Electronic Circuit Analysis

Resistors and Signal Generators

• Resistors in a section have the same value, which can be 1, 10, 100, 1000, and so on, depending on the switch position.
• To select a desired resistance, each switch is turned to the appropriate position, placing resistors in series.
• Signal generators are standard sources of AC energy, used in electronic equipment maintenance to test and align transmitters and receivers.
• They produce AC of the desired frequencies and amplitudes with necessary modulation for testing or measuring circuits.

Signal Generator Features

• The FG-30 signal generator is a multi-purpose, highly reliable, and low-cost 3-MHz sweep function generator.
• It provides six output waveforms, a pulse generator, and a sweep generator.
• Frequency range: 0.5 Hz–3 MHz (2.5 MHz for ramp and pulse) in six steps.
• Output waveforms: sine, square, triangle, positive pulse, and negative pulse.

Time-Domain Reflectometer (TDR)

• A TDR is used for cable length measurement and fault locating on various types of cables.
• It requires access to two conductors from one end.
• The TDR transmits pulses of a known shape and amplitude into one end of a cable, which travel along the cable at a speed determined by its velocity of propagation.
• Reflections are caused by impedance changes in the insulation of the cable, indicative of a fault or cable end.

Velocity of Propagation (Vp)

• Vp is a ratio of the speed of light, measuring how fast a signal travels along a line.
• In twisted pair cable, the velocity of propagation may be between 40% and 75% of the velocity in free space.
• Vp is often stated as a percentage of the speed of light or as time-to-distance.

Avionics Aircraft System Testing

• The MICHEL 2210 Nav/Comm Ramp Tester provides test signals for localiser, glideslope, VOR, MKR, and COMM.
• The IFR 4000 Nav/Comm Test Set is a compact, lightweight, and weatherproof unit, designed for testing ILS, VOR, and MKR receivers, and VHF AM/FM and UHF AM transceivers.

Pitot/Static Leak Testing

• The testing method consists of applying pressure and suction to the pressure heads and static vents using a leak tester and coupling adaptors.
• Pitot/static leak testing machines provide positive and negative pressures for leak checks.
• The rate of pressure increase or decrease should not exceed that specified in the Aircraft Maintenance Manual (AMM).

Precautions and Safety

• Do not use the mouth and lungs to apply pressure and suction to a pitot/static system.
• Do not increase or decrease pressure at a rate exceeding that specified in the AMM.
• Do not place sideways load on pitot heads, as it may compromise their critical alignment.
• Ensure heat is turned off and isolated electrically before testing.

Test Kits and Equipment

• The General Electric Modern GE ADTS 500 Series Pitot Static Test Kit is a modern and advanced test kit.
• The TT1000A is a self-contained, battery-powered aircraft turbine temperature system tester capable of measuring system lead resistance and insulation, and performing indicator run-outs with a range of up to 1000 °C.