Sondes
Section
2
YSI Incorporated
Drinking Water Monitoring Systems Operations Manual
2-32
(1 mS/cm) and 3165 (100 mS/cm) conductivity standards for users who want to assure maximum accuracy
at the high and low ends of the sensor range. Users of the 1 mS/cm standard should be particularly careful
to avoid contamination of the reagent. In fact, because of contamination issues, YSI does not recommend
using standards less than 1 mS/cm. For example:
pH 2-POINT
Using the correct amount of pH 7 buffer standard (see Tables 1-4) 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 (7 in this case) at the prompt. 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 1-4) 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 value of the second buffer 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.
The next calibration instructions are only for the 6920DW sonde. If you do not have this sonde, you
may skip to 2.7, Taking Readings.
AMMONIUM (NH
4
+
) , CHLORIDE (Cl
-
) and NITRATE (NO
3
-
) 3-POINT
The calibration procedures for ammonium, nitrate or chloride are similar to pH except for the reagents in
the calibration solutions. Suggested values for calibrants are 1 and 100 mg/L of either ammonium-nitrogen
(NH
4
-N) or nitrate-nitrogen (NO
3
-N). Suggested values for calibrants are 10 and 1000 mg/L of Chloride
(Cl
-
).
NOTE
: The following procedure requires one portion of the high concentration calibrant and two
portions
of the low concentration calibrant. The high concentration solution and one of the low concentration
WARNING:
AMMONIUM AND NITRATE SENSORS CAN ONLY BE USED AT DEPTHS OF LESS
THAN 50 FEET (15 METERS). USE OF THE SENSORS AT GREATER DEPTHS IS LIKELY TO
PERMANENTLY DAMAGE THE SENSOR MEMBRANE.
