Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
  • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters

Definitions

• the invention relates to a method and a device for detecting a malfunction such as fouling or aging of a flow meter comprising at least one transducer, also making it possible to generate a conditioned signal from an analog signal originating from of said transducer.
• ultrasonic flowmeters can be used in the field of measurement of fluid flow rate such as gas or water for example.
• fluid flow rate such as gas or water
• ultrasonic flowmeters can be used in the field of measurement of fluid flow rate such as gas or water.
• Such flow meters generally include two ultrasonic transducers arranged in a fluid flow. The transducers are used alternately as transmitter and receiver.
• one method like consists in exciting the transmitting transducer by means of an excitation pulse. This pulse will give rise to the emission by the transmitting transducer of an ultrasonic wave in the medium separating the two transducers. This wave will propagate towards the receiving transducer.
• the method consists in detecting the first oscillation of said wave as soon as it arrives on the receiving transducer.
• the propagation time is then the time between the moment when the transmitter transducer is subjected to the excitation pulse and the moment of detection of the first oscillation of the wave arriving at the level of the receiver transducer.
• the method consists in detecting the first oscillation of the wave by detecting that a voltage threshold has been exceeded. This method requires on the one hand to detect very low voltage levels, and on the other hand to precisely control the triggering threshold of the device for detecting the arrival of an oscillation so as not to introduce a delay in the measurement. propagation time.
• the difference between the propagation times of the ultrasonic waves between the two transducers in the upstream direction and in the downstream direction in the flowing fluid makes it possible to calculate the fluid flow rate.
• the two transducers are associated with an electronic circuit. This circuit controls the transducers and analyzes the analog signals delivered by the receiving transducer. Such a device is described in more detail in patent EP 0 426 309. Although the amplitude of the analog signal at the output of the receiver transducer is not a parameter necessary for calculating the flow rate, this quantity must have a minimum value to ensure a correct operation of the electronic system associated with the transducers and to guarantee minimum accuracy of the flow measurements.
• a problem frequently encountered in this type of flowmeter is their fouling by particles entrained in the flowing fluid.
• these particles are deposited on all the so-called hydraulic parts of the flow meter, for example the active surfaces of the transducers and / or the mirrors intended to modify the path of the waves within the fluid.
• Such fouling inevitably leads to an attenuation of the transmitted waves and therefore a reduction in the amplitude of the signals delivered by the receiving transducer.
• a malfunction of the electronic system appears which is no longer able to process the analog signal at the output of the receiver transducer.
• this problem was solved by dismantling and checking the fouling of the flow meter after a fixed period.
• such a solution has a high maintenance cost and is not satisfactory in the sense that the fouling of a flow meter depends on the amount and type of impurity present in the flowing fluid.
• the object of the invention is to overcome these drawbacks, by implementing a method and a device for detecting a dysfunction such as fouling or aging of an ultrasonic flow meter, said flow meter. comprising at least one transducer, said method also making it possible to generate a conditioned signal from an analog signal originating from said transducer.
• a method and device makes it possible to warn the user or the maintenance team of the need to clean the flow meter in the case of its fouling, or to replace it in the case of its aging.
• Another object of the invention is to control some of the parameters of the electronic system to increase the operating range of said electronic system.
• the reference characteristic V REF is a voltage
• the triggering characteristic V DEC is the peak voltage V PI of the reception signal V IN .
• the reference characteristic V REF is a derivative of a voltage
• the trigger characteristic V DEC is a derivative of the peak voltage V PI of the reception signal V ⁇ .
• An advantage of this method of detecting a malfunction lies in the fact that the reception signal V IN at the output of the transducer is used both to generate the signal output V ou ⁇ conditioned and the alarm signal V AL , and also to define the threshold voltage V TU-
• the device includes: - a transducer delivering a reception signal V IN ,
• a conditioning circuit (1) of the reception signal comprising an input IN connected to the transducer, and an output OUT delivering a conditioned output signal V or ⁇ , the conditioning circuit comprising:
• the use of a modular threshold voltage V TH makes it possible to significantly extend the operating range of the electronics with respect to the amplitude of the reception signals unlike a fixed comparison threshold.
• the enslavement of the threshold voltage V ⁇ thus produced makes it possible to carry out propagation time measurements from the second or third oscillation of the reception signal which is not possible with a fixed threshold not subject to the peak voltage V PK .
• the output signal AL is for example in a second state when the entire measurement system is operating correctly. As soon as a malfunction is detected, the output signal AL switches to a first state corresponding to the emission of the dysfunction detection signal V AL .
• the malfunction detection signal can be a pulse, or a succession of pulses emitted during a determined time.
• the reference voltage V REF is initially chosen equal to a first reference voltage V REF,.
• the reference voltage V REFI is chosen so that the alarm signal is generated before the transducer no longer provides any reception signal.
• the reference voltage V REF is modified and is chosen equal to a second reference voltage the second reference voltage V REF2 being lower than the first reference voltage V REF , so that a second alarm signal is generated when the transducer no longer supplies any reception signal.
• the use of a modular reference voltage V REF allows the emission of an alarm signal before the signal at the output of the transducer is completely unusable.
• the reception signal remains sufficient for the entire device to operate until the second alarm is issued, while allowing the necessary measures to be taken for repair, cleaning or changing the device. of measurement.
• Figure 1 shows the diagram of the device for detecting a malfunction according to a first embodiment of the invention, without processing the offset voltage
• ⁇ Figure 1.A shows the diagram of the device for detecting a dysfunction according to FIG. 1, according to a variant analog embodiment
• ⁇ FIG. 1.B represents the diagram of the device for detecting a dysfunction according to FIG. 1, according to a variant digital embodiment
• Figure 2 shows the diagram of the device for detecting a malfunction according to a second embodiment of the invention, with the offset voltage of treatment
• FIG. 2. A represents the diagram of the device for detecting a malfunction according to FIG. 2, according to a variant of analog embodiment, in FIG. 2.B represents the diagram of the device for detecting a dysfunction according to FIG. 2 , according to a variant digital embodiment,
• FIG. 3 represents the reception signal V, N and the output signal
• FIG. 4 represents the succession of steps of the method for detecting a malfunction according to the invention, with processing of the offset voltage
• a device comprises a conditioning circuit 1 conventionally connected to a transducer (not shown) by its input IN and to an ASIC (not shown) by its output OUT, l 'ASIC being intended for the calculation of the propagation time mentioned above.
• the transducer subjected to a mechanical action, for example an ultrasonic wave, delivers an analog signal called reception V IN .
• This signal comprises a series of characteristic oscillations whose amplitude is first increasing over several periods, then constant and finally decreasing over the following periods as shown in FIG. 3.
• the value of the voltage corresponding to a maximum amplitude is called peak voltage V PK .
• the factor K is dependent on the transducer, it can for example be determined by calculation by averaging the amplitudes of two successive oscillations of the reception signal, for example the first two.
• the conditioned output signal V ou ⁇ is in a first state when the voltage of the reception signal V IN is greater than the threshold voltage V m , and in the second state when the peak voltage V PK of the reception signal is less than threshold voltage
• the reception signal V ⁇ proper is in most cases superimposed on an offset voltage V 0F constant over the duration corresponding to a propagation time measurement but which is caused to vary over several measurements in function of parameters such as the temperature or the supply voltage of the entire detection device for example. It is advantageous to take account of the exact value of this voltage and therefore to carry out a processing of the offset voltage to prevent these variations from disturbing V TH .
• the method comprises additional steps consisting in determining an offset voltage V 0F at the output of the transducer, before measuring the reception signal V, N , then in subtracting from the reception signal V IN , the value of the offset voltage V 0F , before the step of determining the threshold voltage V ⁇ TH-
• FIG. 1 represents the device for detecting a malfunction according to the first embodiment of the invention, without processing the offset voltage.
• the conditioning circuit 1 includes a selector 10 and a comparator 20.
• the selector 10 has a first input connected to the input IN receiving the reception signal, and receives on a second input the value of the predetermined reference voltage V REF .
• the selector has two functions, one being to supply at output a threshold voltage V TH subject to the peak amplitude V PK of the reception signal V, N , and the other being to supply at output AL a detection signal dysfunction V AL when the peak amplitude V PK of the reception signal is less than a predetermined reference voltage V REF .
• the comparator 20 has a first input connected to the input IN receiving the reception signal, and a second input connected to the selector 10 receiving the threshold voltage V TH .
• the output of comparator 20 constitutes the output OUT of the conditioning circuit 1 and generates the conditioned output signal V ou ⁇ .
• FIG. A A first alternative embodiment of the device for detecting a malfunction described in connection with FIG. 1 of analog type, is represented in FIG. A.
• the selector 10 comprises a peak detector 11, a clipper 13 , a sample and hold 15, a first comparator 19, and a potentiometric divider 17.
• the peak detector 11 is directly connected to the input IN and receives the reception signal V, N. Its function is to memorize the value of the maximum voltage through which the reception signal has passed.
• the clipper 13 is connected to the output of the peak detector 11. It is intended to eliminate parasites from the reception signal V IN , in particular, it outputs a zero signal when the peak detector has detected only noise, and one eliminates peaks of high amplitude which do not correspond to the signal of interest.
• the clipper 13 is followed by the sampler-blocker 15, the function of which is to store the peak amplitude of the reception signal V PK , until the next reception.
• the sampler-blocker 15 is connected to the first comparator 19 as well as to the potentiometric divider 17.
• the first comparator 19 receives on a second input the reference voltage V REF and generates at output AL, a malfunction detection signal V AL when the peak amplitude of the reception signal V PK is less than the reference voltage V REF .
• the potentiometric divider 17 outputs the threshold voltage V TH .
• the potentiometric divider output 17 is connected to the second comparator 21, which receives the threshold voltage V TI I.
• the comparator 21 receives on a second input the reception signal V, N and generates at output OUT the conditioned output signal V ou ⁇ .
• the device for detecting a dysfunction comprises a peak detector 111, an analog / digital converter 113, a programmer 115 and a programmable comparator 221.
• the peak detector 111 is connected to the JLN input and receives the reception signal V IN .
• the analog / digital converter 113 is connected to the output of the peak detector 111. It is intended to digitize the reception signal V IN .
• the programmer 115 which receives on a second input the reference voltage
• the programmer generates at output AL the malfunction detection signal V AL when the peak amplitude of the reception signal V PK is less than the reference voltage V REF , as well as a programmed threshold voltage V TH .
• the programmer 115 is connected to the programmable comparator 221 via a data bus 118.
• the programmable comparator 221 performs the comparison between the signal applied to its input and the programmed threshold voltage V TH applied via the data bus 118 , and generates the conditioned output signal V ou ⁇ .
• a demultiplexer or a microcontroller can advantageously be used.
• FIG. 2 represents the device for detecting a malfunction according to the second embodiment of the invention, with processing of the offset voltage.
• the conditioning circuit 1 comprises a selector 10, a comparator 20 and a unit for determining the offset voltage 30.
• the unit for determining the offset voltage 30 is connected to the input IN of the conditioning circuit 1.
• the selector 10 Before at the start of each reception of an ultrasonic wave, said unit samples and stores the offset voltage V 0F .
• the selector 10 has a first input connected to the input IN receiving the reception signal, a second input receiving the value of the offset voltage V 0F and a third input receiving the value of the reference voltage V REF .
• the selector 10 supplies at the output, on the one hand a threshold voltage V TH controlled by the peak amplitude V PK of the reception signal V ] N , and on the other hand the malfunction detection signal V AL when the amplitude peak of the reception signal V PK is less than a predetermined reference voltage V REF .
• the comparator 20 has a first input connected to the input IN receiving the reception signal, a second input connected to the selector receiving the threshold voltage V TH , and a third input receiving the value of the offset voltage V 0F .
• the comparator output constitutes the output OUT of the conditioning circuit l and generates the conditioned output signal V ou ⁇ .
• the unit for determining the offset voltage 30 comprises a first sample-and- hold circuit 31 receiving the reception signal V ⁇ N and intended to determine and store the offset voltage V 0F present before the start of the reception of an ultrasonic wave.
• the selector 10 comprises a peak detector 11, a subtractor 12, a clipper 13, a sampler-blocker 15, a first comparator 19, and a potentiometric divider 17.
• the peak detector 11 is connected to the input IN and receives the reception signal V IN .
• the subtractor 12 connected to the output of the peak detector 11 and to the output of the first blocker sampler 3 Lest intended to subtract the offset voltage V 0F from the signal at the output of the peak detector 11.
• the clipper 13 is connected to the output of subtractor 12. It is intended to eliminate parasites of the reception signal V IN , in particular it provides at output a zero signal when the peak detector has detected only noise, and one eliminates the high amplitude peaks which do not correspond to the signal of interest.
• the limiter 13 is followed by the interlocker-blocker 15, the function of which is to store the peak amplitude of the reception signal V PK , until the next reception.
• the sampler-blocker 15 is connected to the first comparator 19 as well as to the potentiometric divider 17.
• the first comparator 19 receives on a second input the reference voltage V REF and generates at output AL, a malfunction detection signal V A when the peak amplitude of the reception signal V PK is less than the reference voltage V REF .
• the potentiometric divider 17 outputs the threshold voltage V TH .
• the comparator 20 comprises an analog adder 22 connected to the output of the potentiometric divider 17 and to the first sample-and-hold circuit 31.
• the analog adder 22 performs the sum of the offset voltage V 0F and the threshold voltage V TH .
• a second comparator 21 connected by a first input to the output of said adder 22 and receiving on a second input the reception signal V IN , generates the output signal V or ⁇ conditioned in a first state when the amplitude of the reception signal is greater at the value of the sum of the voltages, and in a second state when the amplitude of the reception signal is less than the value of the sum of the voltages.
• the device for detecting a malfunction comprises a sampler-blocker 301, a peak detector 111, a subtractor 112, an analog / digital converter 113, a programmer 115 and a programmable comparator 221.
• the sampler-blocker 301 receives the reception signal V 1N , determining and memorizing the offset voltage present before the start of the reception of an ultrasonic wave.
• the peak detector 111 is connected to the input IN and receives the reception signal V, N.
• the subtractor 112 connected to the output of the peak detector 111 and to the output of the first sample and hold 301 is intended to subtract the offset voltage V 0F from the signal at the output of the peak detector 111.
• the analog / digital converter 1 13 is connected to the output of the subtractor 112. It is intended to digitize the reception signal V, N. It is followed by the programmer 115 which receives on a second input the reference voltage V ⁇ . The programmer generates at output AL the malfunction detection signal V AL when the peak amplitude of the reception signal V PK is less than the reference voltage V REF , as well as a programmed threshold voltage V TH .
• the programmer 115 is connected to the programmable comparator 221 via a data bus 118.
• the programmable comparator 221 performs the comparison between the signal applied to its two inputs, to which is added the threshold voltage V TH programmed via the bus 118. Said comparator 221 thus generates the conditioned output signal V ou ⁇ .
• a demultiplexer or a microcontroller can advantageously be used.
• FIG. 4 is a flow diagram representing the different stages of the method according to the first embodiment of the invention, that is to say without processing the offset voltage. Initially the reference voltage V REF is equal to a first reference voltage V REF , (step a).
• the peak amplitude V PK of the reception signal V IN at the output of the transducer is measured (step b).
• This signal comprises a series of characteristic oscillations whose amplitude is first increasing over several periods, then constant, the value of the voltage corresponding to a maximum amplitude being called peak voltage V PK and finally decreasing over the following periods.
• the peak amplitude V PI ⁇ is compared to the reference voltage V REFi determined above (step ç).
• step d When the peak amplitude V PK of the reception signal is less than the reference voltage level V REF1 , an alarm signal V ⁇ L is generated (step d). This first signal is generated while the transducer still provides a reception signal which can be used by the measurement electronics, but nevertheless constitutes a first indication of a future malfunction.
• the reference voltage V REF is then modified and goes from the first reference voltage V REF1 to a second reference voltage V REF2 (step e).
• a threshold voltage V TH proportional to the peak amplitude V PK of the reception signal is determined (step f).
• the reception signal V IN is compared with the threshold voltage V m which was determined during the previous step (step g).
• a conditioned output signal V o ⁇ rr is then generated, this signal being in a first state when the reception signal V 1N is greater than the threshold voltage V ⁇ (step h), and in a second state when the reception signal V 1N is less than the threshold voltage V- m (step i).
• This conditioned signal is shown in FIG. 3.
• step d When the reference voltage V REF is equal to the second reference voltage V REF2 , and if the peak amplitude V PI of the reception signal is less than the reference voltage level V REF2 , another alarm signal V AL is generated (step d).
• the second alarm signal is generated when the transducer no longer provides any reception signal that can actually be used by the measurement electronics. The process is blocked in the loop constituted by the succession of steps ç, d and e as long as the malfunction has not been repaired by a maintenance team allowing the return to step a.
• the method for detecting a malfunction comprises two additional steps which consists firstly in determining an offset voltage V 0F at the output of the transducer, before measuring the signal reception V IN (step b), and on the other hand to subtract from the reception signal V m , the value of the offset voltage V OF , before the step of determining the threshold voltage V TH (step f) .

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Fluid Mechanics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Volume Flow (AREA)
• Ultra Sonic Daignosis Equipment (AREA)
• Measurement Of Current Or Voltage (AREA)

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• 1999
  • 1999-12-29 US US10/169,339 patent/US6766276B1/en not_active Expired - Fee Related
  • 1999-12-29 FR FR9916699A patent/FR2803383B1/fr not_active Expired - Fee Related
• 2000
  • 2000-12-19 EP EP00990063A patent/EP1242792A1/fr not_active Withdrawn
  • 2000-12-19 CN CNB008179379A patent/CN1192212C/zh not_active Expired - Fee Related
  • 2000-12-19 WO PCT/FR2000/003590 patent/WO2001050095A1/fr active Application Filing
  • 2000-12-19 BR BR0017057-7A patent/BR0017057A/pt not_active Application Discontinuation
  • 2000-12-19 RU RU2002120506/28A patent/RU2232978C2/ru not_active IP Right Cessation
  • 2000-12-19 JP JP2001549996A patent/JP2003519375A/ja not_active Withdrawn
  • 2000-12-19 AU AU26868/01A patent/AU2686801A/en not_active Abandoned
  • 2000-12-19 MX MXPA02006401A patent/MXPA02006401A/es unknown

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