Jawaharlal Nehru Technological University Hyderabad B.Tech IV TELEMETRY AND TELECONTROL Previous Question Paper (September - 2021 - R16)

Frequency telemetry systems and non-electrical telemetry methods differ primarily in their signal transmission medium and modulation techniques:

• Frequency Telemetry: These systems involve converting the measured physical quantity into a frequency-modulated signal. The information is transmitted by varying the frequency of a carrier wave proportional to the input parameter. This method is highly resistant to noise and amplitude fluctuations, making it suitable for long-distance transmission over radio or carrier channels.
• Non-electrical Telemetry: These methods involve the transmission of information through mechanical or pneumatic means rather than electrical signals. Examples include hydraulic or pneumatic pressure variations used to represent measured values. These are typically used in hazardous environments where electrical sparks must be avoided, but they are limited by slow response times and restricted transmission distances compared to electrical systems.

A telemetry system is designed to measure a physical quantity at a remote location and transmit the data to a central station for processing and display. The functional blocks are as follows:

• Primary Sensor/Transducer: Converts the physical quantity (e.g., pressure, temperature) into a measurable electrical signal.
• Signal Conditioning: Amplifies, filters, or linearizes the transducer output to ensure it is suitable for transmission.
• Transmitter: Modulates the conditioned signal onto a carrier wave (using AM, FM, or PCM) for transmission over the communication link.
• Transmission Channel: The medium through which the signal travels, such as copper wires, fiber optics, or radio frequency links.
• Receiver: Captures the transmitted signal and performs demodulation to recover the original electrical signal.
• Output/Display Device: Processes the recovered signal to provide a readable output, such as a digital display, chart recorder, or computer interface for monitoring and control.

The system functions by mapping the physical input to a corresponding electrical signal, transmitting it across the medium, and reconstructing the data at the receiving end for analysis.