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Dual mode NOx sensor: measuring both the accumulated amount and instantaneous level at low concentrations.

Groß A, Beulertz G, Marr I, Kubinski DJ, Visser JH, Moos R - Sensors (Basel) (2012)

Bottom Line: Experimental results are presented demonstrating the sensor's integrating properties for the total amount detection and its sensitivity to both NO and to NO(2).The long-term detection of NO(x) in the sub-ppm range (e.g., for air quality measurements) is discussed.Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed.

View Article: PubMed Central - PubMed

Affiliation: Department of Functional Materials, Bayreuth Engine Research Center (BERC), University of Bayreuth, 95440 Bayreuth, Germany.

ABSTRACT
The accumulating-type (or integrating-type) NO(x) sensor principle offers two operation modes to measure low levels of NO(x): The direct signal gives the total amount dosed over a time interval and its derivative the instantaneous concentration. With a linear sensor response, no baseline drift, and both response times and recovery times in the range of the gas exchange time of the test bench (5 to 7 s), the integrating sensor is well suited to reliably detect low levels of NO(x). Experimental results are presented demonstrating the sensor's integrating properties for the total amount detection and its sensitivity to both NO and to NO(2). We also show the correlation between the derivative of the sensor signal and the known gas concentration. The long-term detection of NO(x) in the sub-ppm range (e.g., for air quality measurements) is discussed. Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed.

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Fundamentals of the sensor response of an ideal accumulating-type gas sensor. (a) Increasing sensor signal on the time scale during cyclic gas exposure due to accumulation. (b) Resulting characteristic line: correlation with the total amount Agas. (c) Curve of the signal derivative: correlation with the actual concentration cgas.
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f2-sensors-12-02831: Fundamentals of the sensor response of an ideal accumulating-type gas sensor. (a) Increasing sensor signal on the time scale during cyclic gas exposure due to accumulation. (b) Resulting characteristic line: correlation with the total amount Agas. (c) Curve of the signal derivative: correlation with the actual concentration cgas.

Mentions: The sensor response of an ideal integrating sensor during cyclic analyte gas exposure with the analyte gas concentration cgas is illustrated in Figure 2(a). On the time scale, the sensor response increases in the presence of the analyte gas due to the accumulation of analyte molecules [linearity (1)] but remains constant in the absence of the analyte in the gas stream since the total amount of the stored analyte is not changing [holding capability (2)]. As an undesired effect, in the highly loaded state, the sensitivity may decrease and some of the formerly stored analyte molecules might desorb at 0 ppm analyte gas [saturation effects (3)]. The corresponding characteristic line in Figure 2(b) is obtained by correlating the sensor response with the amount of analyte gas, Agas. Agas here is defined as:(1)Agas (t)=∫cgas (t) d tresulting in the total exposed amount of analyte during the sensing period in the unit ppm·s. Due to the analyte gas accumulation of the sensitive layer, the characteristic line in Figure 2(b) gives a linear correlation between the sensor response and Agas, which is not affected by the analyte gas concentration cgas. Therefore, the total amount of analyte gas (the dose) since the last regeneration period is detected directly with the integrating sensor due to the accumulating properties of the sensitive gas storage material.


Dual mode NOx sensor: measuring both the accumulated amount and instantaneous level at low concentrations.

Groß A, Beulertz G, Marr I, Kubinski DJ, Visser JH, Moos R - Sensors (Basel) (2012)

Fundamentals of the sensor response of an ideal accumulating-type gas sensor. (a) Increasing sensor signal on the time scale during cyclic gas exposure due to accumulation. (b) Resulting characteristic line: correlation with the total amount Agas. (c) Curve of the signal derivative: correlation with the actual concentration cgas.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376581&req=5

f2-sensors-12-02831: Fundamentals of the sensor response of an ideal accumulating-type gas sensor. (a) Increasing sensor signal on the time scale during cyclic gas exposure due to accumulation. (b) Resulting characteristic line: correlation with the total amount Agas. (c) Curve of the signal derivative: correlation with the actual concentration cgas.
Mentions: The sensor response of an ideal integrating sensor during cyclic analyte gas exposure with the analyte gas concentration cgas is illustrated in Figure 2(a). On the time scale, the sensor response increases in the presence of the analyte gas due to the accumulation of analyte molecules [linearity (1)] but remains constant in the absence of the analyte in the gas stream since the total amount of the stored analyte is not changing [holding capability (2)]. As an undesired effect, in the highly loaded state, the sensitivity may decrease and some of the formerly stored analyte molecules might desorb at 0 ppm analyte gas [saturation effects (3)]. The corresponding characteristic line in Figure 2(b) is obtained by correlating the sensor response with the amount of analyte gas, Agas. Agas here is defined as:(1)Agas (t)=∫cgas (t) d tresulting in the total exposed amount of analyte during the sensing period in the unit ppm·s. Due to the analyte gas accumulation of the sensitive layer, the characteristic line in Figure 2(b) gives a linear correlation between the sensor response and Agas, which is not affected by the analyte gas concentration cgas. Therefore, the total amount of analyte gas (the dose) since the last regeneration period is detected directly with the integrating sensor due to the accumulating properties of the sensitive gas storage material.

Bottom Line: Experimental results are presented demonstrating the sensor's integrating properties for the total amount detection and its sensitivity to both NO and to NO(2).The long-term detection of NO(x) in the sub-ppm range (e.g., for air quality measurements) is discussed.Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed.

View Article: PubMed Central - PubMed

Affiliation: Department of Functional Materials, Bayreuth Engine Research Center (BERC), University of Bayreuth, 95440 Bayreuth, Germany.

ABSTRACT
The accumulating-type (or integrating-type) NO(x) sensor principle offers two operation modes to measure low levels of NO(x): The direct signal gives the total amount dosed over a time interval and its derivative the instantaneous concentration. With a linear sensor response, no baseline drift, and both response times and recovery times in the range of the gas exchange time of the test bench (5 to 7 s), the integrating sensor is well suited to reliably detect low levels of NO(x). Experimental results are presented demonstrating the sensor's integrating properties for the total amount detection and its sensitivity to both NO and to NO(2). We also show the correlation between the derivative of the sensor signal and the known gas concentration. The long-term detection of NO(x) in the sub-ppm range (e.g., for air quality measurements) is discussed. Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed.

Show MeSH
Related in: MedlinePlus