A magnetic field of fair uniformity is obtained at the opening laminated C-shaped core of silicon alloy steel rigidly secured together and excited by d. c. or a. c. current. Description is given on a co-ordinates indicating set using a. c. current utilizing the variation of induced voltage in a coil placed at different positions in the opening of the core. With two units combined at right angle or any other angle, two-dimensional position is determined whereby the device can be used in position-and-motion-control system. An example is given of measuring the inclination of a plane by orthogonal co-ordinates. The author points out that the method is applicable to such as the automatic contour tracing mechanism which has recently been developed.
It has been known that the rate of decay of phosphorescence from phosphor is changed by temperature, and its phosphorescence is also quenched or stimulated by infrared radiation. Using these properties, the temperature distribution on a body and the thermal radiation are measured. Two kinds of luminescence paint are used for the purpose; one emits a green phosphorescence and other a blue one.
A stiff wire and a cylinder are hung vertically from a coil spring which is fixed at its upper end. The whole of the cylinder and a part of the wire are immersed in the liquid. A change of specific gravity of the liquid is converted into a change of buoyancy of the cylinder, and then into a vertical displacement of the lower end of the spring, practically independently of the surface level. Two methods of measuring small displacements were applied, one being the method made use of an electric oscillating circuit with a quartz plate, and the other being that of “elec-tromagnetic induction micrometers” devised by Cog with some modifications. The latter method seems more practical. Remote measurement of change of specific gravity of 0.1% is not difficult.
A method of measuring thermal conductivity in varying state of temperature is described. A thin and long cylinder is considered, in a large homogeneous medium of uniform temperature. If the surface of unit length of the cylinder is heated at a constant rate of H cal/sec and if the rise of temperature at the axis of the cylinder from time t1 to time t2 is θ2-θ1, the conductivity k of the medium is derived as _??_ provided that the radius of the cylinder is very small. Measurements are made electrically and the time needed for one observation is 1_??_30 min depending on the states of material used. Experiments were carried out for values of k ranging from 5×10-5 of air to 2×10-2 of Hg. By plotting θ vs ln t, and finding the minimum time tmin required for the relation to become linear, the thermal diffusivity K of the medium is found for the product Ktmin assumes a constant value. Further, by measuring k and tmin for any given material, an estimation of its specific heat cp can be made by the relation K=k/ρcp where ρ is the density.
In view of the tensile strength of vulcanized rubber being the most important and universal measure in physical tests and also on the strength of acquired data on its distribution, a new method of quality control characterized by it is proposed. The asymptotic distribution of mean of two independent measurements of tensile strength being expressed by Hankel function of order zero and the distribution of difference of such two data becoming logistic, these characteristics have enabled the author to, establish the correct method of quality control for vulcanized rubber that is distinct from the customary three sigma method.