Shinku

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According to the theoretical considerations and the method of construction previously reported, some Gulbransen type microbalances of sensitivities lying between 5 and 100×10^-4g/rad have been constructed and tested for their performance in air at varying pressures. Inside a wooden case filled with air at 1 atm., the fluctuation of the zero point is about 2γ. The sensitivity curves are essentialy linear. The inclination of the balance beam and the weight of loads affect the sensitivity in ways not predictable by the existing theory. Particularly the supporting wire at the middle point of beam is not so straight as the theory assumes, but V-shaped. The sag by 1mm can cause the decrease in sensitivity by 24×10^-4 g/rad.
Details of the vacuum system that houses the microbalance are described. The rest point is irregularly affected by the fluctuation of ambient temperature and by the convection currents or the thermol-mole-cular flows when the sample is heated. Buoyancy and desorption are difficultly separable in effects. Disturbance ascribable to electro-static fields was not observed when the sample and counterweight tubes were heated to 300°C. The magnetic field used for damping seems to affect the sensitivity. It is difficult but essential to control all these effects in order to make the best use of the sensitivity attained.

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