YSI 5000 - Manual (Page 22)

19
6. Calibration
From the Main mode, press the [CALIBRATE] soft-key to enter Calibration mode. The bottom
row of the display shows the soft-key menu.
98.0 * % 8.15 mg/L
Calibrate
0.0 ppt 740 mmHg
24.38°C 11:33
AM
AUTO CAL DO CAL SETUP DIAGNOSIS
6.1 Dissolved Oxygen Calibration
Dissolved oxygen calibration can be done automatically with the push of one button (see Auto
Cal) or manually by entering the desired value in milligrams per liter or percent saturation (see
DO Cal).
BEFORE YOU CALIBRATE you must Setup the meter, as discussed in the Setup section of
this manual, and Prepare the DO probe as discussed in the Probe Operations Manual. Before
performing an AUTO CAL on a Model 5100, you must check the barometric pressure reading
and calibrate the barometer, if necessary, as shown under 6.1 Dissolved Oxygen Calibration,
Barometer. The Model 5000 does not contain a barometer, therefore, the current barometric
pressure must be entered before an AUTO Cal is performed.
Dissolved oxygen calibration must be done in an environment with a known oxygen content.
Three such environments will be discussed here: calibration in air (water saturated), calibration
in air-saturated water and calibration by Winkler titration. Choose the one which best fits your
application. Calibration in air is the simplest and most accurate method of calibration.
• For air calibration, place the probe in air at 100% relative humidity. To achieve this, the
probe can be placed in a BOD bottle containing 1
″ of water. No stirring is required in air.
• For air-saturated water calibration, air-saturate a volume of water (300 to 500 mL) by
aerating for at least 15 minutes at a relatively constant temperature. Place the probe in the
aerated water and provide adequate stirring (at least 1 foot per second) while calibrating, such
as that provided by the 5010 self-stirring BOD Probe.
• To calibrate to a Winkler-titrated sample, determine the dissolved oxygen value of a
sample by Winkler titration. Place the probe in the sample and provide adequate stirring (at
least 1 foot per second) while calibrating in the manual mode.
NOTE: If you choose calibration by Winkler titration, you cannot use AUTO CAL, you must use
DO CAL (manual) mode, since AUTO CAL assumes the probe is in a saturated environment.