Abstract

In conventional methods, a physical system is considered more suitable for measurement purposes the greater its linearity is. However, purely linear converting systems are not available. The use of the linear features in the measurement process causes the drawbacks: systematic error due to nonlinear distortions, low signal-to-noise ratio, low measurement range, necessity to evaluate a great number of a priori parameters in order to obtain an absolute result, and low thermal stability because every a priori parameter itself has a temperature dependence. To exclude these drawbacks a method has been developed using nonlinearities in the base of displacements measuring process. The method is implemented using electretic, electrostatic, and photoelectric transducers. The contactless transducer is placed parallel to the surface of the object which displacements are measured. The transducer is driven to harmonic oscillations. Typical time intervals of the coded signal are measured. The object displacements are determined according to the changes of the typical time intervals. The method itself has no errors because approximations have been not made while deriving the relations. The source of errors is inaccurate registration of the start and end of the typical time intervals. The measurement is possible only if the physical system is nonlinear. The results of experimental investigations confirm the theoretical conclusions. The method allows one to increase measurement range significantly (for example, measurement range of the conventional capacitance meters is ∼10−2mm and in the proposed method measurement range using capacitance converter is about 1 mm).

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