SU651283A1 - Seismometer - Google Patents

Description

The invention relates to the field of geophysical instrumentation and, in particular, to seismometers.

A seismometer containing an inert mass suspended on the basis of a seismometer, a magnetoelectric transducer, a parametric transducer of vibrations acting on an inertial mass, and a measuring electronic circuit ij are known.

Its main disadvantage is that the expansion of the frequency range towards longer periods of seismic waves is achieved by increasing the inertial mass, the size of the seismometer, and the use of double differentiation in the feedback circuit. The latter method with a single (zhramennom razigareniya frequency range in the direction of large periods of M times leads to a loss of sensitivity of the seismometer N times 2 ..

The closest technical solution to the proposed seismometer is a seismometer seismic station

DS-BP, containing an inert mass suspended on the basis of a seismometer, a magnetically electroplating transducer, a paracetric inductive transducer of vibrations acting on an inertial mass, and a measuring bridge circuit with a key detector 3j. It has the following disadvantages. To extend the frequency response up to the period of seismic waves, the SO is adjusted for a mechanical period of 15-25 s, which is possible with dimensions of at least 7 «25O mm and a large master mass (weight over 2.5 kg, instrument weight 22 kg). When acted upon by feedback on acceleration, the seismometer extends its period to iOO c. At the same time, its sensitivity decreases by a factor of 25 to a value of 1.2 U V / m, which corresponds to a sensitivity of acceleration of 5g. The measuring bridge with a given sensitivity has a gain of 1 5OO. Further-

neck sensitivity increase due to amplification is impossible due to the noise of the inductive converter.

The purpose of the present invention is to increase the sensitivity of an Lree seismometer while simultaneously expanding the frequency range.

It is achieved due to the fact that two coaxially arranged contacts are inserted into the seismometer, one of which is fixed on the basis of the seismometer, and the second is rigidly connected with an inert mass,. with these contacts are included in the active arm of the measuring circuit, the output of the key detector of which through a resistor and a capacitor connected in parallel with the resistor is connected to the winding of the magnetoelectric transducer,

The drawing shows a block diagram of the proposed device.

Inert mass 1 is rigidly connected to contact 6 via lever 2. Lever 2 has a Vrashegg 3 axis. Inert mass is connected to the winding frame of a magnetoelectric converter 4, the end of which is connected via a 1R resistor and capacitor C to the output of the key detector of the measuring circuit 5. is located relative to the contact .6 and is fixed on the base of the seismometer 8. Contacts 6 and 7 are included in the active shoulder of the measuring bridge circuit 5, the mass of the seismometer is hung out to the horizontal equilibrium state by the spring 9.

The seismometer shown in the drawing is a vertical instrument that responds to oscillations in ver. ticking plane. A horizontal seismometer is simpler than a vertical one. There is no spring for weight. The mass hangs freely on the axis of rotation. All other elements of a horizontal seismic meter are the same as those of a vertical one.

The proposed seismometer works as follows.

When exposed to external vibration, the inertial mass moves relative to the base. As a result of the mass transfer, either the closure of the contacts of the pair 6–7 or their opening occurs. Depending on this, at the output of the bridge circuit 5 with the key detector, the maximum output voltage of positive or negative polarity appears. The voltage through the resistor R causes the current in the coil of the magnetoelectric transducer. The direction of this current is such that in the case of opening the contacts, the mass under the action of the current moves in the direction of the contact of the contacts 6 and 7 and vice versa; when closing the contacts moves in the direction of their opening. The oscillatory process near the contact continues continuously. Feedback received is analogous to mixing feedback. Under its influence, the frequency of mass oscillations rises to 5-2 O Hz. In order to quench the indicated oscillations, a capacitor C is introduced, which forms a differentiating cell with the active resistance of the winding of the magnetoelectric converter. Negative feedback is formed on the speed of movement of the mass, which dampens the oscillation. In the higher frequency region, the cell ceases to differentiate and vibrations with a microscopic amplitude occur at the frequency. Practically, the mass of the seismometer is motionless. At the output of the measuring bridge circuit 5, some effective voltage is established, the value of which is between the maximum, positive and negative voltages. This is due to the fact that the effective contact resistance of the Melsdu 6 and 7, which is formed during microvibration, balances to some extent the active bridge of the measuring circuit. The measuring bridge, in the absence of external oscillations, can be precisely balanced in a vertical seismometer using a trimmer weight or by changing the tension of the spring 9. For a horizontal seismometer, equilibration is achieved by adjusting the tilt of the instrument. With a balanced measuring bridge, the output voltage of the key detector is zero. With external oscillations or changes in gravity, the equilibrium is disturbed and a signal appears at the output of the seismometer, which is proportional to the external effect.

Claims (3)

A negative feedback through a resistor T provides automatic setting of the output voltage to the dynamic range of the seismometer, stabilization of the sensitivity and position of the mass of the seismometer, linearity of the output signal to an external effect, the possibility of simple adjustment using the resistor of the sensitivity of the cmometer. The sensitivity of the seismometer is determined by the ratio. where S is the sensitivity in volts per unit of acceleration} U is the center distance t gesture from the axis of rotation g is the contact point distance of a pair 6-7 from the axis of rotation DD is the mass of the mass Qf is the conversion factor of the contact converter per unit force. The coefficient is easily measured by applying a known force to the mass of the seismometer (for example, a calibrated load). For the seismometer, all known methods of calibration and frequency response are applicable. Testing the layout of the proposed seismometer gave the following results. .., Measured conversion factor Sf 2.5x1O, lN4; e-0,005ft. Calculations using the sensitivity formula give d -. This sensitivity was achieved when the measuring bridge was energized with a voltage of 6.3 V and a signal gain of only 4 times. At the same time, the measuring bridge operates in a pulsed mode of af-extractive saturation, which is a direct consequence of the operation of the contacts 6 and 7 of the yes and no states. Comparison of the proposed seismometer with a DS-BP seismometer shows that with greater sensitivity, the seismometer is reduced by a factor of 25, the maximum linear dimension is reduced by 3 times, the linear gain is replaced by the gain with amplitude saturation, and reduced by 400 times. With a similar linear amplification, the sensitivity of the seismometer can be increased to V /, which is an order of magnitude greater than the required sensitivity value for detecting tidal gravity waves of the Earth with a period of many hours. 36 Therefore, when the sensitivity of the proposed seismometer is increased, it becomes possible to significantly extend the frequency range in the direction of longer periods. Depending on the chosen sensitivity of the seismometer, it can be used for registering small ground accelerations of an object to record the speed of a soil or an object during one-time integration of the output voltage; for registration of displaced soil or object at double. integrating the output voltage to record changes in gravity. The output voltage of the proposed seismometer allows the use of any modern means of the registrar. Claims of the invention A seismometer containing an inert mass suspended on the basis of a seismometer, a magneto-electric converter, a parametric converter of accelerations acting on the inertial mass and a measuring bridge circuit with a key detector, in order to increase the sensitivity while simultaneously expanding the frequency range. Two coaxially arranged e} contacts are entered, one of which is fixed on the base of the seismometer, and the second is rigidly connected with an inertial mass, and The contacts are included in the active arm of the measuring bridge circuit, the output of the key detector of which is connected via a resistor and a capacitor connected in parallel with the resistor to the winding of the magnetoelectric converter. Sources of information taken into account during the examination 1. USSR Copyright Certificate 338869, in O1 V 1/18, 1972. 2.Sb. Apparatus and methods of seismometric observations in the USSR M., Science, 1974, p. 37-42. 3.Catalogue of geo ({) from chesky equipment. Seismic Station DS-Bp, vt. Ill, Institute of Physics of the USSR Academy of Sciences, Moscow, 1976.