Telemetry system

In this presentation there is a description of telemetry system and its types.It give you a brief detail of telemetry system.

1. Telemetry System

2. Telemetry System

3. Introduction Block diagram of Telemetry System Factor influencing Telemetry System Design Classification of Telemetry System Landline Telemetry System RF Telemetry System Merits of land line telemetry Demerits of landline telemetry CONTENTS

4. Telemetry is a process of measurement at a long distance. Telemetry are used to monitor the physical quantity such as- temperature, speed, flow rate, liquid level, water level. In Greek words the meaning of telemetry is--- TELE=REMOTE, METER=MEASUREMENT Telemetry involves three steps- Converting measured quantity to signal. Transmission of that signal over proper channel. Its reconversion to actual data for recording, displaying(CRT), for graphical analysis and further computation. E.g.- Doctor analysing data of patient from remote location. INTRODUCTION

5. Primary criteria for choice and design is accuracy. System is decided whether transmitted data is in Analog or Digital domain. For digital data to be transmitted, error detection, recognition and correction capability make system accurate. Selection of apt. bandwidth for data channel and data link to avoid crosstalk. Power level must be low to reduce noise generation. FACTORS INFLUENCING TELEMETRY SYSTEM DESIGN

6. 1. Landline Telemetry System— The telemetry system in which the signal is transmitted through communication cable like copper, aluminium pair, fiber, cable etc. The physical link between the transmitter and receiver in landline telemetry system is in the form of wire that has its characteristics to transmit the signal from transmitter to receiver . Power Lines, Telephone lines and Electrical Wires. Distance ranges from 50m to 1km e.g. : Labs, Industry . TYPES – Current and Voltage. 2. RADIO FREQUENCY OR WIRE LESS TELEMETRY- Radio links from 1km to 50km at 4MHz. For distance >50km microwave links are used 890MHz to 30GHz. Repeaters are installed after every 30 to 60 km for long distance transmission. CLASSIFICATION OF TELEMETRY SYSTEM

7. TYPES OF LANDLINE TELEMETRY SYSTEM- 1- Voltage Telemetry System 2- Current Telemetry System

8. Measured variable is transmitted in form of voltage. At transmitting end, slide wire is connected in series with battery. Slide wire is further connected to Bourdon tube for pressure measurement. When pressure changes, slider actuates the slider of potentiometer. Thus, change in voltage is transmitted to receiver. VOLTAGE TELEMETRY SYSTEM

9. MERITS - Effective for short distance measurement. V and I can be easily transmitted. Circuitry required is simple. Wide variety of primary sensing elements are available to measure required variable. DEMERITS - Is difficult to calibrate. Need to be protected from EMI ,noises and distortions in the channel. Multiplexing is difficult. Limited frequency response. MERITS and DEMERITS OF LANDLINE TELEMETRY

10. No physical link between telemetry transmitter and receiver . Link is established through radio links. Examples : in spacecraft, rockets and missiles. corrective actions can be taken from stations with help of R.F. links. In Instrumentation the output of transducer is considered as modulating signal. RF TELEMETRY SYSTEM

11. The output of transducer and single conditioner modulates the frequency of a voltage controlled subcarrier oscillator. Many oscillators, each operating in a dedicated part of the frequency spectrum, are mixed for radio transmission. As each voltage controlled oscillator is assigned with a separate frequency of separate frequency spectrum, so each signal can be transmitted without interfering with other signals. At the receiving station, discriminator is tuned to the frequency of each subcarrier. Thus when measurement value change at source, the output voltage of discriminator change accordingly. THE DISADVANTAGE OF FM TELEMETRY SYSTEM IS CAPACITY OF CHANNELS OFFERED IS LESS Explanation OF BLOCK DIAGRAM

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