YSI 6 series User Manual page 48

Sondes
Monitoring Applications
If your instrument will be used in monitoring applications where data is being captured at a longer interval
(e.g. 15 – 60 minutes) to internal sonde memory, a data collection platform or a computer, you need to
activate "Autosleep RS232" as described in Section 2.5, Sonde Software Setup. Then follow the
instructions detailed above for the Sampling Application calibration. With Autosleep active, the calibration
will occur automatically with a display similar to that shown below.
===================================================================
Temp SpCond
C mS/cm
-------------------------------------------------------------------
Stabilizing: 38
After the warm-up time is complete, the readings just before and just after calibration are displayed. When
you press Enter, the screen returns to the DO Calibration menu.
ROX OPTICAL DISSOLVED OXYGEN
Place the sensor either (a) into a calibration cup containing about 1/8 inch of water which is vented by
loosening the threads or (b) into a container of water which is being continuously sparged with an aquarium
pump and air stone. Wait approximately 10 minutes before proceeding to allow the temperature and
oxygen pressure to equilibrate.
Select ODOsat % and then 1-Point to access the DO calibration procedure. Calibration of your Optical
dissolved oxygen sensor in the DO % procedure also results in calibration of the DO mg/L mode and vice
versa.
Enter the current barometric pressure in mm of Hg. (Inches of Hg x 25.4 = mm Hg).
Note: Laboratory barometer readings are usually "true" (uncorrected) values of air pressure and can be used
"as is" for oxygen calibration. Weather service readings are usually not "true", i.e., they are corrected to sea
level, and therefore cannot be used until they are "uncorrected". An approximate formula for this
"uncorrection" (where the BP readings MUST be in mm Hg) is:
True BP = [Corrected BP] – [2.5 * (Local Altitude in ft above sea level/100)]
Press Enter and the current values of all enabled sensors will appear on the screen and change with time as
they stabilize. Observe the readings under ODOsat %. When they show no significant change for
approximately 30 seconds, press Enter. The screen will indicate that the calibration has been accepted and
prompt you to press Enter again to return to the Calibrate menu.
The minor advantages and disadvantages of calibration in air-saturated water versus water-saturated air are
outlined in Appendix M, ROX Optical DO Sensor
NOTE CAREFULLY: As opposed to the 6562 Rapid Pulse Polarographic DO sensor described above,
there is no difference between the calibration routine for sensors which will be used for sampling or
monitoring applications. Usually the Autosleep RS-232 feature in the Advanced|Setup menu will be
activated for ROX calibrations, but there is no problem if it is not active.
Rinse the sonde in water and dry the sonde.
YSI Incorporated Environmental Monitoring Systems Operations Manual
Sal DOsat DO
ppt % mg/L
Depth pH NH4+ N NO3- N Turbid
feet mg/L
Section 2
mg/L NTU
2-42