Table of Contents
Advertisement
TCD Analyzer
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
reference, 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 G
AS
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
concentration 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 G
AS
For the SPAN gas, a supply of the background gas containing
80-100 % of the component of interest is required as a minimum. If
linearization is required, intermediate concentrations of the target gas in
the background gas may be necessary. From one to nine separate span
gases may be used, depending on the desired precision of the
linearization. See chapter 4, Operation.
Teledyne Analytical Instruments
Installation
17
Advertisement
Table of Contents
