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1. INTRODUCTION
1.1 Description
: The Teledyne Analytical Instruments (TAI) Model 311-D is a
portable trace oxygen analyzer which can be operated without an external power source, and
reliably calibrated without the use of cumbersome, questionable, “certified” calibration gases.
The instrument provides for trace oxygen analysis in decade steps ranging from 0-100 to 0-1000
ppm (full scale) plus a 0-1% and 0-100% calibration range that encompasses the known oxygen
concentration of atmospheric air (20.9%, or 209,000 ppm).
Sample oxygen is read from an extremely accurate digital panel meter (0.1% accuracy) whose
range of measurement is determined by the position of the range selector switch.
Sample gas is introduced and vented via a pair of swagelok quick-disconnect fittings that feature
integral shutoff valves that automatically close when the mating male fitting is withdrawn. The
fittings are an integral part of the measuring cell manifold, so that internal sample passage
volume is at an absolute minimum. Sample flow control, although not critical (0.1 to 10
liters/min.), must be accomplished with accessory equipment.
1.2 Method of Analysis
: The sample oxygen is measured by a unique
electrochemical transducer, which functions as a fuel cell; in this instance, the fuel is oxygen.
Oxygen diffusing into the cell reacts chemically to produce an electrical current that is
proportional to the oxygen concentration in the gas space immediately adjacent to the transducer
sensing surface. A two-stage solid state amplifier that features operational amplifiers whose
power consumption per unit is less than (5) milliwatts amplifies the linear, but minute, signal
produced by the transducer from trace oxygen. The dual stages of amplification provide enough
gain to read on the digital panel meter and use a thermistor- controlled network to compensate
for the positive temperature coefficient of the transducer.
1.3 Outstanding Features
: The following unique features are incorporated into the
Model 311-D:
1.3.1 Micro-Fuel Cell
: The Micro-Fuel Cell is a sealed electrochemical
transducer with no electrolyte to change or electrodes to clean. When the cell reaches the end of
its useful life, it is merely thrown away and replaced, as one would replace a worn-out battery in
a flashlight. The life of the cell is warranted by TAI (see Section 4.4) in a fashion similar to that
employed by the manufacturers of automobile batteries. This procedure guarantees the customer
compensation for failure of a given cell to perform as specified.
1.3.2 Reliable Calibration
: The unique qualities of the Micro-Fuel Cell allow
the user to calibrate the instrument with the most economical, reliable
, abundant, standardization
gas there is -- atmospheric air.
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The special “CAL” range of the instrument is meant for calibrating the span in ambient air to
20.9% oxygen. By drawing air through the instrument (see the sample calibration procedure in
Section 3.2) reliable calibration can be achieved.