CN100451573C - Measuring circuit for measuring supersonic wave level meter transit time - Google Patents

Abstract

The utility model discloses a circuit for measuring the transmit time of a ultrasonic level transmitter, comprising a transmit power amplifying circuit module (5) and a echo amplifying comparison circuit module (6) and a FPGA module (7), which is characterized in that the utility model is embedded into a soft core microcontroller with field programmed gate array Cyclone EP1C6Q240,multiplies the input signal of low-frequency active crystal oscillator to 50MHz as the system clock with the phase locked loop and frequency multiplier circuit (The operation frequency of the whole FPGA system is 50 MHz), write ultrasonic transmitting control logic and ultrasonic receiving control logic with Verilog language. The measurement of ultrasonic transmitting time is realized by the FPGA hardware completely, so that the measuring resolution is improved to 20ns.

Description

Measure the metering circuit of supersonic wave level meter transit time

Technical field

The present invention relates to a kind of metering circuit of Measuring Time, relate in particular to a kind of metering circuit of measuring the supersonic wave level meter transit time.

Background technology

The measuring principle of supersonic liquid level/level meter is as follows: reflect (echo) after running into the measured matter phase interface by ultrasonic transducer (sensor) ultrasonic waves transmitted, measure ultrasonic transducer (sensor) trigger pulse constantly and the ultrasound wave echo of meeting tested liquid level/interface, thing position generation return due in; The difference in two moment is called " transit time " of ultrasonic measurement.By the transit time,, just can calculate tested liquid level/thing place value easily again according to the velocity of sound of sound wave in transmission medium.

Supersonic liquid level/level meter, the key that improves measuring accuracy is the accurate measurement of transit time.Present common employing single-chip microcomputer (microcontroller) adds the design and the implementation method of common timer conter, but because single-chip microcomputer operation clock upper limiting frequency is generally about 12 megahertzes, adopt the fastest interrupt mode to measure the transit time, and need software intervention in the measuring process, generally exist 3us above uncertain error.

In addition, the method that common employing is provided with flag-rod in the current measuring methods has realized the real-time measurement to the velocity of sound, the ratio of the transit time of phase interface and flag-rod transit time multiply by the flag-rod setting height(from bottom) and is the phase interface position, thereby eliminated the velocity of sound and be subjected to the influence of the variation of air themperature, density level gauging, suppose that the flag-rod setting height(from bottom) is S, the flag-rod transit time is t0, and the phase interface transit time is t, and then the distance L of phase interface and ultrasonic probe is:

L＝S*(t/t ₀)

Because it is that the velocity of sound is carried out temperature compensation that the velocity of sound is subjected to temperature, density, the pressure of propagation medium air to influence big general adoptable method, but the sonic velocity change that is caused by atmospheric density and pressure still there is not desirable compensation method, thereby when measuring, still exist certain error

Summary of the invention

The invention provides a kind of metering circuit that can improve the measurement supersonic wave level meter transit time of supersonic wave level meter Measurement Resolution.。

The present invention adopts following technical scheme:

A kind of metering circuit of measuring the supersonic wave level meter transit time, comprise that emissive power amplifying circuit module and echo amplification ratio are than circuit module, this metering circuit also comprises the FPGA module, this FPGA module is by soft nuclear micro controller module, ultrasonic emitting control module and ultrasound wave receive control module and form, the input end of clock of wherein soft nuclear micro controller module, the input end of clock that the input end of clock of ultrasonic emitting control module and ultrasound wave receive control module links together, the while input clock frequency, this clock frequency is not less than 50 megahertzes, the pulse control signal output terminal of soft nuclear micro controller module is connected with pulse emission commencing signal input end with the pulse control signal input end of ultrasonic emitting control module respectively with pulse emission commencing signal output terminal, the commencing signal of the pulse of soft nuclear micro controller module emission simultaneously output terminal is connected with the counting commencing signal input end that ultrasound wave receives control module, the wave detector opening time signalization output terminal of soft nuclear micro controller module selects signal output part to select signal input part to be connected with the wave detector opening time signalization input end of ultrasound wave reception control module with wave detector respectively with wave detector, the transit time count results output terminal that ultrasound wave receives control module is connected with the end signal input end with the transit time count results input end of soft nuclear micro controller module respectively with the end signal output terminal, the transponder pulse signal output part of ultrasonic emitting control module is connected with the transponder pulse signal input part of emissive power amplifying circuit module, the drive signal output terminal of emissive power amplifying circuit module is connected with the driving signal input of ultrasonic probe, the echoed signal output terminal of ultrasonic probe is connected with the echoed signal input end of echo amplification ratio than circuit module, the echo amplification ratio is connected than signal input part with the threshold ratio that ultrasound wave receives control module than signal output part than the threshold ratio of circuit module, the echo amplification ratio is connected with ultrasound wave reception control module zero passage comparison signal input end than the zero passage comparison signal output terminal of circuit module, wherein ultrasound wave reception control module is launched the enabling signal of commencing signal output terminal as internal counter with the pulse of soft nuclear micro controller module, the echo amplification ratio receives the stop signal of the ultrasonic echo timing module counter of control module inside as ultrasound wave after obtaining effective echoed signal after the detection of ultrasound wave reception control module than signal output part and zero passage comparison signal output terminal than the threshold ratio of circuit module, thereby obtain the count value of ultrasound wave transit time measurement, this module has realized selecting signal output part that the opening time that ultrasound wave receives the wave detector of control module inside is set respectively according to the wave detector opening time signalization output terminal and the wave detector of soft nuclear micro controller module simultaneously, thereby arrive the back in the time that is provided with different wave detectors is sent enable signal.

Compared with prior art, the present invention has following advantage: the present invention adopts field programmable gate array device FPGA (Field Programmed Gate Array) Cyclone EP1C6Q240 to embed soft nuclear microcontroller, adopt the frequency multiplication of phase locked loop circuit with the input signal frequency multiplication of the active crystal oscillator of low frequency to 50MHz as system clock, the running frequency of whole FPGA system is 50MHz, adopt the Verilog language to write ultrasonic emitting steering logic and ultrasound wave reception steering logic voluntarily, realize the measurement of ultrasound wave transit time fully by FPGA hardware, thereby Measurement Resolution is increased to 20ns.

Simultaneously, write the ultrasonic probe that the ultrasonic emitting control logic module can adapt to different transmission frequencies separately, the dirigibility of system is improved, this module is automatically with characteristic frequency output transponder pulse signal behind soft nuclear microcontroller output pulse emission commencing signal, system design has been simplified in intervention that need not soft nuclear microcontroller in the whole emission process.Ultrasound wave receives steering logic and is made of wave detector module and ultrasonic echo timing module, and each functions of modules is divided rationally, and layer of structure is clearly demarcated, is easy to realize that Module Design reuses.

Description of drawings

Fig. 1 is a FPGA system architecture diagram of the present invention.

Fig. 2 is the partial enlarged drawing of module 4 among Fig. 1.

Fig. 3 is the concrete enforcement circuit diagram of inner each module of FPGA of the present invention.

Fig. 4 is the design drawing of ultrasonic echo trapping module among the present invention.

Fig. 5 is the state transition diagram of ultrasonic echo trapping module among the present invention.

Fig. 6 is the measuring principle synoptic diagram of supersonic wave level meter.

Embodiment

A kind of metering circuit of measuring the supersonic wave level meter transit time, comprise that emissive power amplifying circuit module 5 and echo amplification ratio are than circuit module 6, this metering circuit also comprises FPGA module 7, this FPGA module 7 is by soft nuclear micro controller module 2, ultrasonic emitting control module 3 and ultrasound wave receive control module 4 and form, the input end of clock 21 of wherein soft nuclear micro controller module 2, the input end of clock 401 that the input end of clock 31 of ultrasonic emitting control module 3 and ultrasound wave receive control module 4 links together, the while input clock frequency, this clock frequency is not less than 50 megahertzes and is not higher than 200 megahertzes, the pulse control signal output terminal 22 of soft nuclear micro controller module 2 is connected with pulse emission commencing signal input end 33 with the pulse control signal input end 32 of ultrasonic emitting control module 3 respectively with pulse emission commencing signal output terminal 23, the commencing signal of the pulse of soft nuclear micro controller module 2 emission simultaneously output terminal 23 is connected with the counting commencing signal input end 402 that ultrasound wave receives control module 4, the wave detector opening time signalization output terminal 24 of soft nuclear micro controller module 2 selects signal output part 25 to select signal input part 403 to be connected with the wave detector opening time signalization input end 404 of ultrasound wave reception control module 4 with wave detector respectively with wave detector, the transit time count results output terminal 405 that ultrasound wave receives control module 4 is connected with end signal input end 27 with the transit time count results input end 26 of soft nuclear micro controller module 2 respectively with end signal output terminal 406, the transponder pulse signal output part 34 of ultrasonic emitting control module 3 is connected with the transponder pulse signal input part 51 of emissive power amplifying circuit module 5, the drive signal output terminal 52 of emissive power amplifying circuit module 5 is connected with the driving signal input 91 of ultrasonic probe 9, the echoed signal output terminal 92 of ultrasonic probe 9 is connected with the echoed signal input end 61 of echo amplification ratio than circuit module 6, the echo amplification ratio is connected than signal input part 407 with the threshold ratio that ultrasound wave receives control module 4 than signal output part 62 than the threshold ratio of circuit module 6, the echo amplification ratio is connected with ultrasound wave reception control module 4 zero passage comparison signal input ends 408 than the zero passage comparison signal output terminal 63 of circuit module 6, wherein ultrasound wave reception control module 4 is launched the enabling signal of commencing signal output terminal 23 as internal counter with the pulse of soft nuclear micro controller module 2, the echo amplification ratio receives the stop signal of the ultrasonic echo timing module counter of control module 4 inside as ultrasound wave after obtaining effective echoed signal after the wave detector detection of ultrasound wave reception control module 4 inside than signal output part 62 and zero passage comparison signal output terminal 63 than the threshold ratio of circuit module 6, thereby obtain the count value of ultrasound wave transit time measurement, this module has realized selecting signal output part 25 that the opening time that ultrasound wave receives the wave detector of control module 4 inside is set respectively according to the wave detector opening time signalization output terminal 24 and the wave detector of soft nuclear micro controller module 2 simultaneously, thereby arrive the back in the time that is provided with different wave detectors are sent enable signal, the asynchronous serial communication mouth input/output port 28 of soft nuclear micro controller module 2 is used for and other circuit communications.

Described clock frequency is generated by active crystal oscillator 8 and frequency multiplication of phase locked loop module 1, the clock signal output terminal 81 of active crystal oscillator 8 is connected with the clock signal input terminal 11 of frequency multiplication of phase locked loop module 1, by the signal output part 12 output system clock frequencies of frequency multiplication of phase locked loop module 1, be connected to the input end of clock 21 of soft nuclear micro controller module 2, the input end of clock 31 of ultrasonic emitting control module 3 and the input end of clock 401 that ultrasound wave receives control module 4.

Described ultrasound wave receives control module 4 by ultrasonic echo timing module 41, first detector module 42 and second detector module 43 are formed, the first enable signal output terminal 411 of ultrasonic echo timing module 41 is connected with the enable signal input end 421 of first detector module 42, the second enable signal output terminal 412 of ultrasonic echo timing module 41 is connected with the enable signal input end 431 of second detector module 43, the stop signal output terminal 422 of first detector module 42 is connected with the first stop signal input end 413 of ultrasonic echo timing module 41, the stop signal output terminal 432 of second detector module 43 is connected with the second stop signal input end 414 of ultrasonic echo timing module 41, simultaneously, ultrasound wave is received the input end of clock 415 of the input end of clock 401 of control module 4 as ultrasonic echo timing module 41, ultrasound wave is received the counting commencing signal input end 420 of the counting commencing signal input end 402 of control module 4 as ultrasonic echo timing module 41, ultrasound wave is received the wave detector opening time signalization input end 417 of the wave detector opening time signalization input end 404 of control module 4 as ultrasonic echo timing module 41, ultrasound wave is received the transit time count results output terminal 418 of the transit time count results output terminal 405 of control module 4 as ultrasonic echo timing module 41, the wave detector that ultrasound wave is received control module 4 selects signal input part 403 to select signal input part 416 as the wave detector of ultrasonic echo timing module 41, ultrasound wave is received the end signal output terminal 419 of the end signal output terminal 406 of control module 4 as ultrasonic echo timing module 41, the threshold ratio that ultrasound wave is received control module 4 than signal input part 407 simultaneously as the threshold ratio of first detector module 42 than the threshold ratio of signal input part 423 and second detector module 43 than signal input part 434, ultrasound wave is received the zero passage comparison signal input end 408 of control module 4 simultaneously as the zero passage comparison signal input end 424 of first detector module 42 and the zero passage comparison signal input end 433 of second detector module 43.

Described first detector module 42 and second detector module 43 constitute by two J-K flip flops, with the 3rd input end 1CLRN of 7473a module enable signal input end as the wave detector module, with the four-input terminal 1CLKn of 7473a module as the threshold ratio of wave detector module than signal input part, with the 8th input end 2CLKn of 7473a module zero passage comparison signal input end as the wave detector module, with the 3rd output terminal 2Q of 7473a module stop signal output terminal as the wave detector module, the first input end 1J port and the 5th input end 2J of 7473a module are met high level VCC, the second input end 1K port of 7473a module and the 6th input end 2K are met high electricity GND, with the first output terminal 1Q of 7473a module the 7th input end as the 7473a module.

Below in conjunction with accompanying drawing the principle of work of the present invention and the course of work are done concrete description:

In Fig. 1, frequency multiplication of phase locked loop module 1 is Altera general purpose I P storehouse, and the PLLIN signal is provided by external active crystal oscillator 8, frequency multiplication of phase locked loop module 1 with the PLLIN signal frequency multiplication to the system clock clk of 50MHz as FPGA.Soft nuclear microcontroller 2 is disposed according to the user by Altera SoPC Builder and generates soft nuclear microcontroller 2 by ultrasonic emitting steering logic 3 driving emissive power amplifying circuit modules 5, transmission frequency can be adjusted according to different ultrasonic probes, the transmission frequency of the probe that adopts in this example is 40KHz, soft nuclear microcontroller 2 is provided with according to the user, by output terminal da[0:4] write transponder pulse frequency values and pulse number to ultrasonic emitting module 3.After treating that soft nuclear microcontroller 2 output start transmit, to emissive power amplifying circuit module 5 output plus pulse signals, while start signal also inputs to ultrasonic echo timing module 41 and begins counting 3 beginnings of ultrasonic emitting module with characteristic frequency.Wherein the counting clock source of ultrasonic echo timing module 41 is the system clock of 50MHz, and number of counter bits is 32, and time sense is that 1 digit is 20ns.

After the ultrasonic echo signal is handled than circuit module 6 by the echo amplification ratio, obtain the input signal of first detector module 42 and second detector module 43: ultrasonic echo threshold value comparison signal cp1 and mistake zero balancing detection signal cp2.First detector module 42 and second detector module 43 adopt two J-K flip flops that cp1 and cp2 are judged, when this echo is caught enable signal when effective, it is effective that two signals must satisfy first threshold value comparison signal cp1, the effective condition of back zero passage comparison signal cp2, first detector module 42, second detector module 43 are judged as effective echoed signal at this moment, output useful signal stop to control echo timing module 41.Echo timing module 41 is saved to count results count among the register variable cnt after receiving useful signal.For difference acceptance criteria bar echo and liquid level/thing position echoed signal, first detector module 42 and second detector module 43 are provided with certain opening time respectively, effective by this module enable signal en of ultrasonic echo timing module 41 outputs after the opening time of a certain module arrives.Because the flag-rod setting height(from bottom) is 50cm, so first detector module 42 is arranged to import the effectively back 2.7ms unlatching of start signal, be used to catch the par echo as in this example, the count value that obtains thus is cnt1; Second detector module 43 is arranged to import the effectively back 4ms unlatching of start signal, is used to catch liquid level/thing position echo, and the count value that obtains thus is cnt2.Owing to all finish in the whole measurement count process, need not the program intervention of soft nuclear microcontroller, so the resolution that whole timekeeping system is measured is minimum time of day 20ns by the FPGA hardware circuit.

Soft nuclear microcontroller is by RS485 communication circuit module and main body instrument communication, after receiving the read data order of sending by the main body instrument, from ultrasonic echo timing module 41, read count value cnt1 and cnt2, and send this data with the RS485 communication mode to the main body instrument by the UART mouth.

In Fig. 3, when invalid, no matter how in1 and in2 signal change, it is low invalid that output signal out is always for low for the en signal; When en is high effectively the time, when if the effective change of input in1 becomes low level by high level, 1Q is set, and promptly 2CLRN becomes high invalidly, and this moment is when if input in2 effectively becomes low level by high level, 2Q is output as height, this moment, whole echo was caught submodule output signal out for effectively high, if input in2 is invalid, then the out signal still is low, do not have the effective ultrasonic wave echo to be hunted down, Fig. 4 provides the state transition diagram of this module correspondence.

In Fig. 5, the flag-rod setting height(from bottom) is S, obtains transit time t0 after the flag-rod echo 12 that ultrasonic probe 10 ultrasonic waves transmitted parts are formed by flag-rod 11 reflection backs is at first detected by FPGA; The measured object position echo 13 that another part ultrasound wave generates after the phase interface reflection detects and obtains transit time t, because the velocity of sound is constant in the measuring process, so the distance between phase interface and the ultrasonic probe is:

$L=S\&times;\frac{\mathrm{<figure-callout\; id="0"\; label="t\; t"\; filenames="C20071013209600161.png"\; state="\{\{state\}\}">t</figure-callout>}}{t_{}}.$

Claims (4)

1, a kind of metering circuit of measuring the supersonic wave level meter transit time, comprise that emissive power amplifying circuit module (5) and echo amplification ratio are than circuit module (6), it is characterized in that this metering circuit also comprises FPGA module (7), this FPGA module (7) is by soft nuclear micro controller module (2), ultrasonic emitting control module (3) and ultrasound wave receive control module (4) and form, the input end of clock (21) of wherein soft nuclear micro controller module (2), the input end of clock (401) that the input end of clock (31) of ultrasonic emitting control module (3) and ultrasound wave receive control module (4) links together, the while input clock frequency, this clock frequency is not less than 50 megahertzes, the pulse control signal output terminal (22) of soft nuclear micro controller module (2) is connected with the pulse control signal input end (32) of ultrasonic emitting control module (3), the pulse emission commencing signal output terminal (23) of soft nuclear micro controller module (2) is connected with the pulse emission commencing signal input end (33) of ultrasonic emitting control module (3), the pulse of soft nuclear micro controller module (2) emission commencing signal output terminal (23) is connected with the counting commencing signal input end (402) that ultrasound wave receives control module (4) simultaneously, the wave detector opening time signalization output terminal (24) of soft nuclear micro controller module (2) is connected with the wave detector opening time signalization input end (404) that ultrasound wave receives control module (4), the wave detector that the wave detector of soft nuclear micro controller module (2) selects signal output part (25) and ultrasound wave to receive control module (4) selects signal input part (403) to be connected, the transit time count results output terminal (405) that ultrasound wave receives control module (4) is connected with the transit time count results input end (26) of soft nuclear micro controller module (2), the end signal output terminal (406) that ultrasound wave receives control module (4) is connected with the end signal input end (27) of soft nuclear micro controller module (2), the transponder pulse signal output part (34) of ultrasonic emitting control module (3) is connected with the transponder pulse signal input part (51) of emissive power amplifying circuit module (5), the drive signal output terminal (52) of emissive power amplifying circuit module (5) is connected with the driving signal input (91) of ultrasonic probe (9), the echoed signal output terminal (92) of ultrasonic probe (9) is connected with the echoed signal input end (61) of echo amplification ratio than circuit module (6), the echo amplification ratio is connected than signal input part (407) with the threshold ratio that ultrasound wave receives control module (4) than signal output part (62) than the threshold ratio of circuit module (6), the echo amplification ratio is connected with ultrasound wave reception control module (4) zero passage comparison signal input end (408) than the zero passage comparison signal output terminal (63) of circuit module (6), wherein ultrasound wave reception control module (4) is launched the enabling signal of commencing signal output terminal (23) as internal counter with the pulse of soft nuclear micro controller module (2), the echo amplification ratio receives the stop signal of the inner ultrasonic echo timing module counter of control module (4) as ultrasound wave after obtaining effective echoed signal after the detection of ultrasound wave reception control module (4) than signal output part (62) and zero passage comparison signal output terminal (63) than the threshold ratio of circuit module (6), thereby obtain the count value of ultrasound wave transit time measurement, ultrasound wave reception control module (4) has realized selecting signal output part (25) that the opening time that ultrasound wave receives the inner wave detector of control module (4) is set respectively according to the wave detector opening time signalization output terminal (24) and the wave detector of soft nuclear micro controller module (2) simultaneously, thereby after the time that is provided with arrives different wave detectors is sent enable signal.

2, the metering circuit of measurement supersonic wave level meter transit time according to claim 1, it is characterized in that described clock frequency is generated by active crystal oscillator (8) and frequency multiplication of phase locked loop module (1), the clock signal output terminal (81) of active crystal oscillator (8) is connected with the clock signal input terminal (11) of frequency multiplication of phase locked loop module (1), by signal output part (12) the output system clock frequency of frequency multiplication of phase locked loop module (1), be connected to the input end of clock (21) of soft nuclear micro controller module (2), the input end of clock (31) of ultrasonic emitting control module (3) and ultrasound wave receive the input end of clock (401) of control module (4).

3, the metering circuit of measurement supersonic wave level meter transit time according to claim 1, it is characterized in that described ultrasound wave receives control module (4) by ultrasonic echo timing module (41), first detector module (42) and second detector module (43) are formed, the first enable signal output terminal (411) of ultrasonic echo timing module (41) is connected with the enable signal input end (421) of first detector module (42), the second enable signal output terminal (412) of ultrasonic echo timing module (41) is connected with the enable signal input end (431) of second detector module (43), the stop signal output terminal (422) of first detector module (42) is connected with the first stop signal input end (413) of ultrasonic echo timing module (41), the stop signal output terminal (432) of second detector module (43) is connected with the second stop signal input end (414) of ultrasonic echo timing module (41), simultaneously, ultrasound wave is received the input end of clock (415) of the input end of clock (401) of control module (4) as ultrasonic echo timing module (41), ultrasound wave is received the counting commencing signal input end (420) of the counting commencing signal input end (402) of control module (4) as ultrasonic echo timing module (41), ultrasound wave is received the wave detector opening time signalization input end (417) of the wave detector opening time signalization input end (404) of control module (4) as ultrasonic echo timing module (41), ultrasound wave is received the transit time count results output terminal (418) of the transit time count results output terminal (405) of control module (4) as ultrasonic echo timing module (41), the wave detector that ultrasound wave is received control module (4) selects signal input part (403) to select signal input part (416) as the wave detector of ultrasonic echo timing module (41), ultrasound wave is received the end signal output terminal (419) of the end signal output terminal (406) of control module (4) as ultrasonic echo timing module (41), the threshold ratio that ultrasound wave is received control module (4) than signal input part (407) simultaneously as the threshold ratio of first detector module (42) than the threshold ratio of signal input part (423) and second detector module (43) than signal input part (434), ultrasound wave is received the zero passage comparison signal input end (408) of control module (4) simultaneously as the zero passage comparison signal input end (424) of first detector module (42) and the zero passage comparison signal input end (433) of second detector module (43).

4, the metering circuit of measurement supersonic wave level meter transit time according to claim 2, it is characterized in that described first detector module (42) and second detector module (43) constitute by two J-K flip flops, with the 3rd input end 1CLRN of 7473a module enable signal input end as the wave detector module, with the four-input terminal 1CLKn of 747 3a modules as the threshold ratio of wave detector module than signal input part, with the 8th input end 2CLKn of 7473a module zero passage comparison signal input end as the wave detector module, with the 3rd output terminal 2Q of 7473a module stop signal output terminal as the wave detector module, the first input end 1J port and the 5th input end 2J of 7473a module are met high level VCC, the second input end 1K port and the 6th input end 2K of 7473a module are met high level GND, with the first output terminal 1Q of 7473a module the 7th input end as the 7473a module.

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