Teledyne 3000TA-XLEU - Trace oxygen analyzer - Manual (Page 103)

Trace Oxygen Analyzer Appendix
Teledyne Analytical Instruments 87
A.5 Application notes
3000XL SERIES ANALYZERS
APPLICATION NOTES ON PRESSURES AND FLOW
RECOMMENDATIONS
The 3000 series analyzers require reasonably regulated sample
pressures. While the 3000 analyzers are not sensitive to variations of
incoming pressure provided they are properly vented to atmospheric
pressure. The pressure must be maintained as to provide a useable flow
rate trough the analyzer. Any line attached to sample vent should be 1/4
or larger in diameter.
FLOW RATE RECOMMENDATIONS:
A usable flow rate for a 3000XL series analyzer is one which can
be measured on the flowmeter. This is basically 0.5 - 2.0 SLPM. The
optimum flow rate is 1 SLPM (mid scale).
Note: Response time is dependent on flow rate, a low flow rate
will result in a slow response to any O
2
changes in the
sample stream. The span flow rate should be
approximately the same as the sample flow rate.
CELL PRESSURE CONCERNS:
The sensors used in 3000XL series analyzers are optimized to
function at atmospheric pressure. At pressures other than atmospheric
the diffusion rate of O
2
will be different than the optimum value. Higher
pressures will produce faster O
2
diffusion rates resulting in a higher O
2
reading and shorter cell life. To use a 3000XL series analyzer at a cell
pressure other than atmospheric, the analyzer must be calibrated with a
known calibration gas at the new cell pressure to adjust for the different
diffusion rate. Cell pressures below 2/3 atmospheric are not
recommended because they tend to cause excessive internal expansion
which may result in seal failure.
For operation at cell pressures other than atmospheric, care must
be taken to avoid changing the sample pressure too rapidly or cell