In this paper, a simple and inexpensive low-frequency function generator is described. This instrument consists of a rotary functional pattern, a photo-tube, a direct current amplifier, a speed reduction mechanism and a cathode follower output circuit. A rotating acryl tube a functional wave form "pattern" modulates a narrow light beam towards the photo-tube. This instrument is capable of producing any functional wave form with ±1% accuracy in frequency covering the range from about 0.01 to 80cps several applications of this device other than as a function generator are also described.

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When a current flows through a piece of germanium crystal placed in a magnetic field, Hall electromotive force is developed at right angles both to the magnetic field and to the current. The magnitude of the electromotive force is proportional to sinθ, in which θ is an angle between the current and the magnetic field. We can make a mechanic-to-electric transducer applying the above principle. We can also make a similar transducer, changing the angle between the magnetic field and the direction of Hall leads. We adopted the arrangement by the latter method because we can make the narrowest magnetic pole gap or the strongest magnetic field. By combining the above arrangement and a pneumatic pressure transmitter, We made a pressure to-voltage transducer. It converts a pneumatic pressure (0-1.0kg/cm²) to voltage (0-10mV). Some characteristics of this transducer are as follows:
Hysteresis: less than 0.5per cent of full span. (mainly caused by mechanical parts of the transducer.)
Nonlinearity: less than 0.4per cent of full span.
Ambient temperature effect: almost independent if below 40°C.

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The cascade control system has been used for the purpose of improving the control quality of process. This system brings out better control results than by the single loop control system, especially when the process has a considerable transfer lag. The temperature-to-flow cascade control systems have been used in many processes such as in the temperature control of open hearth furnace. In some processes, however, the same unit cascade control (e.g. temperature-to-temperature) is more effective for vorious disturbances. Given in this paper is an example of simple electric cascade control systems for such processes.

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To make an experimental study on the stability in a precision workshop comparator, the authors as a trial made an electronic microcomparator with a differential transformer.
This device consists of a voltage detector of the differential transformer which produces a voltage that depends solely on the relative position between the coil and core, stand with anvil, oscillator of 3000c/s, amplifier, ammeter and recorder (Figs. 1 & 2). The meter of this device has fullscale readings of ±2μ, ±20μ and ±200μ. The corresponding divisions of the scale are of 0.1μ, 1μ and 10μ respectively, and the desired sensitivity in the scale reading can be obtained by operating the scale selector in the amplifier.
The comparator was designed basing on some preliminary experiments and has an accuracy of 0.5% of full-scale. Such a consistency in repeated readings and a high accuracy were obtained, because:
1) The zero voltage (residual voltage) at the balance position of the differential transformer was compensated into less than 10-6V using a suitable method for the comparator.
2) The B voltage regulator was compensated for the line voltage variation between 90 and 110 volts, and as a heater current source the battery floating method was employed (Figs. 11 & 12). Thus the amplifier became free of drift.
3) The temperature coefficient of frequency of the oscillator was kept under 10-5/deg.
4) The stand is made of normal and strongly ribbed cast iron for better rigidity.

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[in Japanese]

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