Plasma Gas Analyzer
57 02001001A_9
1 AUTOMATIC CALIBRATION OPTION
1.1 Gas Circuit Description
Analyzers with this option are equipped with 3 solenoid valves. These valves are made of
stainless steel and have excellent characteristics for inboard contamination. These valves are
used to select between sample, zero and span gas. All gas connections are made on the
analyzer rear panel. All gas inlets are protected with a 2 micron frit mounted inside the
bulkhead. These are acting as particle filters.
When the analyzer is “ON”, there is always one and only one valve, over the gang of three,
being “ON”. So the gas flows through this valve to the common outlet manifold and then to the
bulkhead labeled “Trap In”. At the same time, the manifold also supplies gas to the two other
unselected valves and the gas exits the valves through the purge port, to a common header,
this one being connected to the bulkhead labeled “Purge Vent”. Purging the valves this way
ensures that there is no unswept dead leg that would bring contamination of the sample and
even eliminates the effect (contamination) of an eventual leaking valve. So, as soon as the
analyzer is “ON”, the three valves are swept by the selected gas and there is a flow going to the
“Purge Vent” bulkhead. The amount of this flow is as the following table:
Inlet Gas Pressure Purge Gas Flow
34 kPa (5 PSIG) 40 ml min-1 (40 cc/min)
69 kPa (10 PSIG) 125 ml min-1 (125 cc/min)
We recommend keeping the inlet pressure between 34 kPa (5 PSIG) to 69 kPa (10 PSIG).
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