To obtain a Pirani gauge acting with rapid response as well as high sensitivity, the author constructed a Pirani gauge, the filament of which was automatically kept at a constant temperature by means of phototube and galvanometer system.
The method is this. The filament constitutes a Wheatstone bridge with the other three resistors, and is heated by the plate current of a vacuum tube. The deflection of a reflecting galvanometer caused by the change of the filament temperature, is detected by two phototubes, which are placed to receive the light reflected by the mirror of the galvanometer and to act differentially. The difference of the photoelectric currents cf the two tubes is sent to the grid impedance of the vacuum tube and controls the heating current. When the gas pressure in the gauge increases, the filament temperature drops, which causes the increase of the heating current, consequently the filament temperature is prevented from dropping and kept nearly constant. The pressure is known from the heating current. In order to stabilize the action of the system, it is effective to adjust the damping resistance of the galvanometer. The time of response of the pirani gauge thus constructed was about 5 seconds, which is about one-10th of that of the Pirani gauge used in usual method. It could measure the pressure from 1 × 10^-5 to 5 ×10^-2 mmHg. The relation between the square of the heating current and the pressure was nearly linear.

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The conventional evacuating system : combination of oil diffusion pump, booster pump and mechanical rotary pump, has serious faults in the case of pumping the chemically unstable matter. For instance, in the degassing stage of the molecular distillation plant, the gas is composed of air, volatile matter, water vapor and mist of unstable compound. These components are decomposed or polymerized in a evacuating system, and damage the normal opperation of pumps, especially in oil rotary pump. This is caused by less circulation of oil, and moving parts would be damaged.
To conquer this difficulty, we tried to select the new pump composion ; diffusion-booster, steam ejector and water jet. This system has not any moving parts, so we can avoid adove difficulty. The performances of these pumps are as follows :
Diffusion booster : Pumping speed (800900 l/sec at 10^-310^-2 mmHg)
Critial back pressure (57mmHg)
Steam ejector : Pumping speed (20 l/sec at 1 mmHg), Back pressure (40 mmHg)
Water jet : Pumping speed (0. 95 l/sec at 5 mmHg), Back pressure (atmosphere).
The overall performance shows very satisfactory result, and this system is now under continious operation for over a year.

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