Xylem 6-Series Multiparameter - Manual (Page 335)

Chlorophyll Measurements Appendix I
YSI Incorporated Environmental Monitoring Systems Operations Manual I-8
Note the significant improvement in the overall noise level of the readings after the screen was installed on
4/2/99. However, there is no guarantee that this solution will completely solve spiking problems caused by
macro algal species. In some applications, it may be necessary to clean the sonde and probes at a frequent
interval to minimize the number of erroneous readings.
CAUTION: If the installed screen becomes completely clogged with algal filaments, it can create an
isolated environment within the probe compartment which does not accurately reflect the water quality
readings of the overall water at the site. Users should periodically remove the screen and check for
immediate changes in parameters such as dissolved oxygen and pH. If gross changes appear in the data
after removal of the screen, then the screen is likely to be retarding water flow to the sensors and should be
cleaned at more frequent intervals.
Another factor that can contribute to repeated spikes in the user’s chlorophyll data is wiper malfunction so
that the wiper assembly parks over the probe optics. This problem is usually due to the edges of the
fluorescent wiper becoming coated with nonfluorescent material such as sediment that, in turn, prevents the
sonde software from detecting the wiper movement. If the spikes are due to this factor, then the problem
will be corrected by manually cleaning the wiper edges so that the fluorescent surface is restored.
How often should I change my mechanical wiper?
For sampling and monitoring studies, YSI recommends periodic inspection of the wiper to assure that it is
not fouled with silt or biological material. If any of these symptoms is noted, debris should be removed
from the wiper, particularly the edges where the pad meets the wiper assembly. If the wiper pad is abraded
or damaged in anyway, the wiper assembly should be changed immediately. YSI also recommends that the
wiper be changed as a precaution prior to each long term monitoring study. Spare wipers are available in
the YSI 6024 Wiper Kit. In addition, users who wish to replace only the pad of the wiper assembly can
purchase the YSI 6144 Optical Wiper Pad Kit.
Caution: When replacing the wiper, be sure that you do not rotate the wiper arm after it is tightened to the
shaft. This may damage the internal motor/gearbox mechanism and could void your warranty.