Chapter 2--Operation 11
Grating Assembly Interchange
The LS-785 grating assembly is initially aligned at the factory and kinematically mounted in the instrument to
enable easy interchange without requiring realignment. Note that if a grating is purchased later, it will require
alignment to the LS-785 and instructions will be provided with the purchased grating assembly.
Tools:
Powderless gloves
5/64” hex wrench
9/64” hex wrench
Procedure:
CAUTION: Optical surfaces of gratings and lenses are extremely delicate and can be permanently damaged by
contact with anything. Do not touch, talk, or breathe on or over the gratings or optical surfaces inside the
spectrometer.
1. Locate the container holding the new grating assembly.
2. Using a 9/64” hex wrench, remove the five socket screws from the
LS-785 cover. Refer to the Caution above.
3. Grating assemblies are held in position by two captive screws at the
base of the grating assembly (one at the front and one at the rear of
the grating assembly) plus a single screw with a knurled knob
located at the top of the assembly (see picture). Loosen the two
captive screws first using a 5/64” hex wrench and then turn the
knurled knob in a counter-clockwise direction until it disengages
from the kinematic mount. The screw is spring-loaded and captive in
the turret. At this point the grating assembly is loose and ready to
remove.
4. Lift the grating assembly straight out of the housing, taking great
care not to allow anything to make contact with the grating. Grasp
the knurled knob and/or top portion of the grating assembly when
handling grating assemblies.
5. Place the removed grating assembly on a clean, dry surface.
6. Remove the cover from the grating assembly storage container.
Remove the grating assembly from the storage by loosening the two
captive screws and the knurled screw. This is similar to Step 3 above.
CAUTION: Do not contact the grating surface or permanent damage will result.
7. With extreme care, place the new grating assembly on the kinematic mount inside the LS-785 housing.
The kinematic mount will only accept the assembly in one orientation.
8. Using your index finger and thumb, simultaneously push straight down and turn the knurled knob
clockwise to engage the kinematic mount. When the screw engages the tapped hole, continue to turn it
clockwise until the grating assembly is secured. Do not over-tighten!
9. Tighten the two captive screws at the base of the grating assembly.
Figure 2-6. Grating Assembly
