1. Telemetry

2. What Is Telemetry? • Telemetry is the process by which an object’s characteristics are measured (such as velocity of an aircraft), andthe results transmitted to a distant station where they are displayed, recorded, and analyzed. • Several Good Definitions: • The measurement of some quantity with the aid of intermediate means which permit themeasurement to be interpreted at a distance from the primary detector. • The process that measures a quantity and then transfers the measurement data to a remotelocation to be recorded, displayed, or to control a process. [Streich, p 1]. • FCC Definition: "use of telecommunication for automatically indicating or recordingmeasurements at a distance from the measuring instrument." [Horan, p 1] • Strictly speaking, "telemetry" is the information that is collected, and "telemetering" is theprocess that collects and transfers the information. [Horan, p 1] introduction

4. A telemetering system includes all components that are used to measure, transfer, and analyze the data. A telemetry system is often viewed as two components, the Airborne System and the Ground System. Telemetry Systems Overview

5. Airborne

6. Data acquisition begins when sensors (transducers) measure the amount of a physical attribute andtransform the measurement to an engineering unit value. Sensors attached to signal conditioners provide powerfor the sensors to operate or modify signals for compatibility with the next stage of acquisition. Since maintaining a separate path for each source is cumbersome and costly, a multiplexer (historically known as a commutator) is employed.

7. Transducers are used to transform a physical parameter into an electrical signal. There are severalmajor classifications of transducers [Horan, p 15, 16]: • Optical or Visual • Pressure, Strain, Force • Environmental • Position Transducer

8. An instrument amplifier is used to amplify the (usually) very small electrical signal that isgenerated by a transducer into a higher intensity signal that is better suited for transmission. Amplifier

9. The multiplexer is used to combine several measurement signals into a single signal to betransmitted to the base station. There are two primary types of multiplexing--Time DivisionMultiplexing (TDM) and Frequency Division Multiplexing (FDM) Multiplexer

10. PCM encodes the amplitude of the multiplexer output in digital form and then transmits that signal. Abilityto add errorcorrection codes into the data stream to correct errors that may occur during transmission. Pulse Code Modulator

11. Transmits the signal that is generated by the multiplexer. The transmission can take place viaseveral different techniques depending on the transmission medium. Transmitter