SU1186935A1 - Apparatus for testing thickness of dielectric coating on dielectric base - Google Patents

Abstract

1. DEVICE FOR THE CONTROL COATING THICKNESS DIELEKTRZHESKOGO dielectric substrate, soderlsaschee capacitive sensor as a dielectric base on which the high-potential and low-potential electrodes, made in the form of concentric coplanar rings mezvdu additional electrode which is placed tak that the initial capacitance between the high potential and the additional electrodes and between additional and low-potential electrodes are equal, the switch, the middle contact of which is connected to an additional electrode, and extreme contacts with high potential and low potential electrodes, a high frequency generator, a bridge circuit connected to it and a recorder, characterized in that, in order to improve the measurement accuracy, it is equipped with a reference capacitor included in one of the bridge circuit arms, the other arm of which includes low-potential and high-potential electrodes, a low-frequency generator, the output of which is connected to the control input of the switch, and series-connected amplifications a high frequency loop, the first synchronous detector whose reference input (A is connected to the output of the high frequency generator, and an information input to the output of the bridge circuit, a logarithmic converter, a low frequency amplifier and a second synchronous detector whose reference input is connected to the output of the low frequency generator, and the output is connected to the recorder input. 00 2. The device according to Claim 1, is a PN and is often equipped with a variable-capacitor capacitor connected between the additional and high-potential electrodes.

Description

one

The invention relates to a measurement technique and can be used to control the thickness of a dielectric coating applied to a dielectric substrate, such as paint and polymeric coatings on leather and textile materials.

The purpose of the invention is to increase the measurement accuracy.

The drawing shows a block diagram of a thickness control device.

The device contains a capacitive sensor in the form of a dielectric base 1, on which an potential-2, additional 3 and high-potential 4 electrodes are located, which in the working position touch a controlled dielectric coating 5 applied to the dielectric base 6, crossing: 71 electrode 3, and extreme contacts with piscopotential 2 and high potential 4 electrodes, a low-frequency generator 8, the output of which is connected to a control input of a switch tel 7, bridge circuit 9, one of the arms of which is connected to a low-potential 2 and high-potential 4 electrodes, a high-frequency generator 10 supplying the bridge circuit 9, a reference capacitor 11 connected to the shoulder of the bridge circuit 9 connected in series at the output of the bridge circuit 9 amplifier 12 high frequency, first synchronous detector 13, logarithmic converter 14, low frequency receiver 15, second synchronous detector 16 and a recorder 17. The device further comprises also a variable capacitor 18, included between

186935 .2

additional 3 and high-potential 5 electrodes.

The device works as follows.

5 Before starting work, a zero is set up with a standard thickness of the sensor applied to the coating with the aid of a variable capacitor 18. At the same time, the capacitances of the electrode systems are equalized by 2–3–3–4, ensuring an equal depth of sounding of the coating.

Switch 7, controlled by a low-frequency generator 8, commutes electrodes 2-4, in one of

The shoulders of the bridge circuit 9, in the other arm of which the reference capacitor 11 is connected. The bridge circuit 9 is powered by the high frequency generator 10.

20 In the position of the switch 7 indicated in the drawing, the electric field created by the sensor electrodes has a greater sounding depth. In the opposite position of ne "switch 7, the power lines of the electric field with a shallow depth of sounding are completely closed in the dielectric coating 5. At the output of the bridge circuit 9, high-frequency voltage packets are formed, which are alternately amplified by a high-frequency selective amplifier 12 and detected by a synchronous detector 13 resulting in video pulses

5, which are nonlinearly converted by a logarithmic converter 14, are amplified by a low-frequency selective amplifier 15, at the output of which a voltage is generated by the low envelope of the video pulses. The low frequency voltage from the output of amplifier 15 is detected by a synchronous detector 16, at the output of which a voltage is formed that is proportional to the deviation of the thickness of the monitored coating from the nominal.

Claims (2)

1. DEVICE FOR THICKNESS CONTROL OF A DIELECTRIC COATING ON A DIELECTRIC BASIS, containing a capacitive sensor in the form of a dielectric base, on which are located high-potential and low-potential electrodes made in the form of coplanar concentric rings, between which there is an additional additional potential electrode and between them electrodes and between the additional and low potential electrodes are equal, the switch, the middle contact of which is connected to the additional a high-frequency electrode, a bridge circuit connected to it and a recorder, characterized in that, in order to improve the measurement accuracy, it is equipped with a reference capacitor included in one of the arms of the bridge circuit, in the other arm of which low-potential and high-potential electrodes are included, a low-frequency generator, the output of which is connected to the control input of the switch, and a high-frequency amplifier connected in series the first synchronous detector, the reference input of which is connected to the output of the high-frequency generator, and the information input - to the output of the bridge circuit, a logarithmic converter, a low-frequency amplifier and a second synchronous detector, the reference input of which is connected to the output of the low-frequency generator, and the output is connected to the input of the registrar. 2. The device according to claim 1, characterized in that it is equipped with a variable capacitor’s capacitor connected between the additional high potential electrodes.