Teledyne BDS-3960 Background Gas Compatibility, Typical Purge-down Curve After Air Saturation

Oxygen Analyzer Operational Theory

Figure 2.4 Typical Purge-down Curve After Air Saturation

Shortening the air exposure will allow a faster sensor recovery. A typical BDS sensor will recover to 1 ppm in approximately 25 minutes, to 100 ppb after 80 min, and 10 ppb in about 8 hours, after suffering a ten-minute exposure to air.

2.2.6 Background Gas Compatibility

The BDS oxygen sensor will work in inert gas backgrounds, including nitrogen, hydrogen, argon, helium and ethane. The sensor output, however, is different in different background gases. For example, the sensor output in a hydrogen background is twice as much as it would be in a nitrogen background. Therefore, it is recommended to calibrate the analyzer with an oxygen standard that has a similar background as the sample gas. If an oxygen standard is unavailable for a particular background, a Gas Factor which is determined at TAI could be used to correct the sensor output in different background (see section 4.3.9).

Note: the gas flow meter in the analyzer is calibrated for air. The error for measuring nitrogen is usually negligible. But for

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