Avionics Test Equipment Overview

A set of flashcards covering vocabulary and core concepts related to avionics general test equipment, including power and frequency measurement, oscilloscopes, and pitot/static testing.

BITE

Built in test equipment found in avionics systems that is often limited because it cannot perform self-tests on itself.

Dynamometer movement

A meter movement used for power measurement consisting of a lightweight moving coil energized by voltage and a stationary coil energized by current.

Wattmeter Rating

A measurement instrument that is always distinctly rated in volts and amperes rather than watts.

Resonant Frequency Meter

A frequency meter that utilizes an inductor and capacitor tank circuit adjusted to find the maximum amplitude of voltage.

Frequency Counter

An instrument used to determine frequency by counting pulses through a gate circuit kept open for accurately timed intervals by a clock signal source.

Direct digital counter

A type of frequency counter where the unknown frequency is calculated by dividing the number of pulses counted by the time the gate circuit was open.

Prescaler

A digital binary counter circuit that divides the frequency of a measured signal by a constant, such as $1000$, to extend the counter input range.

Logic Speed Limit

The maximum frequency limit for counters built of fast digital integrated circuits, which is approximately $1\,GHz$.

Oscilloscope

A versatile item of test equipment used primarily to display time-related voltage waveforms, frequency, and voltage measurements.

Grid $G1$

A part of the cathode ray tube electron gun that remains negative with respect to the cathode to control the quantity of electrons and spot brightness.

Grids $G2$ and $G3$

Positively charged grids that accelerate electrons towards the screen and set up an electrostatic field for focusing.

Time base

A circuit that supplies a sawtooth voltage varying linearly with time to the horizontal deflecting plates for waveform display.

Sweep ($T1$)

The period during which the oscilloscope spot moves linearly from left to right across the screen.

Fly back time ($T2$)

The much shorter period during which the spot returns rapidly to the left side of the oscilloscope screen.

Blanking

The process of applying a negative pulse to grid $G1$ during fly back to hide the trace movement.

Pitot/static system

The probes and ports that provide static and dynamic air pressure to instruments like altimeters, airspeed indicators, and Mach meters.

ADTS / ADTE

Air Data Test Sets or Air Data Test Equipment, which act as pressure generators to simulate altitude, vertical speed, and airspeed.

Bryans leak tester

A basic hand-held unit used for performing pitot/static system leak checks.

Low-range leak check

A quick verification of system integrity carried out after any disconnection of pitot or static lines.

High-range leak check

A test performed using air data test sets to calibrate instruments and test the $ATC$ transponder $MODE\,C$ altitude reporting function.