®
Model No. PS-2230
Dissolved Oxygen
7
012-14325A
Probe has a built-in thermistor, and the temperature changes are compensated for by
proprietary algorithms that use readings from the thermistor.
Barometric Pressure: The partial pressure of oxygen in a sample of air or water is not
affected by barometric pressure, but dissolved oxygen concentration in milligrams per
liter is affected. The Optical Dissolved Oxygen Probe has a built-in barometer, and
the reading from that device is used to determine the oxygen pressure during calibra-
tion.
Salinity: As the salinity of water increases, its ability to dissolve oxygen decreases.
(Note: The user will be able to enter a value for the “salinity constant” in the data
acquisition software.) For precise measurement of salinity, the PS-2195
Salinity Sensor is recommended (see the web site at www.pasco.com).
*Salinity is a unit-less measurement determined from conductivity and temperature
readings according to the Practical Salinity Scale. Historically, salinity values deter-
mined with the Practical Salinity Scale were given the designation “ppt” because
these values were very close to those determine by the previously used method where
the mass of dissolved salts in a given mass of water (parts per thousand) were
reported.
Dissolved Oxygen Calibration
The Optical Dissolved Oxygen Probe is calibrated at the factory and does not need to
be re-calibrated under most circumstances. However, if the Sensor Cap is replaced
with a new Sensor Cap (PS-2587), then the Sensor Cap Calibration Code Coefficients
(included with the new Sensor Cap) will need to be entered into the sensor using the
PASCO data acquisition software. The sensor will then need to be re-calibrated. (See
Appendix B.)
For a one-point calibration, you will need one “known standard” with 100% dissolved
oxygen saturation.
For a two-point calibration, you will need two “known standards”; one with 100%
dissolved oxygen saturation, and one with 0% dissolved oxygen saturation.
Refer to the SPARKvue/SPARK SLS, Capstone, or Xplorer GLX User’s Guide or
Online Help for calibration instructions, or go to the PASCO Web site at
www.pasco.com and enter “Optical Dissolved Oxygen Sensor” or “PS-2196” in the
Search window. Download the instruction manual PDF file under “User Resources”.
Known Standards
One method for a known standard with 100% dissolved oxygen saturation is to use
water-saturated air. Moisten the sponge inside the end of the Probe Cover (included
with the probe) with water, and then put the probe into the Probe Cover for about fif-
teen minutes.
CAUTION
: Do not push the Probe Cover on too tight or it might cause a pressure
increase.
Water Type
Average Salinity
Fresh water
<0.5 ppt*
Brackish water
0.5 to 30 ppt
Sea water
33 to 47 ppt
Saline water
30 to 50 ppt
Brine
>50 ppt
