Dissolved Oxygen Transmitter
Calibration Correction
Teledyne Analytical Instruments
35
5.3 Calibration Example
As an example of a ppm calibration, assume a dissolved oxygen
application where the sample temperature is 30°C at an elevation of
1,500 feet. The calibration is being performed in the sample which is a
brine having a salinity value of 6 ppt.
1.
Determine the oxygen saturation in ppm at 30°C from Table 5-1.
This value is 7.63 ppm.
2.
Determine the relative humidity correction factor (CF
RH
) from
Table 5-2. Because the calibration is being performed in the
sample, a relative humidity of 100% is assumed. At a relative
humidity of 100% and a temperature of 30°C, the relative
humidity correction factor is 0.958.
3.
Determine the elevation correction factor (CF
E
) from Table 5-3.
At 1,500 feet, the elevation correction factor is 0.947.
4.
Determine the salinity correction factor (CF
S
) from Table 5-4. At
6 ppt, the salinity correction factor is 0.94.
5.
Calculate the corrected ppm value as follows:
Corrected ppm = oxygen saturation x CF
RH
x CF
E
x CF
s
Using the data from the tables,
Corrected ppm = 7.63 ppm x 0.958 x 0.947 x 0.94
Corrected ppm = 6.51
5.4 Grab Sample Calibration
In some cases, calibration to a grab sample is desired. If so, the
sensor can be compared to a sample that has been analyzed through a
wet chemical process (Winkler analysis) or by using a laboratory
electrode. After determining the dissolved oxygen concentration by one
of these methods, the SP-1 or SP-2 can be standardized to that value.
