YSI ADV6600 - Manual (Page 197)

Appendix F. Percent Air Saturation
ADV6600
Y S I Environmental
Page 187
F-3. Effects of DO mg/L Calibration
When a user performs a mg/L calibration, no barometer input is required. Values of “DOsat %” will
be calculated by taking the input mg/L value and dividing by the theoretical mg/L value at 1
atmosphere (found in the Std. Methods Table) to yield the reported “DOsat %” value. For example,
if a value of 7 mg/L is entered at a temperature value of 21 C (where 100 % saturation at 1
atmosphere is 8.915), the “DOsat %” value will be (7/8.915) or 78.5. DOsat % values for field
readings are calculated in exactly the same way.
Values of “DOsat %Local” reported after the calibration will be based on the barometer reading
input by the user at the time of the last “DO %” calibration. If the user requires the best possible
accuracy for “DOsat %Local” values after calibration then a “DO %” calibration (with correct
barometer input) should be performed immediately before the “DO mg/L” calibration. If a “DO %”
calibration has never been carried out, then the software will assume that the barometer at the last
calibration was exactly 760 mm Hg.
Thus, after the calibration procedure is complete “DOsat %” values calculated as described above
are then multiplied (in the software) by a factor of (760/BP) to yield the corresponding "DOsat
%Local” values. For example, assume that the temperature of the calibration standard is 21 C
(where air saturation at 760 mm Hg is 8.915 mg/L) and that the oxygen content of the solution has
been determined to be 7 mg/L by Winkler titration. Assume also that the local barometric pressure
was entered as 700 mm at the last “DO %” calibration. After the new “DO mg/L” calibration, the
“DO mg/L” value will be set to 7.00, the “DOsat %” value will be set to (7/8.915)*100 = 78.5, and
the “DOsat %Local” will be set to (760/700)*78.5 = 85.2.
NOTE: As pointed out above, it is important to realize that unless the barometric pressure is known
for every DO reading after calibration, the values of “DOsat %” and “DOsat %Local” will be
incorrect if the barometric pressure has changed since calibration. Thus, even if the barometer had
been input at the time of a mg/L calibration (a method used by some instrument manufacturers, the
values of “DOsat %Local” will still not be exactly accurate after calibration.
F-4. Activation of the “DOsat % Local” Parameter
On receipt of your ADV6600 sonde the “DOsat %Local” parameter will NOT appear in your Report
menu. To activate the parameter, complete the following procedure:
8. Connect the ADV6600 to a computer.
9. Launch the ADVantage 6600 Software for Windows.
10. Choose Connect to System. Verify the COM setting and Baud Rate. Click on Connect.