CHAPTER 7 THE MODE-MENU
Switch between the standard measuring
pulse frequency of 0.6 kHz (LOW) and 20
kHz (HIGH). At 20 kHz the signal/noise is increased by a factor
of 5-6. On the other hand, at this high frequency the measuring light
intensity can induce substantial fluorescence changes. Hence, 20 kHz
normally should be used only when its actinic effect can be
neglected relative to a stronger ambient light (e.g. above 100 µmol
quanta m
-2
s
-1
).
4: M.FREQ: LOW (SET)
F: 448 745Y 6.2E 20L
Switch between normal signal detection
(continuously pulsed measuring light) and
signal detection by short bursts of measuring light. In the latter case,
pulse trains are 0.2 s with dark-intervals of 0.8 s, resulting in a
reduction of integrated measuring light intensity by a factor of 5.
This can be advantageous for assessment of the maximal
photochemical yield after dark-adaptation (∆F/Fm = Fv/Fm). In the
ML-BURST mode the basic frequencies of 0.6 or 20 kHz are
maintained.
5: ML-BURST: OFF(SET)
F: 448 745Y 6.2E 20L
When this function is enabled, the readings
of the external light sensor are averaged
over a period of 15 s, in order to account for fluctuations of light
intensity. It is important that the sensor remains fixed in a given
position for 15 s before the actual measurement of quantum yield.
6:LIGHT AV15s:OFF(SET)
F: 448 745Y 6.2E 20L
Switch to enable display of external
LIGHT-SENSOR readings (in ON-
position). When in OFF-position, the PAR-values stored in an
internal list are effective. This list is created via the LIGHT-CAL
function (see next menu point).
7:EXT.LIGHT-S:ON (SET)
F: 448 745Y 6.2E 20L
Automatized routine for determination of
PAR-values of the 12 ACTINIC LIGHT
Intensity settings in a given measuring geometry. These values are
stored in a list, which is effective whenever the EXT.LIGHT-
8:LIGHT-CALIB: (SET)
F: 448 745Y 6.2E 20L
18
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