SU1004896A1 - Thermoresonance converter - Google Patents

Description

The invention relates to electrical measuring equipment and can be used to measure the magnitude of an electric current or voltage.

A thermal resonance transducer containing an auto-oscillator is known, a piezocrystal with two circular excitation electrodes deposited on its opposite surfaces, provided with leads, which are included in the auto-oscillator's driver circuit, and two. resistive films of chromium, deposited around the perimeter of the Cll piezocrystal. The disadvantage of this converter is its low response time due to the thermal inertia of the "resonance converter".

The purpose of the invention is to increase the speed of the converter.

The goal is achieved by the fact that a thermal resonance transducer containing an oscillator, a piezocrystal with a resistive film on its surface and two excitation electrodes located on its opposite surfaces, the leads of the excitation electrodes are connected to the autogenerator, an additional electrode provided with a terminal and a blocking capacitor are added, This one of the main electrodes and the additional electrode are made in the form of segments bounded by parallel chords, their conclusions and resistive rectangular film connecting the segments rasplozheny a diametral plane perpendicular to the chords of the segments, a bypass capacitor is connected between the terminals of said electrodes and the resistive film is determined from the area ratios SK

30: n p

Zs is the area of the piezocrystal;

Where

Sn is the area of the resistive film. Figure 1 shows a piezocrystal with an electrode 1 and a resistive film deposited on it; Fig. 2 shows the connection circuit of a thermal resonance converter into the circuit of the measured current. A thermal resonance transducer contains a piezocrystal 1, on which, on one side, is applied - a circular main electrode 2, and on the second - a main electrode 3 and an additional electrode 4 interconnected by a resistive film 5, a main electrode 3 and an additional electrode

4 are equipped with terminals 6 and 7, and the main electrode 2 has a terminal 8. The terminals 6 and 7 are interconnected by a blocking capacitor 9.

Pins 7 and 8 are connected to the master circuit of the oscillator 10.

The device works as follows.

The oscillator 10 operates on the basis of a resonance of a piezocrystal 1. When connecting terminals 6 and 7 to the circuit in which the measurement is to be made, in the resistive film 5 there is a heat proportional to the square of the current flowing through it. Due to the fact that the area of the resistive film 5 is small compared to the area of piezocrystal 1, the release of heat in the resistive film 5 leads to a significant temperature gradient along the surface of the piezocrystal 1, which in turn causes the appearance of mechanical stresses in it. The latter lead to a change in the resonant frequency of the piezocrystal 1 and, therefore, of the autogenerator: torus 10.

The blocking capacitor 9 serves to increase the activity of the resonator by shorting the high frequency of the main electrode 3 and the additional electrode 4. The piezocrystal 1 can be AT or BT - cut, or a specially selected cut with maximum sensitivity to local heating.

In Figure 2, the points show the path of the passage of the excitation current, and the dotted line shows the path of the passage of the heating current or the measured current, the value of which is judged by the frequency change at the output of the oscillator 10. Thus, the speed increase in the proposed device is achieved by placing the heating element small area, in the center of the piezo crystal, where the sensitivity to

maximum temperature gradient. At the same time, the measurement does not require the establishment of a uniform temperature field in the volume of the piezocrystal, which significantly reduces the thermal inertia of the converter, which is proportional; (mass of the heated volume and inversely proportional to its thermal conductivity. The thermal resonance converter is very sensitive because of the sensitivity of the quartz resonators to mechanical voltages higher than temperature fluctuations.

Claims (1)

1. USSR author's certificate 279217, cl. B 06 L 1/06, 1970,