Abstract
Capacitive type displacement transducer has a number of advantages over the other types of displacement transducers; it is free from contact failure, simple in construction, etc.
But in general, in the use of capacitive transducer, some, disadvantage arises; it's sensitivity depends on source voltage and source frequency, and output frequency is high. Following technique of this transducer these disadvantages are eliminable.
This transducer has built-in oscillator which works with DC power source, and employs two capacitors whose capacitances change differentially. The transducer obtains a DC voltage in proportion to the difference between the two capacitance through its circuit employing diodes. At the same time, it obtains a DC voltage in proportion to the sum of two capacitance and negative feed back is performed so as to keep the sum constant. Thus the transducer is free from the effect of source voltage variation, frequency change, temperature change, etc., and very stable operation is assured.
Employing cylindrical differential air capactior, linear output voltage of the order of ±5.5V (2kΩ output impedance) is obtained for a variation of ±80 deg. angular displacement.
In this paper, principle, construction, circuit and characteristics of the transducer are described. Also some analysis of capacitance to DC conversion circuits are given.
