Capacitance measuring devices recently have come into universal use as error detectors in automatic control systems for industrial purpose. Needless to say, the most important characteristics required in such type of devices are sensitivity and stability. These two requirements, however, usually run counter to each other. A meter of high sensitivity, when put under long continuous operation condition, will cause a zero drift in its indication which greatly impedes measurement, especially when it is impossible to check the zero point in such case as in process of operation.
Described in this paper are principle of a capacitance meter of high stability and sensitivity, and its some applications to measurements of small displacement and thickness variation of strip.

View full abstract

For accurate measurement of inductance and capacitance, an impedance bridge or a Q-eter has long been used. Each of them, however, is big in size, consumes much power and besides, is a little complicated in use.
The device described in this report is a transistorized precision inductance-apacitance meter which has several characteristics such as low power consumption, long life, easy handling, simple electrical circuit, etc. It consists of a square wave generator, delay circuit, and-gate, amplifier and indicator. Both of the branched square waves are fed to the and-gate, one directly and the other through the delay circuit which delays the time proportional to the value of inductance or capacitance to be measured. Then, pulse width modulated voltage can be obtained as the resultant output of the and-gate. Through such method of measurement, it is easy to keep errors within ±0.5% of the rated value.

View full abstract

On-off temperature controller described here is a modification of the controller whose electric contact is actuated by thermal expansion difference of a metal pipe and a quartz bar set in the pipe. If a part of the quartz bar is replaced by a metal pipe, the response of the inner pipe lags behind that of the outer pipe. Therefore, the expansion difference makes a proportional plus derivative action toward the ambient temperature.
In this controller, derivative action can be adjusted by changing the ratio of quartz length and inner pipe length, but in this case, proportional gain also changes as the ratio of lengths does. In order to adjust the derivative action without changing the gain, thermal resistance between outer and inner pipes is changed by inserting metal pipes of various lengths into the gap. Result of experiments shows a fairly good coincidence with theoretical calculation and accordingly, it seems to be applicable to designing.

View full abstract

In detecting the balance of the A.C. bridge, it is convenient if the unbalance voltage is indicated in the form of vector. An indicator of this type using vacuum tubes has been reported before. Described in this paper is a new type with some advantages as follows:
1) Smaller size by being transistorized.
2) High sensitivity by using transistor synchronous commutator.
3) No power supply source.
When this adapter is connected between the amplifier and C.R. oscilloscope containing d.c. amplifier, 3V output is gained from 0.2V signal voltage to the adapter at 24V reference voltage and this output is large enough for full spot movement on the C.R. tube.

View full abstract