JPH0674817A - Received signal processing device for ultrasonic measurement - Google Patents

Abstract

PURPOSE:To obtain a received signal processing device or ultrasonic measurement which stably measures time in measuring the transmission time of ultrasonic wave with a pulse-echo method. CONSTITUTION:Provided are a first comparator 3 for comparing input signal with the comparison voltage set in advance, a level control means 1 for amplifying and adjusting the input signal, and a second comparator 4 for detecting a zero-cross point using the output of the level control means 1. Also provided are a flipflop 5 input by the output of the first comparator 3 and an AND gate 6 calculating a logical product of the output of this flipflop 5 and the output of the second comparator 4 and outputting the product signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time measurement reception signal processing device, and more particularly to a time measurement reception signal processing device suitable for specifying the reception timing of a reception signal during ultrasonic measurement.

[0002]

2. Description of the Related Art In an ultrasonic bolt axial force meter, an ultrasonic densitometer, an ultrasonic thickness meter, etc., the propagation time of ultrasonic waves is measured using the pulse echo method, and the stress, concentration, thickness, etc. of bolts are measured. Seeking a physical quantity.

Conventionally, a time measuring device for measuring the propagation time of an ultrasonic wave using the pulse echo method converts an electric pulse into an ultrasonic pulse and an ultrasonic pulse into an electric pulse as shown in FIG. Ultrasonic transducer 52, a wide band amplifier 53 for amplifying the electric pulse from the ultrasonic transducer 52, a comparator 54 for comparing the output of the wide band amplifier 53 with a preset voltage VBB, and a high voltage pulse To the ultrasonic transducer 52, a time measuring section 55 for measuring the time from the output of the pulse to the pulser circuit 51 to the input of the pulse output of the comparator 54, and the time measuring section 55 A computer 56 that calculates the propagation time and physical quantity of the ultrasonic wave based on the measurement result and outputs and displays it on the display unit 58. , Temperature for the temperature compensation sensor 59
And an A / D converter 57 that converts the output of the temperature sensor 59 into a digital signal and outputs the digital signal to the computer 56.

The above-mentioned conventional example operates as follows.

.. The pulse output from the time measuring section 55 at a certain time t1 is converted into a high voltage pulse for driving the ultrasonic transducer 52 by the pulser circuit 51 and input to the ultrasonic transducer 52.

[0006] The ultrasonic transducer 52 converts the electric pulse from the pulser circuit 51 into an ultrasonic pulse,
It is propagated through the object 60 which is the object to be measured. The ultrasonic pulse reflected from the end of the object 60 is converted into an electric pulse again by the ultrasonic transducer 52.

[0007]. The electric pulse from the ultrasonic transducer 52 is amplified by the wide band amplifier 53. Further, the output of the wide band amplifier 53 is converted into a digital signal by the comparator 54 and input again to the time measuring section 55 at time t2.

[0008] The time measuring unit 55 measures the time Δt from the time t1 to t2 by the following equation (1) and sends the result to the computer 56.

Δt = t2-t1 (1)

[0010]. The computer 56 stores the time te during which the signal propagates in the electric circuit, and the computer 56 obtains the ultrasonic wave propagation time Δtu by subtracting te from Δt as shown in the following equation (2). .

Δtu = Δt-te = t2-t1-te (2)

The ultrasonic wave propagation time Δtu is the stress, the concentration,
Since it changes depending on the thickness, etc., these physical quantities are obtained from an approximate expression or map of the relationship between the ultrasonic wave propagation time Δtu and these physical quantities stored in advance in the memory of the computer 56, and the results are displayed on the display unit 58. Output to.

Since the relationship between the ultrasonic wave propagation time Δtu and each physical quantity changes depending on the temperature, the computer 56
Is a temperature sensor 59 that is input via the A / D converter 57.
The temperature is compensated based on the measured value.

The comparator 54 in this conventional example binarizes the received pulse signal by comparing it with a certain comparison voltage VBB as shown in FIG. 5, and converts it into a digital signal. If the amplitude of the input signal decreases from a to b for some reason, the comparator 54
The pulse width of the output of is also narrowed from a'to b '. That is, the magnitude of the amplitude of the received pulse signal appears as a measurement error as it is. This makes it impossible to stably measure the propagation time of ultrasonic waves with high accuracy.

To solve this drawback, a comparison circuit using the zero-cross method has been used.

In the conventional comparison circuit, as shown in FIG. 6, the ultrasonic wave reception signal and the preset comparison voltage V are set.
A first comparator 13 for comparing with BB, a second comparator 14 for performing zero cross comparison of ultrasonic reception signals, and a flip-flop 1 having an output of the first comparator 13 as a set terminal input.
5, an AND gate 16 which obtains a logical product of the Q output of the flip-flop 15 and the second comparator 14 and outputs the AND to the time measuring section 55, and an output of the AND gate 16 is inverted to generate a clock of the flip-flop 15. It is composed of a NOT gate 17 which serves as a signal.

When the ultrasonic reception signal is input to the first comparator 13, the voltage of the input signal is compared with the comparison voltage VBB,
If it is lower than the comparison voltage VBB, a "high level" signal is output, and if it is higher than the comparison voltage VBB, a "low level" signal is output.

The flip-flop 15 is the first comparator 1
The Q output is changed from "low level" to "high level" at the timing when the output of 3 falls from "high level" to "low level".

The second comparator 14 outputs a "high level" signal when the input signal level is negative.

The AND gate 16 is a flip-flop 1
When the Q output of 5 and the output of the second comparator 14 are both "high level", a "high level" signal is output.

[0021]

However, in the above-mentioned conventional example, the optimum input signal levels of the first comparator for detecting the received wave and the second comparator for detecting the zero cross point are different from each other. When the input signal level is adjusted to the first comparator, jitter occurs in the output of the second comparator, and conversely, when the input signal level is adjusted to the second comparator, the first comparator fails or is defective. However, there is an inconvenience that the operation is caused and stable time measurement cannot be performed.

[0022]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the conventional example, and in particular, to enable stable time measurement when measuring the propagation time of ultrasonic waves using the pulse echo method. To provide.

[0023]

Therefore, in the present invention, a first comparator for comparing the received ultrasonic wave reception signal with a reference voltage of a predetermined level, and a flip-flop for inputting the output of the first comparator. And a second comparator for inputting the received ultrasonic reception signal and detecting a zero-cross point, and adjusting the level of the ultrasonic reception signal at the input stage of the second comparator by amplification or the like. The level control means is provided, and the AND gate for inputting the output of the flip-flop and the output of the second comparator is provided. This aims to achieve the above-mentioned object.

[0024]

A signal adjusted to about 80% to 95% of the input voltage level range of the first comparator is input to the first comparator. The first comparator outputs a "high level" signal when the input signal voltage is equal to or lower than the comparison voltage, and outputs a "low level" signal when the input signal voltage is equal to or higher than the comparison voltage.

The flip-flop changes the Q output from "low level" to "high level" at the timing when the output of the first comparator falls from "high level" to "low level".

The level control means amplifies and adjusts the input signal to the optimum level for the second comparator 4. The second comparator makes a zero-crossing determination based on the signal from the level control means, and outputs a "high level" signal when the input signal is 0 V or less.

The AND gate outputs a "high level" signal when both the Q output of the flip-flop and the output of the second comparator are "high level".

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The embodiment shown in FIG. 1 is a first one for detecting a received wave which compares an input signal with a preset voltage VBB.
Comparator 3, the level control means 1 for amplifying and adjusting the input signal, the second comparator 4 for performing a zero cross comparison of the output level of the level control means 1, and the output of the first comparator 3 at the set terminal input And an AND gate 6 for obtaining the logical product of the Q output of this flip-flop 5 and the output of the second comparator 4, and the output of this AND gate 6 is inverted to obtain the clock signal of the flip-flop 5. Do N
It is composed of an OT gate 2.

Here, the level control means 1 comprises an amplifier 1A for amplifying the input signal and a limiter 1B for adjusting the output level of the amplifier 1A.

Further, in the first comparator 3, since the input signal is accompanied by the amplitude fluctuation, VBB is controlled so that a stable output pulse can be obtained even if the input signal has some amplitude fluctuation.
Adjust slightly in advance. For example, as shown in FIG. 2, even if the amplitude of the input signal decreases from a to b, the output pulse does not change like c.

In the second comparator 3, the input signal is applied to the "-" input terminal of the second comparator 3, and the operation of comparing the level of 0 V with the input signal level is performed. That is, if the input signal is 0V or higher, a "low level" signal is output, and if the input signal is 0V or lower, a "high level" signal is output.

Next, the operation of this embodiment will be described with reference to the timing chart of FIG.

.. The received signal is input to the first comparator 3. The input signal level here is adjusted to about 80% to 95% of the voltage level range in which the first comparator 3 can input.

This is because when the input signal level is low, the pulse signal output from the first comparator 3 has many jitter components, and conversely, the input signal level is within the voltage level range in which the first comparator 3 can input. This is because if it exceeds, unexpected operation may occur in the first comparator 3 or a failure may occur.

.. The first comparator 3 compares the voltage of the input signal with the comparison voltage VBB, outputs a "high level" signal when the comparison voltage is VBB or lower, and outputs a "low level" signal when the comparison voltage is VBB or higher. Output.

That is, as shown in FIGS. 3 (a) and 3 (b), the output of the first comparator 3 increases when the input signal gradually increases and becomes higher than the comparison voltage VBB at time t1. The "high level" signal changes to the "low level" signal. Then, the input signal gradually decreases, and the time t
When the input signal becomes equal to or lower than the comparison voltage VBB in 2, the "low level" signal changes to the "high level" signal. That is, a square wave pulse is output.

.. In the flip-flop 5, as shown in FIG. 3C, the output of the first comparator 3 is “high level”.
The Q output is changed from "low level" to "high level" at the timing of falling from "low level".

That is, at time t1, the Q output of the flip-flop 5 changes from the "low level" signal to the "high level" signal.

.. The reception signal is input to the second comparator 4 via the amplifier 1A and the limiter 1B. The input signal level here is adjusted to the maximum voltage level range that can be input to the second comparator 4.

This is because the range of voltage that can be input to high speed comparators currently on the market is as small as 2 to 4 V, and is 100 mV.
It has the property that it does not operate correctly unless the input signals before and after it are added. If the input signal level of the second comparator 4 is about the same as the input signal level of the first comparator 3, the input signal level This is because the pulse component output from the second comparator 4 is not sufficient, and the jitter component increases.

In other words, the second comparator needs to increase the rate of voltage change per unit time at the zero-cross point of the input voltage in order to detect the zero-cross point with less jitter, but the frequency of the input signal is extremely high. A signal with a large amplitude is required because it is determined by the frequency of the sound wave.

Then, the second comparator 4 makes a zero-crossing determination and outputs a "high level" signal when the input signal level is negative.

That is, as shown in FIG. 3D, in the second comparator 4, the input signal becomes gradually smaller and time t3
When the input signal becomes 0 V or less at, the output of the second comparator 4 changes from the "low level" signal to the "high level" signal, and the input signal gradually increases and becomes 0 V or more at time t4. The output of the second comparator 4 changes from a "high level" signal to a "low level" signal.

.. Therefore, the output of the AND gate 6 is
As shown in (d), at time t3, the "low level" signal changes to the "high level" signal, and at time t4, the "high level" signal changes to the "low level" signal.

.. When the output of the AND gate 6 changes from the "high level" signal to the "low level" signal at time t4, the CK terminal input of the flip-flop 5 changes from the "low level" signal to the "high level" signal.
As shown in FIG. 3C, the Q output of the flip-flop 5 changes from the "high level" signal to the "low level" signal.

In the above description of the operation, the delay time of the element is ignored for the sake of clarity.

[0048]

Since the present invention is constructed and functions as described above, the comparator for receiving wave detection and the comparator for zero-cross point detection can be operated under optimum conditions. Thus, it is possible to provide a reception signal processing device for ultrasonic measurement, which is excellent in the past and is capable of performing stable time measurement.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an operation of a second comparator in FIG.

FIG. 3 is a time chart for explaining the operation of FIG.

FIG. 4 is a configuration diagram of a conventional ultrasonic propagation time measuring device using a pulse echo method.

5 is an explanatory diagram for explaining the operation of the comparator in FIG. 4. FIG.

FIG. 6 is a configuration diagram of a conventional comparison circuit using the zero-cross method.

[Explanation of symbols]

 1 level control means 1A amplifier 1B limiter 2 NOT gate 3 first comparator 4 second comparator 5 flip-flop 6 AND gate

Claims (1)

[Claims] 1. A first comparator for comparing a received ultrasonic wave reception signal with a reference voltage of a predetermined level, a flip-flop for inputting an output of the first comparator, and the received ultrasonic wave reception. The second to input the signal and detect the zero-cross point
And a level control means for adjusting the level of the ultrasonic reception signal by amplification or the like at the input stage of the second comparator, and the output of the flip-flop and the second comparator. A reception signal processing device for ultrasonic measurement, characterized by being equipped with an AND gate for inputting the output of and.