CN103063274B - Piezoelectric transducer downhole liquid level measuring instrument - Google Patents

Abstract

The invention relates to a downhole liquid level measuring device applied to oil exploitation operation process. A simple and easy system which integrates signal generation, acquisition and analysis is provided so as to directly utilize a high-power ultrasonic probe. The technical scheme includes that a piezoelectric transducer downhole liquid level measuring instrument comprises a probe portion, a tunable frequency sinusoidal signal generating portion, a power amplification portion, a peak value detection portion and a phase difference detection portion, a tunable frequency sinusoidal wave generated by the tunable frequency signal generating portion is subjected to amplitude and power amplification, an ultrasonic signal subjected to power amplification is transmitted to a probe through a cable, the impedance of a piezoelectric transducer in the probe is changed, changed peak values of voltage and current signals are obtained through the peak value detection portion, the phase difference between the voltage and current signals is detected through the phase difference detection portion, and cased well liquid level positions are indicated through abrupt change of the phase difference. The piezoelectric transducer downhole liquid level measuring instrument is mainly applied to measurement of downhole liquid levels.

Description

Piezoelectric transducer downhole liquid level measuring instrument

Technical field

The present invention relates to the measuring equipment being applied to underground liquid level in petroleum recovery operations process, specifically, relate to piezoelectric transducer downhole liquid level measuring instrument.

Background technology

Piezoelectric transducer in atmosphere with liquid in time, its radiation load difference is very large, and namely the resonance frequency of transducer, resistance value, admittance circle difference are obvious.The large power supersonic probe made of multiple piezoelectric transducer is usually used in oil well operation, and the tamper in dredging stratum, improves the penetrating power on stratum.When these probes are gone into the well, technician wishes dynamically to understand the degree of depth residing for probe and stratum by instrument and equipment, again can the position of liquid level in measuring unit pipe well.Utilize the piezoelectric transducer feature that radiation impedance difference is very large in air and liquid, invent underground liquid level measuring system.

At present, domestic many colleges and universities and enterprise have carried out large quantifier elimination to well depth survey, also achieve a lot of achievement.The Guan Jishi of such as Jilin University, in its master's thesis " development of high precision well temperature well-depth measuring instrument " (2006), well temperature-well-depth measuring instrument that to have developed with ARM embedded system be core, solve the problem that depth offset in traditional measurement is larger, improve measuring accuracy.By the position of liquid level in piezoelectric transducer measuring unit pipe well, research at home and product less, simultaneously external equipment is then relatively costly.Therefore, coordinate high-power ultrasonics operation, a kind of effective underground liquid level measuring method of research, and design is a kind of at a low price, sensitive, measuring system easily, to judging that ultrasound wave operation effectiveness will have major and immediate significance.

Summary of the invention

The present invention is intended to overcome the deficiencies in the prior art, directly utilizes large power supersonic to pop one's head in, and measures in the process that it is gone into the well to the liquid level degree of depth in well.There is provided a kind of simple system integrating signal generation, gather and analysis, when probe enters into liquid level, system indicates by reometer.For achieving the above object, the technical scheme of the bright employing of this Hair Fixer is, piezoelectric transducer downhole liquid level measuring instrument comprises five parts: probe, the sinusoidal signal generation of frequency-adjustable, power amplification, peakvalue's checking and phase difference detecting section; It is core that the signal generator of frequency-adjustable divides with integrated chip, and produce the sine wave of frequency-adjustable, frequency range is 10Hz ~ 50kHz; Ultrasonic signal after power amplification, after amplitude, power amplification, is sent to probe by cable by this sine wave; In the process that probe is gone into the well, when entering liquid level when popping one's head in from air, the piezoelectric transducer impedance in probe changes, and the voltage at probe two ends all changes with the current signal flowing through probe; The voltage of these changes, the peak value of current signal is obtained by peak detection section; The phase differential of voltage and current signal is detected by phase difference detecting section.Phase difference detecting section take multiplier as core, output after multiplier is direct current signal and the superposing of two frequency-doubled signals, by superposed signal through the process of RC integrating circuit, the phase differential of direct current signal can be obtained, this phase differential exports eventually through reometer, carrys out indicating sleeve pipe well liquid level position with its sudden change.

Power amplifying part comprises enlarge leadingly and class AB dual power supply mutual symmetry power amplification two parts, the main element of pre-amplification circuit is current feedback amplifier, class AB dual power supply complementary symmetry circuit is formed primarily of triode Q1, Q2, diode D2 and D3, triode Q1 and Q2 forms complementary output level, time static, the pressure drop of the upper generation of diode D2, D3 is that triode Q1, Q2 provide a suitable bias voltage, make it to be in lightly conducting state, when an input signal is present, at the positive half cycle of signal, Q1 conducting, Q2 ends; At the negative half period of signal, Q1 ends, Q2 conducting.

Peak detection circuit forms primarily of three parts: input end emitter follower, RC peak detection section and output terminal emitter follower; Input end emitter follower, output terminal emitter follower are formed by amplifier, access input signal by in-phase end, anti-phase termination feedback, between output terminal emitter follower amplifier and ground and the resistance connect, electric capacity form RC peak detection section.

Probe is large power supersonic probe, is made by 8 piezoelectric transducers, adopts parallel way, and each piezoelectric transducer is by three piezoelectric ceramic tube parallel connections, and radial inside and outside all Prestressings.

Technical characterstic of the present invention and effect:

The present invention is divided by the signal generator of frequency-adjustable, power amplifying part, peak detection section and phase difference detecting section structure, by the amplitude of measured voltage, current sinusoidal signal and the change detection liquid level position of phase differential, have structure simple, measure feature accurately.

Accompanying drawing explanation

The sine wave of Fig. 1 circuit evolving.

Fig. 2 (a) pops one's head in the voltage signal at two ends, and (b) flows through the current signal of probe.

Fig. 3 underground liquid level measuring system circuit board.

Fig. 4 underground liquid level measuring system device.

Fig. 5 underground liquid level measurement function structural drawing.

Fig. 6 Ultrasonic oil production and underground liquid level measuring system workflow schematic diagram.

Fig. 7 ICL8038 signal generator main circuit.

Fig. 8 power amplification circuit.

Fig. 9 peak detection circuit.

Figure 10 phase difference detecting circuit.

Figure 11 integrating circuit.

Figure 12 integrating circuit charging process.

Embodiment

Launch sinusoidal wave on ground to the piezoelectric transducer in underground probe by cable, by the voltage peak at measuring sonde two ends with flow through the current peak of probe and the phase differential of the two instruction probe and to go into the well state residing in process, namely probe is in a liquid or in atmosphere.The position that state changes is the liquid level of cased well.

Native system mainly comprises four parts: the signal generator of frequency-adjustable divides, power amplifying part, peak detection section and phase difference detecting section.The signal generator of frequency-adjustable divides with ICL8038 integrated chip for core, and produce the sine wave of frequency-adjustable, its frequency range is 10Hz ~ 50kHz, and bandwidth can cover the frequency of operation of most piezoelectric transducer.This sine wave is after power amplifying part, and amplitude and power are all exaggerated, by cable, the ultrasonic signal after power amplification is sent to probe.In the process that probe is gone into the well, when entering liquid level when popping one's head in from air, the load of the piezoelectric transducer in probe changes, because the density of air and acoustic velocity differ larger with liquid, the radiation impedance of piezoelectric transducer is caused to change, voltage and the current signal also corresponding change flowing through probe at two ends of at this moment popping one's head in.We obtain the peak value of voltage, current signal by peak detection section.Simultaneously by the phase difference detecting section of dephased for tool voltage, current signal input liquid level measuring system, this part with AD633 multiplier for core, output after multiplier calculates is the superposed signal of direct current signal and two frequency-doubled signals, by superposed signal through the process of RC integrating circuit, can obtain the phase differential into direct current signal, this phase differential indicates, at liquid level position eventually through reometer, phase differential is undergone mutation, and changes to another one numerical value from a numerical value.

The sine wave generated by ICL8038 as shown in Figure 1, the frequency-adjustable of this sine wave, range of adjustment is 10Hz ~ 50kHz, and the frequency of this figure is the resonance frequency (35.285kHz) of probe; Sinusoidal wave dutycycle is also adjustable, and this figure is 50%; In addition, the degree of distortion of this waveform is less, and peak-to-peak value is 3v.

Peak detection circuit output waveform is direct current signal, and Fig. 2 (a) is the voltage at probe two ends, and Fig. 2 (b) is for flowing through the electric current of probe.As can be known from the results, direct current signal size is equal with the peak value of AC signal.

Large power supersonic probe is made by 8 piezoelectric transducers, adopts parallel way.Each piezoelectric transducer is by three piezoelectric ceramic tube parallel connections, and radial inside and outside all Prestressings.

Phase difference detecting circuit output waveform is direct current signal, and table 1 gives the output of phase differential in 4 kinds of out of phase situations.Exporting size by contrasting the theoretical size that exports with actual, showing that phase difference error is less, illustrating that the measurement accuracy of this system is higher.

Table 1 AD633J exports data statistics

Fig. 3 is the circuit board of underground liquid level measuring system, and this main circuit will comprise five parts, respectively: signal generation divides, and power amplifying part, peak detection section, phase difference detecting section and disturbing signal amplifier section.Fig. 4 is underground liquid level measuring system device, and this system is under the prerequisite normally worked at main circuit, additional indicator current table, cabinet and Switching Power Supply.

Be described in detail below in conjunction with the research of accompanying drawing to underground liquid level measuring system of the present invention and method thereof.

The invention relates to the research of underground liquid level measuring system and method thereof, on the one hand, system self can produce the sinusoidal signal of frequency-adjustable, by peak detection circuit and the direct acquisition probe two ends of phase difference detecting circuit voltage and flow through the amplitude of electric current and the phase differential of probe, and then by the level condition of reometer instruction down-hole; On the other hand, add jumper cap in circuit, signal does not directly enter peak detection circuit and phase difference detecting circuit, but gather piezoelectric transducer both end voltage by capture card and flow through the electric current of probe, then peak value and the phase differential of signal is gone out by peakvalue's checking and phase difference detection process, finally, show these changes by computing machine, the degree of depth of the residing liquid level of instruction probe.

Be underground liquid level measurement function structural drawing as shown in Figure 5, the method realizing level gauging is:

Produce safety, stable sinusoidal ultrasound wave signal by ICL8038, the adjustable extent of its frequency is 10Hz ~ 50kHz.Before ultrasound wave operation, this signal is added on probe by special cable, pops one's head in and transfers in well by cable, and probe is in air dielectric before arriving liquid level always, and its radiation impedance is very large, and when entering liquid, radiation impedance diminishes.Because oil well is deep, cable long (usual 3000 meters), therefore, devises power amplifying part in systems in which, and this part can by power amplification to more than original 10 times, and the signal after power amplification gives probe by cable transmission again.

Be illustrated in figure 6 large power supersonic oil production equipment and underground liquid level measuring system workflow diagram, this system contains the major equipment needed for large power supersonic oil producing operation.The large power supersonic power supply that native system adopts produces control signal, namely consistent with piezoelectric transducer resonance frequency two-way batch (-type) high-frequency signal by STM32 single-chip microcomputer.The phase differential of this two paths of signals is 180 °, " Dead Time " is 3 μ s, control IGBT (the Insulated Gate Bipolar Transistor in large power supersonic power supply, i.e. insulated gate bipolar transistor) driving circuit, make the frequency of drive singal consistent with the resonance frequency of piezoelectric transducer, thus excite piezoelectric transducer to produce dither.The ultrasound wave of these dithers is by acting on porous formation after sleeve pipe, cement mantle, huge ultrasonic energy can reduce the viscosity of crude in porous formation, improve fluid barrier characteristics, improve crude oil flow velocity, increase the permeability on stratum, efficient solution, except the blocking on stratum, reaches the object improving oil well recovery ratio.Large power supersonic electric signal transmission to probe, because the electric power of transmission is larger, is generally adopted extraordinary single core coaxial cable by the cable in system.The piezoelectric transducer producing high-power vibrational energy in system adopts the mode of multiple piezoelectric ceramic tube parallel connection, these piezo tube need match use, namely adopted piezoelectric transducer need have identical or close resonance frequency, impedance and admittance circle, under the exciting of HF voltage, produce the vibration of amplitude peak, the vibrational energy of release peak power.The effect of petroleum casing pipe consolidates the borehole wall to prevent oil well from subsiding, isolate oil-water-layer.Analysis display section in system is the underground liquid level measuring system that Fig. 5 describes, and object of the present invention is exactly the function realizing this part---and collection signal also indicates underground liquid level situation by reometer.

One, the generation of sinusoidal signal

Sinusoidal signal of the present invention as shown in Figure 7 circuit produces.ICL8038 is a kind of integrated chip with accurate wave form output, and frequency-adjustable adjusting range is 10Hz ~ 50kHz, and the frequency of output waveform and dutycycle can be controlled by electric capacity or resistance.Basic parameter regulates mainly through pin 1, pin 4, pin 5, pin 8, pin 10 and pin 12.Wherein, pin 1 plays control action with the degree of distortion of pin 12 pairs of signals, as shown in Figure 7, and R ₁with WR ₁, R ₂with WR ₂regulate sinusoidal wave degree of distortion respectively, wherein R ₁with R ₂for 10k Ω fixed value resistance, WR ₁with WR ₂for 100k Ω potentiometer, regulator potentiometer size is about 82k Ω can obtain the less signal of degree of distortion.Duration of charging, the dutycycle of pin 4 and pin 5 pairs of signals play control action, as shown in Figure 7, and R ₄with R ₅be 3.3k Ω fixed value resistance, WR ₃for 1k Ω potentiometer, due to R ₄with R ₅actual resistance and out of true, so by regulate WR ₃improve the dutycycle of signal.The R be connected with pin 5 ₃for the large resistance of 15M Ω, this resistance contributes to the fluctuation reducing dutycycle.Pin 8 plays control action with the frequency of pin 10 pairs of signals, and wherein pin 8 pairs of frequencies play coarse adjustment effect, changes potentiometer WR ₄resistance get final product regulating frequency, electric capacity C herein ₁for electric capacity of voltage regulation.In addition, WR is regulated ₄change the input voltage between power supply+Vcc and pin 8, make highest frequency can reach f with the ratio of low-limit frequency _n/ f _l=1000: 1; Diode D, being reduce chip input voltage to the effect in circuit, makes it lower than the voltage of port 8.The frequency of pin 10 pairs of signals plays fine tuning effect, now frequency and electric capacity C ₂relevant, C ₂size affects the discharge and recharge time.

(1) charging current

I ₁size is by R ₄with WR ₃determine, I ₂size is by R ₅with WR ₃determining, for ease of calculating, supposing R ₄with WR ₃the resistance obtained of connecting is R _a, R ₅with WR ₃the resistance obtained of connecting is R _b.Then I ₁with I ₂computing method as follows:

$I_1=\frac{R_a}{R_a+R_b}\×\frac{(V_{+}-V_{-})}{R_A}=0.22\frac{(V_{+}-V_{-})}{R_A}=0.44\frac{\mathrm{Vcc}}{R_A}---\left(1\right)$

$I_2=\frac{2R_a}{R_a+R_b}\×\frac{(V_{+}-V_{-})}{R_B}-\frac{R_a}{R_a+R_b}\×\frac{(V_{+}-V_{-})}{R_A}=0.88\frac{\mathrm{Vcc}}{R_B}-0.44\frac{\mathrm{Vcc}}{R_A}---\left(2\right)$

Wherein R _a, R _bfor the embedded resistance of chip, its size is respectively 11k Ω, 39k Ω; V+=Vcc, V-=-Vcc.

(2) rise time t ₁with t fall time ₂

$t_1=\frac{C\×V}{I_1}=\frac{C\×\frac{2}{3}\mathrm{Vcc}}{0.44\frac{\mathrm{Vcc}}{R_A}}=\frac{R_A\×C}{0.66}---\left(3\right)$

$t_2=\frac{C\×V}{I_2}=\frac{C\×\frac{2}{3}\mathrm{Vcc}}{0.88\frac{\mathrm{Vcc}}{R_B}-0.44\frac{\mathrm{Vcc}}{R_A}}=\frac{R_A\×R_B\×C}{0.66(2R_A-R_B)}---\left(4\right)$

Dutycycle $D=\frac{t_1}{t_1+t_2}=(1-\frac{R_B}{2R_A})\×100\%,---\left(5\right)$

So, from analyzing above, work as R _a=R _btime, dutycycle is 50%.

(3) frequency f

$f=\frac{1}{t_1+t_2}=\frac{1}{\frac{R_A\×C}{0.66}(1+\frac{R_B}{2R_A-R_B})}=\frac{0.33(2R_A-R_B)}{{R_A}^2\×C}---\left(6\right)$

In like manner, R is worked as _a=R _btime, frequency

Two, the power amplification of signal

Power amplification circuit of the present invention as shown in Figure 8.This circuit comprises enlarge leadingly and class AB dual power supply mutual symmetry power amplification two parts.Enlarge leadingly part can improve the amplitude of sinusoidal signal and the stable of holding signal, and power amplifying part can improve the carrying load ability of power supply, makes signal can be sent to probe and is unlikely to be absorbed completely by cable.The main element of pre-amplification circuit is AD810AN current feedback amplifier, in Fig. 8, pin 3 place of U2 is the input signal of pre-amplification circuit, this signal is the sinusoidal signal SIN produced by signal generator ICL8038 in Fig. 7, and regulator potentiometer WR5, can change the output amplitude of signal.After amplifier AD810AN amplifies, pin 6 output voltage amplitude of U2 is the highest can up to+VCC_1.Class AB dual power supply complementary symmetry circuit is formed primarily of the components and parts such as Q1, Q2, D2 and D3, and compared with Class B dual power supply complementary symmetry circuit, this circuit can effectively overcome intermodulation distortion phenomenon.As shown in Figure 8, Q1 and Q2 forms complementary output level, and time static, the pressure drop of the upper generation of D2, D3 is that Q1, Q2 provide a suitable bias voltage, makes it to be in lightly conducting state.When an input signal is present, at the positive half cycle of signal, Q1 conducting, Q2 ends; At the negative half period of signal, Q1 ends, and Q2 conducting, so just can amplify the power of SIN signal.In circuit diagram 8, the model of triode Q1 and Q2 is respectively 2N3904 and 2N3906, and the two rated current that can bear is 200mA, effectively can improve the output power of signal, the carrying load ability of intensifier circuit.

Three, peakvalue's checking

Peak detection circuit of the present invention as shown in Figure 9.This circuit forms primarily of three parts: input end emitter follower, RC peak detection section and output terminal emitter follower.Wherein, emitter follower input impedance Ri → ∞, output impedance Ro → 0, can play good buffer action to signal, can be used as isolation level.U_in signal in Fig. 9 be probe two ends voltage signal, its acquisition mode has two kinds: (1) when the power of signal is lower, directly using the input signal of signal as peak detection circuit; (2) when the power of signal exceedes the rated power of operational amplifier, input circuit again after gathering by capture card.The voltage signal collected inputs from the pin 3 of operational amplifier U3A, and according to the short rule of the void of amplifier, pin 2 and the pin 3 of U3A have the signal of same amplitude and phase place; U3B is voltage follower, identical with on the voltage magnitude of pin 7 and electric capacity C9, R12 of the pin 6 of U3B.D4, D5, C9, R11 and R12 form peak detection section according to half-wave rectification principle.When input voltage U_in is greater than output voltage Peak_Uout, resistance R11 will produce pressure drop, electric current flows to the right from the left side of resistance R11.To break rule according to the void of amplifier, the pin 2 of U3A can not provide electric current, and D4 is because of reverse-biased and not conducting.Therefore, only have to maintain balance the voltage (being namely the voltage of electric capacity C9) promoting R11 right-hand member, charging current enters C9 and R12 from the pin 1 of U3A through D5.When input voltage U_in is less than output voltage Peak_Uout, resistance R11 will produce pressure drop, electric current flows to the left side from the right of resistance R11.In like manner, to break rule according to the void of amplifier, the pin 2 of U3A can not provide electric current, and electric current can only enter U3A through D4.Because voltage follower U3A output voltage is identical with the voltage on electric capacity C9, diode D5 ends, and electric capacity is not by D5 electric discharge, and voltage is protected.Electric capacity C9 has a discharge resistance R12, and composition RC circuit, discharge time constant τ=RC, calculates 100ms, if do not have pulse to come after 10S, discharges into voltage 0V.The direct current signal obtained can input current table, by size and the change thereof of indicator instructed voltage.

Flow through acquisition method and the peakvalue's checking principle of the current signal of probe, similar to the voltage at probe two ends, therefore no longer describe.

Four, phase difference detection

Phase difference detecting circuit of the present invention as shown in Figure 10.AD633 analog multiplier comprises two-pass DINSAR input X and Y, the summation input Z of high impedance.According to the chip handbook of AD633, exporting W can be expressed as:

$W=\frac{(X_1-X_2)(Y_1-Y_2)}{10V}+Z---\left(8\right)$

As shown in Figure 10, this part is with AD633 analog multiplier for core parts, and the power supply of chip is ± 12V, pin 5 and pin 8 corresponding positive voltage and the negative voltage respectively of chip.X ₁, Y ₁it is identical that two leads ends connect two-way frequency respectively, and phase differential is the AC signal of θ; X ₂, Y ₂, Z pin ground connection.If the voltage signal at piezoelectric transducer two ends is the U_in in Figure 10, make U_in=U for ease of understanding ₁, now U ₁=a cos ω t; The current signal flowing through transducer is the I_in in Figure 10, makes I_in=U for ease of understanding ₂, now U ₂=bcos (ω t+ θ).Regulate slide rheostat WR6 and WR7 respectively, U_in and I_in signal amplifies by operational amplifier U5, and now the pin 1 of U5 exports U respectively with pin 7 _a=Acos ω t, U _b=Bcos (ω t+ θ).By U _athe pin 1, U of input U6 (analog multiplier AD633) _bthe pin 3 of input U6, exports as multiplying signal from the pin 7 of U6:

$W=\frac{(X_1-X_2)(Y_1-Y_2)}{10}+Z=\frac{A\cos \mathrm{\ωt}\·B\cos (\mathrm{\ωt}+\mathrm{\θ})}{10}---\left(9\right)$

$=\frac{\mathrm{AB}\cos (2\mathrm{\ωt}+\mathrm{\θ})}{20}+\frac{\mathrm{AB}\cos \mathrm{\θ}}{20}---\left(10\right)$

From formula 10, the output signal of multiplier is the superposed signal of direct current signal and two frequency-doubled signals, and in order to indicate phase signal by reometer, we wish to obtain direct current signal by after two frequency-doubled signal process.So, by the integrating circuit process that superposed signal is formed through RC, as shown in figure 11, as long as the Selecting parameter of this integrator is suitable, just the superposed signal containing two frequency-doubled signals can be become direct current signal.This direct current signal is exported by the pin 11 of U7.

As shown in figure 12, the resistance R in Figure 11 integrating circuit is 1.5k Ω to the charging process of RC integrating circuit, and electric capacity C is that 22 μ F and 0.1 μ F are in parallel, so,

τ＝R(C ₁+C ₂)＝1.5×10 ³(22×10 ^-6+0.1×10 ^-6)≈33ms

U _ifrequency generally at 10kHz ~ 40kHz, so τ is much larger than U _icycle, so, multiplier export superposed signal after integrating circuit process, just can obtain direct current signal, i.e. direct current phase signal, its size is:

$W=\frac{\mathrm{AB}\cos \mathrm{\θ}}{10}---\left(11\right)$

When voltage and current homophase, namely during θ=0 °, then direct current signal is maximum, for when voltage-phase leading current phase place, namely during θ > 0 °, export as just; When voltage-phase leading current phase place, namely during θ < 0 °, exporting just is still; When voltage and current phase differential is 90 °, direct current signal is minimum value 0V.From formula 11, output signal and increase along with phase differential and reduce gradually.When output signal too small and be not enough to drive current list index swing time, make the output signal after the process of RC integrating circuit again through the operational amplifier U7B of adjustable gain, then output signal can regulate in the scope of 0v ~ 5v, thus there is the beat of pointer of enough power drive DC ammeter, and then judge phase place extent and liquid level variation tendency qualitatively.

The peak value of two reometer difference indicator currents and phase differential, there is no internal relation between the two, instruction be two different values, these two values are all independently measuring amount, electric current respectively and phase differential change, the change of the mould of electric current key reaction probe electrical impedance, the change of the imaginary part of phase differential reaction impedance, two is all judge liquid level position qualitatively.

Claims (4)

1. a piezoelectric transducer downhole liquid level measuring instrument, is characterized in that, comprises five parts: probe, the sinusoidal signal generating portion of frequency-adjustable, power amplifying part, peak detection section and phase difference detecting section; It is core that the signal generator of frequency-adjustable divides with integrated chip, and produce the sine wave of frequency-adjustable, frequency range is 10Hz ~ 50kHz; Sine wave signal after amplitude, power amplification, after amplitude, power amplification, is sent to probe by cable by this sine wave; In the process that probe is gone into the well, when entering liquid level when popping one's head in from air, the piezoelectric transducer impedance in probe changes, and the voltage at probe two ends all changes with the current signal flowing through probe; The voltage of these changes, the peak value of current signal is obtained by peak detection section; The phase differential of voltage and current signal is detected by phase difference detecting section; Phase difference detecting section take multiplier as core, output after multiplier is direct current signal and the superposing of two frequency-doubled signals, by superposed signal through the process of RC integrating circuit, the phase differential of direct current signal can be obtained, this peak value and phase differential export eventually through reometer, carry out indicating sleeve pipe well liquid level position with its sudden change.

2. a kind of piezoelectric transducer downhole liquid level measuring instrument as claimed in claim 1, it is characterized in that, power amplifying part comprises enlarge leadingly and class AB dual power supply mutual symmetry power amplification two parts, the main element of enlarge leadingly part is current feedback amplifier, class AB dual power supply mutual symmetry power amplifying part is primarily of triode Q1, Q2, diode D2 and D3 is formed, triode Q1 and Q2 forms complementary output level, time static, diode D2, the pressure drop of the upper generation of D3 is triode Q1, Q2 provides a suitable bias voltage, make it to be in lightly conducting state, when an input signal is present, at the positive half cycle of signal, Q1 conducting, Q2 ends, at the negative half period of signal, Q1 ends, Q2 conducting.

3. a kind of piezoelectric transducer downhole liquid level measuring instrument as claimed in claim 1, it is characterized in that, peak detection section forms primarily of three parts: input end emitter follower, RC peak detection section and output terminal emitter follower; Input end emitter follower, output terminal emitter follower are formed by amplifier, access input signal by in-phase end, anti-phase termination feedback, between output terminal emitter follower amplifier and ground and the resistance connect, electric capacity form RC peak detection section.

4. a kind of piezoelectric transducer downhole liquid level measuring instrument as claimed in claim 1, is characterized in that, probe is large power supersonic probe, made by 8 piezoelectric transducers, adopt parallel way, each piezoelectric transducer is by three piezoelectric ceramic tube parallel connections, and radial inside and outside all Prestressings.