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1.3.2 Reliable Calibration. Although this instrument can be calibrated with
air, the use of a calibration gas gives better results on the lower PPM ranges. If the instrument is
exposed to high concentrations of oxygen (percent levels), it will take a significant amount of
time to purge the oxygen from the sensor and analyzer for use in the low PPM level
measurements (24 hours or longer).
1.3.3 Integral Power Supply. The differential power +/- 3.6 volts D.C.) of the
instrument amplifier is furnished by two internally mounted 750 milliampere hour nickel
cadmium batteries. Fully charged, these batteries will provide enough power to operate the
instrument continuously for a period of about 30 days. Furthermore, an overnight charge on a
three weeks duty cycle should keep the original batteries supplied usable for many years.
An integral charging circuit and a detectable power cord are provided so that the batteries may
be recharged from any 50 or 60 cycle, 100 to 115 volt, convenience outlet.
The instrument is designed to either sample or have its batteries recharged. Both operations
cannot be carried out simultaneously. TAI has deliberately interlocked the circuitry so that both
operations cannot be carried on at the same time.
Only when the selector switch is placed in the OFF position will the neon lamp on the back plate
of the Model 311XL light up to indicate power to the battery charging circuit.
* U.S. Pat. Nos. 3,767,552 and 3,668,101
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