1.  The zirconia oxygen analyzer is appropriate for measurements of ppm to % ranges of oxygen in a gas or combination of gases. The zirconia cell is an electrochemical galvanic cell employing a substantial temperature ceramic sensor that contains stabilised zirconium oxide.
2.  Within an instrument the zirconia mobile is mounted in a temperature managed furnace with the required electronics to process the signal from the detection cell. Normally measurements are displayed immediately via a electronic display as oxygen concentration in excess of the assortment .01ppm to a hundred%.
3.  The concept behind Systech’s zirconia oxygen analyzer
4.  The zirconia mobile is a high temperature ceramic sensor. It is an electrochemical galvanic cell comprising of two electrically conducting, chemically inert, electrodes connected to both aspect of a sound electrolyte tube. This is shown schematically in Determine one underneath.
5.  The tube is entirely gas restricted and manufactured of a ceramic (stabilised zirconium oxide) which, at the temperature of procedure, conducts electric power by indicates of oxygen ions. (Note: In sensors of this type, the temperature has to be above 450°C just before they turn out to be energetic as an electrolyte conductor). The possible variation across the cell is given by the Nernst equation.
6.  
7.  Exactly where:
8.  E is the likely variation (volts)
9.  R is the gas constant (8.314 J mol-1 K-1)
10.  T is the complete temperature (K)
11.  F is the Faraday consistent (96484 coulomb mol-one)
12.  P1 & P2 are the partial pressures of the oxygen on either aspect of the zirconia tube
13.  The Nernst equation can therefore be reduced to:
14.  
15.  Hence, if the oxygen partial force at one of the electrodes is acknowledged and the temperature of the sensor is controlled, then oxygen measurement of the likely big difference between the two electrodes permits the mysterious partial stress to be calculated.
16.  Observe
17.  The partial stress of the fuel is equal to the molar focus of the ingredient in a fuel mixture times the complete stress of the fuel mixture.
18.  PO2 = CO2 P2
19.  exactly where:
20.  PO2 = Oxygen partial pressure
21.  CO2 = Molar concentration of oxygen
22.  P2 = Overall force
23.  Instance
24.  For atmospheric air:
25.  CO2 = twenty.9%
26.  P2 = 1 ambiance
27.  PO2 = (.209/one hundred) x one
28.  PO2 = .209 atmospheres
29.  Basic principle of Operation
30.  The zirconia mobile employed by Systech Illinois is made of zirconium oxide stabilised with yttrium oxide as the ceramic with porous platinum electrodes. This cell is revealed in Figure one.
31.  
32.  Figure 1: Enlarged cross sectional representation of the zirconia substrate
33.  Molecular oxygen is ionised at the porous platinum electrodes.
34.  PtO → Pt + ½ O2
35.  ½ O2 + 2e- → O2–
36.  The platinum electrodes on each and every aspect of the mobile give a catalytic surface for the alter in oxygen molecules, O2, to oxygen ions, and oxygen ions to oxygen molecules. Oxygen molecules on the large focus reference fuel facet of the mobile achieve electrons to turn into ions which enter the electrolyte. Simultaneously, at the other electrode, oxygen ions drop electrons and are introduced from the area of the electrode as oxygen molecules.
37.  The oxygen content material of these gases, and therefore the oxygen partial pressures, is various. Consequently, the fee at which oxygen ions are produced and enter the zirconium oxide electrolyte at each electrode differs. As the zirconium oxide permits mobility of oxygen ions, the quantity of ions transferring in every direction throughout the electrolyte will rely on the rate at which oxygen is ionised and enters the electrolyte at every electrode. https://www.avcray.com/ of this ion transfer is intricate, but it is known to entail vacancies in the zirconia oxide lattice by doping with yttrium oxide.
38.  The end result of migration of oxygen ions across the electrolyte is a web flow of ions in a single direction based on the partial pressures of oxygen at the two electrodes. For illustration in the Nernst equation:
39.  
40.  If P1>P2 ion stream will be from P1 to P2 i.e. a good E.M.F.
41.  If P1
42.  <p2 ion="" flow="" will="" be="" from="" p2="" to="" p1="" i.e.="" a="" negative="" e.m.f.<br="" />If P1=P2 there will be no net ion flow i.e. a zero E.M.F.
43.  In the zirconia analyzer, the Nernst equation is written
44.  
45.  The zirconia analyzer uses air as a reference, a constant oxygen concentration of 20.9%, and the zirconia cell is mounted inside a furnace whose temperature is controlled to 650&deg;C (923 K).
46.  Thus, our Nernst equation further reduces to:
47.  
48.  
49.  The zirconia analyzer electronically calculates the oxygen partial pressure, and therefore oxygen concentration, of a sample gas with unknown oxygen concentration. This is accomplished by measuring the potential, E, produced across the zirconium cell electrodes, substituting for E in the Nernst equation and anti-logging to obtain PO2. The cell potential output is shown in Figure 2.
50.  
51.  Figure 2 Graph of cell potential vs. oxygen concentration of zirconia cell.
52.  By anti-logging the equation, the output signal can be displayed directly on a digital readout meter as oxygen concentration in ppm or %.
53.  Calibration
54.  As the zirconia instrument uses an absolute measurement principle once built and factory calibrated, it does not require any further factory calibration.
55.  Factory calibration consists of calibration of the electronics to accept the millivolt input signal from the detection cell and checking that the instrument then reads correctly on air, 20.9%. The instrument is then further checked for correct reading on ppm oxygen content in nitrogen.
56.  Applications of zirconia oxygen analyzers
57.  The zirconia analyzers may be used for measurement of oxygen at any level between 0-100% in gases or gas mixtures.
58.  The only restriction on the instrument’s usage is that the gas to be measured must not contain combustible gases or any material that will poison the zirconium oxide detection cell.
59.  Any combustible gas, e.g. CO, H2, hydrocarbons such as methane, in the sample gas entering the instrument will combine with any oxygen in the sample gas in the furnace due to the high temperature at which the furnace is kept. This will actually reduce the amount of oxygen in the sample gas and cause the instrument to give an incorrect low reading.
60.  Materials that will poison the detection cell are:
61.  Halogens e.g. Chlorine
62.  Halogenated Hydrocarbons e.g. Methylchloride
63.  Sulphur containing compounds e.g. Hydrogen Sulphide
64.  Lead containing compounds e.g. Lead Sulphide
65.  Gases or gas mixtures containing any of the above are not suitable for oxygen determination with a zirconia type oxygen analyzer.
66.