Original, complete and working condition WWII German Luftwaffe Fl.20331-2 Doppel- Dampfdruckthermometer. Used in many German aircraft's.
Designation: double vapor pressure thermometer
Requirement sign: Fl.20331-2 (2m measuring line)
Unit no.: 127B 1048
Measuring range: 2 x 0 – 160°C
Manufacturer: gvy = JC Eckardt AG, Sonneberg plant
Year of construction: 1944
This device essentially consists of a "heat sensor" (measuring flask/immersion socket) and the display device. Both parts are connected to each other by a flexible measuring line. The immersion socket, which must be completely immersed in the coolant or lubricant to be measured, and the measuring line contain a liquid that evaporates at relatively low temperatures. With temperature changes, the vapor pressure changes according to the law. This change in pressure is measured using a spring tube (Bourdon tube) in the indicator. This movement is transmitted to the pointer via the lever and toothed segment.
In the case of long supply lines from the heat sensor to the display instrument, a high-boiling liquid that is as temperature-insensitive as possible must be connected between the spring tube and the low-boiling liquid in the immersion socket in order to make the measurement independent of the outside temperature.