CN101464179A - Ultrasonic material level meter - Google Patents

Abstract

The invention provides an ultrasonic wave measuring device, wherein, a central processor of a mainframe drives a transducer to emit sound waves through an energy storage power automatic regulation circuit of an emitting unit and a matching circuit of a matching unit; and as the matching circuit ensures that the impedance output by the transducer is matched with the impedance output by the emitting unit, the maximum emissive power can be realized. An echo enters a front discharge circuit and a rear discharge circuit of an amplifying unit through the matching circuit, and then reaches a filter circuit of a filter unit and a wave shaping circuit of a wave shaping unit, and the wave shaping circuit of the wave shaping unit amplifies the echo signal in order to control noise. The delay sampling is adopted in the emission sampling subroutine, thereby solving the problem that the emitting part cannot take samples. The removal of part of the peak values, narrow pulses and DC components from an echo treatment subroutine can enable the echo data to be more accurate and stable. The treated digital signal is input by a D/A conversion chip of a D/A output unit into the central processor.

Description

Ultrasonic material level meter

Technical field

The present invention relates to the device of material position in the measuring vessel, relate to a kind of ultrasonic measuring device specifically.

Background technology

Adopting ultrasound wave to carry out level gauging is to utilize the acoustic reflection principle, avoids ultrasonic sensor directly to contact with medium, realizes non-cpntact measurement, thereby have advantage in solid granule, viscous medium, solid-liquid blending agent level gauging.The ultrasonic wave measuring method of present employing, based on echometric measurement, but since simple to echo identification, fail to remove interference wave, cause the lower or measurement instability of measuring accuracy.

Summary of the invention

The present invention is directed to the defective that existing supersonic wave level exists, propose a kind of employing high-performance hardware circuit and digital signal acquiring, treatment technology, reach measuring accuracy height, supersonic wave level device that measurement stability is good.

Technical solution of the present invention: a kind of ultrasonic material level meter, comprise transducer, it is characterized in that: ultrasonic material level meter comprises the main frame of software, the central processing unit of main frame (CPU) drives transducer emission sound wave by the accumulation of energy power auto-adjusting circuit of transmitter unit and the match circuit of matching unit, echo enters the discharge filtering circuit of Lu Zaijing filter unit of the preceding discharge road of amplifying unit and back through match circuit, the waveform shaping circuit of wave shaping unit enters the A/D sampling unit, send into central processing unit by the A/D conversion chip, adopt the time-delay sampling in emission sampling subroutine, reject the part peak value in the Echo Processing subroutine, burst pulse, DC component, the digital signal after the processing is exported through the D/A of D/A output unit conversion chip; On main frame, be provided with relay output circuit, house dog and man-machine interface key board unit.

The present invention compared with prior art owing to employing accumulation of energy power auto-adjusting circuit, and finishes transducer and transmitter unit output impedance coupling under match circuit cooperates, realize the emissive power of maximum.Echoed signal is handled through filtering circuit, increases echoed signal, suppresses noise.Emission sampling subroutine adopts the time-delay sampling in software design, has solved the problem that radiating portion can't be sampled, and rejects part peak value, burst pulse, DC component in the Echo Processing subroutine, makes echo data more accurate, stable.

Description of drawings

Fig. 1 is a ultrasonic material level meter theory diagram of the present invention

Fig. 2 is the accumulation of energy power auto-adjusting circuit block diagram of transmitter unit among Fig. 1

Fig. 3 is the match circuit block diagram of matching unit among Fig. 1

Fig. 4 is the amplifying circuit block diagram of amplifying unit among Fig. 1

Fig. 5 is the narrow band filter circuit block diagram of filter unit among Fig. 1

Embodiment: the structure and the principle of work that are described with reference to the accompanying drawings ultrasonic material level meter.

A kind of ultrasonic material level meter, be to constitute by main frame and transducer, Fig. 1 is a ultrasonic material level meter theory diagram of the present invention, the CUSS200 ultrasonic sensor of SENSE company is housed in transducer 4 housings, its frequency optimum traffic is 41kHz, investigative range can reach 20 meters, the transducer enclosure body is an organic glass, in fill with polyester, the acoustic energy window is the reinforced organic glass of epoxy resin, be characterized in noiseless, commercially available temperature sensor is housed in housing, the central processing unit of ultrasonic material level meter main frame (CPU) the 1st, the Philhps product is equipped with in CPU with the ultrasound wave of C51 language compilation and receives, send out timing control program, the emissive power control program, the measuring distance calculation procedure, io control program, serial communication programmer and keyboard display management program; Ultrasonic material level meter is the match circuit driving transducer 4 emission sound waves by the accumulation of energy power auto-adjusting circuit of transmitter unit 2 and matching unit 3, accumulation of energy power auto-adjusting circuit is seen Fig. 2, wherein mainly be that power tube Q3 and Q4 nominal voltage and nominal current should satisfy the circuit design requirement, so Q3 selects N slot field-effect transistor IRF642 for use, Q4 selects positive-negative-positive triode MJE2955T for use, match circuit is seen Fig. 3, it mainly is matching transformer, its technical parameter: turn ratio=1: 5, primary inductance=1.2mH, secondary inductance=22.3mH, magnetic core model: G22*13, under accumulation of energy power auto-adjusting circuit and match circuit cooperation, finish transducer and transmitter unit output impedance coupling, realize maximum emissive power.Ultrasonic reflections is returned transducer 4 when ultrasound wave arrives object, echo enters the preceding discharge road of amplifying unit 5 and the back road of discharging through match circuit, see Fig. 4, preceding discharge road and discharge road, back are formed by the low-pass filter amplifier of RC formation, this circuit has frequency selectivity, only amplify the signal that maximum frequency is 44.3kHz, every gain per stage is 10 times, echoed signal after the amplification is again through the filtering circuit of filter unit 6, see Fig. 5, this circuit utilizes the different of object echo and interference noise spectrum structure, and adopting narrow band filter is that frequency domain technique increases echoed signal, suppresses noise.The waveform shaping circuit that filtered echoed signal enters wave shaping unit 7 will exchange echoed signal and convert the direct current signal that can be the A/D sampling to, waveform shaping circuit adopts logarithmic amplifier AD8307, signal after the wave shaping enters A/D sampling unit 8, send into central processing unit 1 by MX7576 A/D conversion chip, because adopting transmitting-receiving closes-the type probe, x time rise to the received signal sampling only be the blind area time zero hour, in the blind area,, the existence of ring transmits owing to making, ringdown and target echo signal are got together together, be difficult to the true echoed signal of effective recognition, can't sample to radiating portion, the present invention adopts the time-delay sampling in emission sampling subroutine.The echo data of sampling is stored in the sampling storage unit, use the Echo Processing subroutine that data are handled, sampling beginning part has one section also bigger than echo strength peak value, directly influence determining of echo position, moreover because extraneous interference forms amplitude height, the narrow burst pulse of width in sampled data, in sampled data, comprise simultaneously a part of flip-flop, excessive DC component causes in follow-up processing easily overflows, and rejects peak value, burst pulse, DC component in the Echo Processing subroutine.For shortening program execution time, in the data pick-up subroutine, adopt and extract data every 5 points.In order to seek echo, in baseline generation subroutine, utilize extracted data with bigger then with the value replacement of previous point as if a back point from front to back than previous point, form the baseline of the trend that tapers off.Utilize to seek the echo subroutine, at first seek maximum amplitude, seek the valley point then forward, get its average amplitude, seek average point position in extracted data, this position is echo position and the echo strength that maximum amplitude and paddy amplitude are subtracted each other gained is write parameter.Extracted data extracts from sampled data, the position of echo in its average point position and the imprecise corresponding sample data, need in sampled data, to determine average point position according to the average in the extracted data, this point is considered as echo position, by calculating the echo time subroutine, according to the time of counting and putting interlude calculating echo of this point.The temperature value that at first provides with temperature sensor in the computed range subroutine is corrected the velocity of sound, correct the back according to the velocity of sound and echo time computed range, judge with echo strength and blind area whether echo and institute's calculated distance be effective at last, then will be zero if invalid apart from being changed to.Digital signal after the processing constitutes analog quantity output unit 9 outputs with electric isolation features via light lotus root 6N136, D/A conversion chip MAX543, electric current loop chip AD694JN, amplifier LM358.Be provided with relay and export 10 on central processing unit 1, the upper and lower limit that adopts two-way JE1AXN-DC12V-H type relay to finish material level is reported to the police and is exported, and relay output is controlled output after carrying out smoothly according to the control signal subroutine to signal.The house dog 11 that is provided with on central processing unit 1 is to guarantee the reliability service of central processing unit 1.Being set to of man-machine interface 12 realized exchanging of instrument and user, mainly comprise distance display, parameter shows, parameter setting, keyboard adopts the wired connection mode, adopt chip HD7279 to realize 20 button inputs and 4 LED Presentation Functions, its software program has the distance display subroutine, distance results to each measurement shows, this button subroutine is at first sent out and is read the key order to HD7292, then read the physics key assignments, at last the physics key assignments that reads is converted to virtual key assignments, in button processing subroutine, handle accordingly, finish the demonstration and the setting of parameter according to virtual key assignments.Software for communications portion mainly solve instrument synchronously, send character " 1 " by main frame during work, slave is launched avoiding simultaneously receiving the time-delay that character " 1 " carries out separately afterwards, messaging parameter is: baud rate 4800bps/s, 10 bit data.

Above-mentioned ultrasonic material level meter level gauging by software program control accurately and good stable arranged.

Claims (1)

1 one kinds of ultrasonic material level meters, comprise transducer, it is characterized in that: ultrasonic material level meter comprises the main frame of software, the central processing unit of main frame (CPU) drives transducer emission sound wave by the accumulation of energy power auto-adjusting circuit of transmitter unit and the match circuit of matching unit, echo enters the discharge filtering circuit of Lu Zaijing filter unit of the preceding discharge road of amplifying unit and back through match circuit, the waveform shaping circuit of wave shaping unit enters the A/D sampling unit, send into central processing unit by the A/D conversion chip, adopt the time-delay sampling in emission sampling subroutine, reject the part peak value in the Echo Processing subroutine, burst pulse, DC component, the digital signal after the processing is exported through the D/A of D/A output unit conversion chip; On main frame, be provided with relay output circuit, house dog and man-machine interface key board unit.

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