Quantcast Analog Inputs

 

Click here to make tpub.com your Home Page

Page Title: Analog Inputs
Back | Up | Next

Click here for thousands of PDF manuals

Google


Web
www.tpub.com

Home


   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Logistics
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
   
   

 

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Back
Figure 1-24. Analog Outputs Block Diagram.
Up
TM-9-1270-219-13-P Fire and Flight Air Data Subsystem Helicopter Armament: XM 143 PN 03-004-02 Manual
Next
Figure 1-25. Analog Inputs Block Diagram.
TM 9-1270-219-13&P
(7) A n a l o g I n p u t s . The Analog Channel Select sets a
hold
circuits.
The
resolver
output
peak
voltages
are
c o d e corresponding to one of the analog input channels
defined by:
(fig. 1-25). The input selected is routed to a comparator.
T h e microprocessor outputs an initial guess of the digital
value of the analog voltage; this is converted to an analog
value by the DAC, and presented to the comparator
alongside the input value. The comparator's output is used
to
indicate
whether
the
guess
was
high
or
low.
The
Where θ represents a pitch or combined pitch-and-yaw
processor then makes a new approximation, based on the
angle of the probe. Sampled resolver secondary peak
comparator's output. After 12 such approximations the
voltages are fed into the CPU via the A-D converter
digital value is sufficiently close to the analog input.
circuit. The sine and cosine of each relevant angle is
derived
from
the
digital
secondary
peak
voltages
by
trigonometric
relationships.
(8) A-D and D-A Interface. Figure 1-25 shows how
o n l y one DAC and four analog channel select lines are
able to perform all the A-D/D-A conversions. Note also
(a) An AADS interface test is included to allow
t h a t the analog outputs are fed back through the analog
the CPU to test the operation of the sample and hold
multiplexer to enable further checking of errors. Fixed
circuitry. During this test analog switches connect the
reference voltages are used to perform calibration checks
sample and holds directly to the oscillator, bypassing the
on the DAC within the EPU.
AADS.
(9) O u t p u t P r o t e c t i o n . Each ADS output signal is
(2) A i r T e m p e r a t u r e S e n s o r C i r c u i t . T h e A A D S
short
circuit
protected.
Short
circuits
to
ground
will
be
Air Temperature Sensor (ATS) is supplied with constant
t o l e r a t e d indefinitely without damage to the signal output
current from a current source circuit, and the resultant
buffer.
voltage is sensed by a differential amplifier on the analog
interface unit. Voltage ouput from the differential
amplifier is fed to the A-D conversion circuit and the
(a)
Each
output
is
independently
buffered
so
digital result is then stored in the CPU memory. The ATS
t h a t potential damage caused by helicopter primary power
constant current source is switched on for a period of
is confined to that signal output only.
30mS once per second while the A-D conversion is
perfomed. This action is controlled by the processor to
reduce effects of self heating.
c. Analog Interface Unit (AIU). The analog Interface
U n i t (AIU) is the analog input and output interface for
(3) Radar Altimeter Input. The radar altimeter
the ADS LRUs. The signals which are processed include
provides a dc analog output (-7mV/ft) to the EPU to
AADS angle resolver signals, Air Temperature Sensor
allow
correction
of
altitude
outputs
for
ground
effect
(ATS), raw dc analog signals related to PTU pressure
i n d u c e d errors. The input voltage is applied to a buffer
i n p u t s , and outputs to the LAl and to doppler navigation
a n d scaling amplifier, the output of which is fed to the
system. A precision 10 Vdc reference is included on this
A-D conversion circuit. The digital result is stored in the
card. Peak sampling circuitry is used to convert AADS
CPU memory.
resolver
signals
into
dc
voltage
levels
which
can
be
accepted by the A-D converter.
d. P o w e r S u p p l y U n i t . The helicopter 28 Vdc supply
is filtered in a self contained EMC filter module (fig.
(1) AADS Interface. The oscillator provides a 400Hz
and
used
initially
to
generate
+10
Vdc.
Other
s i n u s o i d a l reference signal to the AADS angle resolvers
voltages,-5 Vdc, -6.2 Vdc and -10 Vdc are generated to
(fig. 1-26). The peak of this reference is detected, and
supply the boost regulator which increases the voltage up
used as a reference against which a peak sampling pulse is
to +80 Vdc by the action of a diode booster type circuit.
generated for the sample and hold circuits. Peak voltages
The 80 Vdc voltage is controlled by networks which sense
of the resolver outputs are sampled by the sample and
1-26

Privacy Statement - Press Release - Copyright Information. - Contact Us

Integrated Publishing, Inc.