User guide

Chelsea Technologies Group
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User Guide HB179 Issue 7.0
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7. GLOSSARY
Flash Repetition Rate The rate at which flashes occur in a flash sequence. (~200kHz)
Flash Sequence A series of saturation and relaxation flashes
(usually SFC = 100, DFC =20).
Flash A single burst of light from LED flashlamps, on the order of
microseconds.
Flash Sequence Rate The rate at which flash sequences are repeated (up to 8 Hz).
Acquisition Any combination of flash sequences which lead to one final set of
FRRF data values. Several flash sequences may be averaged to
produce one final acquisition.
Excitation Signal The blue light from the LED flashlamp used to stimulate PSII. Also
referred to as the Reference Signal.
Excitation Channel One of two optical windows on the optical head from which the FRRF
excitation light is delivered. These are labelled channel A and B.
Emission Signal Any red light (fluorescence) observed from the phytoplankton,
including both biological signal and contamination.
Emission Channel The single optical path leading to the PMT from the optical head,
having two optical windows, one for each excitation channel.
PMT Photomultiplier tube, used in the emission optical channel to detect
fluorescence.
Light Channel The Excitation Channel open to solar illumination. Channel A is
configured at the factory to be the Light Channel, and shows the
indicator LEDs.
Dark Channel The Excitation Channel shielded from ambient illumination by means
of the dark chamber assembly. Channel B is configured at the
factory as the Dark Channel, and does not have indicator LEDs.
Signal Contamination Any fraction of the emission signal which does not result from
chlorophyll fluorescence.
Saturation Flashes Closely spaced, brief pulses of light generated by the FRRF to
gradually saturate the phytoplankton photosystems. The factory
default for these is 1 µs in duration, 1µs spacing (i.e. 50% duty
cycle).