Amperometric Gas Sensor Response Times

Abstract

This work examines the relative importance of diffusion and the electrical time constant of the working electrode on the response time of amperometric gas sensors. The response curve of an electrochemical carbon monoxide sensor to a 200 ppm CO test gas was measured as a function of the added resistance that is in series with the working electrode to increase the time constant. It has been found that the response time increases with additional resistance. The experimental behavior was compared to the values predicted on the basis of Fick's second law of diffusion and to the values expected on the basis of the electrical properties of the sensor. The behavior of the sensor was explained using an equivalent electrical circuit, describing the time constants of the working electrode. Values obtained from this model were further compared to experimental values obtained from electrochemical impedance spectra. It has been found that the response time of the sensors depends on both the rate of diffusion and the electrical time constants of the working electrode.

Robust and versatile ionic liquid microarrays achieved by microcontact printing

“…A constant potential of À 1.2 V was applied to ensure that O 2 reduction is mass transport limited, hence all the analytes that reach the electrode will be reduced simultaneously. Under these conditions, the sensitivity of the sensor is governed mainly by the gas flow rate through the tubing, and O 2 diffusion rate from the gas phase inside the flask to the surface of the electrode 40 . Once a stable baseline was achieved, the O 2 sample was introduced into the systems.…”

“…The characteristic T 50 and T 90 values for each sensor type are measured from the time when the sensor response current reaches 50% and 90% of its steady-state value, respectively. It should be noted that response time of a gas sensor is strongly dependent on the diffusion properties of each sensor such as tubing length, flow rates, diffusion NATURE COMMUNICATIONS | DOI: 10.1038/ncomms4744 ARTICLE barriers and so on, and direct comparison between literatures are usually difficult 40 . Our study applied the same sensor configurations and conditions for different sensing electrode designs, which allows for sensible comparisons.…”

Electrochemical Sensors for Monitoring of Indoor and Outdoor Air Pollution

“…The sensor sensitivity could be calculated based on the diffusion properties of the gas path into the sensor. However, attention has to be paid to the possible experimental errors in the measurement of diffusion properties [4].…”

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“…Electrochemical sensors, such as pH sensors, ion selective sensors, and redox sensors, are equipped with electrical conductors to allow electrical signals to be transmitted to and from electrodes contained within the sensor. An electrochemical sensor used for measuring pH, ORP (oxidation/reduction potential), or other specific ion concentrations typically is comprised of three parts: namely, a specimen sensing ion electrode, a reference cell, and an amplifier that translates signal into useable information that can be read [44].…”

“…The main advantage of the potentiostatic circuit is that it requires very low power (low power consumption). The performance of the potentiostatic circuit is significantly dependent on the electrical parameters of the amplifier chosen [29]- [44] and [47]- [49]. A circuit diagram of a potentiostatic circuit is shown in Fig.…”