1-12. DESCRIPTION OF DAYSIDE TEST BENCH 2A1 (cont)
(c) The power supply assembly 2A1A1A6 provides high voltage to the PMT. It
is located behind the main access door and consists of a power supply and resistor/
relay network mounted to a bracket.
(d) The photomultiplier/bracket assembly (PMT tube and shutter) 2A1A1A7
contains the photomultiplier, shutter plate adapter, and Prontor magnetic shutter
assemblies supported by a mounting bracket assembly attached to the OSA plate
The photomultiplier assembly is made up of the PMT housing (Pacific
End-On-Tube Housing, Model 3457), photomultiplier tube (PMT) (model XP2012B), and com-
The PMT is enclosed in the PMT housing keeping it cooled to -40°C. A
fan mounted on the PMT housing forces air past the heat exchanger. OSA chassis intake
and exhaust vents prevent air currents from affecting the PMT cooling function.
anode (plate) of the PMT requires 1200 volts.
The component board contains circuitry
that provides the electrical interface with the PMT.
The PMT is operated in a very
light-sensitive condition and could be damaged by extraneous light. Interlocks on the
PMT and main access doors prevent operation when the doors are open.
The shutter plate adapter assembly and prontor magnetic shutter
assembly combine to provide a filter and shutter action.
(e) Interface assembly 2A1A1A8 interfaces electrically with the PMT and
It is located behind the OSA main access door and consists of a
shielded filter box, circuit card assembly (CCA) and electrical connector.
(f) The relay assembly 2A1A1A12 deactivates the PMT circuitry by electri-
cally interfacing with the main access and PMT door interlock switches.
It is located
behind the OSA main access door and consists of a mounting bracket, four relays (K1
thru K4), and electrical connections.
(g) The filter and detector assembly 2A1A1A14 provides a neutral density
filter that is positioned in or out of the optical path. It is located behind the
mounting plate and access requires removal of the OSA.
It consists of a filter and
bracket assembly, motor, neutral density filter, a relay, actuator switches S1 and S2,
optical switches Al and A3, resistors, and connectors.
(h) Mechanical assemblies include lens cell housings, an exhaust fitting,
light baffles, and a desiccant indicator.
Lens cell housings support lens elements.
The exhaust fitting provides an outlet for heated air currents. Light baffles are
actually light traps.
The indicating desiccator provides moisture conditions within
the OSA chassis.
This indicator will change color when the desiccant has reached
Access to the indicator is through the main access door.
Length 10.00 in
Height 29.75 in
Weight 185 lb