Xylem 6-Series Multiparameter - Manual (Page 92)

Sondes Section 2
YSI Incorporated Environmental Monitoring Systems Operations Manual 2-86
Enter after the readings have stabilized to confirm the calibration and zero the sensor. Then, press any key
to return to the Calibrate menu.
If you select Chl µg/L in the initial calibration routine, there will be a choice of 1-point, 2-point, or 3-point
options. The 1-point selection is normally used to zero the fluorescence probe in a medium that is
chlorophyll-free. If you use this method, you will either choose to utilize the default sensitivity for
chlorophyll in the sonde software or to update a previous multipoint calibration. Usually you will place the
sonde in clear water, and input 0 µg/L at the screen prompt. After pressing Enter the screen will display
real-time readings allowing you to determine when the chlorophyll readings have stabilized. Press Enter
after the readings have stabilized to confirm the calibration and zero the sensor. Then, as instructed, press
any key to return to the Calibrate menu.
Note: For the 2-point and 3-point calibrations described below, standards of known fluorescence are
required. Two general types of standards can be used: (a) phytoplankton suspensions of known chlorophyll
content, and (b) dye solutions whose fluorescence can be correlated to that of chlorophyll. The user is
responsible for determining the chlorophyll content of phytoplankton suspensions, either by employing the
extractive analysis procedure described in Standard Methods for the Examination of Water and
Wastewater,
or by analyzing the suspension in situ using a laboratory fluorometer. See Section 5.14,
Principles of Operation and Appendix I, Chlorophyll Measurements of this manual for more
information about chlorophyll standards.
Select the 2-point option to calibrate the chlorophyll probe using only two calibration standards. In this
case, one of the standards must be clear water (0 µg/L) and the other should be in the range of a known
chlorophyll content of the water to be monitored. For example, if the water to be evaluated is known to be
low in chlorophyll, an appropriate choice of standards might be 0 and 10 µg/L. However, for general-
purpose measurements an appropriate choice of standards is usually approximately 100 µg/L.
To begin the calibration, immerse the sonde in the 0 µg/L standard, as instructed, and press Enter. It is
mandatory that the 0 µg/L standard be calibrated first. The screen will display real-time readings that will
allow you to determine when the readings have stabilized. Pressing Enter will confirm the first calibration.
Following the instructions on the screen, place the sonde in the second chlorophyll standard, input the
correct value in µg/L, press Enter, and view the stabilization of the values on the screen in real-time. After
the readings have stabilized, press Enter to confirm the calibration. Then, as instructed, press any key to
return to the Calibrate menu.
Select the 3-point option for maximum accuracy over the entire range of 0 to 400 µg/L. As with the 2-
point procedure, one of the standards must be 0 µg/L. The user can select any values for the second and
third standards that are deemed appropriate. The procedure for this calibration is the same as for a 2-point
calibration, but the software will prompt you to place the sonde in the additional solution to complete the 3-
point procedure.
For all chlorophyll calibration procedures, be certain that the standard and sensor are thermally equilibrated
prior to proceeding with the calibration
CAUTION: To be assured of the accuracy for field measurements made with your chlorophyll sensor, you
must either initially calibrate the sensor using a phytoplankton suspension of known chlorophyll content or
post calibrate your sensor in a spreadsheet by comparing the fluorescence values obtained in field studies
with those obtained by laboratory analysis for chlorophyll on grab samples collected during the field study.
The use of chemical dye standards for “calibration” of the sensor may not result in accurate correlation
between fluorescence and actual chlorophyll readings and is designed primarily to evaluate the sensor for
drift. See Section 5.14, Principles of Operation and Appendix I. Chlorophyll Measurements for more
information on the proper calibration of your chlorophyll sensor.
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