JP2000146674A - Ultrasonic level meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make measurable the level at high sensitivity by the multi-phase synchronous integration of a signal of echo wave, the AD conversion of obtained signal components, the moving addition, the moving difference operation, the addition and the level calculation. SOLUTION: A synchronous integrator circuit 13 extracts signal components X, Y of an echo wave according to signals of the same period as that of an ultrasonic wave emitted from a transducer 3, integrates them and extracts signal components cleared from noise signals, moving adders 172, 173 moving-add the two integrated signals X, Y respectively and remove harmonics to shape the waveform, moving subtractors 174, 175 output signals of squared difference operation values from them respectively, an adder 176 adds the two signals X, Y subjected to the moving subtraction and the square operation to provide a waveform with a peak, and a level detector 177 detects the level from the peak of this waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting ultrasonic waves from a transmitter toward a reflecting surface, receiving the ultrasonic waves reflected by the reflecting surface with a receiver, and transmitting the ultrasonic waves from the transmitter. An ultrasonic level meter that detects the level of a reflecting surface based on the time required for a receiver to receive a reflected wave, and more specifically, the time required for the receiver to receive a reflected wave. More specifically, the present invention relates to an ultrasonic level meter that can correctly detect a signal component even in an echo wave having a low S / N ratio by improving a calculation method for detecting a level of a reflection surface.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a conventional ultrasonic level meter. In the figure, the conventional ultrasonic level meter receives a short time (0.1 to 0.2 seconds) from the ultrasonic transceiver 3.
By transmitting an ultrasonic wave and receiving the echo wave with the same ultrasonic transmitter / receiver 3, the ultrasonic wave is transmitted and then reflected by the reflection surface 4 of the detection target 1 which has entered the tank 2 and transmitted again. The distance from the ultrasonic transmitter / receiver 3 to the reflection surface 4 (hereinafter referred to as a level) is measured by measuring the time required to return to the device 3 and converting the distance.

In FIG. 8, an ultrasonic transmitter / receiver 3 transmits an ultrasonic wave to a reflection surface 4 and receives an echo wave reflected by the reflection surface 4. The ultrasonic transceiver 3 outputs a received echo wave signal (hereinafter referred to as an echo signal).

[0004] The echo signal is amplified by an amplifier 5 and input to a full-wave rectifier circuit 6. Here, the echo signal subjected to full-wave rectification is converted into a digital value by the A / D converter 7 and input to the calculator 8.

The calculator 8 detects the level based on the echo signal based on the time required for the transceiver 3 to transmit an ultrasonic wave and to receive an echo wave.

FIG. 9 is a waveform diagram of an ultrasonic wave and an echo wave.
As shown in the figure, the transmitter / receiver 3 generates the ultrasonic wave P1 and after the time T1 has elapsed, the transmitter / receiver 3
To receive. The time T1 is proportional to the distance between the transceiver 3 and the reflection surface 4. If the installation position of the transceiver 3 is known, the level of the reflection surface 4 can be detected from the time T1.

FIG. 10 is a diagram showing an example of a waveform of an echo signal after passing through the amplifier 5. As shown in the figure, the echo signal contains a signal component S1 and a noise component S2. Although the figure shows the signal component S1 and the noise component S2 separately for the sake of explanation, the waveform actually observed is a waveform in which the noise component is superimposed on the signal component.

FIG. 11 is a diagram showing an example of a full-wave rectified signal after passing through the full-wave rectifier circuit 6. In the figure, a signal S3 is a signal obtained by full-wave rectifying the signal component S1,
4 is a signal obtained by full-wave rectification of the noise component S2.

The arithmetic unit 8 adds the full-wave rectified signal each time the echo signal arrives, determines the signal component from the added signal by the comparator, and detects the signal component based on the time when the component signal appears. Calculate the level.

[0010]

However, in the conventional example of FIG. 8, since both the signal component and the noise component are full-wave rectified, the noise component is added together with the addition of the echo signal. Therefore, when the signal component is sufficiently weaker than the noise component of the echo signal, there is a problem that an error is likely to occur in the level measurement result due to the effect of the noise component added one after another.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and correctly detects a signal component from a noise component even when the signal component is sufficiently weaker than the noise component of the echo signal. It aims to realize an ultrasonic level meter that can be used.

[0012]

According to a first aspect of the present invention, there is provided an ultrasonic level meter, wherein a signal having the same cycle as that of the ultrasonic wave is used in the ultrasonic level meter. A polyphase synchronous integration circuit that extracts a plurality of signal components from a signal and outputs an integration signal of the plurality of signal components by integrating the signal components; and an A / D converter that performs analog / digital conversion of each of the plurality of integration signals A D converter, a moving adder for moving and adding the output of the A / D converter, and a signal obtained by performing a moving difference operation on the output of the moving adder with a constant data width and squaring this operation value. And a level difference calculator for calculating the level of the reflection surface from an output waveform of the adder. Is shall.

Thus, the ultrasonic level meter can realize highly sensitive and accurate level measurement using a plurality of component signals obtained from the polyphase synchronous integration circuit.

According to a second aspect of the present invention, in the first aspect of the present invention, the multi-phase synchronous arithmetic unit uses a signal having the same cycle as the ultrasonic wave to generate a half cycle of the echo wave. , The inverted signal of the echo wave is extracted over the remaining half period, and the extracted signals are added to obtain an inverted signal of 9% from the echo wave.
A first method of extracting an X component signal and a Y component signal having phases different by 0 degrees and integrating the X component signal and the Y component signal, respectively.
And a two-phase synchronous integration circuit for outputting a two-phase synchronous integration signal of the echo wave by a second integration circuit.

Thus, the ultrasonic level meter can be configured using a two-phase synchronous integration circuit having a simple structure.

According to a third aspect of the present invention, in the first aspect of the present invention, the second moving adder obtains a moving addition value U (n) in five data sections. is there.

This makes it possible for the ultrasonic level meter to perform filtering for removing harmonic components from the signal waveform.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the moving difference calculator calculates a digital data value U of a data number n output from the moving adder.
(N) and the digital data value U that is five data earlier than this
A difference operation value D (n) from (n-5) is obtained, and a value obtained by squaring this value is output.

Thus, the ultrasonic level meter can easily obtain the peak value of the integrated waveform output from the polyphase synchronous integration circuit.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the level calculator determines a peak value of an output waveform output from the adder, and determines a data position corresponding to the peak value. The data Ds (n) is searched from the time when the ultrasonic wave is transmitted by sequentially searching the data in the direction of returning the time from the data, and detecting the data Ds (n) which is smaller than 1/4 of the peak value first. , The time until the arrival of the target is reached, and the level is detected from this time.

Thus, the ultrasonic level meter maintains its reproducibility even when detecting the arrival point of the data Ds (n) in a waveform in which a large number of data having a size close to the peak value exists. You. The reason will be described later.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the level calculator calculates the data Ds corresponding to １ ／ of the peak value of the addition signal.
Data D (n) from (n) to 10 data before is searched, and if there is data satisfying D (n)> Ds (n), the detected level value of the reflecting surface is discarded as a measurement abnormality. It is characterized by having been constituted so that.

As a result, the ultrasonic level meter can discard abnormal measurement values.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the multi-phase synchronization calculator uses a signal having the same cycle as that of the ultrasonic wave to generate a signal of 120 degrees from the echo wave signal. Extract three signal components with different phases by
A three-phase synchronous integration circuit that integrates these signal components to output an integrated signal of three signal components is used.

Thus, the accuracy of the ultrasonic level meter can be further improved as compared with the case where the two-phase synchronous integration circuit is used.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of an ultrasonic level meter according to the present invention.

In FIG. 1, the same components as those in FIG. 8 described in the conventional example are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 2, an echo signal generated from the ultrasonic transceiver 3 is input to a preamplifier 10, amplified, and then input to a D / A converter 11.

The D / A converter 11 converts the echo wave input from the preamplifier 10 into a TVG (Time Variab) signal.
le Gain) processing.

The TVG process is a process of increasing the gain with the passage of time after the transmitter / receiver 3 transmits an ultrasonic wave. That is, when the time from transmission of the ultrasonic wave by the transmitter / receiver 3 to the return of the echo signal is long, it is a case where the distance to the detection target is long, and the attenuation of the echo signal is expected to increase. Therefore, it is intended to increase the gain at the time of reception and receive the echo wave at a constant level regardless of the reflection distance of the ultrasonic wave. This T
The gain of the VG process is given from the control unit 178.

The echo signal that has been subjected to TVG processing by the D / A converter 11 is amplified by the intermediate amplifier 12, and its output is input to the synchronous integration circuit 13.

Switch SW constituting synchronous integration circuit 13
Switches 1 to SW4 are provided for extracting an echo signal. The inverting circuit 131 includes the switches SW2 and S
This is an inverting circuit that is provided before W4 and inverts the echo signal. The signal extracted from the switch SW1 and the signal extracted from the switch SW2 are added. This added signal is defined as an X component signal.

The signal extracted from the switch SW3 and the signal extracted from the switch SW4 are added. This added signal is defined as a Y component signal.

The integration circuit 132 integrates the X component signal and outputs the integrated signal. Further, the integration circuit 133 integrates the Y component signal and outputs the integrated signal.

The drive signal generation circuit 14 is provided with the switch S
This is a drive signal generation circuit that generates a drive signal for driving W1 to SW4. The cycle of these drive signals is the same as the cycle of the ultrasonic wave generated by the transceiver 3.

The flip-flops 141 and 142 constituting the drive signal generating circuit 14 have a Q output and a Q-output (inversion of Q is represented by Q-; hereinafter, the inversion is similarly represented), and a P output and P-output. Occurs.

The drive signal generation circuit 14 drives the switch SW1 with the Q output, and outputs 18 to the Q output.
The switch SW2 is driven by the Q-output which is out of phase by 0 degrees. Further, the switch SW3 is driven by the P output having a phase shift of 90 degrees with respect to the Q output, and the switch SW4 is driven with the P output having a phase shift of 180 degrees with respect to the P output.

The A / D converters 15 and 16 convert the output of the integration circuit 132 and the output of the integration circuit 133 from analog to digital, respectively, and output the result to the arithmetic unit 17.

The storage means 171 constituting the operation unit 17 includes:
This is storage means for temporarily storing the integrated signal converted into a digital value by the A / D converters 15 and 16.

The moving adder 172 obtains a moving added value U (n) x of the integrated value of the X component signal stored in the storage means 171 in five data sections by the following equation (1). U (n) x = d (n-2) x + d (n-1) x + d (n) x + d (n + 1) x + d (n + 2) x (1) where d (n) x is the A / D converter 15 is the digital data of the data number n output.

The moving adder 173 calculates the moving added value U (n) y of the integrated value of the Y component signal stored in the storage means 171 in five data sections by the following equation (2). U (n) y = d (n-2) y + d (n-1) y + d (n) y + d (n + 1) y + d (n + 2) y (2) where d (n) y is the A / D converter 16 is digital data of a data number n output from the MPU 16.

The moving subtractor 174 calculates the digital data value U (n) x of the data number n output from the moving adder 172 by the following equation (3) and the digital data value U (n) five data before this. -5) Difference calculation value D from x
(N) x is obtained, and a value obtained by squaring this is output. {D (n) x} ² = {U (n) x-U (n-5) x} ² (3)

The moving subtracter 175 calculates the digital data value U (n) y of the data number n output from the moving adder 173 according to the following equation (4) and the digital data value U (n) five data before this. -5) Difference calculation value D from y
(N) Obtain y and output a value obtained by squaring this. {D (n) y} ² = {U (n) y−U (n−5) y} ² (4)

The adder 176 adds the outputs of the moving subtractor 174 and the moving subtractor 175.

The level detector 177 is provided with the adder 176.
The arrival time of the echo wave is detected from the output waveform of
Is calculated.

Here, the operation of the embodiment shown in FIG. 1 will be described with reference to signal waveform diagrams of respective parts shown in FIGS.

FIG. 2 is a diagram showing an example of the waveform of the echo signal after passing through the intermediate amplifier 12, and FIG.
FIG. 3 is a diagram showing waveform examples of an X component signal and a Y component signal input to 32 and 133.

In FIG. 2, T0 is the period of the signal component in the echo signal, which is equal to the period of the ultrasonic wave generated by the transceiver 3.

The relationship between the P output and the Q output generated by the flip-flops 141 and 142 is that the P output is a two-phase synchronization signal whose phase is shifted by 90 degrees with respect to the Q output as described above.

In such a relationship, it is assumed that the switch SW1 is turned on by the Q output at time t. As a result, an echo signal is extracted from the switch SW1 over the period A1. The switch SW2 echo signal is applied after being inverted by the inversion circuit 131. The Q-output is turned on at a timing delayed by T0 / 2 from the Q output. Thus, an inverted signal of the echo signal is extracted from the switch SW2 over the period A2. Period A1 and period A2
Are each T0 / 2.

Hereinafter, similarly, the switches SW1 and SW2
Are alternately turned on every half cycle (T0 / 2). The signal extracted from the switch SW1 and the inverted signal extracted from the switch SW2 are added. FIG. 3A shows the X component signal added as a result.

The P output is turned on at a timing delayed by T0 / 4 from the Q output. As a result, an echo signal is extracted from the switch SW3 over the period A3. The switch SW4 is supplied after the echo signal is inverted by the inverting circuit 131. The P- output is turned on at a timing delayed by T0 / 2 from the P output. Thus, the period A
An inverted signal of the echo signal is extracted from the switch SW4 over four times. The lengths of the periods A3 and A4 are each T0 / 2.

Hereinafter, similarly, the switches SW3 and SW4
Are alternately turned on every half cycle (T0 / 2). The signal extracted from the switch SW3 and the inverted signal extracted from the switch SW4 are added. FIG. 3B shows the Y component signal added as a result.

By driving the switches SW1 to SW4 using the four drive signals having the same period as the period of the ultrasonic wave transmitted from the transmitter / receiver 3 and having a phase shift of 90 degrees, two echo signals are obtained from the echo signals. Signal components are extracted. As is apparent from FIG. 3, the X component signal is the SIN component signal of the echo wave S1, and the Y component signal is the COS component signal of the echo wave S1.

FIG. 4A shows a waveform obtained by integrating the X component signal shown in FIG.
FIG. 3 (b) shows the integration of the Y component signal shown in FIG.
33 is a waveform integrated by 33.

The echo wave S1 shown in FIG.
The noise signal S2 superimposed on the (X component signal shown in (a))
Generally have positive and negative regions at random. Therefore, by integrating the X component signal shown in FIG. 3A by the integrator 132, the positive and negative regions of the noise signal are canceled each other, and it is possible to remove these noise signals from the integrated output signal. .

As described above, the synchronous integration circuit 13 extracts the X and Y component signals from the echo wave by using a signal having the same cycle as that of the ultrasonic wave transmitted from the transceiver 3, and integrates the extracted signals. It is possible to extract a signal component from which the noise signal has been removed.

X, Y2 extracted by the above operation
The two integrated signals are subjected to moving addition processing by moving adders 172 and 173 according to the above equations (1) and (2). This is a digital filter provided for the purpose of removing harmonic components from the two integrated signals X and Y temporarily stored as digital data and performing filtering for smooth waveform shaping. FIG. 5A shows an example of a waveform obtained by moving and adding the integrated signal of the X component signal, and FIG. 5B shows an example of a waveform obtained by moving and adding the integrated signal of the Y component signal.

Next, the X and Y two moving addition signals subjected to the moving addition processing by the moving adders 172 and 173 are converted by the moving subtracters 174 and 175 into the above (3).
According to the equation and the equation (4), a signal obtained by squaring the difference operation value is output. FIG. 6A shows an example of a waveform obtained by performing the arithmetic processing according to the formula (3) on the moving addition of the X component signal, and FIG. It is an example of the processed waveform.

Next, the adder 176 adds the two signals X and Y that have been subjected to the movement subtraction processing and the squaring processing by the movement subtracters 174 and 175, respectively. As a result, FIG.
A waveform having a peak as shown in (c) is obtained. The level calculator 177 detects a level from the peak of the waveform.

Here, the method of level detection performed by the level calculator 177 will be described in detail with reference to FIG. FIG. 11 is an example of a composite wave obtained by square addition according to the method described above.

First, the level calculator 177 obtains the peak value Dp in the entire section of the composite wave S3.

Next, the level calculator 177 obtains the magnitude of 1/4 of the peak value Dp, and stores this as a threshold voltage Vth. Vth = １ ／ Dp (5) Next, the level calculator 177 searches for data in the direction of returning time from the data of the peak value Dp (the direction of K in FIG. 7), and the threshold voltage Vth Look for data below. At this time, the data that first falls below the threshold voltage Vth is determined by the arrival point Ds of the echo wave.
(N), the time from when the ultrasonic wave is transmitted to the arrival point Ds (n) of the echo wave is obtained, and the level is detected from this time.

That is, as described above, the level calculator 177 detects the level from the data corresponding to the threshold voltage Vth having a magnitude of 1/4 of the peak value Dp, thereby achieving high reproducibility. Level measurement is realized. The reason is as follows.

In the case where the level calculator 177 is configured to measure the level based on the arrival point Sdp1 of the data corresponding to the peak value Dp in the waveform shown in FIG. Represents the peak value as Dp1
And the level is detected with the arrival point of the echo wave as the point of Sdp1. However, when the second measurement is performed, the peak value may be detected as the data of Dp2 depending on the state of the echo wave.

In this case, the level detection value differs between the first measurement and the second measurement, so that reproducibility cannot be obtained. However, when the level is detected by the method of the present invention, even when the peak value is detected as Dp1, Dp2
, The same data is recognized as the arrival point Ds (n) of the echo wave. Therefore,
By detecting the level by the method of the present invention,
Even when the measurement is repeated, the same level can be detected regardless of the difference in the data detected as the peak value.

At this time, the level calculator 177 outputs 10 times in the direction of returning time from the arrival point Ds (n) of the echo wave.
The data D (n) up to the data is searched, and if any one of them satisfies D (n)> Ds (n), the detected level of the reflecting surface is discarded as a measurement abnormality. It is configured to be.

That is, the ultrasonic level meter according to the present invention
The X component signal, which is a SIN component, and the Y component signal, which is a COS component, are extracted from an echo signal in which an ultrasonic wave enters at an arbitrary phase depending on the distance, and a moving difference operation is performed on an integrated signal obtained by removing a noise signal from those signals. By obtaining the level from the peak waveform obtained by squaring the waveform having the peak value obtained by the above, even when the signal component is sufficiently weaker than the noise component of the echo signal, Signal components can be detected correctly.

Generally, the echo wave is transmitted and received by the transceiver 3
It returns to the transmitter / receiver 3 while its phase changes every moment due to the influence of the wind and the temperature distribution existing in the space from the to the reflecting surface 4 and the influence of dust and dirt. The actual ultrasonic wave has a complicated waveform having an initial rising portion W1 and a residual portion W2 as shown in FIG. These are also major factors that change the phase of the echo wave momentarily. Therefore, the X component signal and the Y component signal extracted from the echo wave are equal to the distance Lx from the transceiver 3 to the reflection surface 4.
Due to its size is not constant.

FIG. 12 illustrates the relationship between the ultrasonic wave P1 and the echo wave P2. If the distance Lx is constant and the space from the transmitter / receiver 3 to the reflection surface 4 has no fluctuation, the waveform ei of the echo wave P2 has the wavelength of the ultrasonic wave as λ and the amplitude of the echo wave as A. Then, ei = Asin θ (6) Here, θ is θ = (Lx / λ−N) × 2π (rad). Here, N is an integer part of the amplitude number from the transmission of the ultrasonic wave P1 to the reception of the echo wave P2.

Therefore, the output signal eix of the X component and the output signal eiy of the Y component when the echo wave of the above equation (6) is integrated by the synchronous integration circuit 13 are as follows: eix = {A sin θ · dt (7) eiy =} Acos θ · dt (8), and each effective component appears as an integrated output.

In this case, if the phase θ is constant, the time t
By square-rooting the respective integral values with respect to, an integral value proportional to the amplitude A can be obtained. That is, {Adt = {({Asin θ · dt) ² ) + ({Acos θ · dt) ² } (9)

However, in practice, the phase θ changes every moment due to the fluctuation of the echo wave for the reason described above. If this is directly calculated by the above equation (9), an error occurs due to the change in the phase θ in the calculation result.

Therefore, in the ultrasonic level meter of the present invention, in FIG. 13, if the time T3 is sufficiently shorter than the transmission time T2 of the ultrasonic wave, the phase θ of the echo wave is considered to be constant, The X and Y signal components extracted from the echo wave in the time width of T3 are subjected to the above-described moving addition processing and moving subtraction processing, and further squared to obtain a waveform having a peak shown in FIG. It is configured. In addition, although it is originally desirable to perform the square root processing on the square-added signal as in the above equation (9), in the ultrasonic level meter of the present invention, in order to speed up the processing of the arithmetic unit 17, Instead of performing a square root process on a waveform having a peak, the level is detected based on data having a size of 1/4 of the peak value. This makes it possible to remove the influence of the phase of the echo wave, which changes every moment, and makes it possible to detect the level with high precision that is overwhelming the conventional method.

In the ultrasonic level meter of the present invention, an ultrasonic wave having a transmission frequency of 40 kHz (one cycle is 25 μsec.) Is transmitted for 0.1 to 0.2 sec., And a period of seven cycles of the echo wave (175 μsec. Is regarded as having a constant phase θ. Further, the A / D converters 15 and 1
The sampling period of No. 6 is 34.5 μsec. Therefore, the number of data sampled during the period of seven cycles of the echo wave is five. Therefore, the above-described moving adder 1
The 72 and 173 and the shift subtracters 174 and 175 are configured to perform shift operation processing using five data widths.

Also, instead of the two-phase synchronous integration circuit, three
When the ultrasonic level meter of the present invention is configured using the phase-synchronous integration circuit, it is possible to realize an ultrasonic level meter with higher accuracy.

The foregoing description merely illustrates certain preferred embodiments for purposes of explanation and illustration of the invention. Therefore, the present invention is not limited to the above-described embodiments, and includes many more modifications without departing from the spirit thereof.
This includes deformation.

[0077]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first aspect of the present invention, in the ultrasonic level meter, a plurality of signal components are extracted from the echo wave signal using a signal having the same period as the period of the ultrasonic wave, and the signal components are integrated. A polyphase synchronous integration circuit for outputting integrated signals of the plurality of signal components, an A / D converter for analog-to-digital conversion of each of the plurality of integrated signals, and moving and adding outputs of the A / D converter, respectively A moving adder, a moving difference calculator for performing a moving difference calculation on the output of the moving adder with a constant data width, and outputting a signal obtained by squaring the calculated value; and adding the outputs of the moving difference calculator. And a level calculator for calculating the level of the reflection surface from the output waveform of the adder, so that the signal can be returned at an arbitrary phase while obtaining a large S / N ratio which is an advantage of synchronous integration. Come process it is possible to perform, including the phase information to the echo waves, it is possible to measure the precise echo arrival time against echo wave including a lot of noise signals. Also, the ultrasonic level meter of the present invention realizes the above-described signal processing using all general-purpose components, so that it is possible to detect the level with high accuracy that is overwhelming the conventional method at a low cost. Was.

According to a second aspect of the present invention, in the first aspect of the present invention, the multi-phase synchronous calculator uses a signal having the same cycle as that of the ultrasonic wave and performs a half of the cycle of the echo wave. Extracting the signal over the period of the cycle, extracting the inverted signal of the echo wave over the remaining half period, and adding the extracted signals from the echo wave,
Extract the X-component signal and the Y-component signal that are 90 degrees out of phase,
By using a two-phase synchronous integration circuit that outputs a two-phase synchronous integration signal of the echo wave using first and second integration circuits that respectively integrate the X-component signal and the Y-component signal, a simple structure 2 It is possible to provide an ultrasonic level meter having the above features at low cost by using a phase-synchronous integration circuit.

According to a third aspect of the present invention, in the first aspect of the present invention, the moving adder determines a moving addition value U (n) in five data sections, thereby affecting a signal waveform. Filtering can be performed easily without any additional processing.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the moving difference calculator includes a digital data value U of a data number n output from the moving adder.
(N) and the digital data value U that is five data earlier than this
A difference operation value D (n) x from (n−5) is obtained, and this is calculated as 2
By being configured to output the raised value, the peak value of the integrated waveform output from the polyphase synchronous integration circuit can be easily obtained.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the level calculator determines a peak value of an output waveform output from the adder, and determines a data position corresponding to the peak value. The data Ds (n) is searched from the time when the ultrasonic wave is transmitted by sequentially searching the data in the direction of returning the time from the data, and detecting the data Ds (n) which is smaller than 1/4 of the peak value first. Is obtained, and the level is detected from this time. Thus, in a waveform in which a large amount of data having a size close to the peak value exists as in the waveform shown in FIG.
Even when the arrival point of the data Ds (n) is detected, the reproducibility can be maintained.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the level calculator calculates the data Ds corresponding to １ ／ of the peak value of the addition signal.
Data D (n) from (n) to 10 data before is searched, and if there is data satisfying D (n)> Ds (n), the detected level value of the reflecting surface is discarded as a measurement abnormality. With such a configuration, it is possible to remove the abnormal measurement value.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the multi-phase synchronous calculator uses a signal having the same cycle as that of the ultrasonic wave to generate a signal of 120 degrees from the echo wave signal. Extract three signal components with different phases by
By using a three-phase synchronous integration circuit that outputs an integrated signal of three signal components by integrating each of these signal components, the accuracy is further improved as compared with the case where a two-phase synchronous integration circuit is used. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an ultrasonic level meter according to the present invention.

FIG. 2 is a diagram illustrating the operation of the present invention.

FIG. 3 is an operation explanatory diagram of the present invention.

FIG. 4 is a diagram illustrating the operation of the present invention.

FIG. 5 is an operation explanatory diagram of the present invention.

FIG. 6 is a diagram illustrating the operation of the present invention.

FIG. 7 is a configuration diagram showing an example of a conventional ultrasonic level meter.

FIG. 8 is an operation explanatory diagram of the ultrasonic level meter of FIG. 8;

FIG. 9 is an operation explanatory diagram of the ultrasonic level meter of FIG. 8;

FIG. 10 is an operation explanatory diagram of the ultrasonic level meter of FIG. 8;

FIG. 11 is an operation explanatory diagram of the ultrasonic level meter of FIG. 8;

FIG. 12 is a diagram illustrating the operation of the present invention.

FIG. 13 is a diagram illustrating the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detection target 2 Tank 3 Transceiver 4 Reflection surface 10 Preamplifier 11 D / A converter 12 Intermediate amplifier 13 Synchronous integration circuit 14 Drive signal generation circuit 15, 16 A / D converter 17 Operation unit 131 Inversion circuit 132, 133 Integration circuit SW1, SW2, SW3, SW4 Switch 141, 142 Flip-flop 171 Storage means 172, 173 Moving adder 174, 175 Moving subtractor 176 Adder 177 Level calculator

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshinori Ishii No. 85 Hisamatsu-cho, Ashikaga-shi, Tochigi Yokogawa Wezac F-term (reference) 2F014 FB01 GA01

Claims (7)

[Claims] 1. An ultrasonic wave is transmitted from a transceiver toward a reflection surface of a level detection target, and the ultrasonic wave reflected by the reflection surface is received by the transceiver, and after the transceiver transmits the ultrasonic wave, In an ultrasonic level meter that detects the level of the reflection surface based on the time required to receive an echo wave, a plurality of signals are obtained from the echo wave signal using a signal having the same cycle as the cycle of the ultrasonic wave. A polyphase synchronous integration circuit that extracts components and integrates the signal components to output integrated signals of the plurality of signal components; an A / D converter that performs analog / digital conversion of each of the plurality of integrated signals; Said A
A moving adder that moves and adds the outputs of the / D converters; a moving difference calculator that performs a moving difference calculation on the outputs of the moving adders with a fixed data width and outputs a signal obtained by squaring the calculated value; And an adder for adding the output of the moving difference calculator, and a level calculator for calculating the level of the reflecting surface from the output waveform of the adder. 2. The multi-phase synchronization arithmetic unit extracts a signal using a signal having the same cycle as that of the ultrasonic wave over a half cycle of the echo wave, and extracts the echo wave over the remaining half cycle. A first component that extracts an X component signal and a Y component signal having phases different from each other by 90 degrees from the echo wave by extracting the inverted signals of the above, and integrating the X component signal and the Y component signal, respectively. 2. The ultrasonic level meter according to claim 1, wherein a two-phase synchronous integration circuit that outputs a two-phase synchronous integration signal of the echo wave by a second integration circuit is used. 3. The ultrasonic level meter according to claim 1, wherein said moving adder obtains a moving addition value U (n) in five data sections by the following equation. U (n) = d (n-2) + d (n-1) + d (n) + d
(N + 1) + d (n + 2) where d (n) is digital data of data number n output from the A / D converter. 4. The moving difference calculator according to the following equation:
A difference operation value D (n) between the digital data value U (n) of the data number n output from the moving adder and the digital data value U (n-5) five data before this is calculated, and this is calculated. The ultrasonic level meter according to claim 1, wherein the ultrasonic level meter is configured to output a squared value. {D (n)} ² = {U (n) -U (n-5)} ² 5. The level calculator calculates a peak value of an output waveform output from the adder, searches data sequentially in a direction of returning time from a data position corresponding to the peak value, and searches for the peak value. By detecting data Ds (n) that is smaller than 1/4 first, the time from when the ultrasonic wave is transmitted to when the data Ds (n) arrives is obtained, and the level is detected from this time. The ultrasonic level meter according to claim 1, wherein the ultrasonic level meter is configured as follows. 6. The level calculator searches for data D (n) 10 data before the data Ds (n) corresponding to a quarter of the peak value of the addition signal, and obtains D (n). 2. The ultrasonic level meter according to claim 1, wherein when there is data satisfying the following condition:> Ds (n), the detected level value of the reflecting surface is discarded as a measurement abnormality. . 7. The multi-phase synchronization arithmetic unit according to claim 1, wherein the multi-phase synchronous operation unit uses the signal having the same cycle as the cycle of the ultrasonic wave to calculate 12
3. A three-phase synchronous arithmetic unit which extracts three signal components having phases different by 0 degrees and outputs an integrated signal of three signal components by integrating these signal components, respectively. Item 7. The ultrasonic level meter according to Item 1.