Span Standardization; Bypass - Teledyne 212R Instruction Manual

Thermal Conductivity Analyzer
After the analyzer stabilizes adjust the "ZERO" control until the recorder
indicates the impurity concentration of the zero gas composition. Be sure that
the range switch is on position #1 and that the sample path flowrate is 0.3 scfh.
NOTE if the"ZERO" or "FINE ZERO" pot runs out of adjustment and
the analyzer can not be calibrated, set this pot back to mid-scale. Then use
the "COURSE ZERO" pot to readjust the zero calibration as close as pos-
sible to zero calibration. And last use the "ZERO" ot "FINE ZERO" pot to
fine adjust the zero calibration.
3.6
After the zero has been standardized, switch the selector valve to "Span",
and reset the sample path flowrate to 0.3 scfh. The recorder should come to
balance on, or close to, the composition of the span gas.
The analyzer is factory calibrated to make sure that the output is linear over
all three ranges of interest. Calibration is achieved with mixing block technique
and the span setting recorded in Section 7 is derived at that time.
If the analyzer performed as described in the warm-up procedure (Section
3.4), and fails to closely approximate the composition of the span gas, there is
grounds for doubting the span gas mixture. Because of the difficulty involved in
obtaining precise analysis of small amounts of impurities in cylinder gas, and
because of the ease with which the gas can be contaminated subsequent to
analysis, any large error in response to the span gas should be suspect. In such a
case TAI recommends that the analyzer be operated at the recommended span
setting until the span gas is reanalyzed.
If adjustment of the span control is necessary to compensate for minor
discrepancies between the recorded setting and the span gas reading, TAI
suggests that the zero and span procedures be repeated until no further adjust-
ment is required.
3.7
The integral gas control panel features a bypass flowmeter and throttle
valve that is located downstream from the input manifold (see the analyzer
piping schematic in the drawing section). The bypass system can be used to
speed the response of the analyzer to changes in the process. The bypass
flowmeter will indicate flowrates that are a factor of ten greater than the
sample path flowmeter. TAI recommends that the bypass system be used
whenever the sample path is switched and particularly after using the span
gas. The time required for the analyzer to stabilize on an impurity concentra-
tion within the limits of Range #1, after having been exposed to a concentra-
tion within the limits of Range #3, is not a function of cell response which is
14

Span Standardization.

Bypass.

Teledyne Analytical Instruments
Model 212R