Xylem EXO Series User Manual page 23

Total Algae (Chl & BGA-PC)
1.10
Sensor Overview
The EXO total algae sensor is a dual-channel fluorescence sensor that generates two independent data sets;
one resulting from a blue excitation beam that directly excites the chlorophyll a molecule, present in all
photosynthetic cells, and a second from an orange excitation beam that excites the phycocyanin accessory
pigment found in blue-green algae (cyanobacteria). This orange excitation triggers a transfer of energy from
the phycocyanin to the central chlorophyll a, where photosynthesis is initiated.
Although blue-green algae contain chlorophyll a, the chlorophyll fluorescence signal detected by in situ
fluorometers is weaker than in eukaryotic phytoplankton. This results in an underestimate of algae biomass when
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using a single-channel chlorophyll sensor when blue-green
algae are present. The EXO total algae sensor generates a more
accurate total biomass estimate of the planktonic autotrophic
community by exciting chlorophyll a and phycocyanin.
Specifications
Units
Chlorophyll
RFU, µg/L Chl
BGA - PC
RFU, µg/L PC
Temperature
-5 to + 50°C
Operating
-20 to + 80°C
Storage
Chl: ~0 to 400 µg/L Chl; 0 to
100 RFU
Range
BGA-PC: 0 to 100 µg/L PC;
0 to 100 RFU
Response T63<2 sec
Chl: 0.01 µg/L Chl; 0.01 RFU
Resolution BGA-PC: 0.01 µg/L PC;
0.01 RFU
Sensor Type Optical, fluorescence
Chl: R >0.999 for serial dilution
2
of Rhodamine WT solution from 0
to 400 µg/L Chl equivalents
Linearity
BGA: R
of Rhodamine WT solution from 0
to 100 µg/L PC equivalents
Detection Chl: 0.09 µg/L Chl
Limit BGA-PC: 0.04 µg/L PC
Optics: .
Chl Excitation 470±15 nm
PC Excitation 590±15 nm
685±20 nm
Emission
(see pg 12)
>0.999 for serial dilution
2
pg
(continued)
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