Telemetry

Telemetry ( from Ancient Greek: τῆλε tēle " far" and μέτρον métron " measure, scale " - Remote measurement) is the transmission of measured values ​​of a measuring point located on the probe (sensor ) to a remote location. At this reception location, the measured values ​​can be either collected and recorded or evaluated immediately.

Telemetry is often supplemented by an effective path for detecting sensor to react to readings delivered with suitable measures. This return path is referred to as a remote control ( Telekommandierung, Tele -Command ).

Pure telemetry

A telemetry that transmits the measurement data over long distances is referred to as the far field telemetry. This is for example in the collection of weather data, technical data from a moving vehicle (aircraft, spacecraft, racing cars), the tracking of migratory animals such as lynx and Honey Buzzard in wildlife telemetry, in the transmission of decentralized traffic information or even at the transfer of medical data inserted probes applied to the outside world.

As near field telemetry refers to applications in which data over short distances from moving machine parts are sent to dormant receiver. For example, status data of gas turbine rotors, or the tire pressures of rotating vehicle wheels are received.

Often the data are recorded at spatially widely separated locations, and sent by telemetry to a central location to be recorded and / or evaluated.

Realization

Generally

In general, the required measuring values ​​must first be brought into a suitable form so that they can be tracked all the way.

Special attention requires the transmission of DC signals, such as those with resistive or capacitive sensors arise (eg change in voltage at a constant current flowing through it, the temperature-dependent resistor). Appropriate measures such measurement voltage is put into an AC voltage or a pulse train, so supply voltage change and temperature drift of the transmission blocks pretend no change in measurement. Suitable is, for example, a pulse train, whose pulse rate and pulse duration depend on the value of the resistance or capacitance sensor.

The transmission frequency of the telemetry transmitter to be modulated by such a pulse sequence or with a direct AC power supplied by the sensor signal.

In the receiver, the signal is recovered by a suitable demodulation and derived from the corresponding measured value. An applied with analog measurement signals of process is, for example a pulse shaper with a downstream low-pass filter.

Today, practically only digital telemetry systems in use. The acquired measurement value is implemented locally by an analog -to-digital converter (ADC A / D Converter =) into a binary string, which can then be telemetered with suitably modulated carrier and reconstructed at the receiving end without loss of information. The differences in the available data bandwidth are enormous: simple near-field and far-field most telemetries have to make do with a few kbit / second, which is sufficient for the monitoring of stationary states of a few parameters. Nahfeldtelemetrien for turbomachinery and gas turbines can total up to 180 Mbits / second transfer ( RF technology ). Optical transmission to the rotor axis over 600 Mbit / s are possible. Such systems may monitor a plurality of vibration measuring points with high bandwidth simultaneously.

Sensor networks can be considered as a new technology telemetry consideration in which many sensors combine the signal strength of their neighbors for distance determination. This results in numerous participants a precise radiolocation with simple means.

In the telemetry as a method of Zoology enhanced GPS receiver are used to enable comparison with the use of conventional radio direction finding or satellite telemetry less on labor and more extensive and more accurate data collection. If animals are provided with telemetry transmitters, one speaks of radio-marking.

Implementation using GSM

In the era of "Mobile phones " (cell phones ) comes increased data transmission via GSM / UMTS used. In this technique, the communication between the sensors is done with the place of receipt by a GSM module.

It is here de facto mobile phone technology is used. Simple systems transmitted via CSD or HSCSD or via SMS. With the advent of increasingly intelligent processors in the GSM modules communicate with the sensors is now often via GPRS and Internet protocol, which can mean additional cost savings.

The use of this technique has the advantage of a large, global reach. Local " dead spots " in the GSM network, however, are to be accepted, since mobile phones were designed for mobile use. So pay special attention for a reliable work of the design and the site of the GSM antenna.

Combination with a remote control

Here, data traffic between two stations takes place in the receiving Controlling readings (downlink ) and the sensor -bearing can follow the derived from the measured values ​​commands ( uplink). The sensor carrier is locally provided with actuators which can be controlled by an operator from a distance due to the supplied sensor data. Examples are special robots, or provided with the camera and telemetry flying objects (called drones ).

History

The telemetry is used since the late 1920s for communication from weather balloons. She experienced a big boost with the development of large rockets in the 1940s.

Report guided missiles its course to a ground station; the base station can transmit control signals.