Excellent condition, original, FUNCTIONAL WWII German Luftwaffe VARIOMETER Fl.22382 +/- 0 - 15 m / s.
Requirement mark: Fl.22382
Type: Var 7
Measuring range: +/- 0 - 15 m / s
Manufacturer: Dr.Th.Horn, Leipzig
Year of construction: 1939
Special features: metal housing
The variometer enables the pilot to maintain a certain altitude or a desired rate of climb or descent when flying blind. The vertical speeds of this device are determined by the fact that changes in air pressure are displayed in a specific time unit. The size of the air pressure change can be measured with this sensitive baffle disk device.
The device consists of the actual display instrument (variometer) and the expansion vessel, which is designed as a thermos bottle for thermal insulation. Both parts are connected with a hose. In the sealed housing of the variometer there is a baffle whose movement is transmitted to the pointer mechanism.
The baffle plate is mounted in an annular pressure chamber with a rectangular cross-section and fills this up to a small pressure compensation gap. This divides the chamber into 2 parts. A pressure connection leads into each of the chamber sides. One side is connected to the static external pressure, the other to the expansion tank.
If an aircraft moves at a constant altitude for a long time, the pressure is the same on both sides of the baffle plate as a result of the equalization through the pressure equalization gap. In this state, the pointer is held at the zero mark by a spring shackle (spiral spring). If the aircraft changes its flight altitude, a pressure difference arises at the baffle plate, since the pressure on the side of the expansion tank lags behind the pressure change on the static pressure side. The baffle plate and the pointer connected to it rotate against the spring force on the side with the lower pressure. The greater the rate of rise or fall, the greater the pressure difference and the pointer deflection it causes.
The advantage over the diaphragm can variometer is the greater measurement sensitivity and the smaller display inertia. Overloading the device due to excessive pressure differences (e.g. during a dive) is excluded.