5.3 Flashcards
What type of instruments are in cockpits?
Both Analogue and digital instrument displays
What type of current do Analogue signals have and what values can it produce?
Alternate current and it can produce a variety of both positive and negative values
What is the fastest type of ADC?
The direct comparison converter
How many values does an 8 bit resolution require?
256 known values
What is the most optimal resolution for the Direct comparison converter?
8 bit resolution
What are the advantages of the direct comparison converter?
Fastest ADC type
Instant conversion without latency
What are the disadvantages of the direct comparison converter?
The circuit gets bigger and more power consuming with each bit
The resolution is effectively limited to 8 bit
Applications for a DCC are?
Fastest digital oscilloscopes
Microwave measurements
Fibre optics
RADAR detection
Wideband ratio
What is another word for the Ramp ADC?
Counter type ADC
How does the RAMP ADC work?
It uses a binary counter to feed to a digital analogue converter (DAC)
In which applications does an ADC work best in?
It works best in applications where the analogue signal level varies at a SLOW rate such as a temp sensor
What counter does a successive approximation ADC have?
The normal counter is replaced with a Successive Approximation Register (SAR)
How does a Successive Approximation ADC work?
The SAR counts by changing the bits from MSB to LSB according to input.
What is a Digital to Analogue Converter (DAC)?
A DAC is a device that takes binary numbers or combinations of binary numbers and changes them into corresponding voltages
How does a DAC work?
A DAC converts a sequence of binary digits into impulses, which are then processed by a reconstruction filter to smooth out the step response into continuous curves
How does a Binary weighted ladder DAC work?
Each bit of a binary input controls a solid state switch. The solid-state switch connects either a reference voltage (VR) or grounds to a corresponding binary weighted resistor
How does a R-2R Resistor ladder work?
Each bit of the binary input controls a solid-state switch, connecting either a reference voltage or a ground to the resistors. The ladder is made up of resistors of only two values: R or 2R.
What is the difference between a Binary Resistor Ladder DAC and a R-2R Resistor Ladder DAC?
In the R-2R network, the actual resistor values are not as critical as in the binary-weighted ladder
What are the limitations of having a DAC?
Reconstructing a signal from digital to analogue, or from analogue to digital can degrade the signal by background noise and loss of signal.
What type of sensors do aircraft digital instruments use?
Pressure sensitive solid state sensors
What is the fastest type of Analogue to Digital Converter?
Direct Comparison Converter (Flash ADC)
What are the four main types of Digital to Analogue converter?
Binary weighted resistor
Binary ladder or R–2R ladder
Segmented DAC
Delta-sigma DAC
What type of wave is an AC analogue signal?
Continuous wave
What type of signal only have two levels of voltage?
Digital
