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telemetry
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What is telemetry?
Telemetry is an automated communication process for collecting measurements and data from remote or inaccessible locations, then transmitting them to receiving equipment for monitoring, display, and recording. Modern systems commonly use radio transmission, though early systems used wires.
A typical system includes a transducer (an input device), a transmission medium like radio waves, receiving and processing equipment, and recording or display devices. Telemetry is applied in areas like monitoring power plants, gathering weather data, and tracking space flights. Other uses include biomedical research, oceanography, and mechanical engineering.
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How is telemetry used in communications?
Telemetry is a highly automated communication process used to collect measurements and data from remote or inaccessible locations, transmitting them to receiving equipment for monitoring and recording. Modern telemetry commonly uses radio transmission, though original systems used wires.
Telemetry systems handle multiple information channels through multiplexing, combining channels into one composite signal for transmission over the communications link. This can be achieved through time division, where channels are combined sequentially, or frequency division, where each channel is assigned a discrete frequency band for simultaneous transmission.
Telemetry is used in many fields, including monitoring electric power plants, gathering meteorological data, and monitoring manned and unmanned space flights. It is also used in biomedical research, oceanography, and mechanical engineering.
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What types of information can telemetry send?
Telemetry is an automated communication process for collecting measurements and data from remote or inaccessible points, transmitting them to receiving equipment for monitoring and recording. Modern telemetry commonly uses radio transmission, though early systems used wires.
Telemetry can transmit various types of information, including:
* Meteorological data (temperature, pressure, humidity, wind speed)
* Oceanographic data (water temperature, salinity)
* Mechanical engineering data (temperature and pressure inside engines)
* Data on position, altitude, and speed of rockets and satellites
* Biomedical data (blood pressure, respiration, heart rates)
* Radiation levels2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does data travel from a remote location to a control center using telemetry?
Telemetry transmits data from remote locations to a control center using specialized components. A transducer at the remote location converts physical stimuli like temperature or pressure into electrical signals. These signals are then transmitted via a communication medium, often radio waves, to the control center.
To manage multiple data channels, multiplexing combines these channels into one composite signal. This can occur through time division, where channels are combined sequentially, or frequency division, where each channel gets a unique frequency band. At the receiving end, the signal undergoes demodulation and demultiplexing to extract the original data, which is then displayed or recorded for real-time monitoring and analysis.
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Why is telemetry important in fields like space exploration or weather monitoring?
Telemetry is crucial in space exploration and weather monitoring because it enables the automated collection and transmission of data from remote or inaccessible locations to receiving equipment for monitoring, display, and recording. In space exploration, telemetry obtains data on a spacecraft's position, altitude, speed, temperature, air pressure, and radiation. Weather forecasters rely on telemetry to map weather patterns, while in space missions, it monitors astronauts' vital signs like blood pressure and heart rate. This data is transmitted via radio or wire links. Additionally, in oceanography, telemetry is used to gather oceanographic and meteorological data from unmanned buoys.
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telemetry, highly automated communications process by which measurements are made and other data collected at remote or inaccessible points and transmitted to receiving equipment for monitoring, display, and recording. Originally, the information was sent over wires, but modern telemetry more commonly uses radio transmission. Basically, the process is the same in either case. Among the major applications are monitoring electric-power plants, gathering meteorological data, and monitoring manned and unmanned space flights.
The original telemetry systems were termed supervisory because they were used to monitor electric power distribution. In the first such system, installed in Chicago in 1912, telephone lines were used for transmitting data on the operation of a number of electric-power plants to a central office. Such systems spread to other fields besides power networks and underwent extensive improvements, culminating in the introduction in 1960 of the so-called interrogation-reply principle, a highly automated arrangement in which the transmitter-receiver facility at the measuring point automatically transmits needed data only on being signalled to do so. The technique is applied extensively throughout the world in such fields as oil-pipeline monitor-control systems and oceanography, in which a network of buoys transmits information on demand to a master station.
Aerospace telemetry dates from the 1930s, with the development of the balloon-borne radiosonde, a device that automatically measures such meteorological data as temperature, barometric pressure, and humidity and that sends the information to an Earth station by radio. Aerospace telemetry for rockets and satellites was inaugurated with the Soviet satellite Sputnik, launched in 1957, and systems have grown in size and complexity since then. Observatory satellites have performed as many as 50 different experiments and observations, with all data telemetered back to a ground station. The techniques developed in aerospace have been successfully applied to many industrial operations, including the transmission of data from inside internal-combustion engines during tests, from steam turbines in operation, and from conveyor belts inside mass-production ovens.
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Telemetering systems and components.
A typical telemetering system consists of an input device called a transducer, a medium of transmission (usually radio waves), equipment for receiving and processing the signal, and recording or display equipment.
The transducer.
The transducer converts the physical stimulus to be measured, such as temperature, vibration, or pressure, into an electrical signal and thus operates as the actual measuring instrument. Transducers can take many forms. They can be self-generating or externally energized. An example of the self-generating type is a vibration sensor based on the use of a piezoelectric material—i.e., one that produces an electrical signal when it is mechanically deformed. Many externally energized transducers operate by producing an electrical signal in response to mechanical deformation. Typical physical inputs producing such deformations are pressure, mechanical stress, and acceleration. A simple mechanical transducer-sensing device is a strain gauge based on the change in electrical resistance of a wire or a semiconductor material under strain. Another externally energized transducer, called the variable-reluctance type, is one in which the magnetic circuit is broken by an air gap. The mechanical movement to be measured is used to change this air gap, thus changing the reluctance, or opposition, to the production of a magnetic field in the circuit. The change in reluctance is then translated into an electrical signal.
Temperature sensors can be divided into two classifications: temperature-dependent resistance elements and self-generating thermocouples. Thermistors are of the first type; they have a high negative temperature coefficient—i.e., their resistance drops very rapidly as the temperature increases. The thermistor is small and provides rapid response to changes in temperature. Thermocouples are wire junctions of dissimilar metals that produce an electrical current when heated; they have a very low output, and each must be used with a second thermocouple held at a constant cold temperature for a reference point.
There are many types of specialized sensors and transducer systems. One is the previously mentioned radiosonde system, designed specifically to radio weather data from a balloon to a ground station. Most weather-sensing and transmitting elements measure temperature, pressure, and humidity. In manned space probes, sensors for measuring such factors as the astronaut’s blood pressure, heartbeat, and breathing rate are employed. Sensors have also been developed to indicate the rate of flow of a fluid through a pipe.
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Communications links. Communications facilities for telemetry consist primarily of radio or wire links. Alternatives such as light beams or sonic signals are used in a few cases, but environmental factors (e.g., atmospheric obstructions) and local masking noises make them impractical for most applications.
Radio communication is used for aerospace work and for supervisory systems in which it is impractical to provide wire line links. For public utility installations in built-up areas, radio communication is usually ruled out by the difficulty of finding antenna sites and unobstructed line-of-sight radio paths. In such cases, cables and line links are used.
An important consideration in radio links is the choice of operating frequency, a choice limited to bands allocated by international agreement. Propagation varies enormously over the range of frequencies involved. For aerospace applications in which transmissions must penetrate the atmosphere, the frequency range is 100 megahertz (100,000,000 cycles per second) to 10,000 megahertz. Line links for supervisory applications usually employ a comparatively narrow band. They may utilize the whole or only a section of a conventional voice channel with a bandwidth of 3,000 hertz (cycles per second). The link may be either a direct wire circuit or one of the channels in a carrier communications system.