Telemetry is thein situcollection of measurements or other data at remote points and their automatictransmission to receiving equipment (telecommunication) for monitoring.[1] The word is derived from theGreek rootstele, 'far off', andmetron, 'measure'. Systems that need external instructions and data to operate require the counterpart of telemetry:telecommand.[2]
Although the term commonly refers towireless data transfer mechanisms (e.g., usingradio, ultrasonic, orinfrared systems), it also encompasses data transferred over other media such as a telephone orcomputer network, optical link or other wired communications like power line carriers. Many modern telemetry systems take advantage of the low cost and ubiquity ofGSM networks by usingSMS to receive and transmit telemetry data.
Atelemeter is a physical device used in telemetry. It consists of asensor, 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 ordigital. Other technologies are also possible, such as mechanical, hydraulic and optical.[3]
Telemetry may becommutated to allow the transmission of multiple data streams in a fixedframe.
The beginning of industrial telemetry lies in thesteam age, although the sensor was not calledtelemeter at that time.[4] Examples areJames Watt's (1736-1819) additions to his steam engines for monitoring from a (near) distance such as themercury pressure gauge and thefly-ball governor.[4]
Although the original telemeter referred to a ranging device (therangefinding telemeter), 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 (for instance, in the patent of an "Electric Telemeter Transmitter"[5]). General telemeters included such sensors as thethermocouple (from the work ofThomas Johann Seebeck), theresistance thermometer (byWilliam Siemens based on the work ofHumphry Davy), and the electricalstrain gauge (based onLord Kelvin's discovery that conductors under mechanical strain change theirresistance) and output devices such asSamuel Morse'stelegraph sounder and therelay. In 1889 this led an author in theInstitution of Civil Engineers proceedings to suggest that the term for the rangefinder telemeter might be replaced withtacheometer.[6]
In the 1930s use of electrical telemeters grew rapidly. The electrical strain gauge was widely used in rocket and aviation research and theradiosonde was invented formeteorological measurements. The advent ofWorld War II gave an impetus to industrial development and henceforth many of these telemeters became commercially viable.[7]
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 (such as infrared lasers) 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.[8] During theCold War telemetry found uses in espionage. US intelligence found that they could monitor the telemetry fromSoviet missile tests by building a telemeter of their own to intercept the radio signals and hence learn a great deal about Soviet capabilities.[9]
Telemeters are the physical devices used in telemetry. It consists of asensor, a transmission path, and a display, recording, or control device. Electronic devices are widely used in telemetry and can bewireless or hard-wired,analog ordigital. Other technologies are also possible, such as mechanical, hydraulic and optical.[10]
Telemetering information over wire had its origins in the 19th century. One of the first data-transmission circuits was developed in 1845 between theRussian Tsar'sWinter Palace and army headquarters. In 1874, French engineers built a system of weather and snow-depth sensors onMont Blanc that transmitted real-time information toParis. In 1901 the American inventor C. Michalke patented theselsyn, 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. ThePanama Canal (completed 1913–1914) used extensive telemetry systems to monitor locks and water levels.[11]
Wireless telemetry made early appearances in theradiosonde, developed concurrently in 1930 by Robert Bureau in France andPavel Molchanov inRussia. Molchanov's system modulated temperature and pressure measurements by converting them to wirelessMorse code. The GermanV-2 rocket used a system of primitive multiplexed radio signals called "Messina" to report four rocket parameters, but it was so unreliable thatWernher 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 onpulse-position modulation (PPM).[12]Early Soviet missile and space telemetry systems which were developed in the late 1940s used either PPM (e.g., the Tral telemetry system developed by OKB-MEI) orpulse-duration modulation (e.g., the RTS-5 system developed by NII-885). In the United States, early work employed similar systems, but were later replaced bypulse-code modulation (PCM) (for example, in the Mars probeMariner 4). Later Soviet interplanetary probes used redundant radio systems, transmitting telemetry by PCM on a decimeter band and PPM on a centimeter band.[13]
Although the two terms are closely related, telemetry andtelematics 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:
Telematics, by contrast, emerged later as a broader, more applied concept that combines telemetry with telecommunications, informatics, anddigital fleet platforms. The term is most often used in industries that involve connected, mobile assets, including:
In short, telemetry is the enabling technology (remote measurement and data transmission), while telematics describes the integrated, digitalized applications that build on telemetry to deliver business, safety, and operational insights.
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Weather balloons use telemetry to transmit meteorological data since 1920.
Telemetry is used to transmit drilling mechanics and formation evaluation information uphole, in real time, as a well is drilled. These services are known asMeasurement while drilling andLogging 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 (sana) is translated into useful information after DSP and noise filters. This information is used forFormation evaluation,Drilling Optimization, andGeosteering.
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 asFormula 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 (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) theFIA 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 (even while it is out on the track). 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.[citation needed] For the 2003 season, the FIA banned two-way telemetry from Formula One;[18] however, the technology may be used in other types of racing or on road cars.
One way telemetry system has also been applied inR/C racing car to get information by car's sensors like: engine RPM, voltage, temperatures, throttle.
In the transportation industry, aFleet telematics system is used to provide information about a vehicle or driver's performance by collecting data from on-board sensors, such as aGPS tracking unit or atelematics control unit (TCU). This is undertaken for various reasons ranging from staff compliance monitoring, insurance rating,fuel management to predictive maintenance.
As part of anIntelligent transportation system, telemetry is used to linktraffic counter devices to data recorders to measure traffic flows and vehicle lengths and weights.[19]
Telemetry is used by the railway industry for measuring the health oftrackage. This permits optimized and focused predictive and preventative maintenance. Typically this is done with specialized trains, such as theNew Measurement Train used in the United Kingdom byNetwork Rail, which can check for track defects, such as problems withgauge, and deformations in the rail.[20] Japan uses similar, but quicker trains, nicknamedDoctor Yellow.[21] Such trains, besides checking the tracks, can also verify whether or not there are any problems with theoverhead power supply (catenary), where it is installed. Dedicated rail inspection companies, such asSperry Rail,[22] have their own customized rail cars and rail-wheel equipped trucks, that use a variety of methods, including lasers, ultrasound, and induction (measuring resulting magnetic fields from running electricity into rails) to find any defects.[23]
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 andrelative humidity,precipitation andleaf wetness (for disease prediction models), solar radiation and wind speed (to calculateevapotranspiration), water deficit stress (WDS) leaf sensors and soil moisture (crucial to irrigation decisions).
Because local micro-climates can vary significantly, such data needs to come from within the crop. Monitoring stations usually transmit data back by terrestrialradio, although occasionallysatellite systems are used. Solar power is often employed to make the station independent of the power grid.
Telemetry is used inwater management, includingwater quality andstream 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 engineers to intervene with assets such as pumps and by remotely switching pumps on or off depending on the circumstances.[24]
Telemetry is used in complex systems such as missiles, RPVs,spacecraft,oil rigs, andchemical plants since it allows the automatic monitoring, alerting, and record-keeping necessary for efficient and safe operation. Space agencies such asNASA,ISRO, theEuropean Space Agency (ESA), and other agencies use telemetry and/or telecommand systems to collect data from spacecraft and satellites.
Telemetry is used in the development of missiles, satellites and aircraft because the system might be destroyed during or after the test. Engineers need critical system parameters to analyze (and improve) the performance of the system. In the absence of telemetry, this data would often be unavailable.
Telemetry is used by crewed or uncrewed spacecraft for data transmission. Distances of more than 25.1 billion kilometers (May 2025)[25] have been covered, e.g., byVoyager 1.
In rocketry, telemetry equipment forms an integral part of therocket range assets used to monitor the position and health of a launch vehicle to determine range safety flight termination criteria (Range purpose is for public safety). Problems include the extreme environment (temperature, acceleration and vibration), theenergy supply,antenna alignment and (at long distances, e.g., inspaceflight) signaltravel time.
Today nearly every type ofaircraft,missiles, orspacecraft carries a wireless telemetry system as it is tested.[26] Aeronautical mobile telemetry is used for the safety of the pilots and persons on the ground during flight tests. Telemetry from an on-boardflight test instrumentation system is the primary source of real-time measurement and status information transmitted during the testing of crewed and uncrewed aircraft.[27]
Intercepted telemetry was an important source of intelligence for the United States and UK whenSoviet missiles were tested; for this purpose, the United States operated a listening post inIran. Eventually, the Russians discovered the United States intelligence-gathering network and encrypted their missile-test telemetry signals. Telemetry was also a source for the Soviets, who operated listening ships inCardigan Bay to eavesdrop on UK missile tests performed in the area[citation needed].
In factories, buildings and houses, energy consumption of systems such asHVAC are monitored at multiple locations; related parameters (e.g., temperature) are sent via wireless telemetry to a central location. The information is collected and processed, enabling the most efficient use of energy. Such systems also facilitatepredictive maintenance.
Many resources need to be distributed over wide areas. Telemetry is useful in these cases, since it allows the logistics system to channel resources where they are needed, as well as provide security for those assets; principal examples of this are dry goods, fluids, and granular bulk solids.
Dry goods, such as packaged merchandise, may be tracked and remotely monitored, tracked and inventoried byRFID sensing systems,barcode reader,optical character recognition (OCR) reader, or other sensing devices, coupled to telemetry devices, to detectRFID tags,barcode labels or other identifying markers affixed to the item, its package, or (for large items and bulk shipments) affixed to its shipping container or vehicle. This facilitates knowledge of their location, and can record their status and disposition, as when merchandise with barcode labels is scanned through a checkout reader atpoint-of-sale systems in a retail store. Stationary or hand-held barcodeRFID scanners orOptical reader with remote communications, can be used to expedite inventory tracking and counting in stores, warehouses, shipping terminals, transportation carriers and factories.[28][29][30]
Fluids stored in tanks are a principal object of constant commercial telemetry. This typically includes monitoring of tank farms in gasoline refineries and chemical plants, and distributed or remote tanks, which must be replenished when empty (as with gas station storage tanks, home heating oil tanks, or ag-chemical tanks at farms), or emptied when full (as with production from oil wells, accumulated waste products, and newly produced fluids).[31] Telemetry is used to communicate the variable measurements of flow and tank level sensors detecting fluid movements and/or volumes bypneumatic,hydrostatic, or differential pressure; tank-confinedultrasonic,radar orDoppler effect echoes; or mechanical or magnetic sensors.[31][32][33]
Telemetry of bulk solids is common for tracking and reporting the volume status and condition ofgrain andlivestock feed bins, powdered or granular food, powders and pellets for manufacturing, sand and gravel, and other granular bulk solids. While technology associated with fluid tank monitoring also applies, in part, to granular bulk solids, reporting of overall container weight, or other gross characteristics and conditions, are sometimes required, owing to bulk solids' more complex and variable physical characteristics.[34][35]
Telemetry is used for patients (biotelemetry) who are at risk of abnormalheart activity, generally in acoronary care unit. Telemetry specialists are sometimes used tomonitor many patients within a hospital.[36] Such patients are outfitted with measuring, recording and transmitting devices. A data log can be useful indiagnosis of the patient's condition bydoctors. An alerting function can alertnurses if the patient is suffering from an acute (or dangerous) condition.
Systems are available inmedical-surgical nursing for monitoring to rule out a heart condition, or to monitor a response toantiarrhythmic medications such asamiodarone.
A new and emerging application for telemetry is in the field of neurophysiology, or neurotelemetry.Neurophysiology is the study of the central and peripheral nervous systems through the recording of bioelectrical activity, whether spontaneous or stimulated. In neurotelemetry (NT) theelectroencephalogram (EEG) of a patient is monitored remotely by a registered EEG technologist using advanced communication software. The goal of neurotelemetry is to recognize a decline in a patient's condition before physical signs and symptoms are present.
Neurotelemetry is synonymous withreal-time continuous video EEG monitoring and has application in the epilepsy monitoring unit, neuro ICU, pediatric ICU and newborn ICU. Due to the labor-intensive nature of continuous EEG monitoring NT is typically done in the larger academic teaching hospitals using in-house programs that include R.EEG Technologists, IT support staff, neurologist and neurophysiologist and monitoring support personnel.
Modern microprocessor speeds, software algorithms and video data compression allow hospitals to centrally record and monitor continuous digital EEGs of multiple critically ill patients simultaneously.
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.
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Telemetry is used to study wildlife,[37] and has been useful for monitoring threatened species at the individual level. Animals under study can be outfitted with instrumentation tags, which include sensors that measure temperature, diving depth and duration (for marine animals), speed and location (usingGPS orArgos packages). Telemetry tags can give researchers information about animal behavior, functions, and their environment. This information is then either stored (with archival tags) or the tags can send (or transmit) their information to a satellite or handheld receiving device.[38] Capturing and marking wild animals can put them at some risk, so it is important to minimize these impacts.[39]
At a 2005 workshop inLas Vegas, a seminar noted the introduction of telemetry equipment which would allowvending machines to communicate sales and inventory data to a route truck or to a headquarters.[citation needed] This data could be used for a variety of purposes, such as eliminating the need for drivers to make a first trip to see which items needed to be restocked before delivering the inventory.
Retailers also useRFID tags to track inventory and prevent shoplifting. Most of these tags passively respond to RFID readers (e.g., at the cashier), but active RFID tags are available which periodically transmit location information to a base station.
A telemetry-basedTracking system is useful for tracking persons and property in law enforcement. Anankle collar worn by convicts on probation can warn authorities if a person violates the terms of his or herparole, such as by straying from authorized boundaries or visiting an unauthorized location. Telemetry has also enabledbait cars, where law enforcement can rig a car with cameras and tracking equipment and leave it somewhere they expect it to be stolen. When stolen thetelemetry equipment reports thelocation of the vehicle, enabling aStolen vehicle recovery process where law enforcement can deactivate the engine and lock the doors when it is stopped by responding officers.
In some countries, telemetry is used to measure the amount of electrical energy consumed. The electricity meter communicates with aconcentrator, and the latter sends the information throughGPRS orGSM to the energy provider's server. Telemetry is also used for the remote monitoring of substations and their equipment. For data transmission, phase line carrier systems operating on frequencies between 30 and 400 kHz are sometimes used.
Infalconry, "telemetry" means a small radio transmitter carried by abird of prey that will allow the bird's owner to track it when it is out of sight.
Telemetry is used in testing hostile environments which are dangerous to humans. Examples include munitions storage facilities, radioactive sites, volcanoes, deep sea, and outer space.
Telemetry is used in many battery operated wireless systems to inform monitoring personnel when the battery power is reaching a low point and the end item needs fresh batteries.
In the mining industry, telemetry serves two main purposes: the measurement of key parameters from mining equipment and the monitoring of safety practices.[40] The information provided by the collection and analysis of key parameters allows for root-cause identification of inefficient operations, unsafe practices and incorrect equipment usage for maximizing productivity and safety.[41] Further applications of the technology allow for sharing knowledge and best practices across the organization.[41]
In software, telemetry is used to gather data on the use and performance of applications and application components, e.g. how often certain features are used, measurements of start-up time and processing time, hardware, application crashes, and general usage statistics and/or user behavior. In some cases, very detailed data is reported like individual window metrics, counts of used features, and individual function timings.
This kind of telemetry can be useful to software developers to receive data from a wide variety of endpoints that can't possibly all be tested in-house, as well as getting data on the popularity of certain features and whether they should be given priority or be considered for removal. Due to concerns aboutprivacy since software telemetry can easily be used toprofile users, telemetry in user software is often user choice, commonly presented as an opt-out feature (requiring explicit user action to disable it) or user choice during the software installation process.
As in other telecommunications fields, international standards exist for telemetry equipment and software. International standards producing bodies includeConsultative Committee for Space Data Systems (CCSDS) for space agencies,Inter-Range Instrumentation Group (IRIG) for missile ranges, and Telemetering Standards Coordination Committee (TSCC), an organisation of the International Foundation for Telemetering.
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