1-23. DAYSIDE TEST BENCH 2A1 (cont)
(4) Main Access Door Interlock Switch 2A1A1A5.
(a) The photomultiplier tube could be damaged by ambient light. There is a
interlock switch on the main access door to prevent operation of the photomultiplier
tube if the light seal is broken, and thus prevent the photomultiplier tube from being
(b) The DOOR INTERLOCK line (+28 VDC) is applied to one side of the main
access door interlock switch.
If the door is closed, the switch is enabled, and +28
VDC is applied to OA SHUTTER line.
The OA SHUTTER LINE enables four relays in the
relay assembly 2A1A1A12.
One of these relays applies +28 VDC to enable the OSA
(5) Power Supply Assembly 2A1A1A6 and PMT Access Door Interlock 2A1A1A11.
(a) The power supply assembly supplies high voltage (300 VDC) necessary to
operate the PMT.
(b) The OR PMT HV signal from multiprogrammer assembly 2A2A6 is routed
through relay contacts of relay assembly 2A2A7A4 (energized by FIFO CCA 2A2A7A6A5),
and applied to one side of PMT access door interlock 2A1A1A11. If the PMT access door
is closed, +28 VDC is applied to power supply PSI in the power supply assembly.
Output (300 VDC) of the power supply assembly is supplied to the PMT and a HV/300
signal is sent to analog to digital converter assembly 2A2A13.
(6) Photomultiplier Bracket Assembly 2A1A1A7 and Interface Assembly 2A1A1A8. The
PMT is a measurement device for counting the number of photons being emitted by the
CRT of the unit under test.
It is enclosed in a housing which is cooled by
thermoelectric elements that pump heat to a heat exchanger, where a fan moves the
heated air out of the optical signal analyzer.
There are temperature and overheat
sensors used for temperature control.
A shutter protects the PMT from damage and is
opened during testing.
(a) The PMT output signal A2 PMT is applied to interface assembly 2A1A1A8
where it is filtered electronically and output to connector P6 (output signal A1 PMT
(A TPS cable is connected from connector P6 to the programmable digitizer 2A2A1
during test.) Digital output data from multiprogrammer assembly 2A2A6 controls
electronic filtering of the interface assembly 2A1A1A8.
(b) A temperature sensor attached to the PMT transmits signals SB1, SB2, and
SBG to temperature measurement CCA 2A2A7A6A4, and signal SBG to analog to digital
converter assembly 2A2A13.
These signal are used by the computer to correct for
temperature change of the PMT.
(c) During operation of the PMT, multiprogrammer assembly 2A2A6 transmits an
OSA SHUTTER signal to relay assembly 2A2A7A4 contacts.
When relay assembly 2A2A7A4 is
energized by FIFO CCA 2A2A7A6A5, the OSA SHUTTER signal is routed to contacts in relay
When relay assembly 2A1A1A12 is energized, OSA SHUTTER signal
activates a linear solenoid which pulls the PMT shutter vanes to the open positon.
Optical switch assemblies A1 and A2 transmit shutter position signals OSA SHUTTER
CLOSED and OSA SHUTTER OPEN, respectively, to multiprogrammer assembly 2A2A6.