Once collected by late Graham Winbolt
Page 3 of this series
The Hypsometer is a rather curious instrument, which will be herewith explained briefly.
Marine-Hypsometer box (Marine = Navy)
The above metal box standing vertically
The yellow label stating that it concerns a fragile instrument and being handled with care.
The way the cover lid is to be released. The cylindrical plate is used for fixing the Hypsometer onto the lid when it is positioned horizontally at the surface of a desk
The content of the open box
The wooden module pulled a bit out of the box is the holder to the measuring Hg thermometer. (to be explained later)
The Naval Hypsometer mounted at the box. On top of it the inserted 'Thermometer' device
Why do we have a power cord, which apparently needs a mains connection?
When you have looked closely, some of the previous photos showing a liquid container. Why? After brief consideration, it is clear that a liquid should be heated up.
I consider this being H2O (aquadest)
The Hypsometer water boiler being opened
When you look closely at the upper section, you can see that its centre is not entirely open, but that the cylindrical section (diaphragm) is hold by three tiny strips, allowing the steam vapour to pass through the slits freely.
I encountered some decades ago an old book describing how explorers measured the altitude of the site they were. This was done by determining the actual H2O boiling point.
In Meyer's Lexikon of 1895 the Hypsometer is mentioned. Its principle goes thus at least back to the late 1800s.
The Hypsometer as it was obtained from late Graham Winbolt
(my wife Karin has covered the 'Kriegsmarine' Swastika, by means of Photoshop)
This device carries serial number 375/Obs.
We do know, from the list of captured devices onboard U-889, that they also have had one. The text Obs. near to the Naval Swastika (KM Hoheitsadler) already points onto its purpose, as 'Obs.' was the designation of 'weather-report' service, or WWW Meldung (Wetter-Meldung)*. A regular service very important to them, as only by far away measurements of pressure, wind-speed, temperature etc. make long-term weather-forecast reliable.
* these were heard in the ether by the Morse signals: www. Please consider for further information my book: Funkpeilungs als alliierte Waffe gegen deutsche U-Boote 1939-1945. By the way, for the sending submarine highly dangerous, and later in the war, by the boat captains, often neglected (omitted); as not to be DFed upon.
Looking through the lens in the upper section at the the thermometer like scale
Using for it light radiated from behind the apparatus.
What we are reading off is a scale calibrated in mB (mili bar). Thus: the actual vapouring-point, which is straight converted into a physical (pressure) dimension.
The Hg thermometer calibrated in mili bar (mb) (milli bar)
Scale calibrated between 958 to 1047 mB
The white mounting strip inside glass-tube is a bit transparent as to ease scale reading.
According this text label the to be checked barometer device should be placed next to the Hypsometer
Zur laufenden Berichtigung ??
Nacheichung täglich und nach besonderen Beanspruchungen
Hypsometer und Barometer
müssen benachbart stehen
The actual knowledge of the value of air pressure is essential for artillery operations, as it influences the behaviour of ballistics.
Finally a brief drawing of the Hypsometer principle
At the opposite (in the rear) of the lens is an opening as to allow light coming in. Whether a special provision was used is unknown, but some indicates that the latter is likely.
What the implication of steam vapour fluctuation is is not known to me. Maybe its effect being averaged by the mass of Hg involved.
Our only aim is to explain its basic principle roughly.
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Please continue with page 3 on the Hypsometer
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