VAISALA RS41-SG - radiosonde

Traduzione dall'Italiano eseguita dagli studenti del V anno dell'IISS "Galilei/Sani" - Latina.

Achille De Santis - tecnatronATgmail.com

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Description

The radiosonde RS41-SG was introduced by Vaisala on October 15 th 2013 at the "World Expo 2013" in Bruxelles. On Vaisala’s website it is possible to find very detailed specifications of the RS41-SG.

 

Beyond the slogan: "less expensive, more accurate, easier," this new sonde  has a clear advantage on the RS92-SGP: 109g against 260g, so the quantity of helium is reduced. The case is composed of two half-shells in polistirene for thermal insulation and other two thin half-cups in rigid plastic material; it has a tapered shape which should help it fall from the trees and reduces the risk of seeing entangled among the branches of some trees.

Inside the case there is a single board with the integrated circuits on both faces. At the top end we can see the  particularly small GPS receiver antenna. Compared to RS92, the RS41-SG is not fitted with the pressure sensor which, however, is optional.

Data transmission is no longer continuous but in form of a frame, like on the M10, for example, so transmitting only for half time, which allows to reduces the battery capacity (two AA lithium batteries are required).

Before the flight, the sonde performs a calibration phase in a special calibration station. The local connection between the probe and calibration station is made by wireless transmission. A small control panel includes the power switch and various LEDs that indicate the device status.

Picture on the right shows:

• H: Bar suspension where it binds the cord;
• S: "Sensor-carrying", for the temperature and humidity;
• T: Panel with LEDs that indicate probe status, calibration channel and  on-off switch;
• A: Antenna 400 Mhz

Characteristics:

• Case Size: 272 x 63 x 46 mm with the supporting arm of sensors;
• Weight: 109g with batteries;
• Frequency range: adjustable from 400.150 to 405.990 MHz, 10kHz step;
• Power: 2XAA lithium batteries;
• Battery life:  more than 240 minutes; 
• Modulation: GFSK 4800 bit/s;
• Bandwidth: 5 kHz;
• Output power: greater than 60 mW.

Sensors: 

• Temperature: probe plate; 
• Humidity: capacitive. The altitude is measured by GPS, which also allows the indirect measurement of pressure.  
• On request an optional pressure sensor can be supplied.

Photo (of Vlado, SWL)

• (R) Unwinding of twine 
• (S) carrying arm sensors
• (P) electronic Platelet
• (B) outer shell of hard plastic
• (Y) Inner shell in polystyrene foam
• (A) Antenna 400 MHz

The set of inner shells in polystyrene for thermal insulation and outer shells of hard plastic weatherproof.

Modulation

Example of modulation in narrow FM.

The hunting of RS41-SG

Making a radiogoniometric measurement is a bit more difficult than for the RS92-SGP that transmits a continuous modulated carrier.

The figure shows the spectrum of a RS41, which highlights that the channel bandwidth is very narrow.