Takeo Saegusa

An RC Discharge Digital Capacitance Meter

A simple digital capacitance meter which utilizes the RC discharge is proposed and the wide range capability from 0.1 pF to 10 mF and the excellent linearity to ± (0.02 percent of reading + 1 digit) are shown. The RC discharge capacitance meter provides the capacitance to be measured at a frequency which is reciprocal to the product of the discharge resistance and the measured capacitance. Therefore, the meter can be used to test the frequency dependence of the capacitor even though the test signal is a dc voltage. The proposed RC Discharge Capacitance Meter can also be used in applications such as the measurement of the deviation from the preset value, or the torellance check of capacitance to make the GO or NO-GO decision by adding a few logic gates.

A self-balance-type capacitance-to-DC-voltage converter for measuring small capacitance

A simple self-balance-type capacitance-to-dc-voltage (CV) converter is proposed for the measurement of small capacitance. The balancing loop operates so as to drive the capacitor to be measured and the ac-dc converter, which is used to detect the signal corresponding to the capacitance, with an arbitrary constant voltage. Therefore, good conversion linearity can be expected. Using a prototype system, very good conversion linearity has been obtained in measuring small capacitance. The error has been estimated as less than ±0.1 percent when measuring a capacitance smaller than 100 pF. Also, a dispersion of less than ±0.001 pF and a temperature coefficient of less than +50 ppm/°C have been observed. These results show that the converter is convenient to operate in capacitive sensor applications.

A phase encoding method for improving the resolution and reliability of laser interferometers (displacement measurement)

An electronic method is proposed for improving the resolution and reliability of a laser interferometer commonly used for measuring displacement. By assigning code numbers to the divided segments of the interference fringe interval, the displacement of the moving device is measured with 1/170 of the lightwave length resolution (about 4 nm with He-Ne laser). Since the error caused by environmental noise is not integrated in the counting process, the measured values become more reliable than those of conventional pulse-counting methods. >

Digital Phase Meter Using Relative Counting A/D Conversion System

As an example of digital measuring system for improving the measuring processes, etc., the authors have developed and improved the phase meter using relative counting A/D conversion system, by measuring the duty factor of repetition pulse with arbitrary frequency. The digital phase meter with errors at most within 0.01 percent and 0.001 percent up to 10 Hz-100 kHz, about 0.1° at 1 MHz has been obtained by applying the theoretical and experimental investigations on it.

Wide-band digital tan-δ meter using a phase comparison system

The demand for precision in measurement of dielectric loss (tan δ), which is important to clarify the electrical characteristics of dielectrics of capacitors, etc., is increasingly becoming raised in level these days. The authors have published a direct-reading system of tan δ using the phase comparison method and developed a digital tan-δ meter based on the above. The next experiment was construction of a more compact sized all-electronic-type automatic digital tan-δ meter by using a MOSFET as the resistance element for the direct reading of tan δ. As the result of repeated investigations on the main circuits, an automatic digital tan-δ meter was successfully produced having a precision of 10-3- 10-4 at several 10 Hz-several 100 kHz.