SU1262308A1 - Force measuring device - Google Patents

Abstract

1. A DEVICE FOR MEASURING EFFORTS, containing a piezoelectric plate with jumpers on which electrodes are attached, connected to the measuring circuit, about which, in order to increase the sensitivity, the jumpers have the shape of a thinned plate sections formed by a recess filled in so that the thickness of the jumpers does not exceed half of the plate thickness, and the jumpers are offset one relative to another in the plane of the plate, as well as in thickness relative to the middle plane of the plate for a distance not less than half the thickness of its webs. 2. Device pop.1, differing in that the bridges are shifted in thickness relative to the median plane in opposite directions. (L $ i T1 Fi. /

Description

The invention relates to a measurement technique, namely, piezoelectric frequency sensors of mechanical quantities. Known piezoelectric frequency force sensors, containing two differential resonator with exciting electrodes, made in a plate made of a piezoelectric material, having a measuring circuit with a frequency output l. However, these devices do not have the necessary sensitivity. The closest to the invention in its technical essence is a device for measuring forces, comprising a piezoelectric plate with jumpers on which electrodes are applied, connected to measuring circuit 2. A disadvantage of the known device is the low value of the maximum useful change in the frequency of the resonators, limited by a relatively small margin of static stability of the plate design. As a result of a small value of the useful signal, the relative instability of the sensor, due, for example, to the effect of aging or a change in temperature, is unacceptably large, and the measurement accuracy is low. The purpose of the invention is to increase the sensitivity. The goal is achieved by the fact that in a device for measuring an overwhelming piezoelectric plate with jumpers on which electrodes are attached, connected to the measuring circuit, the jumpers have the shape of thinned plate sections formed by a recess, made in it so that the thickness of the jumpers does not exceed half of the plate thickness moreover, the bridges are displaced one relative to another in the plane of the plate, as well as over the thickness relative to the median plane of the plate by a distance of not less than half the thickness of the first mpki. Bridges can also be adjacent in thickness to the median plane in opposite directions. Figure 1 shows the proposed device, top view; in Fig.2, section A-A in Fig.1; figure 3 - se08-p; figure 1; in fig. 4 - deformation plots in the plates; Device contains a piezoelectric plate 1, in which jumpers 4 and 5 are formed by depressions 2 and 3. Couples of electrodes 6 and 7 connected to the measuring circuit are applied to the jumpers. The plate is fixed at the base of the sensor 8, and the measured force F acts on its edge. The device operates as follows. When exposed to the measured force F (in the direction indicated in Figures 2 and 3), the plate is subjected to transverse bending, in which the lower part of the plate is compressed and the upper part is stretched. If the tolqcin lintel does not exceed half the plate thickness, and the lintel is offset relative to the median plane of the plate over a distance of not less than half the lintel thickness, then (Fig. 4) it will either shrink completely as lintel 4 or stretch (lintel 5). As a result, the frequency of the resonator is either increased, as for the resonator formed by electrodes 6, or reduced - as for the resonator formed by electrodes 7. The resonant frequencies of the resonators are measured by the measuring circuit and the resonant frequencies of the oscillators are computed, which make up the differential circuit. Since the edges of the jumpers are rigidly clamped in the plate, the jumpers have a large margin of static stability, which helps to obtain the maximum values of the useful frequency deviation of the resonators and, consequently, improve the accuracy of the sensor, the proposed design also has high sensitivity, because when the plate is bent and, therefore, in bridges, large mechanical stresses arise. Due to the fact that the thickness of the bridges can be chosen to be very small, but not less than the thickness corresponding to the tensile strength of the material and the static stability of the bridges to compression, the stresses in them can be very large. Technologically, it is more convenient to make jumpers shifted to the same 12 (S230S

BOM direction. Therefore, in practice, both versions of the device can be used depending on the specific situation.

Compared with the known, the proposed technical solution makes it possible to increase the accuracy and sensitivity of the sensor by almost an order of magnitude.

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Claims (2)

1. DEVICE FOR MEASURING EFFORTS, containing a piezoelectric plate with jumpers, on which electrodes are applied, connected to the measuring circuit, which consists in the fact that, in order to increase the sensitivity, the jumpers are in the form of thinned sections of the plate formed by a recess made in so that the thickness of the jumpers does not exceed half the thickness of the plate, and the jumpers are offset one relative to the other in the plane of the plate, and also in thickness relative to the middle plane of the plate by a distance of not less than than half the thickness of the webs. 2. The device pop. 1, excellent. characterized in that the jumpers are offset in thickness relative to the middle plane in opposite directions.