_{j}^{a}

are the mole fractions of a gas component “ j ” within the chamber and outside.…”

Section: Theoretical Descriptionmentioning

confidence: 99%

“…An alternative measurement technique applicable for representative CO 2 measurement in mixed liquid and gaseous phases with spatially varying CO 2 content first demonstrated in [27] is based on the selective permeation of gases through membranes into hollow measurement chambers.…”

Section: Introductionmentioning

confidence: 99%

“…During the consecutive measurement step, a characteristic change of mole numbers is caused within the measurement chamber near the adjusted steady-state gas flows. This change can be monitored either in terms of a volumetric change or a pressure change, and can be used to determine individual gas concentration, e.g., combining different selective measurement cells (combinations of membrane-coated chamber and a gas-tight reference chamber) [27,28]. Such membrane-based gas sensors could be advantageous in measurement tasks where only a single gas component changes.…”

Section: Introductionmentioning

confidence: 99%

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Approach for Self-Calibrating CO2 Measurements with Linear Membrane-Based Gas Sensors

Lazik

Sood

2016

Sensors

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Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO2 in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO2 analysis in dry air with tubular PDMS membranes for various CO2 concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (<1%) of the non-calibrated sensor response, and comparable statistical uncertainty.

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“…The presented gas sensing technology was introduced in [16] and was first demonstrated in the field in [14]. The gas sensor allows the phase-independent measurement of different gases in fluids using the same measuring method, i.e., the sensors works in the vadose zone, in the zone of saturation, as well as within groundwater [20].…”

Section: Linear Sensor For Areal Subsurface Gas Monitoringmentioning

confidence: 99%

Setup of a large-scale test field for distributed soil gas sensors and testing of a monitoring method based on tomography

Neumann

Werner

Petrov

et al. 2016

Tm - Technisches Messen

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Abstract:A 400 m 2 soil test field with gas injection system was built up for the purpose of large-scale validation, optimization, and characterization of a novel comprehensive monitoring method for underground gas storage areas. The method combines gas sensing technology with linear form factor for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct time-series of gas distribution maps based on samples of orthogonally-aligned linear gas sensors. Several injection experiments with carbon dioxide (CO 2 ) at different days with varying boundary conditions indicates the potential of the method for, e.g., rapid leakage detection with respect to Carbon Capture and Storage (CCS) issues.

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A new method for membrane-based gas measurements

Cited by 21 publications

References 6 publications

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensor

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensor

Approach for Self-Calibrating CO2 Measurements with Linear Membrane-Based Gas Sensors

Setup of a large-scale test field for distributed soil gas sensors and testing of a monitoring method based on tomography

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