SU1452953A1 - Azimuth transducer - Google Patents

Abstract

This invention relates to field geophysics. The goal is to increase accuracy by eliminating the effect on the measurement of the detuning azimuth and temperature drift of the parameters of the phase shifter. The converter contains sensor 1 with two differential flux-probes with orthogonal sensitivity axes, generator 2, frequency divider 3, switch 4, phase shifter 5, selective amplifier 6, time interval unit 7, and control unit 8. The latter has timeout counters and subcycles, logic elements, and a D-flip-flop. Block 7 contains a comparator and a D-trigger. To eliminate additive and multiplicative error of the converter, one of the inputs of the phase shifter 5 is connected in series to the outputs of sensor 1 and the common wire. The second input of the phase shifter 5 is supplied with the reference signal from oscillator 2. The output signal phase corresponds to the deviation of the signal levels of the flux probes of the sensor 1 to the reference signal level. In block 7, the phase value is converted into a pulse duration. The operation of the device is divided into sub-cycles controlled by block 8. In each sub-cycle, a phase measurement is carried out depending on the connection of the phase shifter 5 to the inputs of the switch 4. The result obtained by processing results in a magnetic azimuth value. The use of a converter allows to achieve high accuracy by eliminating the influence of detuning and temperature drift of the parameters of the phase shifter. 2 Il. I cl

Description

The invention relates to field geophysics and can be used as part of inclinometers to determine magnetic azimuth.

The aim of the invention is to improve accuracy by eliminating the influence on 5 the result of measuring the azimuth of detuning and temperature drift of the parameters of the phase shifter.

In FIG. 1 shows a block diagram of an azimuth converter; in FIG. 2 - jq implementation of functional blocks phase transformation of the output signal of the phase shifter becomes proportional to the angle of the slot.

The azimuth transducer contains a sine-cosine sensor 1, including two differential fluxgates 1 - 1 and 1-2 with orthogonal sensitivity axes, a generator 2 connected through a frequency divider 3 to the excitation circuits of the fluxgates 1 - 1 and 1-2, connected in series to the switch 4, phase shifter 5, selective amplifier 6 and block 7 time intervals, as well as control unit 8, the input of which is connected to the second output of generator 2, the first output is connected to the control input of block 7 time intervals, the second output is connected to the input of the switch 4. In this case, the first and second inputs of the switch 4 are connected to the signal outputs of the flux gates 1 - 1 and 1-2, and the third input is connected to the common wire of the circuit, the second output of the generator 2 is also connected to the second input of the phase shifter 5, the output of which is connected with selective amplifier 6.

The control unit 8 (Fig. 2) contains a time delay counter 9, a sub-cycle counter 10, logic elements 11, 14 and a ΰ-trigger 15. The time interval unit 7 (Fig. 2) consists of a comparator 16 and a D-trigger 17 forming a latitudinal -modulated pulses. Switch 4 is a multiplexer controlled by a digital code coming from a counter 10 of sub-cycles of control unit 8.

Consider the operation of a single RC phase shifter. The phase of its output signal v = arc + tf wRCjUjA-Uj)

U ^ wRCY-Ui ⁷ (1)

The phase shifter introduces a constant phase shift of 45 °, which should be attributed to the additive measurement error Δφι. In addition, when the phase shifter is detuned, equality (3) is not satisfied and an error appears with the additive and multiplicative components

Δφ2 = [θ, 5-0.5 dry (f - 45 ° J (wCAR + (с \ + coRAC-ERCAro), where AR, AC are the scatter of the phase shifter parameters caused by inaccurate tuning and temperature drifts;

Δω is the change in the frequency of the signals. From (5) it is seen that in order to increase the accuracy of converters with phase shifters, the following conditions must be fulfilled:

(6) where R and C are the nominal values of the elements of the phase shifter;

w is the circular frequency of the signals;

ί / ι, 0 ^ 2 are the amplitude values of the input signals.

If the latter produces a sine sensor, then they have the form

i.e., select temperature coefficients that are identical in magnitude but opposite in sign; the equality Δω = 0 implies stabilization of the signal frequency. The need to fulfill the above conditions is a significant drawback of the known devices.

One of the inputs of the phase shifter 5 is connected in series to the outputs of the sine-cosine sensor 1 and to the common circuit wire, as a result of which the signal U \ takes the values U _n = U _m sintysin (i) t, U \ 2 = and ί / ₁₃ —0. The second input of the phase shifter 5 is supplied with a constant reference signal

U2 = Uo = Uo _m sin (at. (7)

As a result, the phase of the output signal takes values

U ί = U msin ^ sinwt ·, U 2 = U mCOS ^ SitWyt, where U _m is the maximum amplitude of the signals; f is the angle of rotation of the sensor element,

1 £> CR U from

U _om ^ CRf ~. - π 4 4 g / (^ CR {Uom). (ΰ \ ^? q ₀ ; (yy ^) ^ - & φ ⁷

Fz. ^ Aqs-ttf <aCR (UmCosA> + U orn), ⁴ i7 _om (wCR) ² —Ci ^ co5f (2)

If we now measure the values of the phase of the sigal, phase shifter 5 and find the differences (<p ₃ | -fzz), (fz2 - <rzz), then they will make

The obtained relations uniquely determine the angle of rotation of the sensitive element of the sine-cosine sensor 1, since

---, ^ (фз1 — фзз) / ₍₂₎ * tg (<P32- <f> 33) ', the result does not depend on the parameters of the phase shifter 5, and therefore, on their spread and drift, as well as on the frequency signals. The latter indicates that the phase shifter 5 may not be tuned, and the frequency of the signals vary widely, thereby increasing the accuracy of azimuth measurement.

In contrast to the known devices in which both signals of the sensor 1 are simultaneously fed to the inputs of the phase shifter 5, the signals of the sensor 1 are sequentially processed in the proposed converter using the same phase shifter 5, and service information about the current state of the parameters of the phase shifter 5 is additionally generated. it became possible by increasing the number of inputs of the switch 4 to three and connecting one of them with a common wire, which allows to obtain service information, as well as by introducing control unit 8, intended primarily for controlling a three-input switch 4.

The generator 2 generates a continuous periodic signal of a rectangular or sinusoidal shape.

The frequency of the main harmonic of the signal of the generator 2 is divided into two using a frequency divider 3. The latter generates a powerful signal, necessary for the excitation of flux gates 1 - 1 and 1-2. The flux gates 1–1 and 1-2 give polyharmonic signals, in the composition of which information harmonics are doubled with respect to the frequency excitation signal. Due to the use of a frequency divider 3, the frequency of the fundamental harmonic of the generator 2 coincides with the frequency of information harmonics of the signals of flux gates 1–1 and 1-2. The switch 4 alternately connects the signal windings of the flux gates 1 - 1 and 1 - 2 and the common wire of the circuit to the first input of the phase shifter 5. The phase shifter 5, to the second input of which the reference signal from the generator 2 is supplied, converts the ratios of the signal harmonics of the flux rods 1 - 1 and 1-2 to the level of the fundamental harmonic of the reference signal in the corresponding phase change. Using a selective amplifier 6, the main harmonic is extracted from the total signal of the phase shifter 5, thereby achieving the required quality of the information signal. In block 7 time intervals, the indicated phase changes of the information signal taken from the output of the selective amplifier 6 are transformed into pulse durations. The control unit 8, clocked by the signal of the generator 2, is designed to generate switching signals of the switch 4, the time delay necessary for the end of transient processes in the phase shifter 5 and the selective amplifier 6, as well as to control the time interval unit 7 in order to prevent information from reaching the output of the converter the passage of time of transients.

The operation process of the azimuth transducer consists of identical cycles, each of which is divided into three sub-cycles. In the first sub-cycle, the phase shifter 5 is connected to the signal winding of the flux gate 1 - 1 through the switch 4. the harmonic has the form U \ i - U (13) where U _m \ \ is the harmonic amplitude, and to the second input, the reference signal with the main harmonic of the form (7). The phase of the ω-harmonic at the output of the phase shifter · ^a,)

Using a selective amplifier 6 tuned to the frequency ω, the information harmonic is extracted from the polyharmonic signal at the output of the phase shifter 5. Therefore, a pure sinusoidal signal whose phase with respect to the phase of the main harmonic of the generator signal 2 <P1 = f )) + <₽6, c5) where φ ₆ is the phase shift introduced by the selective amplifier 6.

In a block of 7 time intervals, the phase shift (15) is converted into the pulse duration

At the same time, the output of the block of 7 time intervals, the pulse-width modulated pulses begin to arrive only with a certain delay time, which is formed by the control unit 8 and is necessary to complete the transients in the phase shifter 5 and the selective amplifier 6.

Then the second and third sub-cycles of the converter come, during which the first input of the phase shifter 5 is connected to the signal winding of the second flux gate 1-2 and the common circuit wire. The phase of the ω-harmonic at the output of the phase shifter takes the values ^ ^{= αΓίΙιι} υί ^^ ~ ^ακΙ ^ 'where U „, | ₂ - amplitude;

ω are harmonics in the composition of the signal of a flux gate 1-2.

At the output of the block of 7 time intervals, pulses appear, the durations of which respectively are ^{τ2 =} 360% / ^{φΐ2 + φΐ6); T1} “z8k ^(<P13 + ^%) · ^fe0)

After measuring the duration of the output pulses of the converter according to relations (16), (19) and (20) and processing the information in conditional codes according to algorithm (12), we obtain ψ = —ί? (<Ρι ι - <Ριз) ι ί £ (ψΐ2— ф1з) *

The angle ψ is uniquely determined by the ratio of the amplitudes of the information harmonics of the signals of the flux gates 1–1 and 1–2. Since the sensitivity axes of flux-gates are orthogonal and are set, for example, with movable coils and weights, in the horizontal plane, the amplitudes of information harmonics change according to the following laws;

U _m \\ = U _m sina., U _m \ 2 = U _m cosa, (22) where a is the magnetic azimuth,

U _m - the maximum swing of the levels of information harmonics. Consequently, φ = a, i.e., the result of measuring and processing information gives the value of magnetic azimuth.

Functional blocks of the azimuth transducer operate as follows.

The input of the time counter 9 of the control unit 8 receives a sequence of rectangular pulses from the generator 2. The counter 9 operates in the 'Continuous counting mode. He counts out every six pulses of the generator 2, thereby achieving a time delay. On the leading edge of every seventh pulse, state “1” is thrown through elements 11 and 12 and on the leading edge of every eighth pulse, it switches the Counter 10 sub-cycles, which, in its turn, opens the corresponding channel of switch 4. Trigger 15 is set to 6 state "1" the first pulse received at the input of the control unit 8 from the generator 2, as a result of which the first channel of the switch 4 is opened and this moment of time corresponds to the beginning of the operation cycle ⁵ of the converter. The comparator 16 captures the zero transition points of the sinusoidal output signal of the selective amplifier 6 and periodically resets the trigger 17 to the state "0". By the 10th time, the time difference between setting the trigger 17 to state “1” and its reset is proportional to the phase shift between the signal of the generator 2 and the signal of the selective amplifier 6. After the end of the third sub-cycle, the circuit through the logic'5 elements 13 and 14 is initialized .

The time intervals taken from the output of the converter are filled with pulses from an external high frequency generator and are converted into proportional digital codes. Processing of measuring information according to algorithm (21) is performed using a specialized computing device based on a microprocessor or in a mini-computer of a logging laboratory25 (not shown).

The main advantage of the converter is the high accuracy of the final measurement result, which is achieved by completely eliminating the influence of detuning and temperature drift of the phase shifter parameters. The additive error (10) due to the principle of operation of the phase shifter 5 is automatically excluded, and at the same time, the additive error φ ₆ caused by the residual detuning of the selective amplifier 6 and the temperature drift of its parameters.

The principle of operation of the converter allows it to be used with other types of sensors. For example, when using a sine-cosine 40 transformer (SKT) instead of flux gates, the latter is connected directly to the generator 2, and the frequency divider 3 is excluded from the circuit. If the generator generates a sinusoidal signal, then the selective amplifier 6 is replaced by a simple linear amplifier ⁴⁵ , acting as a buffer stage. Thus, when using SKT, the converter circuit is greatly simplified.

Claims (1)

An azimuth transducer containing a sine-cosine sensor, including two orthogonal fluxgates, a generator, the first output of which is connected to a frequency divider55, a phase shifter, a switch, series-connected selective amplifier and a block of time intervals, characterized in that, in order to improve accuracy due to exclusion influence on the result of measuring the azimuth of detuning and temperature drift of the parameters of the phase shifter, it is equipped with a control unit, the first and second outputs of which are connected to the control inputs and, accordingly, a block of time intervals and a switch, the output of the frequency divider connected to the excitation inputs of the flux gates, the signal outputs of which are connected to the first and second inputs of the switch, the third input of which is connected to a common wire, the output of the switch is connected to the first input of the phase shifter, the output of which is connected to the input selective amplifier, the second input is connected to the second output of the generator and the input of the control unit.