Telemetry is the 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. A telemeter is a device used to remotely measure any quantity. It consists of a sensor a transmission path, and a display, recording, or control device. Telemeters are the physical devices used in telemetry.Electronic devices are widely used in telemetry and can be wireless or hard-wired, analog or digital.

Working of Wireless telemetry  :

• Measurement and transmitting end (distant or remote end)
• Receiving and processing end (local end)

The measurement information is transmitted from the distant end and received at the local end. Electromagnetic energy, usually transmitted at radio frequencies (RF), carries the information.

Telemetry has wide range of applications such as

(1) Meteorology : Telemetry has been used by weather balloons for transmitting meteorological data since 1920

(2) Space science : Telemetry is used by manned or unmanned spacecraft for data transmission. Distances of more than 10 billion kilometres have been covered.

(3) Motor racing : It allows race engineers to interpret data collected during a test or race and use it to properly tune the car for optimum performance. Examples of measurements on a race car include accelerations (G forces) in three axes, temperature readings, wheel speed, and suspension displacement. In Formula One, driver input is also recorded so the team can assess driver performance and (in case of an accident) the FIA (governing body for auto racing events) can determine or rule out driver error as a possible cause.

(4) Agriculture : Most activities related to healthy crops and good yields depend on timely availability of weather and soil data. Therefore, wireless weather stations play a major role in disease prevention and precision irrigation. These stations transmit parameters necessary for decision-making .

(5) Water management : Telemetry is important in water management, including water quality and stream gauging functions. Major applications include AMR (automatic meter reading), groundwater monitoring, leak detection in distribution pipelines and equipment surveillance. Having data available in almost real time allows quick reactions to events in the field. Telemetry control allows to intervene with assets such as pumps and allows to remotely switch pumps on or off depending on the circumstances.

(6) Rocketry : In rocketry, telemetry equipment forms an integral part of the rocket range assets used to monitor the position and health of a launch vehicle to determine range safety flight termination criteria.

(7) Flight testing : Flight test programs typically monitor data collected from on-board flight test instrumentation. This data is analyzed in real time for safety reasons and to provide feedback to the test pilot.The bandwidth of the telemetry link is often insufficient to transfer all data acquired; therefore, a limited set is sent to earth for real-time processing while an on-board recorder ensures the full data set is available for post-flight analysis.

(8) Resource distribution : Many resources need to be distributed over wide areas. Telemetry is useful in these cases, since it allows the system to channel resources where they are needed; examples of this are tank farms in gasoline refineries and chemical plants.

(9) Medicine/Healthcare : Telemetry is a powerful tool for real-time monitoring of a patient's heart rhythm and QRS pattern. A data log can be useful in diagnosis of the patient's condition by doctors. An alerting function can alert nurses if the patient is suffering from an acute (or dangerous) condition.Neurotelemetry and continuous EEG monitoring provides dynamic information about brain function that permits early detection of changes in neurologic status, which is especially useful when the clinical examination is limited.