•Mounting
to customer requirements with or without: pressure module, temperature
module, humidity module C/A code correlated GPS module, additionally sensors
•
Take-off without a ground-check• Calibration-data
stored in EEPROM on radiosonde•
Programmable frequency•
Micro-processor controlled•
Elimination of faults by code-spreading and interleaving•Code
correlated differential GPS with protected antenna for windfinding•
Free inputs for additional sensors (e.g. ozone)•
High-power environmental friendly lithium battery•
Light weight of 225 gFunction
and design
The DFM-97 radiosonde is designed to measure the profile of air pressure,
air temperature, air humidity, wind speed and wind direction from ground
level up to 40km altitude. One set of the measured data per second is
sent down to a receiving station (ground station) as the radiosonde is
carried aloft by a balloon. If not all sensors are needed, custom-specific
configurations can be provided.
Advantages of data transmission
The radio data transmission meets extremely exacting requirements. In
order to evaluate the quality of the radio signal and to deal with any
errors occurring, code spreading is applied to 8 bits. This feature enables
two errors to be detected and one error to be corrected. Furthermore,
interleaving is carried out to minimise burst errors.
Measurement
and processing of three PTU data sets are performed in a time window of
less than one second. Within this time window, reference measurements
are carried out in an additional channel to check and correct the electronics.
In order to enable the sonde data in multiple sonde applications to be
uniquely assigned, the serial number of the sonde is included in the data
transmitted.
The calibration data for the individual sensors are stored in a non-volatile memory on the radiosonde. These are transferred shortly before take-off into the computer of the ground station by means of the RS232 communication cable. At the same time, all functions of the radiosonde are verified automatically.
After this calibration process, the radiosonde is immediately ready for launching without any further manual ground checks.
The radiosonde transmits in the meteorological frequency range of 402 to 406 MHz. Due to the highly sophisticated receiver unit, the transmission range is more than 250 km without the need for a beam antenna.
The concept of the freely programmable PLL synthesiser is of interest in particular for large-scale users with many ascent stations. After connecting the radiosonde to the groundstation via an RS232 interface, the desired transmitting frequency is automatically tuned immediately before take-off. This involves storing the frequency information in a non-volatile memory on the radiosonde.
This affords substantial streamlining of inventories and logistics for the user because only one radiosonde type has to be stored in a central store for all ascent stations.
Microprocessor-controlled features
All important functions of the radiosonde (initialising before take-off, processing and control of measured sensor data and of telemetry data) are controlled by a microprocessor installed in the radiosonde.
Wind observation
There is a choice of two methods of obtaining wind data:
It is possible to determine wind data by means of GPS. In this case, there is no need for a pressure sensor to measure the pressure, resulting in savings in the cost of the sonde equipment. Significant advantages of GPS-positioning are lower first cost and lower operating costs compared to radar systems.
Alternatively, wind data can be determined by means of a radiotheodolite or radar system. In this case, there is no need for a GPS to be provided on the sonde, but a pressure sensor is required.
Differential C/A-code GPS
The radiosonde is standard with a C/A-code-correlated GPS receiver for evaluation of the exact position of the radiosonde. The position information is calculated by the GPS module in the radiosonde. The position is transmitted to the ground station, where it is corrected with the stationary GPS signal of the ground station (differential GPS). Flights with this differential GPS method have shown that the error of vertical position (altitude) is less than 20 meters, of the horizontal position less than 10 meters. C/A-code-correlated GPS windfinding can also be used on moving platforms (e.g. ships).
The energy of the radiosonde is supplied by a high-power lithium battery. The main advantages of this battery are ease of use, low weight and environmental friendliness. A storage time of several years is also guaranteed.
Activation of the battery is done by simply connecting a plug. In contrast to water-activated systems, the battery can be deactivated at any time by just unplugging the connector.
Scientific or
research tasks
The radiosonde incorporates additional channels for direct inputs from
supplementary sensors with resistances, capacitances and frequencies.
Matching-up to sensors with different electric properties is possible
and provided for. Solutions of complex sensor systems are feasible where
several parameters have to be measured simultaneously.
Thanks to these features, the radiosonde has established an excellent
reputation as a multi-channel radiosonde with high reliability and flexibility.
Ozone sensors
All commonly known ozone sensors can be combined with the radiosonde either
directly or with a small low-cost adapter.
Detail view of
Radiosonde
• Mirrored surface reduces errors due to solar radiation
• Fast reaction time due to low weight and low thermal capacity
• Protected against heating and water ingress by a mirrored capsule
• Stable measurement due to high capacity
• Minimal influence of hysteresis due to ascent-simulated calibration
• Minimal weight due to use of styrofoam
| DFM-97 type code | ||||||||||||||||||
Type
code: DFM97-abcdef |
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Sensors |
GPS |
Packing |
Reserved |
Reserved |
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2 |
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