111
Modulation light source intensity
Set up screen #2
The modulation light source intensity is adjustable between 0.1
:
mol and 1
:
mol.
Settings between 5% to 100% can be made in 5% increments. The correct value depends
upon the distance from the fiber optic to the sample, and nature of the sample.
Put a leaf, of the type to be measured in a study, in a dark clip or in a PAR Clip and dark
adapt. Place the fiber optic probe all the way into the dark clip or PAR Clip, and expose
the dark adapted area of the leaf to the modulated light that is always coming out of the
end of the fiber bundle when a measuring screen is viewed. If the intensity is too high, it
can be seen as a slow rise in “Current Signal” visible on the set up screen or the “Ft”
value visible on the Fv/Fm measuring screen. After setting the modulation intensity,
watch either value. If the average value increases over a 30 second period, the intensity
should be reduced because it is driving photosynthesis. The modulated light is set
correctly if it is high enough to get a reading when the measuring button is pressed, but
not too high so that it is driving photosynthesis. The setting is linear.
The “Gain” should
be as low as possible for the best signal to noise ratio.
Set up screen #2
New -automated modulation light set up
“Auto Gain”
– On the set up screen, this option automatically adjusts the modulated
light setting to a detection range that will work for the sample. It is known from samples
tested, that this automated modulated light level does not drive photosynthesis. Place a
sample leaf, of the type to be tested, into either a dark clip or with a shrouded PAR clip.
Dark adapt for five minutes and press “Auto Gain”. The instrument automatically goes
through a routine that sets the modulation intensity correctly.
Modulation intensity should be critically set when doing
quenching measurements. It must be high enough to prevent a
fluorescence signal too low error message, but not high
enough to drive photosynthesis.
To use the automated modulation light setup mode,
press “Auto Gain”. The system then adjusts the
modulation light source into an acceptable minimum
reading range for the PIN diode detector.
