Telemetry
Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment for monitoring. The word is derived from the Greek roots tele, 'far off', and metron, 'measure'. Systems that need external instructions and data to operate require the counterpart of telemetry: telecommand.
Although the term commonly refers to wireless data transfer mechanisms, it also encompasses data transferred over other media such as a telephone or computer network, optical link or other wired communications like power line carriers. Many modern telemetry systems take advantage of the low cost and ubiquity of GSM networks by using SMS to receive and transmit telemetry data.
A telemeter is a physical device used in telemetry. It consists of a sensor, a transmission path, and a display, recording, or control device. Electronic devices are widely used in telemetry and can be wireless or hard-wired, analog or digital. Other technologies are also possible, such as mechanical, hydraulic and optical.
Telemetry may be commutated to allow the transmission of multiple data streams in a fixed frame.
History
The beginning of industrial telemetry lies in the steam age, although the sensor was not called telemeter at that time. Examples are James Watt's additions to his steam engines for monitoring from a distance such as the mercury pressure gauge and the fly-ball governor.Although the original telemeter referred to a ranging device, by the late 19th century the same term had been in wide use by electrical engineers applying it refer to electrically operated devices measuring many other quantities besides distance. General telemeters included such sensors as the thermocouple, the resistance thermometer, and the electrical strain gauge and output devices such as Samuel Morse's telegraph sounder and the relay. In 1889 this led an author in the Institution of Civil Engineers proceedings to suggest that the term for the rangefinder telemeter might be replaced with tacheometer.
In the 1930s use of electrical telemeters grew rapidly. The electrical strain gauge was widely used in rocket and aviation research and the radiosonde was invented for meteorological measurements. The advent of World War II gave an impetus to industrial development and henceforth many of these telemeters became commercially viable.
Carrying on from rocket research, radio telemetry was used routinely as space exploration got underway. Spacecraft are in a place where a physical connection is not possible, leaving radio or other electromagnetic waves as the only viable option for telemetry. During crewed space missions it is used to monitor not only parameters of the vehicle, but also the health and life support of the astronauts. During the Cold War telemetry found uses in espionage. US intelligence found that they could monitor the telemetry from Soviet missile tests by building a telemeter of their own to intercept the radio signals and hence learn a great deal about Soviet capabilities.
Types of telemeter
Telemeters are the physical devices used in telemetry. It consists of a sensor, a transmission path, and a display, recording, or control device. Electronic devices are widely used in telemetry and can be wireless or hard-wired, analog or digital. Other technologies are also possible, such as mechanical, hydraulic and optical.Telemetering information over wire had its origins in the 19th century. One of the first data-transmission circuits was developed in 1845 between the Russian Tsar's Winter Palace and army headquarters. In 1874, French engineers built a system of weather and snow-depth sensors on Mont Blanc that transmitted real-time information to Paris. In 1901 the American inventor C. Michalke patented the selsyn, a circuit for sending synchronized rotation information over a distance. In 1906 a set of seismic stations were built with telemetering to the Pulkovo Observatory in Russia. In 1912, Commonwealth Edison developed a system of telemetry to monitor electrical loads on its power grid. The Panama Canal used extensive telemetry systems to monitor locks and water levels.
Wireless telemetry made early appearances in the radiosonde, developed concurrently in 1930 by Robert Bureau in France and Pavel Molchanov in Russia. Molchanov's system modulated temperature and pressure measurements by converting them to wireless Morse code. The German V-2 rocket used a system of primitive multiplexed radio signals called "Messina" to report four rocket parameters, but it was so unreliable that Wernher von Braun once claimed it was more useful to watch the rocket through binoculars.
In the US and the USSR, the Messina system was quickly replaced with better systems; in both cases, based on pulse-position modulation.
Early Soviet missile and space telemetry systems which were developed in the late 1940s used either PPM or pulse-duration modulation. In the United States, early work employed similar systems, but were later replaced by pulse-code modulation . Later Soviet interplanetary probes used redundant radio systems, transmitting telemetry by PCM on a decimeter band and PPM on a centimeter band.
Relationship to telematics
Although the two terms are closely related, telemetry and telematics are used differently depending on the field.Telemetry refers to the remote measurement and transmission of data and has been traditionally used in highly specialized areas such as:
- aerospace and rocketry,
- meteorology and environmental monitoring,
- medicine,
- military and defense systems.
- automotive and fleet management,
- insurance,
- logistics and asset tracking,
- Video telematics which often incorporates devices such as a Dashcam,
- public safety and emergency services,
- mobility and smart city applications.
Applications
Meteorology
Weather balloons use telemetry to transmit meteorological data since 1920.Oil and gas industry
Telemetry is used to transmit drilling mechanics and formation evaluation information uphole, in real time, as a well is drilled. These services are known as Measurement while drilling and Logging while drilling. Information acquired thousands of feet below ground, while drilling, is sent through the drilling hole to the surface sensors and the demodulation software. The pressure wave is translated into useful information after DSP and noise filters. This information is used for Formation evaluation, Drilling Optimization, and Geosteering.Motor racing
Telemetry is used in modern motor racing, allowing race engineers to interpret data collected during a test or race and use it to properly tune the car for optimum performance. Systems used in series such as Formula One have become advanced to the point where the potential lap time of the car can be calculated, and this time is what the driver is expected to meet. Examples of measurements on a race car include accelerations 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 the FIA can determine or rule out driver error as a possible cause.Later developments include two-way telemetry which allows engineers to update calibrations on the car in real time. In Formula One, two-way telemetry surfaced in the early 1990s and consisted of a message display on the dashboard which the team could update. Its development continued until May 2001, when it was first allowed on the cars. By 2002, teams were able to change engine mapping and deactivate engine sensors from the pit while the car was on the track. For the 2003 season, the FIA banned two-way telemetry from Formula One; however, the technology may be used in other types of racing or on road cars.
One way telemetry system has also been applied in R/C racing car to get information by car's sensors like: engine RPM, voltage, temperatures, throttle.
Transportation
In the transportation industry, a Fleet telematics system is used to provide information about a vehicle or driver's performance by collecting data from on-board sensors, such as a GPS tracking unit or a telematics control unit. This is undertaken for various reasons ranging from staff compliance monitoring, insurance rating, fuel management to predictive maintenance.As part of an Intelligent transportation system, telemetry is used to link traffic counter devices to data recorders to measure traffic flows and vehicle lengths and weights.
Telemetry is used by the railway industry for measuring the health of trackage. This permits optimized and focused predictive and preventative maintenance. Typically this is done with specialized trains, such as the New Measurement Train used in the United Kingdom by Network Rail, which can check for track defects, such as problems with gauge, and deformations in the rail. Japan uses similar, but quicker trains, nicknamed Doctor Yellow. Such trains, besides checking the tracks, can also verify whether or not there are any problems with the overhead power supply, where it is installed. Dedicated rail inspection companies, such as Sperry Rail, have their own customized rail cars and rail-wheel equipped trucks, that use a variety of methods, including lasers, ultrasound, and induction to find any defects.
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 to a base station: air temperature and relative humidity, precipitation and leaf wetness, solar radiation and wind speed, water deficit stress leaf sensors and soil moisture.Because local micro-climates can vary significantly, such data needs to come from within the crop. Monitoring stations usually transmit data back by terrestrial radio, although occasionally satellite systems are used. Solar power is often employed to make the station independent of the power grid.