Teledyne BDS-3960 operating instructions Calibration of the Analyzer, Zero Cal

Oxygen Analyzer Maintenance

Filter	5 minutes
Gas Factor	1.00
Temperature Coef.	0 ppb/degree centigrade
Alarm 1 setpoint	1000 ppb
Alarm 2 setpoint	100 ppb

Pressing the Set Defaults button brings up a confirmation dialog box. Press Yes to reset to the defaults or No to keep the current values.

4.4Calibration of the Analyzer

The analyzer must be calibrated prior to use. For most applications where the desired range of measurement is 0 to 10 ppm, or less we recommend the analyzer be calibrated using a span gas with a concentration between 7.0 to 9.0 ppm oxygen in nitrogen. This will require that calibration be performed in the 0-10 ppm analyzer range.

Before the cell is ready for calibration, it must be purged with sample gas to a low oxygen level—preferably below 0.1 ppm. If the oxygen content of the sample gas is higher than 0.1 ppm, a zero gas such as nitrogen having an oxygen concentration below 0.1 ppm may be required.

4.4.1Zero Cal

The BDS Sensor has a zero offset of less than 5 ppb oxygen. Normally, the offset slowly decreases during the first 7 to 10 days of operation, and is expected to reach a steady value after this time.

Generally, the value of the zero offset is part of the oxygen reading of the sample gas as shown by the analyzer readout. As an example, a reading of 5 ppb oxygen may include 0.4 ppm oxygen in the sample gas and a 5 ppb zero offset.

The determination of the zero offset requires the use of oxygen free gas to the analyzer. The BDS 3960 has an oxygen scrubber as an integral part of its sample system. The software and electronics automatically re-route the sample gas through the scrubber to provide the sensor with oxygen free gas. Best results as well as prolonged scrubber life is attained when the oxygen concentration of the sample gas is below 1 ppm oxygen.

Teledyne Analytical Instruments 49