Oxymat 7; Selection Of The Reference Gas; Reference Gases; Table 9-1 Selection Of The Reference Gas - Siemens SIPROCESS GA700 Operating Instructions Manual

Commissioning

9.3 OXYMAT 7

9.3 OXYMAT 7
9.3.1

Selection of the reference gas

The various measuring spans must have at least one common value. This value is then defined
as the "physical zero point" and applies to all the measuring ranges. The reference gas can
be selected on the basis of the "physical zero point".
The following example with four measuring ranges illustrates this:
Table 9-1
Measuring range
17 to 22% O
15 to 25% O
0 to 25% O
0 to 100% O
Exception: If the smallest measuring span is ≥ 5% O
amounts to no more than 16% O
range. The purity of the reference gas has to be appropriate for the measuring task.
9.3.2

Reference gases

Overview
Table 9-2
Measuring range
0 to vol. % O
to 100 Vol. % O
pressed zero point with full-
scale value 100 vol. % O
0 ≤ 21 ≤ 100% O
pressed zero with 21 vol. %
O within the span)
2
Reference gas "Air"
Air only has a constant O
104
Selection of the reference gas
Criterion for selection of the reference gas
The span of 17 to 22% O2 is part of all measuring ranges. The physical zero
2
point may lie within this range. Air (20.95% O2%) is suitable as the reference
2
gas.
2
2
, the physical zero point can also lie outside the measuring
2
Overview of the reference gases
Recommended
reference gas
N
2 2
(sup‐ O
2 2
)
2
(sup‐ Air
2
share if the humidity is constant. Therefore use dry air.
2
and the distance to the reference gas
2
Reference gas connection
pressure range
2 000 to 4 000 hPa above
sample gas pressure
(max. 5 000 hPa absolute)
100 - 150 hPa with respect
to sample gas pressure
Operating Instructions, 05/2015, A5E31874006-03
Comment
The reference gas flow
is set automatically to
between 5 and 12 ml/
min.
The sample gas pres‐
sure can fluctuate from
the atmospheric pres‐
sure by max. 50 hPa
Rack-mounted device