The term Radio Telemetry refers to the delivery of information using a radio carrier. Radio Telemetry systems range from simple point-to-point links through to complex data gathering networks spanning entire cities.
With the ever increasing cost of installing cables and the lowering cost of technology, the application of modern radio telemetry devices is limited only by the imagination. Modern telemetry systems often now also include the sensing device, such as for example a pressure transducer, strain gauge or temperature sensor. Similarly it is very common for devices to be battery operated with battery lives measured in decades.
City Wide Radio Telemetry
Radio Telemeter can also be combined with cellular and internet technology to provide a low cost, low power extension to the networks where many thousands of radio telemetry nodes can report back to a single cellular or internet gateway.
The operating distance of a radio telemetry system depends upon a number of factors. These include the operating RF power level, the radio channel modulation, antenna gain, path topology, receiver sensitivity and receiver dynamic performance such as blocking immunity. In practice links ranging from a few tens of meters to many km can be established with high degrees of reliability.
Form a legal perspective the power limits and operational duty cycle permitted for radio telemetry system within Europe are as given ERC recommendation 70-30 and in the US by the FCC under Part-15 or Part 90. In general radio telemetry technology can be deployed on any band that is defined as “General Purpose” or for “Telemetry and Telecommand” applications.
However, if the application of the system is critical, where failure could result in loss of life or damage to the environment, the system should be designed to fail safe in the even of the radio links failure. This can be simply accomplished by including a regular hart beat within the communications strategy.
Less obvious advantages of Radio Telemetry
Every year millions of lightning bolts hit the surface of the Earth, inducing voltages into cables, damaging electrical appliances, causing fires and on occasion killing people. Radio telemetry can be an effective way of improving safety in areas prone to electrical storms as it provides infinite isolation between elements of the network limiting the initial inducement and subsequent propagation of the electrical surge.
However, please remember that a radio antenna installation itself can induce a lightning strike. Antenna structures must be bonded to Earth using lightning conductors and surge diverters should be used in antenna feeders.