Double-walled rain gauge according to Hellmann, 200 cm² collecting area, stainless steel

The only difference between the double-walled rain and snow gauge and the double-walled rain gauge is that in the former version all the parts required for processing snow into meltwater are present twice; the time required for thawing is therefore not lost for recording precipitation (DIN 58 666).

The double-walled design serves to reduce evaporation. By reducing the evaporation error, the measuring accuracy of the rain gauge is increased.

It is advisable to place both devices on level ground in such a way that they are at least as far away from neighbouring buildings, trees or bushes as they are high; this applies especially to the weather side.

The collecting vessel to be used is suspended from its holder, which is screwed to a pole so that the collecting surface is horizontal and 1 m above the ground. A snow cross in the device prevents snow from being whirled out by the influence of wind.

To measure the rainfall height, the upper part is unhooked, the collecting vessel is removed from the lower part and emptied into the measuring cylinder. After a snowfall, the observer exchanges the whole device for an empty one, carefully removing the snow cross from the filled one and inserting it into the other. Then the snow-filled collecting vessel is moved to a warmer room and the collecting opening is closed with a lid. After the snow has thawed, the height of the meltwater can be determined as usual with the measuring cylinder, where 1 graduation mark corresponds to a precipitation height of 1/10 mm.  In unsettled weather conditions, it is possible that a downforce of the atmospheric precipitation, as can occur due to vortex formation on the casing shell, leads to a deficit in the amount of precipitation collected compared to that actually fallen. Such erroneous measurements are to be prevented with the Woelfle windscreen, which consists of a ring of 840 mm diameter with 16 elastic screen blades. A common support carries the instrument and the windscreen, with four struts orienting the latter towards the collecting surface. The whole device is attached to a tubular column of about 75 mm diameter, which itself is generally not included in the delivery.

Double-walled rain gauge n. Hellmann,
collecting area: 200 cm²
Material: stainless steel sheet
consisting of:
     1 upper part with catch ring
     1 lower part
     1 collecting can
     1 holder
     1 measuring cylinder RM25 T171 (for 10 mm rain height, divided into 0.1 mm rain height, according to DIN 58667B, material: plastic)
Dimensions: ø190 mm, height: 445 mm
Weight: approx. 3 kg

 Double-walled rain and snow gauge n. Hellmann,
as above,
but consisting of:
     2 upper parts with collecting ring
     2 lower parts
     2 collecting cans
     2 snow crosses
     1 protective cover
     1 holder
     1 measuring cylinder RM25 T171
Weight: 4,7 kg

 

The main features of the Hellmann rain gauge are:

    Collecting surface 200 cm²
    Material V2A
    low evaporation error
    simple service
    excellent reliability
    maintenance-free