Internal Halogen Lamp As Actinic Light Source - Walz MINI-PAM Manual

CHAPTER 8
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Chlorophyll emission:
As the cut-off wavelength of the detector filter is shifted from
710 nm in the standard version to 650 nm in the blue version, the
latter also detects the main chlorophyll emission peaking around
685 nm which originates mainly from photosystem II and, hence,
shows higher values of variable fluorescence.
8.1.3

Internal halogen lamp as actinic light source

A miniature 8 V/20 W halogen lamp (type Bellaphot, Osram)
serves as light source for saturation pulses and for continuous actinic
illumination. The light is filtered two-fold by a heat-reflecting filter
(Balzers, Calflex-X, special) and by a short-pass filter (Balzers, DT
Cyan, special), such that white light with negligible content of
wavelengths beyond 700 nm (standard version) or beyond 640 nm
(MINI-PAM/B) is obtained.
It is not recommended to operate the internal halogen lamp for
extended periods of actinic illuminations as this would lead to
excessive internal heating. This aspect must be taken particularly
serious when light curves are automatically recorded (menu points
17 and 18) and when the range of actinic intensities is increased by
AL-FACT (menu point 16). A temperature-sensor, which is mounted
in the vicinity of the lamp, causes turn-off of the lamp power supply
when 70 °C is reached. It is turned on again when temperature has
dropped to approx. 55 °C. The internal temperature, the value of
which is displayed under menu point 35, affects the output of the
measuring light LED. A 1 °C temperature rise leads to approx. 1 %
lowering of the measuring light intensity. While not affecting the
actual YIELD-measurement (i.e. ∆F/Fm'), this will lead to a
corresponding drop in the fluorescence signal. For prolonged actinic
illumination, particularly at high intensities, the External Halogen
COMPONENTS OF THE MINI-PAM
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