Reference Gas; Zero Gas; Span Gas - Teledyne 2000A-EU Operating Instructions Manual

Thermal Conductivity Analyzer

3.4.5 REFERENCE Gas

A gas of fixed composition is needed as a reference to which the
sample gas will be compared. The reference gas is normally selected to
represent the main background gas of the analysis.
For most applications, a constant supply of reference gas flowing at
the same rate as the sample is required for best results. However, in many
cases the flow of reference gas can be slowed to about 0.08 scfh
(40 cc/min) with good results.
For some applications, an optional sealed air reference is installed. In
sealed-reference sensors the reference side of the detector cell is filled with
air and sealed. This eliminates the need to have reference gas constantly
passing through the cell.
NOTE: For instruments equipped with the optional sealed air refer-
ence, there is no REFERENCE inlet or reference VENT port.
It is highly recommended that the same cylinder of gas be used for
both the REFERENCE gas and the ZERO gas.
Pressure, flow, and safety considerations are the same as prescribed
for the SAMPLE gas, above.

3.4.6 ZERO Gas

For the ZERO gas, a supply of the background gas, usually containing
none of the impurity, is required to zero the analyzer during calibration.
For suppressed zero ranges the zero gas must contain the low-end concen-
tration of the impurity.
NOTE: Because most cylinder gases are between 99.95 and 99.98%
pure, it is highly recommended that the same cylinder of gas
be used for both REFERENCE and ZERO gas.
NOTE: It is essential to the accuracy of the analyzer that the purity of
the zero gas be known. Otherwise, when the zero control is
adjusted during zero standardization, the reading will indicate
the impurity content of the zero gas, rather than zero.

3.4.7 SPAN Gas

For the SPAN gas, a supply of the background gas containing 80-
100 % of the component of interest is required as a minimum. If lineariza-
tion is required, intermediate concentrations of the target gas in the back-
ground gas may be necessary. From one to nine separate span gases may be
Teledyne Analytical Instruments
Installation 3
3-15