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1.1 Telemetry
By Definition Telemetry is the science and technology of automatic measurement and transmission of data by wire, radio, or other means from remote sources, as from aircraft, to receiving stations or a drive shaft to a stationary location on the vehicle [13]. Telemetry is the process by which an object’s characteristics are measured (such as velocity of an aircraft), and the results transmitted to a distant station where they are displayed, recorded, and analyzed. The transmission media may be air and space for satellite applications, or copper wire and fiber cable for static ground environments like power generating plants. In today's telemetry applications, which support large numbers of measurands, it is too costly and impractical to use separate transmission channels for each measured quantity. The telemetry process involves grouping measurements (such as pressure, speed, and temperature) into a format that can be transmitted as a single data stream. Once received, the data stream is separated into the original measurement’s components for analysis [12].
1.2 The purpose of telemetry[13]
Telemetry lets stay in a safe (or convenient) location while monitoring what's taking place in an unsafe (or inconvenient) location. Aircraft development, for example, is a major application for telemetry systems. During initial flight testing, an aircraft performs a variety of test maneuvers. The critical flight data from a maneuver is transmitted to flight test engineers at a ground station where results are viewed in real time or analyzed within seconds of the maneuver. Real-time monitoring allows the "safety officer" to make instant decisions on whether to proceed with or terminate a test. With real-time analysis, the flight test engineer can request a maneuver be repeated, the next maneuver be performed, or test plan alternatives be substituted. Real-time data is also captured to storage media, such as disk and tape, for later analysis and archiving.
1.3 Reason for Telemetry[13]
Telemetry(or Remote Monitoring, or M2M, or Telematics, or Machine2Man, Man2Machine, Machine2Machine... ) can be used for too many applications to mention here, but vehicle and mobile asset tracking, storage tank level monitoring, remote meter reading, pump condition monitoring, vending machine monitoring all have one thing in common and that is reducing costs. The technology is now sufficiently proven, the mobile network operators have now embraced the solution and the cost of the solutions have fallen dramatically over the years opening most if not all of these applications. Using telemetry can seriously help business - know where things are, how things are, be the first to react to a potential problem, know what has caused the problem before set off on a long journey, get more from operatives and assets.
1.4 Types of Telemetry transmission[14]
• Landline
• Cell phone – It can use GSM and GPRS. CDMA technology is also used in this. Data phones and modems are very cheap. It is limited to areas having cell phone coverage.
• VHF or UHF Radio – It requires radio system usually with repeaters in required locations.
• Satellite receiving systems – Transmission is one way (data acquisition) only. It is very expensive and slow.
• Satellite phone (satphone) – The operation is similar to cell phone telemetry, but more expensive (both hardware and calls). It will work almost anywhere in the world. Costs are coming down gradually.