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Sondes Section 2
YSI Incorporated Environmental Monitoring Systems Operations Manual 2-43
DEPTH AND LEVEL
For the depth and level calibration, make certain that the depth sensor module is in air and not immersed in
any solution.
From the Calibrate menu, select Pressure-Abs ( or Pressure-Gage if you have a vented level sensor) to
access the depth calibration procedure. Input 0.00 or some known sensor offset in feet. Press Enter and
monitor the stabilization of the depth readings with time. When no significant change occurs for
approximately 30 seconds, press Enter to confirm the calibration. This zeros the sensor with regard to
current barometric pressure. Then press Enter again to return to the Calibrate menu.
For best performance of depth measurements, users should ensure that the sond
e‟
s orientation remains
constant while taking readings. This is especially important for vented level measurements and for sondes
with side mounted pressure sensors.
pH 2-POINT
Using the correct amount of pH 7 buffer standard (see Tables 1-8) in a clean, dry or pre-rinsed calibration
cup, carefully immerse the probe end of the sonde into the solution. Allow at least 1 minute for
temperature equilibration before proceeding.
From the Calibrate menu, select ISE1 pH to access the pH calibration choices and then press 2- 2-Point .
Press Enter and input the value of the buffer at the prompt.
NOTE:
The actual pH value of all buffers is somewhat variable with temperature and that the correct value
from the bottle label for your calibration temperature should be entered for maximum accuracy. For
example, the pH of YSI “pH 7 Buffer” is 7.00 at 25 C, but 7.02 at 20 C.
After entering the correct pH value of the buffer, press
Enter
and the current values of all enabled sensors
will appear on the screen and change with time as they stabilize in the solution. Observe the readings under
pH and when they show no significant change for approximately 30 seconds, press Enter . The display will
indicate that the calibration is accepted.
After the pH 7 calibration is complete, press Enter again, as instructed on the screen, to continue. Rinse
the sonde in water and dry the sonde before proceeding to the next step.
Using the correct amount (see Tables 1-8) of an additional pH buffer standard into a clean, dry or pre-
rinsed calibration cup, carefully immerse the probe end of the sonde into the solution. Allow at least 1
minute for temperature equilibration before proceeding.
Press Enter and input the correct value of the second buffer for your calibration temperature at the prompt.
Press
Enter
and the current values of all enabled sensors will appear on the screen and will change with
time as they stabilize in the solution. Observe the readings under pH and when they show no significant
change for approximately 30 seconds, press Enter . After the second calibration point is complete, press
Enter
again, as instructed on the screen, to return to the Calibrate menu.
Rinse the sonde in water and dry. Thoroughly rinse and dry the calibration containers for future use.
NOTE:
The majority of environmental water of all types has a pH between 7 and 10. Therefore, unless
you anticipate a pH of less than 7 for your application, YSI recommends a two point calibration using pH 7
and pH 10 buffers.