IOP 011C.3
Effective Date: 1/09/2017
Page 5 of 6
8. If unsuccessful, an error message will appear on the screen. Press the Cal key to
exit the calibration error message and return to the run screen. See the trouble
shooting guide in the Instruction Manual for a possible solution.
C. Normal Calibration Method (for % DO). This is the preferred method. Recording
calibration values in this Instrument Operation Manual is required by the Standard
Operating Procedures.
1. Select Menu on the meter keypad.
2. Scroll down and de-select the One Touch Calibration Method by pressing Enter
◄-- when highlighted.
3. Scroll down to and select the Esc box at the bottom of the display. The run
screen should now be displayed.
4. Press and hold the Cal key for three seconds.
5. Scroll to select a calibration mode, either calibrate in ppm or %, Select %.
6. Press ENTER
◄--. The meter will display a calibration value, temperature in
degrees C, and the % air saturation. The Calibration Value is base on the
current barometric pressure. Wait at least three seconds, then record the
information in the SOP log book.
7. Press Enter
◄--. Calibration Successful should be displayed on the screen for 3
seconds.
8. If Unstable Reading is displayed on the screen, press Cal on the key pad to
cancel calibration and repeat procedure.
9. The meter will return to the run screen. If an error occurred, check the
troubleshooting guide for a possible solution.
IV. Measurements
A. Insure the cable/probe is connected to the meter.
B. Be sure the YSI Pro20 DO Meter has been calibrated.
C. Turn the instrument on and wait 10-15 minutes while the probe remains in the
calibration/storage sleeve.
D. Place the probe in the sample to be measured.
E. Shake the probe in the sample to release air bubbles.
F. Allow temperature reading to stabilize.
G. Stir the sample water with the probe at a moderate pace. You must provide 6 inches of
water movement per second across the sensor membrane to obtain an accurate reading.
Be careful not to create a vortex which allows air bubbles to pass against the membrane.
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