Galvanic Sensor Research Articles

Advanced principles of sensors based on solid state ionics

The general principle of solid state ionic sensors is the transduction of the chemical energy of the galvanic cell reaction into electrical energy and vice versa. Recent developments are increasingly based on kinetic phenomena of the galvanic sensor cell. The applied voltage or current allows the kinetics of the chemical reaction to be measured or controlled. Parameters such as intermediate surface phases, catalytic surface activities, geometrical configuration, current densities and the temperature have a strong influence. Relations between thermodynamic and kinetic responses are currently employed in order to overcome limitations of cross-sensitivities high operating temperatures and long response times. employed

A galvanic sensor for monitoring corrosion of steel in carbonated concrete

The construction and operation are described of a galvanic sensor which responds to changes in the corrosion intensity of mild steel in carbonated mortars or concretes. The sensor is simple to construct and operate; it is robust and has potential for development as an inexpensive method of long–term continuous nondestructive corrosion monitoring of steel in concrete. Its possible applications include laboratory and field studies of effects of environmental exposure conditions and cement matrix variables on corrosion rates of steel in reinforced concrete structures. Information derived from such investigations is needed to provide an improved basis for service–life prediction.

Gas sensitivity of AgCl interfaces

In extension to the previous work on composite electrolytes, two new concepts with respect to sensor research are investigated: (a) the change of the ionic boundary conductance by using Lewis acid-base interaction between additional nucleophilic (nucleo-phobic) gases and the mobile ions in ionic conductors (here: Ag + in AgCl); (b) the possibility of improving response time in galvanic sensors (Ag|AgCl|Cl 2,Pt) by the use of composite electrolytes. As far as the first topic is concerned, the postulated space-charge effects are suggested experimentally. However, another effect mostly dominates the conductance response in polycrystal-line samples: the change of the transfer resistance due to gas adsorption in the grain boundaries. This phenomenon can, in view of reproducibility and response time, be used as a gas sensing property. The correlation with the gas partial pressure is quantitatively discussed. As regards the galvanic chlorine sensor (an example of the second concept), beneficial effects of γ-Al 2O 3 are investigated. The effect on the response time is more pronounced under contamination with water vapour.

Electrochemical gas sensor using peo electrolyte

A new galvanic sensor for monitoring nitrogen dioxide was developed by using a poly (ethylene oxide) complex of silver trifluoromethane sulphonate electrolyte. The sensor, which is expressed as Au/P(EO) 4.5AgCF 3SO 3/Ag, is a small disk (id, 13 mm). The thickness of gold, film and silver are 25 nm, 30 μm and 1 mm, respectively. The current flowing in the external circuit of the cell was linearly related to the concentration of nitrogen dioxide from 20 ppb to about 10 ppm.

4827246 Hydrocarbon and water level sensor system used to monitor underground storage sites

Combination hydrocarbon and water level sensor systems for use in connection with underground storage sites, such as gasoline storage tanks, industrial waste sites, and the like, with a solar cell power source and an LCD display located above ground and providing directly viewable indication of the presence or absence in the underground environment of "HYDROCARBON" and/or "WATER", with the absence of such being indicated by "OK". In the preferred form, a pod containing an adsorptive type hydrocarbon gas sensor and a galvanic cell type liquid water sensor is suspended by electrical cable means from a well cap in which the solar cell and LCD display are installed.

A galvanic gas sensor using poly (ethylene oxide) complex of silver trifluoromethane sulphonate electrolyte

A galvanic sensor for monitoring nitrogen dioxide was developed by using a poly(ethylene oxide) complex of silver trifluoromethanesulphonate electrolyte. The sensor, which is expressed as Au/P(EO)4.5 AgCF3SO3/Ag, is a small disk (i.d. 13 mm). The polymeric electrolyte film was made by casting the mixture of acetonitrile solutions of both P(EO) (MW 6×105) and AgCF3SO3. The working electrode was made by sputtering of gold in argon. The thicknesses of the desposited gold, polymeric electrolyte film and silver are 25 nm, 30 μm and 1 mm, respectively. When the sample gas containing nitrogen dioxide impinges at 20 ml min−1 on the gold cathode, the current flowing in the external circuit was linearly related to the concentration of nitrogen dioxide from 20 ppb to about 10 ppm. The current efficiency of the cell was 0.051%. The cell's response time was about 2 min for 0.5 ppm of nitrogen dioxide.

Design of temperature-compensated reference electrodes for non-isothermal galvanic sensors

The criterion for the design of a temperature-compensated reference electrode for non-isothermal galvanic sensors is deduced from the basic flux equations of irreversible thermodynamics. It is shown that when the Seebeck coefficient of the non-isothermal cell using a solid oxygen ion-conducting electrolyte under pure oxygen is equal to the relative partial molar entropy of oxygen in the reference electrode divided by 4 F, then the EMF of the non-isothermal cell is the same as that of an isothermal cell with the same electrodes operating at the higher temperature. By measuring the temperature of the melt alone and the EMF of the non-isothermal galvanic sensor, one can derive the chemical potential or the concentration of oxygen in a corrosive medium. The theory is experimentally checked using sensors for oxygen in liquid copper constructed with various metal+oxide electrodes and fully stabilised (CaO)ZrO 2 as the electrolyte. To satisfy the exact condition for temperature compensation it is often necessary to have the metal or oxide as a solid solution in the reference electrode.

High Temperature Humidity Sensing Materials

AbstractNew proton conducting materials were prepared and characterized for potential applications in humidity sensing at temperatures higher than 100°C by complex impedance or galvanic cell type techniques. Calcium metaphosphate, β-Ca(PO3)2as a galvanic cell type sensor material yields reproducible signals in the range from 5 to 200 nmm Hg water vapor pressure at 578°C, with short response time(-30 sec). Polycrystalline samples of α-Zr(HPO4)2and KMO3P5.8Si2O25, and the gel converted ceramic, 0.10Li2O-0.25P2O5-0.65SiO2as impedance sensor materials show decreases in impedance with increasing humidity in the range from 9 nmn Hg to 1 atm water vapor pressure at 179*C.

On-line sensors in industrial water analysis

The advantage of electrochemical sensors and the problems inherent in their use in industrial environments are highlighted by a description of some current on-line analytical systems employing potentiometric and galvanic sensors and their performance in specific applications. A wide variety of aqueous samples is encountered, ranging from extremely dilute, relatively clean solutions to mixtures containing high levels of both dissolved and undissolved species. Sensor design is discussed in the light of these factors and of some of the other constraints within which the manufacture of sensors occurs. Some present trends in the design and use of electrochemical sensors are reviewed to indicate the prospects for the future in this field.

Der potentialverlauf galvanischer sensoren bei pulsförmiger probenaufgabe

It has been shown that by sample application as a pulse the voltage—time relation of a galvanic sensor can generally be described by the equation ▪ where U a is the voltage output change, U o the maximum voltage change at open circuit, R a and R the external and total resistance, k 1 and k 2=1/ RC the rate constants of charging and discharging and C the total capacity of the cell (→condenser model). k 1 is related to the over-all reaction of charging and gives no immediate indication to the rate determining step. For instance k 1 can be the rate constant of chemisorption or an other first order reaction. In the case of a diffusion controlled reaction it is ▪ where K is the partition and D the diffusion coefficient in the electrolyte, S the electrode surface, d the mean thickness of the electrolyte film, V 0 the cell and V L the electrolyte volume above the catalyst. The deduced equation can also be extended to a quite chemical reaction, for instance when the measuring electrode is depolarized by oxygen. k 2 has then analogous meanings to k 1. The mentioned formulas give some indication to the optimalisation of the cell geometry and the preparation of the electrodes. The experimental treatment includes the response of an alcohol sensor, also the determination of k 1 is described and its kinetic meaning is discussed.