Teledyne 6200A - Sulfides analyzer - Manual (Page 16)

TAI - Thermal Converter Operator Manual - Page 12
2.6 Operation and Calibration
Refer to the 6200A manual for the overall operation of the SO2 analyzer. This unit has some unique
operating characteristics and calibration procedures detailed below.
2.6.1 Calibration Theory
The basic purpose of this instrument is to analyze CO2 sample gas for sulfur containing impurities.
Unlike similar analysis, there is not any zero air available. The following procedure will to allow the
instrument to be zeroed and spanned using the CO2 sample gas that may contain impurities.
The CO2 gas used for zero air is routed from the sample inlet through a charcoal scrubber to remove any
SO2 present.
This gas then passes through the converter and into the reaction cell for measurement. When the signal is
stable, the value Z1 is stored.
Since there are numerous other sulfur containing gasses, it is not possible to determine how well the
charcoal will scrub compounds other than SO2. A 3-way valve is used to bypass the M501TRS converter,
so the sample gas now passes through a charcoal scrubber, then directly to the reaction cell.
The instrument is allowed to collect data with the converter bypassed and this reading is stored as Z2.
This is the actual instrument zero reading.
Span calibration uses span gas generated by a H2S permeation tube, which has been diluted by scrubbed
CO2 described above.
During this phase, the converter MUST be in the pneumatic pathway so the H2S can be oxidized to SO2
and thus measured. However, the converter will not only convert the H2S, but also any impurities that
were not scrubbed by the charcoal, thus producing an anomalously high reading. (If there is no additional
impurities in the CO2 gas, the correction factor will be zero.)
To correct for this error, the software computes a span correction by the following equation:
Z3 = Z1 - Z2
Where:
Z2 = Zero reading with the converter bypassed.
Z1 = Zero reading with the converter in place
Z3 = Zero gas impurity correction factor