EP0066583A1 - Procede pour la mesure de la pression partielle d'un gaz et sonde pour la mise en oeuvre du procede - Google Patents

Procede pour la mesure de la pression partielle d'un gaz et sonde pour la mise en oeuvre du procede

Info

Publication number
EP0066583A1
EP0066583A1 EP81903251A EP81903251A EP0066583A1 EP 0066583 A1 EP0066583 A1 EP 0066583A1 EP 81903251 A EP81903251 A EP 81903251A EP 81903251 A EP81903251 A EP 81903251A EP 0066583 A1 EP0066583 A1 EP 0066583A1
Authority
EP
European Patent Office
Prior art keywords
medium
partial pressure
probe
probe according
gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP81903251A
Other languages
German (de)
English (en)
Inventor
Erik Aslaksen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PROGRAMMELECTRONIC ENGINEERING AG
Original Assignee
PROGRAMMELECTRONIC ENGINEERING AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by PROGRAMMELECTRONIC ENGINEERING AG filed Critical PROGRAMMELECTRONIC ENGINEERING AG
Publication of EP0066583A1 publication Critical patent/EP0066583A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases

Definitions

  • the present invention relates to a method for determining the partial pressure of a gas in a medium, in which a phase of matter which is ion-selective with respect to the gas ions is introduced between the medium to be measured and a second medium, and a discharge electrode is introduced into both media for measuring the electrical potential difference therebetween and a probe for Execution of the method with a hollow body which delimits a space for a first medium with its wall against a second medium, the wall having at least one ion-selective wall section which is permeable to ions of the gas, one electrode being arranged on each side of the wall and wherein further the first or second medium is a reference medium, corresponding to the second or first one to be measured.
  • Such probes are known for determining the oxygen partial pressure in a medium, as an ion-selective membrane, with a tube made of stabilized ZrO 2 , for example described in "Chemical plants and processes", issue 6/1973, pages 167 to 169 and 198 and 199.
  • the medium the oxygen content of which is to be determined
  • the medium is drawn through the pipe, the outside of the pipe being surrounded by a reference gas.
  • the purpose of the present invention is to propose a method of the type mentioned at the outset, in which the knowledge and the maintenance of a reference medium is considerably less critical than in the known methods.
  • this object is achieved in that the volume of the one medium is selected to be substantially smaller than that of the other medium, at least once a certain amount of electrical charge is passed through the ion-selective material phase and determined beforehand and then the potential difference between the lead electrodes and from the potential differences found and the determined amount of charge determines the partial pressure in one and / or in the other medium.
  • the forced flow of charge only changes the partial pressure of the medium whose volume is significantly smaller than that of the other. This does not change the partial pressure in the "medium sea” of the latter medium.
  • the matter phase is previously heated to a temperature of at least 873 Kelvin.
  • the heating can be carried out by the medium to be measured itself, or by a specially provided organ.
  • the reproducibility of the measured values is also increased in that a compensation pause is made in which the system stabilizes between the passage of the determined amount of charge and the measurement of the potential difference. It is also proposed to measure the potential difference in each case over a certain period of time and to center it over this period In principle, it is relatively insignificant how closely the two media are separated from one another. It is only essential that the diffusion time constant of the gas molecules of interest from one medium to another is significantly greater than the measuring times. However, in order to keep the influence of diffusion as low as possible, it is proposed that the size and polarity of the amount of charge be selected so that the partial pressure in one medium - the small volume - approximates the partial pressure in the second - large volume.
  • a probe of the type mentioned at the outset which is particularly suitable for carrying out the method mentioned, is characterized in that the space against the ambient atmosphere is completely closed after the introduction of the first medium.
  • the first medium is preferably the reference medium, enclosed in the room, in particular if the probe is used to detect changing environments, such as in industrial plants.
  • the second medium is then appropriate to use the second medium as a reference medium, if measured by only small volumes are available as samples for the medium.
  • the probe according to the invention enables it to be introduced directly into this medium, with voltage measuring devices and further units, possibly assigned, for example also a computer, being able to be set up at a distance therefrom, for example in a measuring and monitoring center.
  • means for temperature detection are arranged at least in the immediate area of this ion-selective wall section. These means are preferably designed as a thermocouple for generating a thermal voltage, which enables the temperature to be detected directly by measuring an electrical voltage.
  • At least the wall section consists of stabilized ZrO 2 and that preferably the first medium is the reference medium.
  • an electrical conductor of an electrode is at the same time an electrical conductor of the means for temperature detection.
  • a further simplification of the structure results from the fact that at least part of an electrical conductor of an electrode, preferably that in the reference medium or the electrode itself, is part of a thermocouple.
  • the electrode arranged in the room can be connected to a rhodium conductor within the room by means of a platinum conductor to form the means for temperature detection. This connection then acts as a thermocouple.
  • the temperature of at least the ion-selective wall section may be desirable to influence the temperature of at least the ion-selective wall section.
  • the ion-selective wall section consisting of ZrO 2
  • these organs are designed such that the wall section can be heated to at least 873 ° Kelvin, to a temperature at which the material mentioned only becomes permeable to oxygen ions .
  • the wall of the hollow body delimiting the space, at least partially, is surrounded by a chamber open to the ambient atmosphere, mechanical protection of the wall with the ion-selective part is achieved on the one hand, and on the other hand there is an improved, dynamic, thermal behavior of the arrangement, which in particular is essential if the temperature of the ion-selective wall section is to be influenced.
  • mechanical protection of the wall with the ion-selective part is achieved on the one hand, and on the other hand there is an improved, dynamic, thermal behavior of the arrangement, which in particular is essential if the temperature of the ion-selective wall section is to be influenced.
  • this probe is intended for measuring the oxygen partial pressure.
  • this probe is intended for measuring the oxygen partial pressure.
  • the measuring probe shown has a base 1 made of heat-resistant material with parallel bores 2, 3 and 4 '.
  • a tubular piece 6 made of alumina is placed on a cylindrical extension 5 of the base 1 and fastened thereon by means of a sealing compound 7.
  • the pipe section 6 encases a thermal insulation insert 8 made of asbestos cement, earthenware or the like, which forms a cylindrical chamber 9.
  • the insulating insert 8 is further provided with bores 10, 11 and 12, which connect coaxially to the bores 2 to 4 and open into the chamber 9.
  • An opening 13 in the insulating insert 8 connects the chamber 9 to the ambient atmosphere.
  • An annular cylindrical heating resistor 14 is inserted coaxially into the chamber 9, the connecting lines 15 of which are guided outwards through the bores 2, 3, 10 and 11 and are held therein by a sealing compound 16.
  • a cylindrical support 17 is mounted, which consists of an electrically insulating, ceramic material. This is of two parallel ones Longitudinal bores 18, 19 penetrated. A platinum wire is guided through the bore 19 and a platinum-rhodium wire is passed through the bore 18, the ends of which are connected to one another at 22 to form a thermocouple. The exit of wires 20 and 21 from the holes
  • a tube 25 made of stabilized ZrO 2 and closed on one side is attached to an annular rib 24 of the carrier 17 as an ion-selective wall.
  • the interior 27 of the tube 25 containing a reference gas as a reference medium is sealed gas-tight by the carrier 17 and by the insulating materials 26 and 23.
  • a platinum conductor 28 is connected, which is formed at 29 as a porous platinum electrode. Accordingly, the platinum wire 20 contacts the tube 25 on the inside by likewise forming a porous platinum electrode at 30.
  • a medium such as a gas atmosphere
  • it is brought into this gas atmosphere and, if necessary, brought to a temperature of at least 873 Kelvin with the heating resistor 14 and kept at this temperature, which is done with a corresponding control circuit can.
  • a temperature equalization occurs between the chamber 27, the tube 25 and the ambient atmosphere of the tube 25, which is connected to the gas atmosphere through the opening 13.
  • the difference in the oxygen partial pressures between the interior 27 and the ambient atmosphere creates a measurable potential difference (U) between the electrodes 29 and 30.
  • the oxygen partial pressure resp. generally the partial pressure of the gas from P to ⁇ P, where ⁇ can be calculated using the following equation:
  • the potential difference between the electrodes 29 and 30 is when no current is flowing:
  • a constant current (e.g. 10 mA) with positive polarity is sent through lines 25 and 28 over lines 20 and 28 for five or ten seconds.
  • the tube 25 is kept in a currentless state for five or ten seconds so that an equilibrium can be established.
  • the potential difference between electrodes 29 and 30 is measured and averaged over 2.5 seconds.
  • the duration of the current flow in method step a is preferably determined by a potential difference previously determined. If the voltage is negative (P ⁇ P x ), the duration is 5 seconds.
  • the duration of the current flow in method step d is preferably complementary to that in method step a, so that a complete period always has the same length, preferably 30 seconds. The time between measurements is therefore 15 seconds.
  • the amount of charge transported should preferably be dimensioned in such a way that the partial pressure of the medium in space 27 approaches that of the medium outside as far as possible in order to minimize the effects of any leaks in space 27.
  • the oxygen partial pressures P in the interior 27 and the oxygen partial pressures P x are calculated twice from equations (4) and (6) and the mean value of these calculated values is considered as the measured value.
  • the value for the internal pressure P is calculated according to equation (6) and that for the external pressure P x can be calculated according to the equation
  • the probe described and the measuring method are suitable on the one hand for use in industrial systems for monitoring the air in terms of environmental protection, etc., but also for the analysis of medium samples that are taken far from the laboratory, such as in the context of space research, and then examined in the laboratory to become. Of course they are on given areas of application, which necessarily result in commercial usability, are not exhaustively listed.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

Dans un procede pour la mesure de la pression partielle d'un gaz dans un milieu qui ne soit par critique quant au choix de ce milieu, on envoie une quantite de charge sur une matiere ayant une selectivite par rapport aux ions. On mesure avant et apres la difference de potentiel entre les milieux au moyen d'electrodes de derivation et on determine la pression partielle. La condition essentielle pour ce procede est que le volume d'un des milieux soit sensiblement plus petit que le volume de l'autre. Une sonde pour effectuer ce procede presente un corps creux (25) avec une chambre (27) de preference pour un milieu de reference. Les parois de la chambre la separent du milieu exterieur. On prevoit dans la paroi une zone permeable pour les ions gazeux et une electrode est prevue de chaque cote de la zone (25). La chambre (27) est entierement separee de l'atmosphere ambiante. Pour commander les conditions de temperature dans la zone selective pour les ions (25) on a prevu une disposition de mesure de temperature (21, 22) et/ou des organes de refroidissement (14) ou de chauffage sur la sonde.
EP81903251A 1980-12-12 1981-12-08 Procede pour la mesure de la pression partielle d'un gaz et sonde pour la mise en oeuvre du procede Withdrawn EP0066583A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH9187/80 1980-12-12
CH918780 1980-12-12

Publications (1)

Publication Number Publication Date
EP0066583A1 true EP0066583A1 (fr) 1982-12-15

Family

ID=4349285

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81903251A Withdrawn EP0066583A1 (fr) 1980-12-12 1981-12-08 Procede pour la mesure de la pression partielle d'un gaz et sonde pour la mise en oeuvre du procede

Country Status (6)

Country Link
EP (1) EP0066583A1 (fr)
BE (1) BE891476A (fr)
ES (1) ES507912A0 (fr)
IT (1) IT1145999B (fr)
WO (1) WO1982002093A1 (fr)
ZA (1) ZA818612B (fr)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1218737A (en) * 1967-01-24 1971-01-13 Bailey Meters Controls Ltd Improvements in apparatus for measuring the oxygen content of hot gases
FR1561135A (fr) * 1967-11-17 1969-03-28
FR1590683A (fr) * 1968-09-12 1970-04-20
DE1953580A1 (de) * 1968-10-28 1970-11-12 Asea Ab Tauchmess-Sonde zum Messen des Sauerstoffgehalts in Metallschmelzen
GB1313508A (en) * 1969-05-09 1973-04-11 Kent Instruments Ltd Measurement of gas mixture properties
NL7309537A (nl) * 1973-07-09 1975-01-13 Philips Nv Gasanalyse-apparaat.
DE2365872C3 (de) * 1973-11-15 1979-09-27 Kernforschungszentrum Karlsruhe Gmbh, 7500 Karlsruhe Verfahren zum Einstellen eines geringeren Sauerstoffgehaltes als die Ausgangssauerstoffkonzentration in multinären flüssigen oder festen Systemen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8202093A1 *

Also Published As

Publication number Publication date
WO1982002093A1 (fr) 1982-06-24
IT8112706A0 (it) 1981-12-11
BE891476A (fr) 1982-03-31
ES8302303A1 (es) 1983-01-16
ES507912A0 (es) 1983-01-16
ZA818612B (en) 1982-11-24
IT1145999B (it) 1986-11-12

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Inventor name: ASLAKSEN, ERIK