APPLICATION NOTE NO. 13-5
Application note in pdf format
The original SBE 13 Dissolved Oxygen Sensor produces two output signals: an oxygen-dependent output in the range of 0 to + 5 volts, and a temperature-dependent output in the range of -5 to + 5 volts. For the SBE 911plus CTD as well as other applications requiring that both signals be in the 0 to +5 volt range, the sensor electronics may be easily modified as follows:
The new resistors can be standard 1% types, which should be available from any reasonably well-stocked electronics supplier. Sea-Bird can supply these resistors if necessary.
The calibration values shown are nominal, but should give sufficient accuracy for the intended purpose of temperature compensating the membrane current. The coefficients can be more exactly defined if desired by comparing the DO temperature readout with the temperature of a controlled bath (be sure to let the sensor fully equilibrate thermally). Calculate the adjusted coefficients as follows:
K = (Thi - Tlo)/(Vhi - Vlo)
C = Thi - KVhi
drawing 40115 (click on thumbnail to view full size)
drawing 40117 (click on thumbnail to view full size)
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