SU977935A1 - Two-layer dielectric material coating thickness gauge - Google Patents

Description

, (54) COATING THICKNESS METER. TWO-LAYER DIELECTRIC

one

The invention relates to a measuring technique and can be used to control the technological parameters of two-layer dielectric materials.

A device for monitoring technological parameters of two-layer dielectric materials is known, comprising two oscillators, a capacitive sensor, a mixer, a band-pass filter, and a frequency detector 1., d

A disadvantage of this device is the low measurement accuracy.

The closest in technical drying to the invention is a coating thickness gauge for two-layer dielectric materials containing a measuring and reference generator, a measuring capacitive sensor, a clock signal generator, a frequency modulator, the input of which is connected to the generator output of 20 clock signals, and the input of the reference generator, the mixer, the inputs of which are connected to the outputs of the measuring and reference generators. MATERIALS

a band-pass filter connected in series with the pulse output, a pulse shaper, a frequency detector, a selective amplifier, a synchronous detector, the reference input of which is connected to the output of the clock signal generator, and the output - to the control input of the measuring generator C2.

The disadvantage of this meter is the low measurement accuracy due to the presence of an error caused by destabilizing factors that alter the parameters of the primary converter and the channel for processing the measurement information.

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

This goal is achieved by the fact that the coating thickness gauge of two-layer dielectric materials containing a measuring and reference generator), measuring capacitive sensor, clock generator, frequency modulator, the input of which is connected to the output of the clock generator, and the output with control input of the reference generator, mixer, the inputs of which are connected to the outputs of the measuring and reference oscillators, serially connected to the output of the mixer., a band-pass filter, a pulse shaper, a frequency detector, A selective amplifier, a synchronous detector, the reference input of which is connected to the generator output of the CSC, and the output is connected to the control input of the measuring generator, is equipped with an exemplary capacitive sensor, the first switch, whose inputs are connected to the outputs of the measuring and reference, respectively capacitive sensors, and the output - with the input of the measuring generator, reversible counter, the counting input of which is connected to the output of the pulse former, phase inverter, the output of which is connected to the control input tchika, second commutator. the input is connected to the output of the clock signal generator, and the outputs, respectively, to the phase inverter input and to the control input of the counter, the part divider, the input of which is connected to the output of the clock signal generator, and the output to the control inputs of the switches, the strobe pulse generator The input is connected to the output of the frequency splitter, by a delay unit whose input is connected to the output of the strobe pulse former, and the output to the installation input of the counter, element I, the inputs of the coupling are connected respectively to the output of the counting output a and to the output of the strobe pulse, the decoder having an input for the key to output of AND and recorder whose input is connected to the output deschifratora. . The drawing shows a block diagram of the thickness gauge POK {N 1TIA. The meter contains measuring 1 and reference 2 generators, the first switch 3, the frequency modulator 4, measuring 5 and exemplary 6 capacitive sensors, a mixer 7, whose inputs are connected to the outputs of the generators 1 and 2, the generator 8 clock signals, a band-pass filter 9 connected to output of the mixer 7, frequency divider 10, pulse shaper 11, turned on at the output of bandpass filter 9, second switch 12, phase inverter 13, strobe pulse shaper 14, the input of which is connected to the output of frequency divider 1O, frequency detector 15, reversing th counter 16, block 17 of the delay, the input of which is connected to the output of the driver 14, the element And 18, the selective amplifier 19, the synchronous detector 20 connected to the output of the amplifier: 19, the decoder 21, included at the output of the element 18, and the recorder 22, included at the output of the decalphator 21. The meter works as follows. The output signals from the measuring and reference oscillators 1 and 2 are fed to mixer 7. The output signal of the reference oscillator 2 is modulated by a square wave voltage from the frequency modulator 4. The frequency of the modulating voltage is equal to the frequency Si. given by the signal from the output of the generator 8 sync signals. At the same time, in the first half-period of frequency, the output signal of the reference generator 2 has a frequency response, and in the second half-period JT / Q (Jn. The frequency of the signal of the measuring generator 1 is determined by the parameters of capacitive sensors with the measured object and control sample, periodically connected to the frequency generating circuit of the measuring generator 1 The first switch 3 is controlled by a square-shaped signal, with divider 10, whose frequency is also set by the generator of 8 clock signals and is equal to 6Z / n, where r is an integer. In the first half-period of frequency C2 / P, The reference capacitive sensor 6 (correction mode) is connected, the frequency of the measuring generator 1 is m, and when the measuring capacitive sensor 5 is connected (measuring mode), the frequency of the measuring generator 1 is equal to 10. The parameters of the sensors and the frequency of the reference generator 2 are selected so that the measured object and the control sample and when introduced into the sensitivity zones of the respective sensors, the condition w (u), u) was preserved: |) U) 2. (I After mixing the output voltages of the generators 1 and 2 in the mixer 7 and isolating the difference frequency signal by the band-pass filter 9, the frequency-modulated voltage with the modulation frequency and the carrier frequencies uj, oo, and uJ, corresponding to the half-period of the modulating signal 31 / I and the signal (with the half-period Jn /), controlling the first switch 3 and setting the mode of the meter bots. Therefore, in the first half-37 (correction mode) the bandpass filter is allocated the frequency-modulated signal with carrier frequencies that are equal in the first half period of ШШШ is ujg and in the second half-period JT / U): u) 2- U). Accordingly, in the measurement mode (the second half period Jn /), the lowest frequency frequencies of the extracted frequency-modulated signal are equal in the first half period (L / U)) - U, and in the second half period / Q / V W ш 2 - u. I. At the output of the pulse former 11 pulses, which are simultaneously an amplitude limiter, eliminating the parasitic amplitude modulation of the signal, periodic sequences of pulse packets are transmitted. The frequency of the pulses in the packet (the duration of the J / Q packet), equal to the frequency of the input difference signal entering the given half-period y / yi, varies periodically (with the modulation frequency Q), alternately taking two within one sequence (one half-period Lp / S) the meanings are either shish or u). After the frequency-modulated voltage pulses are converted in the frequency detector 15, an amplitude-modulated voltage is generated at the output of the latter with a carrier frequency O. and an envelope frequency CZ / n. The amplitude of the carrier frequency signal will be proportional to the deviation of the difference frequency I d} in the correction mode (the first half-period In / и) and in the measurement mode, with luj- u. ) ((hey with - total detuning of clock 1W °) of measuring generator 1 with sample capacitive sensor 6 in the frequency-generating circuit, inserted by the parameters of the control sample and the additive component of the primary converter error: 5 - additional LO frequency detuning caused by connecting to the frequency-generating circuit of the measuring eh cocTHoro sensor 5 with the object to be measured and depending on the difference of the technological parameters of the object being measured and the control sample (u) u); 4 n is the frequency of measuring generator 1, corresponding on the frequency axis to a point symmetrical with respect to the frequencies uin and U9 of the reference generator 2. It is proposed that, in the absence of the object being measured and the control sample, the parameters of the measuring and exemplary capacitive sensors 5 and 6 are identical ( The sensors are made on the same substrate using the same technology and are connected in a differential scheme), and that under the influence of external factors (climatic conditions, etc.), changes in their parameters are equivalent. Amplified by a selective amplifier 19, tuned to a frequency and converting square-wave voltage into sinusoidal, the signal enters a synchronous 2O detector, to the input of which voltage is applied from the generator 8 frequency sync signals. Since the output of the synchronous detector 2O is connected to the control input of the measuring generator 1, the changes in the amplitude of the output signal of the detector - (having the form of packets of rectified semi-; waves Jin / C), proportional to the measured value A X, affect the frequency of the measuring generator 1, changing it in such a way that in both sexes of the Jin / Me period. (in both tacts of the meter) the conditions of the balance of the frequency generators 1 and 2 were fulfilled: LU - U} A tO-UJ U) - UJ, j-UJ with an accuracy of up to the error of non-compensation of the closed-loop system consisting of links 7, 9, 11, 15, 19, 20, 1. Moreover, the amount of non-compensation is proportional to the values of | сЛ | and (in the corresponding half-period Jn / 52. The measured technological parameter, proportional to the value of Aj (, it is determined, is based on ratios (2) and (3), as, |. || wsh | -1i. (b) .

A reversible counter 16, to the counting input of which a pulse frequency modulated signal is output from the output of the pulse generator II, performs the operations of calculating the value according to the algorithm given by (6), and the pulse packets periodically arrive at its counting input pazhtov;), the frequency of which in the first half period Jn / S is equal to y 1shi w, and in the second half period. or and). At the same time, the synchronizing signals from the generator 8 through the second switch 12, controlled by the frequency divider 10, arrive at the control input of the reversible counter 16, and the summation of pulses at the counting input occurs at the BbicoKOM level of the synchronization voltage, and the subtraction at a low.

In the first half period of jfil / I (the mode of

reaction) as a result of the alternation of the operations of addition and subtraction of pulses is numeric, the value of the code of the reversible counter will be equal to

. V (-).

and in the second half period of LP / I (measurement mode), the phase inverter 13 is connected to the output of the 8 sync signal generator and inversion of the control voltage occurs, i.e. the order of the summation and subtraction operations will change to the opposite, as a result of which the reading of the reversible counter changes by a value35

N.

In this case, the resulting output 7SOD reversible counter for a period of 2J / n / Si operation meter will be equal to 0

) - () V), (7)

g

and will not depend on the magnitude of the total detuning with /, which is determined 45 both by the parameters of the control sample and by the additive fault associated with the drift of the primary transducer and the forward path of amplification and separation of the measurement information.

As follows from the description of the operating modes of the reversible counter and the ratios (6) and (7), the unambiguous correspondence of the output code of the counter Nj (to the measured technological parameter q j {will be observed only under the condition

w (w, io) uj

u) (s, i.) h ujj, (8)

about

those. when the change in the frequency o) of the measuring generator 1 under the influence of the parameters of the measuring and exemplary capacitive sensors 5 and 6 with the object being measured and the test sample will be of the same sign. This condition is fulfilled with an appropriate selection of the parameters of the reference sample against which measurements are made.

At the end of the control pulse from the frequency divider Yu, the strobe pulse driver 14 outputs a signal allowing the information signal to pass from the output of the reversible counter 16 through the AND 18 element to the decoder 21 and, further, to the recorder 22. The display time of the measurement result is determined by a period of 2 L. n / S, and the rewriting time of the result from the output of the reversible counter 16 to the decoder 21 is determined by the delay time of block 17, after expiration of which the output signal from the strobe pulse generator 14, having passed the delay block 17, goes to. The installation input of the ram {syvnogo counter 16 and will transfer all its bits to the state. O. The counter width is determined by the maximum number of pulses arriving at its counting input for a period Jn /, and the value of the division coefficient n of the divider 1O, i.e., based on relation (7-), the size of the reverse count should be no less than magnitude

- X max c ;, to, to, s Ds-sh) -,

K-u;) f

For the sake of simplicity, the measurement result is n divided by a factor of twenty, which results in the transfer of a comma when reading the result. In addition, it is necessary to observe the condition that the frequency of the sync signals should be less than the frequency of the switched signals.

f - «5« min {u3 oj, uj, u).

To eliminate measurement error

associated with non-identical parameters

Claims (2)

Capacitive sensors are manufactured by pre-setting zero. The measured object and the control sample are derived from the sensitivity zones of the respective capacitive sensors and with the help of the tuning elements of the frequency-measuring circuits of the measuring 1 and reference 2 oscillators, the conditions for the balance of the oscillators (4) and (5) are satisfied. In this case, the frequencies of the measuring generator 1 will become equal to each other u); and the equality of the frequencies of the difference signals 1g., | (s - and UJn U) U) where uJ is the average value of the frequency of the difference signal allocated by the bandpass filter 9. Then, according to expression (7), the recorder 22 reads O Thus, the use in the measuring device of the closed structure of the analog path reduces the influence and stability of the forward channel of amplification and measurement information, and the introduction of a push-pull mode of operation with a coherent technological parameter in the digital part, realizing uyuschey operation subtracting additive was kshey error of the sum signal, makes it possible to increase the measurement accuracy. In addition, due to the alternation of the operations of summation and subtraction, as well as the inversion of the sequence of these operations between the correction and measurement cycles, the size of the reversible counter is reduced, while the specified accuracy can be achieved by increasing the division factor n of the frequency divider. The invention The measurer of the thickness of the coating of two-layer dielectric materials, containing measuring and reference generator pb1, measuring capacitive sensor, clock generator, frequency modulator, the input of which is connected to the output of the clock generator, and the output - reference input of the reference generator, mixer, inputs which are connected to the outputs of the measuring and reference generators, generators connected in series with the mixer output, a bandpass filter, a pulse shaper, a frequency detector, A booster amplifier, a synchronous detector, the reference input of which is connected to the output of a clock signal generator, and the output is connected to a control input of a measuring generator, characterized in that, in order to improve measurement accuracy, it is equipped with an exemplary capacitive sensor, the first switch, whose inputs are connected to the outputs according to the measuring and exemplary capacitive sensors, and the output - to the input of the measuring generator, reversible counter, the counting input of which is connected to the output of the pulse former, the phase inverter The output of which is connected to the control input of the counter, the second switch, the input of which is connected to the output of the clock signal generator, and the outputs corresponding to the input of the phase inverter and the control input of the counter, frequency divider, the input of which is connected to the output of the clock generator, and the output - to the control inputs of the switches, the strobe pulse shaper, whose input is connected to the output of the frequency divider, the delay unit, the input of which is connected to the output of the strobe pulse shaper, and the output to the installation ode counter, AND gate whose inputs are respectively connected to the output of the counter and to the output of the strobe pulse, the decoder having an input sub key K and the output of AND recorder whose input is connected to the output of the decoder. Sources of information taken into account in the examination 1. US Patent No. 4О48844, cl. G, O1 N 27/22, 1977. 2. USSR author's certificate for application No. 2868124 / 18-21 (ОО3151) Cl. G01N 27/22 (prototype).