Teledyne BDS-3000 - Oxygen analyzer - Manual (Page 63)

Oxygen Analyzer Operation
Teledyne Analytical Instruments 49
0.00 ppb/degree C
The number on the second line is adjustable using the Up and
Down arrow keys between 0.00 and 10.0. The coefficient is different
from sensor to sensor and it’s entered into the analyzer at the factory
before shipping. If the sensor is replaced, a new coefficient must be
entered. TAI can give the coefficient or it may be estimated.
To estimate it in the field:
1. Set the coefficient to zero.
2. Run the analyzer on “Zero” calibration gas for two weeks or
once stability of its baseline is reached.
3. After the sensor has been purged for at least two weeks and it’s
baseline is stable, monitor the reading and ambient temperature
over a minimum period of 24 hours.
Take the maximum and minimum readings, and the maximum
and minimum temperature readings.
4. Calculate the coefficient using the relation:
Coefficient = (O
2
max - O
2
min) ÷ (Temp max - Temp min)
For example:
In a 24 hour run:
O
2
max = 3.55 ppb
O
2
min = 1.75 ppb
Temp max = 24.5 degrees C.
Temp min = 22.1 degrees C.
Coefficient = (3.55-1.75)ppb ÷ (24.5-22.1) °C = 0.75 °C.
4.4 Calibration of the Analyzer
The analyzer must be calibrated prior to its 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