40 Questions
What is the relationship between the peak voltage VM and the RMS voltage VRMS for a sine or cosine wave?
VRMS = 0.707 VM
What is the main purpose of a decade box?
For load substitution
What is the significance of the number of sections (dials) on a decade box?
It determines the range of values that can be set
What type of waveforms is the formula VRMS = 0.707 VM applicable to?
Sine or cosine waves
What is the purpose of the selector switch on a decade box?
To set the desired value within the range of the box
What is the significance of the symmetry line CD on the oscilloscope?
It represents the zero voltage reference
What is the name of the device used to accurately set resistance, capacitance, or inductance values?
Decade box
What type of decade boxes are available?
Resistance, capacitance, and inductance types
What is the minimum pulse width that some logic probes can detect?
10 ns
How do most IC failures typically show up in a circuit?
As a constant high or low level
What is the advantage of using a logic probe over an oscilloscope?
It can detect high-speed transient pulses
What is the purpose of connecting the croc clip to the 0-V rail in a basic logic probe?
To check the logic levels during logic gate experiments
What happens when both LEDs turn on dimly in a basic logic probe?
A high-frequency pulse train is being detected
What is the function of an oscilloscope?
To measure the voltage and frequency of an electrical signal
How are pins 7, 8, 9, 12, and 13 of the CD4011 IC connected in the basic logic probe circuit?
To the negative supply rail
What is the advantage of using a logic probe in conjunction with an oscilloscope?
It can detect high-speed transient pulses that are hard to detect on an oscilloscope
What can be determined by comparing the amplitude of the reflected step in a time-domain reflectometer?
Both the distance to and the nature of the fault
What can be revealed by time-domain reflectometry?
Both the distance to and the nature of the fault, as well as the characteristic impedance of the line
What is the primary function of the IFR NAV-402AP Nav/Comm Test Set?
To test and calibrate MKR, VOR, ILS, and COM avionics
What feature does the IFR NAV-402AP offer for VOR testing?
A VOR bearing selectable in 0.1° steps
What type of frequency modes are available in the IFR NAV-402AP signal generator?
Both XTAL and VAR frequency modes
What is the purpose of the sweep LOC DDM function in the IFR NAV-402AP?
To test autopilot capture mode
What type of tester is the IFR NAV-402AP designed to be used as?
Both a bench and ramp tester
What avionics systems can be functionally tested and calibrated using the IFR NAV-402AP?
MKR, VOR, ILS, and COM avionics
What is the primary function of the oscillator stage in an RF signal generator?
To accurately set the signal frequency
What type of circuit is used in low-frequency signal generators to produce the correct range of resonant frequencies?
LC circuit
What is the purpose of the modulating circuit in an RF signal generator?
To produce an audio or video voltage
What type of modulation is used in specialized signal generators that allow for pulse modulation?
Pulse modulation
What does the output-level meter in an RF signal generator indicate and control?
The output voltage of the generator
What is the range of output readings indicated by the output-level meter in an RF signal generator?
Tenths through the value of 1.0
What is the purpose of the calibrated attenuator in an RF signal generator?
Not specified in the text
What is the typical source of the modulating signal in an RF signal generator?
Either of the above
What is one of the functions of an FQI test set when used with a capacitance-type fuel gauging system?
Measures insulation resistance of tank units and cabling
What is the purpose of introducing adequate capacitance in an FQI test set?
To simulate the function of the compensator
What is a potential hazard when using an FQI test set?
Fire due to sparks
What does loop resistance testing analyze in cables?
The resistance at two locations of interest within a loop
What is the primary cause of corrosion in electrical ground paths?
Chemical reactions with air
What is the result of corrosion in electrical ground paths?
Increased resistance
What is the purpose of ensuring correct earthing of the test box when using an FQI test set?
To prevent sparks and fires
What is the typical power source for FQI test sets?
115 V AC at 400 Hz
Study Notes
Logic Probes
- Detect and display high-speed transient pulses as small as 10 ns wide
- Connected directly to the power supply of the device being tested, or have internal batteries
- Provide a quick, inexpensive way of locating faults in IC failures
- Can display single, short-duration pulses that are hard to detect on an oscilloscope
Basic Logic Probe
- Can be used to check logic levels during logic gate experiments
- Red LED turns on if the level is high, green LED turns on if the level is low
- If both LEDs turn on dimly, a high-frequency pulse train is being detected
Oscilloscopes
- A sophisticated voltmeter with a two-dimensional graph display
- Used to measure voltage (amplitude) and frequency (time) of an electrical signal
- The peak or maximum voltage seen on the scope face is VM volts
- Vrms = 0.707 VM (for a sine or cosine wave)
Decade Boxes
- An assembly of precision resistors, coils, or capacitors
- Can be set to any desired value within its range
- Used for load substitution
- Types available: resistance, capacitance, and inductance
Decade Resistance Boxes
- Each switch section represents a decade, or a multiple of 10
- Can be set to any desired value within its range
Signal Generators
- Produce a signal that can be accurately set in frequency at any point in the range
- The oscillator stage produces a signal which can be accurately set in frequency
- The modulating circuit produces audio (or video) voltage which can be superimposed on the RF signal
- Modulation types: sine wave, square wave, pulse modulation
Time-Domain Reflectometer (TDR)
- Measures the distance to a fault as well as the nature of the fault
- Indicates the characteristic impedance of the line and whether losses are shunt or series
- Used to locate and analyze connectors and splices
IFR NAV-402AP Nav/Comm Test Set
- A self-contained unit for functional testing and calibration of MKR, VOR, ILS, and COM avionics
- Can be used both as a bench and ramp tester
- Features: signal generator, VOR bearing, LOC-G/S output, sweep LOC DDM
Fuel Quantity Indicator (FQI) Test Sets
- Used to measure capacitance values of individual or sets of tank units
- Inserts appropriate capacitance values of a fuel gauge circuit for functional calibration
- Introduces adequate capacitance to simulate the function of the compensator
- Measures insulation resistance of tank units and cabling
Loop Resistance Testers
- Analyze circuits of cables by measuring and recording the resistance at two locations within a loop
- Used to detect corrosion in electrical ground paths
Learn about logic probes that detect high-speed transient pulses and locate faults in IC circuits. Understand how they work and their advantages in debugging.
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