SU1285394A1 - Method of determining difference of resonance frequencies of transducers - Google Patents

Abstract

The invention relates to the field of measuring the frequency of electrical oscillations. The goal is to increase the accuracy of determining small detuning. The method of determining the difference of the resonant frequencies of the sensors (D) is as follows. The high-frequency oscillations excite two resonant D, the voltage envelopes (VOLs) are selected, after which) T two time intervals and the detuning frequency D. The goal is achieved by differentiating the VLRs, after which the alternating voltage curve with two is obtained. extreme points corresponding to the points of maximum curvature of the resonance curve, the formation of time intervals is carried out at these points, and by measuring half a volume 1 at these intervals, the detuning frequency D is determined regardless of their good Nost. The description of the device that reproduces the method. The method allows to significantly reduce the measurement error of small values of the detuning frequency due to the elimination of the influence of the dead and the dead zone of the trigger operation at close to time trigger pulses and asymmetry of the limiting levels. in the amplifier of pulse formers, 2 Il. 00 sd b o 4:

Description

The invention relates to the field of measuring the frequency of electrical oscillations and can be used to determine the detuning of two resonant sensors.

The purpose of the invention is to increase the accuracy of measuring the frequency of small detuning of sensors by forming and measuring half the sum of two time intervals between the extreme points of the differentiated envelopes of the voltages of the resonant sensors when they are excited by a signal with a linearly varying frequency.

Fig. 1 shows time diagrams, in accordance with the essence of the method for determining the difference of the resonant frequencies of the sensors; Fig. 2 is a functional diagram of the device for implementing this method.

A device for measuring the resonant frequencies of the sensors (FIG. 2) contains high frequency oscillations re iepaTop 1, the modulation input of which is connected to the output of the frequency modulator 2, the output connected to the measuring 3 and the reference 4 resonant sensors, to the outputs of which serially connected amplitude are connected detectors 5 and 6, differentials 7 and 8 and amplifiers-formers 9 and 10, and distribution circuit P. Phase inverters 12 and 13 are connected to the middle points of the resistors, the outputs of which are connected to opposite ones the inputs of the triggers 14, 15. The same outputs of the triggers through the filters 16 and 17 of the lower frequencies are connected to the corresponding inputs of the adder 18, the output of which through the divider 19 is connected to the input of the indicator 20.

The essence of the method is as follows.

High frequency oscillations with a linearly varying frequency excite two resonant sensors. When the oscillation frequency enters the passband of the sensor, the envelope that repeats the shape of the resonant curve of the resonant sensor is separated at the output of the amplitude detector (Fig. 1, plot a). As the frequency further expands, the oscillations fall into the passband of another resonant sensor, and at the output of the amplitude detector, an envelope is produced, repeating

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the shape of the resonance curve of this sensor (figure 1, plot b).

After differentiating the voltage of the envelope, we obtain an alternating stress curve with two extreme points corresponding to the points of maximum curvature of the resonance curve (Fig. 1, plot b).

According to the frequency values corresponding to the extreme values of the curve after differentiation, two time intervals are formed. The first time interval is formed between the frequency L, corresponding to the maximum differentiated voltage envelope of the first resonant sensor and the minimum differentiated envelope of the second resonant sensor. I

By measuring the half-sum of the first and second time intervals, you can determine the frequency of the detuning of two resonant sensors, regardless of their quality factor.

The device works as follows.

The frequency of the high frequency oscillations of the oscillator 1 under the action of the control voltage of the frequency modulator 2 varies linearly from the minimum value to the maximum frequency value. When the oscillation frequency of the high-frequency generator 1 hits the bandwidth of the resonant sensors 3 and 4, bell-shaped pulses repeating the resonant curves of the sensors appear at the outputs of the first and second amplitude detectors 5 and 6. The pulse voltage is differentiated using differentiators 7 and 8 and it enters the input of the shaper amplifiers 9 and 10. From the outputs of the first and second shaper amplifiers 9 and 10, positive and negative pulses are associated with extreme values of differentiated coefficients. O voltages applied to the inputs of the distribution circuit 11.

Positive pulses that correspond to the maximum value of the voltage curve at the output of the differentiator 7 are transmitted to the input of the first phase inverter 12. Negative pulses, corresponding to the minimum value of the voltage curve at the output of the second differentiator 8, also arrive here.

Similarly, the input of the second phase inverter 13 passes through the distribution circuit 11 positive pulses, corresponding to the maximum value of the voltage curve at the output of the differentiator 7.

As a result, unipolar pulses are received to the first trigger (to its separating inputs) 14 through the first phase inverter 2, which correspond in time to opposite polarity pulses at one output of the distribution circuit 11. To the inputs of the second trigger 15, they go through the second phase inverter 13 unipolar pulses corresponding in time to opposite-polar pulses at another output of the I 1 distribution circuit. The duration of the pulses at the unit output of the trigger 14 is determined by the temporal (frequency) shift - fj (figure 1, plot c). The duration of the pulses at the unit output of the second flip-flop 15 is determined by the time shift (frequency shift) f - f (Fig. 1, plot g). The signals from the outputs of the first and second triggers are fed to the inputs of the corresponding low-pass filters, from which the voltage is constant, proportional to the pulse duration. t.sub.t and At are fed to the respective inputs of the adder 18, where they are added together. From the output of the adder 18, a signal proportional to the doubled frequency detuning of the measuring and reference resonant sensors goes to divider 19, where it is divided into two. As a result, the indicator 20 is given a signal proportional to the detuning frequency of the measurement and reference resonant sensors.

Obtaining all four extreme values of the differentiated envelopes over the period of the frequency sweep of the exciting oscillations allows, in comparison with the known method, to significantly reduce the measurement error of small values of

detuning taps due to the elimination of the impact of the dead zone of triggering at triggered impulses and asymmetry of levels, limiting the amplifiers of x-impulses to the amplifiers.

When an asymmetry of the array occurs in the amplifiers of the x-formers, the transition moments through the extreme point of the transformable stresses are shifted to opposite sides. The duration of the pulses at the outputs of both triggers is changed. However, the sum signal determining the voltage applied to the indicator remains unchanged.

Claims (1)

The invention The method of determining the difference of the resonant frequencies of the sensors, which consists in exciting resonant sensors with oscillations with a linearly varying frequency, detecting voltage envelopes, forming a temporal impedance between the maximums of the voltage envelopes the fact that, in order to improve the accuracy of determining small detunings, the allocated voltage envelopes differentiate, form the first The interval corresponding to the frequency difference of the maximum differentiated envelope voltage of the first resonant sensor and the minimum of the differentiated voltage envelope of the second resonant sensor forms the second time interval corresponding to the frequency difference of the maximum differentiated voltage envelope of the second resonant sensor and minimum of the differentiated envelope voltage of the second resonant sensor, and the time interval between the maxima of the voltage envelopes is formed as usummu first and second time slots.