SU808840A1 - Device for measuring mechanical parameters - Google Patents

Description

one

The invention relates to the field of measuring mechanical parameters, such as mechanical stresses, displacements, pressures, accelerations, etc.

A device for measuring strain is known, comprising a piezoplast with two delay lines at surface acoustic waves and two exciters of acoustic waves, a frequency subtraction unit 1.

However, this device has a low signal stability due to the scattering of the acoustic wave at the ends of the piezoplates, which reduces the accuracy and sensitivity of the measurement.

It is also known a device for measuring mechanical parameters comprising a housing in which an elastic and sensing elements are placed, two exciters of acoustic waves placed at one end of an elastic element on either side of it two receivers of acoustic waves placed at the other end of an elastic element on both sides of him and opposite the corresponding causative agents of acoustic waves L2l.

However, this device does not provide a sufficiently high accuracy and sensitivity of measurement due to the relatively high rigidity of the structure of the elastic element.

The purpose of the invention is to improve the accuracy and sensitivity of measurement,

To achieve this goal, the elastic element is designed as an S-shaped piezoplate, the plate ends are fixed in the housing and on each of them are placed along the causative agent of acoustic waves. From him .

For convenience of adjustment, the device is equipped with an adjusting microscrew 0 mounted on the housing and connected to one of the ends of the piezo-plate.

The drawing shows a schematic diagram of the proposed device.

5 The device contains an elastic element in the form of an S-shaped pieoplast 1, at the ends of which exciters 2 and 3 of acoustic waves are marked, including identical emitters 4 and 5 of acoustic waves. and 7, the outputs of which are connected to the input of the frequency subtraction unit B. In the center of symmetry of the plate 1, the sensing element 9 is reinforced (for example, Maccaj inertia. On both sides of the sensing element 9 are placed receivers 10 and 11 of acoustic waves connected to the input of the detector 12 phase or amplitude differences. One of the ends of the plate 1 is fixed directly in the housing 13 and the other is connected with an adjusting micro-screw 14 on the one mounted on the housing 13.

The device works as follows.

In the absence of a measured signal at the sensing element 9, the amplitudes of the acoustic signals excited by oscillators 6 and 7 and radiators 10 and 11 are equal and, therefore, the output signal of the phase difference or amplitude detector is equal to zero.

When acting on the sensing element 9 of the parameter being measured, for example, the force F, both parts of the piezoplates 1 deform with different signs, i.e. one part is stretched and the other part is compressed. As a result, the symmetry of the plate 1 and the identity of the conditions for the passage of acoustic waves from emitters 4 and 5 to receivers 10 and 11 are violated. At the same time, the output of detector 12 is a signal

UU -2KMuiMlf) 2l n ntFl Z KpuRKplF),

where is the output voltage

detector 12;

К ,, Кц, ККР - respectively, the steepness coefficients of the transformation into the output voltage of the detector 12;

ufy (F) d ff (F) - respectively, changes in the resonant frequency of the emitters and receivers under the action of the measured parameter T

 change of the critical radius of curvature of the plate under the action of the measured parameter R.

The magnitude of the coefficient can be set abnormally high due to an abrupt change in the transmittance of the acoustic wave as the radius of curvature of the piezoplate approaches the acoustic waveguide to a critical value.

The sensitivity of the proposed device at the frequency output is

Afbbixn 2Uf HlFli ufn Fl fxlF)

dEDfc (F) is the change in the frequency of the emitters from the measured f impact due to a change in the impedance of the reflection of the acoustic wave-back into the emitters from the bent regions of the piezoplate;

Af and (P) and af (F), respectively, changes in the resonant frequency of the emitters and receivers

0from measurable exposure P;

 - output signal at the output of the frequency subtraction unit 8.

5 The proposed device for measuring mechanical parameters makes it possible to increase accuracy by reducing thermal error, and sensitivity by reducing the stiffness of the bone of an elastic element.

Claims (2)

1. A device for measuring mechanical parameters, comprising an elastic housing and a sensing element, two drivers and two acoustic wave receivers, characterized in that 0 to increase accuracy and sensitivity, the elastic element is designed as an S-shaped piezoplate, the ends of the plate are fixed in the housing and on each of them is placed along the pathogen 5 acoustic waves in the center of symmetry of the plate reinforced perceiving element, and the receivers of acoustic waves are located on both sides of it. Q 2. POP.1 device characterized in that it is provided with an adjusting micro-screw mounted on the housing and connected to one of the ends of the piezo-plate. Sources of information taken into account in the examination 1. US Patent I 3888115, cl. 73-88.5, 1975. 2. For France No. 2225719, cl. G 01 B 17/04. 1974. and flux.