Siemens 7MB3000 Series Operating Instructions Manual

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The following example with four measuring ranges illustrates this:Table 9-2 Selection of the reference gasMeasuring range Criterion for selection of the reference gas17 to 22% O2 The span of 17 to 22% O2 is part of all measuring ranges. The physical zero pointmay lie within this range. Air (20.95 % O2%) is suitable as the reference gas.15 to 25% O20 to 25% O20 to 100 % O2Exception: If the smallest measuring span is ≥ 5% O2 and the distance to the reference gasamounts to no more than 16 % O2, the physical zero point can also lie outside the measuringrange. The purity of the reference gas has to be appropriate for the measuring task.9.4.1.2 ULTRAMAT 7In an analyzer module without physically suppressed zero point, meaning with characteristicinitial value of zero, use nitrogen as the reference gas (purity 4.6).In an analyzer module with a physically suppressed zero point, use an appropriate referencegas. The concentration of the reference gas generally corresponds to the characteristic initialvalue or, in special cases, the full-scale value or intermediate values.In order to compensate for interference, the reference gas compartment can be subjectedto the purified sample gas of the measured component (absorber mode) or gas out of thecylinder, which corresponds to the average interference gas composition.9.4.2 Requirements for reference gas from the gas cylinderThe reference gas pressure must be 2 000 hPa above the sample gas pressure for sufficientmeasuring ability.1. Use a reference gas line with the following characteristics at measuring spans of < 2% oxygen:– Small cross-section, e.g. pipe diameter 2 mm– Made of metal, e.g., stainless steel2. Flush the reference gas line thoroughly with reference gas before commissioning.9.4.3 Introducing reference gas• Set the flow of sample gas and reference gas to the same level.• Always introduce the reference gas before introducing the sample gas.Commissioning9.4 OXYMAT 7 / ULTRAMAT 7: Introduction of reference gasWall-mounted device128 Operating Instructions, 07/2023, A5E31930403-AB