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MIXCHEK
Appendix
Teledyne
Analytical
Instruments
33
and the other with approximately 90% helium and air. These two gas
cylinders can be kept on hand to validate the analyzer at any time. The
mixed gas cylinders do not need to be very large. For this system you
will need one additional cylinder of air to calibrate the oxygen analyzer.
This method will require a regulator and a gas flow control and sampling
device. Scuba equipment can be used to build this system. Pony tanks
are suitable, and a standard primary regulator can be used as well. A
power inflator sample adapter is a convent method to sample the gas
cylinders at the correct flow rate. To use this system, the regulator is
first attached to the air cylinder to calibrate the oxygen section (set the
span to 20.9%). The next step is to sample each of the other cylinders.
The results are compared to the Air /Helium chart.
The most important issues are:
•
Accurately calibrating the oxygen analyzer using air to 20.9
% before the test
•
Ensuring that the other cylinders contain a mixture of air and
helium only.
The use of the power inflator sample adapter will ensure that the
sample flow rate is correct.
If the analyzer fails the test, first verify that the oxygen span has
been correctly set, and that it was done with standard air. Standard air
has oxygen content of 20.9%.