Teledyne 311 - Portable trace oxygen analyzer - Manual (Page 8)

3. OPERATION
3.1 Introduction. The Model 311 is supplied completely assembled and ready for
instant use. The Micro-Fuel Cell is in place within the manifold, and prior to shipment the mani-
fold was purged with an inert gas to eliminate all but traces of oxygen from the internal sampling
system. The integral shut-off valves in the quick disconnect sample fittings, if not disturbed, will
maintain this inert atmosphere within the manifold indefinitely. This can be demonstrated by
advancing the range selector switch to the X100 (0-1,000 ppm) position.
When the range selector is advanced from the “OFF” position, power to the instrument’s
circuitry is established. The meter will constantly respond to the residual oxygen within the
integral sample passages.
It is impossible to achieve a “perfect” seal of the internal sample system, and what the meter is
indicating is the diffusion -- consumption balance point of internal sample system and the Micro-
Fuel Cell.
This “balance” point, with a properly calibrated instrument is always within the limits of the
X100 range. If the reading climbs off the limits of this scale, a leak in the manifold assembly is
indicated.
TO EXTEND CELL LIFE AND MINIMIZE THE TIME REQUIRED TO MAKE THE
NEXT ANALYSIS, THE INSTRUMENT SHOULD ALWAYS BE PURGED WITH THE
SAMPLE OR AN INERT GAS PRIOR TO BEING TAKEN OUT OF SERVICE FOR
STANDBY OR STORAGE.
3.2 Calibration. The inherently constant output of the cell during its useful life
precludes a definitive calibration cycle. TAI feels that the interval between calibrations should
be dictated by the customer’s application. If the instrument is being used to certify the oxygen
content of a product for delivery, then, a calibration prior to certification would certainly be in
order. If, on the other hand, the instrument is being used to monitor or guard a sample and the
evidence provided by the analyzer will in themselves determine when a calibration check is in
order. The sensitivity of the analyzer should be checked at two to four week intervals.
DO NOT CALIBRATE THE INSTRUMENT UNLESS THERE IS A TRACE OXYGEN
GAS READILY AVAILABLE FOR PURGING IMMEDIATELY FOLLOWING THE
CALIBRATION PROCEDURE.
3.2.1 Air Calibration Procedure. Employ the following step by step
procedure to calibrate the instrument.
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