Agilent Technologies 1100 Series Reference Manual page 180

6
Introduction to the Variable Wavelength Dector
Cutoff filter
Figure 43
Mirror Assemblies M1 and M2
The instrument contains two spherical mirrors (M1 and M2). The beam adjustable is
vertically and horizontally. Both mirrors are identical.
The mirrors are coated with magnesium fluoride. They should not be touched or cleaned.
NOTE
This will destroy the surface and reduce the light reflection.
Grating Assembly
The grating separates the light beam into all its component wavelengths and reflects the
light onto mirror #2.
The grating has 1200 lines/mm and is directly rotated by the grating drive stepper
motor, depending on the wavelength entry. The whole range (190 to 600 nm) is equal to
1550 steps (15.5 °). The stepper motor is controlled and driven by the detector main
board (VWM). The step angle of the stepper motor rotation is electronically reduced by
0.01 ° per step. This system has no mechanical reduction mechanism, accordingly the
grating is mounted directly onto the motor shaft.
The stepper motor reference position is determined by a plate fitted onto the motor
shaft, interrupting the beam of a photo sensor. The wavelength calibration of the grating
is done at the zero order light position and at 656 nm, which is the emission line of the
deuterium lamp.
The grating surface should not be touched or cleaned. This will destroy the surface and
NOTE
reduce the light reflection.
Beam Splitter Assembly
The beam splitter splits the light beam. One part goes directly to the sample diode. The
other part of the light beam goes to the reference diode.
178 1100 Series Variable Wavelength Detector Reference Manual
Filter Assembly
Holmium oxide filter
with cutoff filter