APPLICATION NOTE NO. 13-3

SBE Dissolved Oxygen Sensor Calibration Note; 
New Value for PCOR Coefficient
Revised March 2001

Application note in pdf format

Note: This Application Note does not apply to the SBE 43 Dissolved Oxygen Sensor.

Based on the observations of our customers and analyses of oxygen data, Sea-Bird recommends a new value for the coefficient "pcor" used in the calibration equation for polarographic oxygen sensors (Application note 13-1):

pcor = 0.00015, with units of [inverse decibars].

This value should be used in the SEASOFT calibration equation unless a better value can be determined by pressure calibrations of individual sensors against titrated oxygen values. We estimate a residual error in the pressure correction term of less than 0.2 ml/l per 1000 decibars using the new pcor value.

SEASOFT uses the Owens and Millard (JPO 1985) algorithm as a calibration equation. The algorithm incorporates a term for pressure dependence of oxygen permeability of the Teflon membrane:

oxygen concentration = (terms) * exp [pcor * P]

where exp is the natural exponential function and P is pressure measured in decibars.

Sources for estimates of the value of pcor are:

Source	pcor value
Beckman 1971, MINOS DOM dissolved oxygen sensor operating and maintenance instructions	0.00024
Beckman, Dissolved Oxygen monitor polarographic oxygen sensor, Technical Memorandum ATO-1019A	0.00017
Owens and Millard (1985, J. Physical Oceanog., v15 (5) )	0.0001438 (typ)
Owens and Millard (preprint of JPO 1985), numerical fits of data from 144 profiles of oxygen data	0.000156 (avg)
Sea-Bird analysis of oxygen data supplied by customers	0.00014 to 0.00016

Last modified: 06-Apr-2007

Sea-Bird Home     Phone: 425-643-9866     Fax: 425-643-9954     E-mail: seabird@seabird.com