MICROELECTRONIC AUTOGENERATOR DEVICES FOR MEASURING THE THICKNESS OF MATERIALS

Abstract

The main characteristics of devices for measuring the thickness of materials with a frequency output signal, the design of which is built on the basis of transistor structures with negative differential resistance, are proposed and investigated. Capacitors with rectangular and round covers act as the primary transducers for thickness measurement, which are passive elements of autogenerators, which simplifies the design of thickness measurement devices. Mathematical models of devices were developed based on the principle of converting the energy of a constant electric field into the energy of an alternating electric field, which made it possible to calculate the conversion functions and sensitivity of the devices without using the complex method of obtaining Kirchhoff equations from the equivalent circuits of transducers and their calculation by numerical methods on modern computers. It is shown that the main contribution to the change in the conversion functions and sensitivity is made by the change in the thickness of the measuring material, which causes a change in the equivalent capacity and negative differential resistance in the oscillating system of autogenerators, which, in turn, changes the output frequency of the devices. The sensitivity of thickness measuring devices varies from 0.4 kHz/μm to 1.775 kHz/μm in the thickness range from 0 to 500 μm. The calculated analytical expressions of the conversion and sensitivity functions clearly demonstrate the influence of each element of the primary transducers and autogenerator elements on the output frequency of the devices. Devices for measuring thickness with a frequency output do not require analog-digital transducers and amplifiers for further processing of information signals, which makes the information and measurement equipment cheaper. When the devices work at ultra-high frequencies, it is possible to transmit information over a distance.