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Selection of Oxygen Analyzers 4 (1) Oxygen analyzers for oxygen purity analysis. Generally, a range of 98–100% O2 is selected, and four-digit readings of the measurement results are required; therefore, a magnetic oxygen analyzer is an essential instrument. Although both the zirconia-type and fuel cell-type instruments also have an upper limit of 100% O2 in terms of the detection range, they are unable to provide readings accurate to four decimal places when measuring >98% O2. C (2) Oxygen analyzer for constant oxygen analysis. The typical range is set between 0–100% O2 (excluding levels above 98% O2), and magnetic and zirconia types are commonly used. Since magnetic types are further divided into two categories, one of them is the magnetic pressure type, which requires pure oxygen as a reference gas during operation, thus adding complexity to maintenance. The other type is the magnetic mechanical type; although it eliminates the need for a reference gas, its price is more than 50% higher than that of the magnetic pressure type. Many customers choose chemical or permanganate-based oxygen analyzers, which are 30% cheaper than magnetic ones; they are easy to use, do not require a reference gas or maintenance, and yield excellent results, although the batteries need to be replaced. pH3!wH (3) Oxygen analyzer for the analysis of trace oxygen in argon or nitrogen. Generally, a range of 0.01 ppm to 100 ppm O2 is most commonly selected. At this point, although zirconia and Hertz cell oxygen analyzers can also provide such a wide measurement range, they are not suitable for use because when measuring levels below 10 ppm O2, zirconia or permanganate analyzers are affected by trace amounts of reducing gases present in the gas, resulting in significant data inaccuracies. Fuel cell-type oxygen analyzers are all suitable for measuring trace amounts of oxygen. However, different priorities are considered when choosing based on specific circumstances. For example, fuel-cell oxygen analyzers are inexpensive, easy to use, and require no maintenance, which are their unique advantages; hence they are widely used abroad. Hertz batteries or strontium oxide analyzers offer interference resistance against acidic gas components; although their price is higher than that of fuel cell types, they are still viable options. +Furthermore, for certain higher-standard requirements, such as the detection of 1 ppm–1 ppb of O2 in gases, the Hertz cell has distinct advantages; other instruments simply cannot meet such requirements. In the case where the sample gas contains trace amounts of acidic gases, only special types of Hz cell oxygen analyzers can eliminate such interference, prevent sensor poisoning, and provide accurate analysis results. By the way, the oxygen analyzers we use here are from ABB and SERVOMEX; they require some maintenance on a regular basis, but overall they’re quite good! ;P