What is Telemetry? How do Wireless Telemetry Systems Work? What are the Applications & Advantages of Telemetry?

Telemetry:

Telemetry is an automated communications process, which is usually associated with SCADA systems. The word is derived from Greek roots: tele = remote, and metron = measure. Telemetry is defined as the sensing and measuring of information at some remote location and then transmitting that information to a central or host location. There, it can be monitored and used to control a process at the remote site. The information can be measurements, such as voltage, speed or flow. These data are transmitted to another location through a medium such as cable, telephone or radio. Information may come from multiple locations. A way of addressing these different sites is incorporated in the system.

Figure -1: A saltwater crocodile with a GPS-based satellite transmitter attached to its head for tracking.

Although the term commonly refers to wireless data transfer mechanisms (e.g., using radio, ultrasonic, or infrared systems), 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 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. Other technologies are also possible, such as mechanical, hydraulic and optical.

Working Procedure:

The most basic system has a...

1. Distant or remote site (Measurement and transmitting end).
2. Local site or base station (Receiving and processing end).

Figure -2: A typical wireless telemetry system.

At the remote site (see the figure -2), a sensor or sensors are typically the data source. The output of the sensor(s) is converted to digital data by a small computer device or RTU (Remote Terminal Unit). The RTU is interfaced to a modem device that converts the digital data into an analog signal that can be transmitted over the air. The radio transmitter then transmits the signal to the host site radio receiver. Now the process is reversed. The modem takes the analog signal received and converts it back to a digital form that can be processed by the data recovery equipment.

In a typical application, the base or host site requests data from the remote site(s). The base transmits a request to the remote unit telling it to send its data. The base reverts to a receive mode and awaits the transmission from the remote site. After the remote sends its data, it goes back to a receive mode waiting for further instructions to come from the base. Once the base receives the remote site information, it may send additional instructions to that site or continue on to request data from the next remote site. This polling process continues until all the remotes in the system have sent their data. 

Applications:

• Meteorology: Telemetry has been used by weather balloons for transmitting meteorological data since 1920.
• Motor racing: Telemetry is a key factor 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.
• Transportation: In the transportation industry, telemetry provides meaningful information about the driver’s performance by collecting data from the vehicle, leading to better fuel efficiency through driver feedback, which includes in-cab coaching. Other benefits include fewer traffic violations and lower insurance cost for trucking companies.
• 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 (for disease prediction models), solar radiation and wind speed (to calculate evapotranspiration), water deficit stress (WDS) leaf sensors and soil moisture (crucial to irrigation decisions).
• 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. Watershed telemetry is an excellent strategy of how to implement a water management system.
• Swimming pools: Telemetry is used to transmit data in real time to server-based databases and applications with interfaces allowing monitoring and control. Server-side data storage and interpretation offers increased pool reliability. Additional data points, such as weather telemetry locally gathered or from Internet sources, can offer increased refinement of the control functions, reducing the requirement for consumables to manage water quality. Telemetry is also used to monitor health and usage of local equipment in the pump house. 
• Defense, space and resource exploration: Telemetry is used in complex systems such as missiles, RPVs, spacecraft, oil rigs, and chemical plants since it allows the automatic monitoring, alerting, and record-keeping necessary for efficient and safe operation. Space agencies such as ISRO, NASA, the European Space Agency (ESA), and other agencies use telemetry and/or telecommand systems to collect data from spacecraft and satellites.Telemetry is vital 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.
• Space science: Telemetry is used by manned or unmanned spacecraft for data transmission. Distances of more than 10 billion kilometers have been covered, e.g., by Voyager 1.
• 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 (Range purpose is for public safety). Problems include the extreme environment (temperature, acceleration and vibration), the energy supply, antenna alignment and (at long distances, e.g., in spaceflight) signal travel time.
• Flight testing: Today, nearly every type of aircraft, missiles, or spacecraft carries a wireless telemetry system as it is tested. Aeronautical mobile telemetry is used for the safety of the pilots and persons on the ground during flight tests. Telemetry from an on-board flight test instrumentation system is the primary source of real-time measurement and status information transmitted during the testing of manned and unmanned aircraft.
• Military intelligence: Intercepted telemetry was an important source of intelligence for the United States and UK when Soviet missiles were tested; for this purpose, the United States operated a listening post in Iran. 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 in Cardigan Bay to eavesdrop on UK missile tests performed in the area.
• Energy monitoring: In factories, buildings and houses, energy consumption of systems such as HVAC 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 facilitate predictive maintenance.
• 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.
• Medicine/Healthcare: Telemetry is used for patients (biotelemetry) who are at risk of abnormal heart activity, generally in a coronary care unit. Telemetry specialists are sometimes used to monitor many patients with a hospital.[12] Such patients are outfitted with measuring, recording and transmitting devices. 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. Systems are available in medical-surgical nursing for monitoring to rule out a heart condition, or to monitor a response to antiarrhythmic medications such as amiodarone. 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) the electroencephalogram (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 with real-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.
• Fishery and wildlife research and management: A bumblebee worker with a transponder attached to its back, visiting an oilseed rape flower. Telemetry is used to study wildlife, 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 (using GPS or Argos 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. Capturing and marking wild animals can put them at some risk, so it is important to minimize these impacts.
• Retail: At a 2005 workshop in Las Vegas, a seminar noted the introduction of telemetry equipment which would allow vending machines to communicate sales and inventory data to a route truck or to a headquarters. 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 use RFID 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.
• Law enforcement: Telemetry hardware is useful for tracking persons and property in law enforcement. An ankle collar worn by convicts on probation can warn authorities if a person violates the terms of his or her parole, such as by straying from authorized boundaries or visiting an unauthorized location. Telemetry has also enabled bait 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 the telemetry equipment reports the location of the vehicle, enabling law enforcement to deactivate the engine and lock the doors when it is stopped by responding officers.
• Energy providers: In some countries, telemetry is used to measure the amount of electrical energy consumed. The electricity meter communicates with a concentrator, and the latter sends the information through GPRS or GSM 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.
• Falconry: In falconry, "telemetry" means a small radio transmitter carried by a bird of prey that will allow the bird's owner to track it when it is out of sight.
• Testing: Telemetry is used in testing hostile environments which are dangerous for humans to be present. Examples include munitions storage facilities, radioactive sites, volcanoes, deep sea, and outer space
• Communications: 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.
• Mining: In the mining industry, telemetry serves two main purposes: the measurement of key parameters from mining equipment and the monitoring of safety practices. 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. Further applications of the technology allow for sharing knowledge and best practices across the organization.
• Security Detection & Alarms:

Advantages:

• No transmission lines to be cut or broken.
• Real-time data collection.
• Ease of use in remote areas where it is not practical or possible to use wire or coaxial cables.
• Easy relocation.
• Functional over a wide range of operating conditions.
• Reduces risks on human life.
• Prevents natural disasters.
• Collects data from moving objects.
• Lower cost compared to leased lines.
• Reduce maintenance.

References: 

• Telemetry, Wikipedia
• Benefits of telemetry, http://www.ferret.com.au

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