SU1509770A1 - Device for operative calibration of seismic channels - Google Patents

Abstract

The invention relates to seismometry and can be used to calibrate recording channels during seismic and seismic surveys. The purpose of the invention is to improve the calibration accuracy, simplify the device and simplify operation. By introducing into the device a block of drivers and a source of symmetric bipolar stabilized constant voltage, as well as the use of the square wave generator and scaling circuit, the device is simplified, the synchronization of the supplied frequencies and high accuracy of measurement of the amplitudes of the input signals are ensured, which improves the accuracy of determining the amplitude-frequency characteristics up to 0.3 - 0.5%. 2 Il.

Description

The invention relates to seismometry and can be used to calibrate recorded channels in seismological and seismic surveys.

The purpose of the invention is to improve the accuracy, simplify the device and simplify the work with it.

FIG. 1 shows a block diagram of a calibration device; Fig, 2 - graphs of time diagrams of the device.

The device contains a seismometer 1 calibrated channel, connected to the recorder 2, the generator 3 meander connected to the scaling circuit 4 connected to the block 5 drivers, the source 6 of the symmetric bipolar

stabilized constant voltage, connected to the block of formers, and adder 7, connected to the outputs of the block of formers, the input of the accumulator is connected to the circuits of the calibration windings of the seismometers.

The scaling circuit has outputs 8-14, the driver unit has control 15-21 and potential inputs 22 and 23, as well as outputs 24-30, a stabilized voltage source has outputs 31 and 32, the adder has inputs 33-39, weight resistors 40 -46, scaling resistor 47, operational amplifier 48, as well as free outputs for connecting the same type of channels to be calibrated.

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Plot 49 shows the voltage at the output of generator 3, plots. 50-52, respectively, the voltage at the outputs 8–10 of the scaling circuit 4, g, graph 53, the voltage at the output of the Matopa 7, and curve 54, the response of the channel being calibrated at the output of the recorder 2.

The device works as follows:

From the output of the generator 3, a meander voltage is supplied with an amplitude sufficient to control the recalculation circuit 4. Its frequency is chosen such that 15 at the highest-frequency output 8 of the recalculation circuit, the frequency of the meander, f, ball, is greater than or equal to the upper limit frequency of the operating band amplitude-frequency response (AFC) 20 calibrated channel. At each postduction 9, 10 and t, d, recalculation -

g

The frequency of the meanders f and t, d, is two times less than the frequency of the signals, the number of frequencies calibrated is determined by the width of the -frequency range of the channel, for definiteness, a device is considered that allows calibration at seven frequencies.

The voltage at the outputs of the scaling circuit is unipolar, and its amplitude depends both on the supply voltage of the circuit and on the individual characteristics of the elements at the output of each variable cell, therefore the signal from each of the scoring circuit's outputs controls the corresponding shaper of the shaper unit 5 drivers Inputs 15-21. At the outputs of the formers, the negative amplitude of each square wave is equal in magnitude to the positive voltage and the source 6 of the stabilized voltage is supplied

adder 7, which through the weight resistors 40-46 are connected to the subtracting input of the operational amplifier 48, depending on the type of channel, the weight resistors have different values: for the seismograph, resistor 41 is more than 40 times 4, resistor 42 is 3 times more and t , d ;; for the volosigraph, the resistor 41 is 2 times the resistor 40 (), the resistor 42 is 2 times more than the resistor 41, and all resistors 40-46 are equal to d-accelerograph.

A scaling resistor 47 (R,) connected between the subtractive input and the output of the operational amplifier, the signal level at the output of the adder is set in such a way. so that the double response amplitude of the channel being calibrated is 0.75 - 0.85 of the maximum allowable output signal of the recorder.

After supplying voltage to the Calibrated channel input and termination of the transient process, which lasts (3-5) 1 / f f. , where f is the lower limiting frequency of the operating frequency response of the seismic channel, register m periods of the lowest frequency square wave (y = 10-12) required to calibrate this seismic channel. Typically, the frequency of the frequency meander f is chosen such that f p 6 f n, g the frequency of the pre-firing meander f „satisfies

 p- (ng | (- The recorded response is analyzed by Fourier only at the frequency of the c. meanders constituting the input signal, and determines the frequency response of the seismic channels at these frequencies by

From output 31 to potential input 22, and positive amplitude to negative voltage U applied from output 32. potential input 23, Since the output voltage of the stabilized source can be well adjusted and measured with a high-end digital voltmeter, the amplitudes of the output voltages of the meanders at the outputs 24-30 of the driver unit are also symmetrical and known with high accuracy,

From outputs 24-30 of the block of formers, meanders are fed to the inputs 33-39

45 formula

u (fj (u; iTu: T) W

Where 1:: K6p;

U (f, {) is the frequency response value at the frequency of the K-th square wave; (c) - 4 ′ modulus of the amplitude response spectrum at the frequency of the K-th meander;

h is the number of frequencies used to measure the frequency response;

m is the number of periods of the frequency fj in the analyzed response; :

 for accelerograph, for velocograph, for seismograph; W - constant coefficient

seismometer. tick seismometer

W

GSK Is

where, is the magnetoelectric constant of the calibration coil of the seismometer; Ry - total resistance in the circuit

calibration winding seismometer;

Ig is the reduced length of the tomb; Kg is the moment of inertia of the ticker. For reciprocating seismometer

W

-2fi &

Shd Rj.

where s

 - electromechanical coupling coefficient (KEMS) of the calibration coil of the seismometer;

Shd is the inertial mass of the seismometer.

Accurate measurement of input signal amplitudes using a high-end digital voltmeter, high input signal amplitude over time, synchronism of all applied frequencies, thus allowing the orthogonality condition to be accurately observed, can increase calibration accuracy to 0.3-0.5% and simplify the very process of performing an operational calibration of seismic channels, which makes it possible to effectively control the stability of the frequency response over time when conducting precision seismological observations,

Claims (1)

Invention Formula An on-line seismic channel calibration device containing a generator and an adder, the outputs of which are connected to the calibration winding circuits of calibrated channels seismometers, characterized in that, in order to improve calibration accuracy, simplify the device and simplify operation, a scaling circuit, driver unit and source are entered into the device symmetric bipolar stabilized constant voltage, and the generator is made in the form of a square wave generator, while the output of the square wave generator is connected to the input reschetnoy circuit, the outputs of which are connected to the control input of the unit, the positive and negative voltage inputs of which are connected respectively to the positive and negative outputs source symmetric bi-polar stabilized DC voltage, and outputs the block formers are respectively connected to the inputs of the adder. Thebes. 7 shlshshll lg one