SU51533A1 - Device for dynamic seismograph research - Google Patents

Description

In recent years, mining and exploration by seismic methods has gained a large scale and has acquired a significant national economic significance. Issues of so-called engineering seismic are no less important: the study of the efforts of machines and industrial buildings. For both of these purposes, various organizations make seismographs and labor meters in a fairly large number. A distinctive feature of the use of these devices in geological prospecting and engineering seismic is, firstly, at a relatively high frequency of the studied oscillations, reaching 50–100 lane / s, and secondly, in small amplitudes of oscillations, usually not exceeding several microns. As is well known, for any mechanical system consisting of a mass M suspended on some spring, the period of its own oscillations can be expressed in the form:

where D is the static elongation caused by the weight of the mass M. From this it follows that either a loose fitting or a spring is attached to the mechanism

a seismograph that permits a span, measured in fractions of a millimeter, can form an oscillating system with a period of the order of hundredths of a second, i.e., over a period and amplitude of one order with the oscillations under study. Therefore, the slightest defects in the assembly and as parts of the instrument lead to the appearance of parasitic oscillations that introduce distortions in the recording of the processes under study and affect the sensitivity of the instrument.

These features impose on the instruments used in these areas of seismology, special, very high requirements, leading to the need to develop a special technique for their study and testing both when accepting newly manufactured devices and periodically during the field work. It should also be added that, both in exploration seismic and engineering, research is carried out by simultaneously registering oscillations with a number of identical instruments located at different points, therefore the requirements of perfect identity of all instruments of one set are presented.

These investigations of devices should consist in removing 1) the frequency response — the dependence of the sensitivity of the instrument on frequency, 2) the amplitude response — the dependence of sensitivity on the amplitude of the specified oscillations at a constant frequency, and 3) the phase response — phase shift between the exciting oscillations and the recording of these oscillations at different frequencies. To remove these characteristics, a source of mechanical oscillations is needed — a vibrator that allows you to adjust the frequency while maintaining strict amplitude constancy, as well as adjust the amplitude at a constant frequency. The difficulty in constructing such an instrument is that in a mechanical vibrator it is almost impossible to avoid resonance effects, which lead to an inequality of amplitudes with a constant exciting force. In addition, the vibrator mechanism must be distinguished by simplicity and a small number of parts due to the parasitic oscillations mentioned above, which introduce unacceptable errors in measurements in the region of relatively high frequencies and small amplitudes. In particular, vibration platforms and tables used for the study of conventional long-period seismographs are not applicable here. The literature describes two techniques for studying such seismographs. (R. Koieg Z. f. Geophysik, 1932 No. 1-2) proposed to use a light, slightly eccentric wheel, the axis of which is placed in a frame rigidly attached to the mass of the seismograph. The wheel starts up like a top and, gradually stopped, sets the seismograph to a periodic excitation with a gradually decreasing frequency, which gives the complete frequency dependence curve during oscillography. The disadvantage of this method is the difficulty of obtaining the required frequencies (above 50-60 lane / s) and the high level of spurious oscillations. C. R, HeilandoM in Transactions of Lite. : lnst. of Min. and MetalL Eng. In 1934, a method adopted in American practice for the study of induction seismographs was described. It consists in a kind of reversal of the work of these seismographs, which are essentially converters of mechanical energy into electrical energy: their coils are supplied with a current of different power and frequency, which causes the moving mass of the seismograph to oscillate, recorded optically. This method is methodically erroneous, since it does not give a correct judgment about the operation of the device in normal conditions, it is very complicated and limited in its application only to induction seismographs.

The present invention aims to implement a device for the dynamic study of seismographs, largely free from the indicated disadvantages.

In the proposed apparatus, a leaf spring is applied to the oscilloscope to communicate with the seismograph, which is attached to the oscillation by two inductively coupled coils, connected one to the anode circuit of the anode and the other to the grid circuit, and forming a self-generating generator with this triode. oscillations of which are used to support mechanical oscillations of the spring.

The proposed device for the dynamic investigation of seismographs is illustrated in FIG. 1 of which a mechanical diagram of the device is shown, and FIG. 2 electric.

The device under study (seismograph) 7 and additional weight 2 are screwed to a rigid leaf spring 3 fixedly fixed at point 4. The distance between the attachment point of the device 7 and the load 2 from point 4 can vary, thereby changing the proper period of the oscillatory system formed by these parts. . The load 2 serves to reduce the reverse effect of the oscillations of the mass of the seismograph on the oscillations of the mechanical system / -2-3.

The limits of frequency variation are selected according to the range of frequencies required in the study.

Spring 3 carries the coil 6. The other coil 5 is fixed motionless against the coil b. One of the coils is connected to the input of the lamp-generating circuit, the other to the output of the same circuit, with a triode 7 forming a self-exciting system, which is ablated by the oscillating system / - 2-3. As the mechanical oscillations of the latter occur, due to the mutual movement of the coils 5 and b, the electric oscillations of the same frequency supported by the lamp circuit are created. Thus, stable oscillations are established with a frequency determined by the frequency of the mechanical system. By the property of self-excited lamp circuits, the amplitude of mechanical oscillations of coil b is automatically self-limited, and these amplitudes are kept constant at all frequencies, unless the amplification of the lamp circuit remains constant at these frequencies. Amplitude adjustment is performed by ycile regulation. Due to the small number of mechanical parts and their rigid connection, parasitic oscillations are minimized. Finally, the simplicity and compactness of the device allows them to be supplied with field surveys for periodically examining the devices, all the more so since the lamp scheme is similar to that shown in FIG. 2 is present in all batches in the form of a tuning fork generator supporting oscillations of a reference tuning fork used to mark the time.

The subject matter of the invention.

A device for dynamically examining seismographs, characterized in that the leaf spring to which the seismograph is attached is connected to a moving coil b freely entering the fixed coil 5, and one of the coils is connected to the anode circuit, and the other is connected to the circuit of the triode grid 7 , in order to maintain the mechanical oscillations of the seismograph with the help of stabilized electrical oscillations created in the self-excited generator, formed by coils 5 and b and triode 7.

fig 2