Teledyne 238 - Thermal conductivity analyzer - Manual (Page 16)

Teledyne Analytical Instruments 3-2
3 Operation Model 235 Series
1. Check to see that the span control is set at about 50% of its
travel. Some readjustment of this control may be necessary
during standardization, but our concern at this point is to see
that a reasonable level of output signal is available to the
recorder for zero standardization.
2. With multi-range analyzers, make sure that the range selection
switch is on the “Range 1” position. As in Step No. 1, this
insures a proper signal level for deriving a correct zero setting.
3. Check the sample path flowmeter to see that the zero gas
flowrate is 0.3 SCFH.
4. Adjust the Zero control on the analyzer control panel until the
meter indicates the impurity (if any) contained in the zero gas.
3.4 Span Standardization
After the zero setting has been accomplished, the span (or sensitivity)
of the analyzer can be checked as follows:
1. Arrange the sample path so that span gas is flowing through the
analyzer.
2. Check the sample path flowmeter to see if the span gas is
flowing at a 0.3 SCFH rate.
3 With mufti-range instruments, set the range selector switch on
the position that provides the highest resolution of the span gas
concentration.
4. Adjust the span control until the meter reads the correct value of
impurity in the span gas.
3.5 Onstream Operation
After standardization has been successfully concluded, arrange the
sample path so that sample gas is flowing through the analyzer at approxi-
mately. 0.3 SCFH.
With multirange instruments, select the range of analysis that gives the
best recorder resolution of the process stream. The analyzer is now
“onstream” and ready for use.