SU1117466A1 - Quartz force-sencing element - Google Patents

Abstract

A QUARTZ SENSITIVE ELEMENT, containing two cantilever quartz plates with electrodes, separated by spacers outside the active vibration zones, characterized in that, in order to increase its sensitivity, the electrodes are filled in the form of parallel combs with rectangular teeth and are located on the outer sides of the quartz plates the displacement of the teeth of the electrodes of one comb relative to the other, determined by the ratio Ж e 0,2. 0.8, where uE - the displacement of the teeth of the electrodes; E is the width of the teeth of the electrodes, and the distance between the teeth is greater than the specified maximum displacement, the ratio of the thickness of the gasket to the thickness of the quartz plate is selected from 0.1 to 1.0, and the ratio of the width of the teeth b of the electrode to its length is chosen from 0.2 to 1 , 0.

Description

This invention relates to a technique for measuring non-electric quantities, in particular, parameters of pressure, forces, etc.

A piezoelectric element for a differential frequency piezoelectric transducer is known, consisting of a piezoelectric two-resonator plate, one edge of which is rigidly fixed, and the other edge of the piezoelectric plate is located on a support and is somewhat supporting it, with the transverse force applied to this ledge in such a way that two acoustically developed piezoresonator located in areas with different curvature signs l.

However, this piezoelectric element has insufficient mechanical strength, since the action of force is transmitted to the working oscillation zones through a shoulder formed by a fragile piezoelectric plate.

The closest in technical essence to the present invention is a quartz force-sensitive piezoelectric element containing two cantilever-mounted quartz plates with electrodes separated by spacers outside the active vibration zones 2.

The effect of converting the applied force to the frequency is based on using only the strain sensitivity of quartz plates operating in bending, which limits the sensitivity of the sensor.

The purpose of the invention is to increase the sensitivity of the element.

 The goal is achieved by the fact that in a quartz force-sensitive element containing two cantilever-mounted quartz plates with electrodes separated by spacers outside the active oscillation zones, the electrodes are made in the form of parallel combs with square teeth and are located on the outer sides of the quartz plates with offset electrodes of the electrodes comb relative to another, defined by the ratio

de

0,2, 8,

where LE is the displacement of the teeth of the electrodes, t is the width of the teeth of the electrodes, the distance between the teeth being greater than the maximum displacement, the ratio of the thickness of the gasket to the thickness

quartz plate is selected in the range of 0.1-1.0, and the ratio of the width of the teeth of the electrode to its length is selected in the range of 0.2-1.0.

Fig. 1 shows the construction of the element, front view; figure 2 - the same, top view, fig.Z - the working position of the element under the action of effort, front view; figure 4 is the same, top view; FIG. 3 is a block diagram of a device for processing the output information of an element.

The quartz force-sensitive element consists of two quartz plates 1 with thickness fluctuations separated outside the active zones of vibrations by the pads 2. On the outer sides of the quartz plates 1 there are comb-shaped electrodes 3. The teeth of the upper electrode 4 are displaced relative to the teeth of the lower electrode 5. The quartz force-sensitive element is fixed console and connected to the multi-frequency oscillator 6, at the output of which frequencies are allocated, and 2; . In addition, FIG. 3 shows the execution of the information processing circuit in the form of filters 7, adders 8, generator 9 and mixer 10.

Quartz force-sensitive element works as follows.

In the initial state, the quartz plates 1 are separated by gaskets 2, and the gasket 2 on the free loose end of the quartz force-sensitive element is rigidly connected to the lower one in Fig. 1 by the quartz plate 1 and does not have a rigid connection to the upper plate 1.

Based on the sensitivity requirements, taking into account strain sensitivity and mass sensitivity, the value of the electrode teeth displacement is calculated, after which the plates 1 can be fixed. Electrodes 3 are connected to the multi-frequency oscillator 6, the output of which has signals with frequencies f, -, and.

in this case, the number of teeth of the electrodes is four. Each pair of teeth of the electrodes overlaps, forming four interelectrode spaces, indicated in Figures 2 and 4 by shaded areas. Each of these areas is 5,,.

It tj corresponds to a pair of resonant chrono Ots, 12 13, 14 21, 2d, 2 and 4. As a result of the influence of the measured force P, quartz plates are bent, which leads to a change in the displacements of the teeth of the electrodes E 2 4 and areas overlapped in the interelectrode spaces ( fig). The impact of the overlapping areas was chosen to be approximately the same 5, -52 (Fig. 2). In the result of the action of force P, the change of the indicated areas occurs so that 5, 4 Sj 5 5 (Fig.4). The change in the area leads to a change in the mass of the teeth of the electrodes, which causes a change in the frequency of generation. Each of these hours is ii- and I, 2; gets increments i, r; o ii; ir 3 n The 2iMulti-frequency signal from the output of the oscillator 6 is fed to filters 7, each of which is tuned to one of the frequencies i and 31. Signals with frequencies ii,, t, ,, 21 ijj, 2 are fed to two adders 8 frequencies, in which they are added. B; The adders 8 also provide signals of the frequency If of the oscillator 9, and. At the output of the adders 8, the signals of the difference frequencies p., Ip, f.io- -X it ,, are selected: -, uio,. r O, r1 1 l 1 where the components Jl & i and C ii 1 l Ui take into account the change in the oscillation frequencies caused by the quartz plates 1 strain gages 1:) At the output of the mixer 10, a difference frequency is selected that varies with the mass-sensitivity tensors quartz plates 1 with electrodes 3, F, „-L. -.- -2fr. i2n 1лхч 71лI From the analysis of relations (1), it follows that compared with the initial strength sensation. The strength of the quartz force-sensitive element due to the stress sensitivity. (4l, L 2h the introduction of distinctive signs led to an additional change in the frequency of LR, 2 was caused by mass sensitivity. The studies allowed ) Find the optimal solution for the proposed quartz force-sensitive element. In the best case, the relative displacement of the teeth of the electrodes is 0.5, the distance between the teeth of the electrodes is equal to their width, which practically excludes acoustic. Any connection between the resonators, the ratio of the thickness of the strip to the thickness of the quartz plate is 0.5J the ratio of the sides of the teeth of the electrodes is 0.4. Optimization of the proposed force-sensitive element was carried out according to two parameters, sensitivity and stable operation in a multi-frequency oscillator. With the marked construction parameters, the proposed element above is excited and stably operates in the multi-frequency mode, and the sensitivity increases approximately by 3-4 times. Quartz force-sensing element has two sets of limiting values of the design parameters indicated above. At the boundaries of these values, the quartz element either is unstable or does not detect the effect of mass sensitivity. The proposed quartz element has a higher sensitivity and linearity of the conversion characteristic, ensuring the latter is achieved by choosing the geometry of the teeth of the electrodes and their relative displacement during the measurement process. In addition, it is possible to obtain the desired shape of the conversion characteristic by changing or selecting the geometry of the teeth of the electrodes. The manufacturing complexity is reduced, since the electrodes are printed from only one cTipOH of each plate.

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FIG. five

Claims (2)

QUARTZ STRONG SENSITIVE ELEMENT, containing two cantilever -–. fastened quartz plates with electrodes separated by spacers outside the active vibration zones, characterized in that, in order to increase its sensitivity, the electrodes are made in the form of parallel combs with rectangular teeth and are located on the outer sides of the quartz plates with the displacement of the teeth of the electrodes of one comb relative to the other, defined ratio 0.2.6 60.8, where eE is the displacement of the teeth of the electrodes; 2 - the width of the teeth of the electrodes, and the distance between the teeth is greater than the specified maximum displacement, the ratio of the thickness of the strip to the thickness of the quartz plate is selected in the range of 0.1-1.0 and the ratio of the width of the teeth of the electrode to its length is selected in the range of 0.2-1.0 . SU »» 1117466>