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Y S I
Environmental
YSI 550A
DISSOLVED OXYGEN CALIBRATION
Dissolved oxygen calibration must be done in an environment with known oxygen content. The YSI
550A DO Instrument can be calibrated in either mg/L or % saturation. Sections below include
instructions on how to calibrate in either mode.
BEFORE YOU CALIBRATE
To accurately calibrate the YSI 550A, you will need to know the following information:
•
The approximate salinity of the water you will be analyzing. Fresh water has a salinity of
approximately zero. Seawater has a salinity of approximately 35 parts per thousand (ppt). If you
are uncertain what the salinity of the sample water is, use a YSI 30 Salinity-Conductivity-
Temperature instrument to determine a salinity value.
•
For calibration in % saturation mode, the approximate altitude (in feet) of the region where you are
located is required. This information can be obtained over the internet or from a local airport or
weather station. To convert from meters to feet, divide by 0.3048.
For best results:
•
Check calibration with each use and recalibrate as necessary to prevent drift. Dissolved oxygen
readings are only as good as the calibration.
•
Calibrate at a temperature within
±
10°C of the sample temperature.
CALIBRATION IN % SATURATION
1.
Ensure that the sponge inside the instrument's calibration chamber is moist. Insert the probe into
the calibration chamber.
2.
Turn the instrument on. Allow it to warm up and readings to stabilize for about 15-20 minutes.
3.
Press and release both the
UP ARROW
and
DOWN ARROW
keys at the same time to enter the
calibration menu.
4. Press
the
Mode
key until “%” is displayed on the right side of the screen for oxygen units. Press
ENTER
.
5.
The LCD will prompt you to enter the local altitude in hundreds of feet. Use the arrow keys to
increase or decrease the altitude. When the proper altitude appears on the LCD, press the
ENTER
key.
EXAMPLE:
Entering the number 12 here indicates 1200 feet.
