Siemens ULTRAMAT 23 Series Equipment Manual page 164

Application note
Sample switchover between raw gas / pure gas
The sensor only functions correctly if the values at the measuring point do not greatly differ from
one another. We cannot recommend switching over between measuring points on the raw gas
side (high H
difference between the H
measurement.
Pressure influence
Abrupt changes in pressure must be avoided. Although the sensor compensates pressure
variations within approx. 20 seconds, it cannot handle pressure surges which may occur when
switching over between samples.
Flow
The sample gas should flow continuously and at a constant rate, also during an AUTOCAL. While
an AUTOCAL is being carried out, the sample gas flow must be diverted by means of appropriate
valve switching.
Reason: H
increases as the sample gas pressure increases. This effect can result in significant delays in the
response time.
Gas moisture
The calibration gas must have the same moisture as the sample gas.
If the sensor is used with a very dry gas for a longer period, e.g. when feeding biogas into the
natural gas network, it is necessary to carry out an AUTOCAL with ambient air every 60 minutes.
The dew point of the air should be in the range of approx. 9 °C ... 12 °C (48°F ... 54°F). The
AUTOCAL purge time should be at least 5 minutes. This prevents premature drying-out of the
sensor.
H influence
2
Due to its internal design, the H
NH influence
3
Loading of 300 vpm NH
AUTOCAL / zero
An AUTOCAL of the zero point should be carried out every 60 minutes. On the one hand, this is
used to protect the sensor, but it also compensates the influence of temperature variations
during the day.
164
S concentration) and the pure gas side (low H
2
S concentrations of the two gas flows is too large for a reliable
2
S is highly soluble in water and accumulates in the condensate. This accumulation
2
S sensor is immune to the influence of H
2
results in destruction of the H
3
S concentration), since the
2
.
2
S sensor within 2 to 3 days.
2
Equipment Manual, 04/2022, A5E37100388-012
ULTRAMAT 23