YSI ADV6600 - Manual (Page 73)

Section 4. Calibration and Diagnostics
ADV6600
Y S I
Environmental
Page 63
periodic 2-point calibrations using a dye sample more frequently during initial studies with the YSI
6025 to empirically determine its drift rate and use these results to set up the calibration frequency.
If post-calibration of the sensor with phytoplankton suspensions is being done to obtain accurate
readings relative to chlorophyll as determined by laboratory extractive analysis, then effectively a 2-
point calibration is being performed for every sampling or monitoring study.
The Fluor zero option is used to zero the fluorescence probe in a medium that is chlorophyll-free. If
Fluor %FS is selected as a parameter in Report Setup, the sonde will report only relative values of
fluorescence in the sample being measured. These values could then be converted into actual
chlorophyll concentrations in µg/L by using a post-calibration procedure, after the chlorophyll
content of grab-samples taken during a sampling or monitoring study has been analyzed in a
laboratory. This determination can involve conducting the extractive analysis procedure described
for chlorophyll in Standard Methods for the Examination of Water and Wastewater or by carrying
out an in situ measurement of chlorophyll using a commercial benchtop fluorometer.
A 1-point calibration 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 multi-point. This procedure will use the
default sensitivity for calculation of chlorophyll concentration in µg/L, allowing fluorescence
measurements that are only semi-quantitative with regard to chlorophyll. However the readings will
reflect changes in chlorophyll from site to site, or over time at a single site.
A 2-point calibration is performed using two calibration standards of known fluorescence. One of
the standards must be chlorophyll-free water (0 µg/L) and the other should be in the range of known
chlorophyll content for 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. Or, for
general-purpose measurements an appropriate choice of standards is usually 0 and 100 ug/L.
A 3-point calibration assures maximum accuracy over the entire range of 0 to 400 µg/L. One of the
standards must be 0 µg/L. The user can select any values for the other two standards that are
deemed appropriate.
Warning: The Chl temp co %/C must be set to zero before calibration with Rhodamine WT.
Fluor zero Calibration:
1. With the ADV6600 in the upright position, place the correct amount of chlorophyll-free water
into a clean, dry or pre-rinsed calibration cup. Immerse the probe end of the ADV6600 into the
solution. Allow at least one minute for temperature equilibration before proceeding.
2. From the Calibrate menu, select Optic Chlorophyll to access the chlorophyll calibration
choices and select a Fluor zero calibration.
3. Input 0 at the screen prompt for Fluor %FS.