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M5 > 5.3 data conversion > Flashcards

5.3 data conversion Flashcards

1
Q

digital computers are being used in new areas such as

A

thrust management and engine controls

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2
Q

the use of digital systems means the flight crews workload is

A

reduced

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3
Q

important considerations in using digital computers are

A

reducing system weight and size increasing data handling speed
improved system reliability

this contributes to an increase in overall aircraft efficiency

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4
Q

data is transmitted in analogue form e.g. hands on a clock

digital form e.g. numbers on a computer screen

A

.

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5
Q

aircraft systems typically convert data from analogue to digital and vice versa

A

.

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6
Q

Analogue and digital signals CAN BOTH contain the same information

A

.

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7
Q

digital data signals have two set signals in the

A

0 V represents OFF
5 V represents ON

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8
Q

Analogue singals vary continously with time and have many different values

A

.

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9
Q

Alternating current (AC) analogue singals can be bipolar

A

in that they have positive and negative limits

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10
Q

Direct Current (DC) analogue signals are unipolar

A

they fluctuate between 0 V AND either a positive or negative value but they never alternate between positive and negative voltages

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11
Q

by locating the transmitter of a synchro system remotely

A

an indicator can show fluid quantity or pressure, without the need to run tuning through the cockpit

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12
Q

Analogue signal can have an infinite number of possible values

A

as it varies from its minimum to its maximum extremes

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13
Q

digital data signals differ from analogue singals. why

A

they only have two (Binary) levels of voltage:
high for “ON” and low for “OFF”

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14
Q

a digital signal is a sequence of ones and zeros

A

.

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15
Q

fibre optic cable transmits data with light pulses on or off 1 or 0

A

.

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16
Q

digital signal must be what in some way before its understandable

A

decoded

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17
Q

a binary digit is also called a what

A

a bit

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18
Q

a bit or binary digit is what

A

smallest unit of information in a computer

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19
Q

analogue signals vary in magnitude uniformly e.g.

A

a dimmer switch

20
Q

digital signals by contrast are simply ON/OFF e.g.

A

a simple light switch without dimming

21
Q

digital computers process information faster and more efficiently than analogue computers but what is their disadvantage

A

(Digital) only process data in 1’s and 0’s

22
Q

temperature varies and has to be converted to a digital representation of temp for digital computers to process temp information

A

.

23
Q

the circuits used to interface digital computers to analogue computers are called

A

digital to analogue (D/A) converters DAC
Analogue to digital (A/D) converters ADC

24
Q

D/A converters change

A

the digital data words of a digital computer to an equivalent analogue signal as either a voltage or current source
many different types of D/A converters but each one has same basic decription

25
Q

A/D converters change

A

the analogue signals received from sensors to digital data understood by the digital computer
- many types of A/D converters exist
- type depends

26
Q

aircraft with digital instruments use

A

pressure sensitive solid state sensors

output digital signals for collection and processing by aircraft computers

27
Q

an ADC converts a continuous

A

input voltage into a digital data stream

28
Q

an ADC can be used to convert analogue output from a microphone to digital signals for what

A

storage on a compact disc (CD)

29
Q

three types of ADC are

A

Direct comparison converter
ramp generation A/D converter
successive approximation converter

30
Q

fastest type of ADC is what and is often called what

A

Direct comparison converter
(DCC) AKA Flash ADC

31
Q

DCC are fast and operate virtually without delay (LATENCY) before a transfer of data begins following an instruction

A

.

32
Q

what is used when the highest possible sample rates are needed

A

DCC’s
- they convert analogue to digital
- comparing with known reference values. more reference values known the greater the accuracy

33
Q

the greater resolution, the bigger and more power hungry the DCC becomes what happens to the sample rate

A

must be reduced

34
Q

optimal resolution for DCC is

A

8-bit

35
Q

applications for a DCC include

A

fibre optics
RADAR detection
wideband radio
fastest digital oscilloscopes
microwave measurements

36
Q

ramp generation ADC is AKA

A

Counter-type ADC
uses a binary counter to feed a digital to analogue converter (DAC)
uses a counter for conversion from analogue to digital

37
Q

advantages of ramp generation (Counter-Type) ADC

A

simple and easy to use
very accurate and the precision can be increased by increasing the number of bits
fair balance of accurate output and cheap hardware costs

38
Q

disadvantages of ramp generation (counter-type) ADC

A

every time a new conversion starts, the counter is reset and has to start counting from all zeros
hence conversion time is significant
it cannot sustain high-frequency input

39
Q

successive approximation ADC is an advanced version of the digital ramp type ADC

A

designed to reduce the conversion and increase speed of operation

40
Q

successive aprroximation ADC the normal counter is replaced with a

A

(SAR) successive approximation register.
-the SAR counts by changing the bits from MSB to LSB according to input

41
Q

Digital to analogue conversion is the reverse of the A/D process

A

with each binary number being converted back into nominal levels by reconstructing the original waveform

42
Q

there are four main DAC circuits

A

Binary weighted resistor D/A converter circuit
Binary ladder or R-2R ladder D/A converter circuit
segmented DAC
Delta-sigma DAC

43
Q

binary weighted ladder DAC is one of the simplest DAC each bit..

A

of a binary input controls a solid-state switch.
the switch connects either a reference voltage or grounds to a corresponding binary weighted resistor

44
Q

advantages of R-2R ladder DAC

A

uses only two types of resistors
easily scalable to any number of bits
output impedance is always same despite the number of bits

45
Q

disadvantages of weighted resistor DAC

A

Increasing the number of input bits requires a large value resistors(increases exponentially)
the value of large resistors are not accurate

46
Q

reconstructing a signal from digital to analogue or from analogue to digital can degrade the signal by

A

background noise and loss of signal

47
Q
A

M5 (12 decks)

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