TM 11-6625-3081-23
1-24. TEST CONSOLE TEST BENCH 2A2 (cont)
1-24
l. ANALOG TO DIGITAL CONVERTER ASSEMBLY 2A2A13
(1) General.
The analog to digital converter assembly 2A2A13 (FO-30) is a data
acquisition distribution system capable of processing analog signals to digital
data and digital data into analog signals. In this system, it is used only in the
analog to digital configuration.
It simply serves as a high-accuracy, digital volt-
meter with 16-bit accuracy.
It consists of a chassis containing two power supplies,
internal backplane, display/control panel, and user CCA backplane.
(a) The standard power supply provides +15 vdc, -15 vdc, and +5 vdc to the
system.
An optional power supply is used to increase the current-carrying capacity
of the system.
It is identical to the standard power supply.
(b) The internal backplane contains the signal processor CCA (slot J73),
A/D converter CCA (slot J74), and three computer interface CCAs (slots J75 thru
J77).
(c) The display/control panel contains timing logic used by the control
signals and the displays that show the current signal processor range code, channel
address, and data value.
It also contains control logic that comes into action in
the local control mode allowing manual access to all system functions. In addition,
it has high-speed registers for digital address multiplexing and address and range
storage.
(d) The user CCA backplane, accessible from the rear of the chassis, has
18 CCA slots, labeled J1 thru J18.
It contains the simultaneous sample and hold CCA
(slot J1), three multiplexer CCAs (slots J4,J7,J8), two isoplexer CCAs (slots J5,
J6), the self-test CCA (slot J16), and two expansion CCAs (slots J17, J18).
(2) Internal Backplane CCAs
(a) Signal Processor CCA.
The signal processor CCA receives analog sig-
nals from the expansion CCAS and buffers these signals to drive the A/D converter.
Additionally, certain timing and control functions related to the measurement
process take place on the signal processor CCA.
The signal processor CCA contains a
sample and hold located just before the A/D converter.
This sample and hold is
commanded into “hold” mode just before every conversion, returning to “sample”
immediately after the conversion is complete.
This sample and hold is necessary in
all data systems because of the nature of successive approximation A/D converters.
These converters must have a constant input during the conversion process. Valid
measurements may be made on a changing signal only if the signal is temporarily held
constant during the conversion process.
(b) A/D Converter CCA.
The A/D converter CCA performs very high speed,
analog-to-digital conversion.
(c) Computer Interface CCAs.
The general purpose interface (consisting of
CCAs 13082276-2 and 13082276-3) is a data buffer for the input/output data words.
The control CCA (AC471-1B) detects and decodes the upper four bits of the input data
word from the computer.
These bits contain an operation code that directs a speci-
fic operation within the A/D converter.
The result of the decoding operation is the
generation of the control signals required to perform the activity directed.
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