Teledyne 356WA instruction manual Degrees C = 5 F Degrees K = C +

Trace Oxygen Analyzer Appendix

When span gases are used or when sample gas is being analyzed the flow can vary ±10–20% and more without changing the reading. It is best, however, to keep the sample flow so that the float in the flow tube is at or near the center of the target. Otherwise, a different humidifier setting may be required.

If positioning the float in the center of the target is in error by plus or minus one-quarter of the float’s diameter, an error of approximately ±1.5% of reading* will be produced.

There are instances when it will be necessary to reset or check the exit flow of sample gas and set or reset the position of the target on the flow tube:

•When a different background gas is being analyzed.

•When the target has been accidently repositioned on the flow tube.

The vent flow should be measured either with a volume displacement flow device (e.g. a “bubble-o-meter”) or a calibrated rotometer with correc- tion factors for ambient temperature and pressure, and sample gas density and viscosity. When using a volume displacement flow device it will be necessary to correct the 150 cc/min flow rate for ambient temperature and pressure. It will also be necessary, using either type of flow measuring device, to compensate for the increase in flowrate due to humidifying the sample gas. (The flow tube inside the analyzer is measuring the dry gas flowrate.)

To determine the corrected vent flow rate it will be necessary to know the ambient temperature (in °K), the ambient pressure (in mm Hg) and the vapor pressure of water at ambient temperature.

Ambient temperature can be measured in °Centigrade or °F and con- verted to °K.

Degrees C = 5 (°F -32)

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Degrees K = °C + 273

Ambient pressure can be measured with an accurate barometer.

P(mm Hg) = P(in Hg) x 760 30.00

*If the actual oxygen concentration were, for example, 8.0 ppm, the resultant reading would be 7.9 (float high) or 8.1 (float low).

Teledyne Analytical Instruments A-5