TELEMETRY

This is a technique of measurement at a distance, where the sensor work is carried out at a distance away from the display. The good example is nuclear reactor where there are radiation and temperature sensors to monitor and measure conditions inside the reactor. It is unsecure for humans to enter these places and to take readings directly, so the displays are outside the reactor in a shielded control room. There is another example of a balloon sent up by meteorologist experts to measure atmospheric temperature at very high altitudes.

Telemetry is used where it is dangerous, difficult, or simply inconvenient for a person to go and take the measurements directly. The telemetric instrumentation system therefore has few extra stages.

The telecommunication link used may be a cable, and optical fibre cable or radio signal. It may be either analogue or digital. If it is medium used is digital, it will include phases for analogue-to-digital conversion, error checking and corrections, it also include encoding and decoding. However, these extra stages make no impact to the essential function of converting a physical quantity to a displayed electrical quantity. Thing to be noted is that telemetry is not to be mixed with remote sensing. Example of remote sensing process is the use of a satellite to investigate soil properties over a vast area of land. The sensor is directed towards a remote site. There is a substantial distance between the site and the sensor. An example of smaller scale application is when the temperature level of a furnace is measured by way of directing a radiation pyrometer at the open doorway of the furnace for measuring the thermal radiation being emitted. Again here the sensor is at a distance from the site of measurement is carried, the simple reason it that it will be damaged if it brought closer.