JPS5914173B2 - Ultrasonic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the time difference between the counting time required for a counter to count the output of an oscillator to a set value and the propagation time required for an ultrasonic wave to propagate in a fluid to be measured. , based on this difference signal, change the oscillation frequency of a separate oscillator so that the time difference becomes a predetermined value, so that the oscillation frequency is opposite to the oscillation frequency when the ultrasonic wave is emitted in the forward direction to the flow of the fluid to be measured. The present invention relates to an ultrasonic measuring device that measures the flow velocity or flow rate of a fluid to be measured based on the difference between the oscillation frequency and the oscillation frequency when emitted in a direction.

FIG. 1 is a block diagram of a conventional ultrasonic flowmeter.

In FIG. 1, reference numeral 10 denotes a measurement pipe through which the fluid to be measured flows in the direction of the arrow, and transducers 13 and 14 are attached to the outer wall of the measurement pipe 10 via mounting elements 15 and 16. . The transducers 13 and 14 are conversion elements that convert an electrical signal into an acoustic signal or an acoustic signal into an electrical signal. In a certain mode, the transducer 13 becomes a transmitter and the transducer 14 becomes a receiver; In other modes, transducer 14 is the transmitter and transducer 13 is the receiver. This mode switching is performed by a mode switch 9. This mode switch 9 is connected to a transducer 13.
, 14 are controlled by mode switching signals A and B via a gate circuit 6 so that the transducers 13 and 14 alternately act as transmitters and receivers. 1 is an oscillator element, which includes two oscillators 11, 12 and controllers 19, 2.
Consists of 0.

The oscillators 11 and 12 are voltage controlled oscillators whose control voltages are changed by controllers 19 and 20 in accordance with the output signal of the time difference detection circuit 8, thereby changing their oscillation frequencies. This controller 19, 20
In a certain mode, one of them is selected to accept the output signal of the time difference detection circuit 8 by the mode switching signals A and B of the mode switching device 9. Reference numeral 2 denotes a synchronizing pulse generating circuit which generates an output signal synchronized with the output signal of one of the oscillators 11 or 12 selectively designated by the mode switch 9.

3 is a counter for counting the output signal of the oscillator element 1, which starts counting operation based on the output signal of the synchronous pulse generation circuit 2, and the count value is a preset number N according to the diameter of the measurement pipe 10, etc. When it reaches , it sends a counting operation end signal.

Reference numeral 4 denotes a delay element that starts its operation in response to the output signal of the counter 3 and outputs an output signal after a certain period of time has elapsed.

The output signal V of this delay element 4 is guided to a time difference detection circuit 8. Reference numeral 5 denotes a transmitting circuit that transmits an electric signal to drive the transducers 13 and 14 based on the output signal of the synchronous pulse generating circuit 2.

The output electrical signal of this transmitting circuit 5 is selectively guided to a transducer 13 or 14 via a gate circuit 6.
Similarly, the received signal from the transducer 14 or 13 is guided to the receiving circuit 7 via this gate circuit 6.
This receiving circuit 7 transmits a trigger signal Z based on the detection of the received signal, and controls the time difference detecting circuit 8.

FIG. 2 is a circuit diagram of the time difference detection circuit 8, in which a NAND circuit 100 is arranged at the front stage to which the trigger signal Z of the receiving circuit 7 and the output signal v of the delay element 4 are guided. When the trigger signal Z and the output signal V match and the output signal F of the NAND circuit 100 stops transmitting, the transistor Q becomes 0.
It becomes an FF, and a charging current flows from the constant current circuit 90 to the capacitor C via the diode D, thereby charging the capacitor C. Constant current circuit 90, transistor Q1, diode D
O and capacitor C constitute a RAMP circuit, and the output signal R of this RAMP circuit, that is, capacitor C
The charging voltage is led to a differential amplifier 80. A set voltage E5O for propagation time measurement is set in this differential amplifier 80, and the difference voltage between this set voltage E5O (output signal R of the 5RAMP circuit) is transmitted as an output signal S of the time difference detection circuit 8. The output signal S is led to the oscillator element 1.
Note that Q1 is a field effect transistor for discharging the charging voltage of the capacitor C, and it is set to 0N-0 by the signal K.
FF controlled. Furthermore, E5O is set to about 5V. The operation of the ultrasonic flow rate measuring device configured as described above will be briefly described.

First, the mode switching signal A of the mode switching circuit 9 causes the transducer 14 to become a receiver, the oscillator 11 of the oscillator element 1 is connected to the synchronizing pulse generating circuit 2 and the counter 3, and the gate circuit 6 is connected to the transmitting circuit 5. It is assumed that the control is such that the output signal is guided to the transducer 13 and the output signal of the transducer 14 is guided to the receiving circuit 7. After a predetermined period of time has elapsed, when the output signal V is transmitted from the delay element 4, the output signal M of the NAND circuit 100 is stopped, and the capacitor C of the RAMP circuit starts charging. Thereafter, the output signal of the transducer 14 is transmitted, and when the arrival of the ultrasonic wave is detected, the transmission of the output signal Z of the receiving circuit 7 is stopped, so that the output signal F of the NAND circuit 100 is transmitted again. As a result, charging of the capacitor C of the RAMP circuit is stopped. Let the value of the output signal R of the RAMP circuit at this time be w. This output signal w is compared with a set voltage E5O, and the difference voltage ε is transmitted as an output signal S of the time difference detection circuit 8. The oscillation frequency of the oscillator 11 is controlled according to this differential voltage ε. By repeating such operations, the voltage difference ε is finally controlled to be zero, that is, the output signal w is equal to the set voltage E5O. In this way, the forward propagation time Ta when emitting an ultrasonic pulse in the forward direction with respect to the flow of the fluid to be measured is determined by the oscillator 11.
is replaced by the oscillation frequency of Thus, the measurement of forward propagation time is completed. Next, the mode switching signal B of the mode switching circuit 9 causes the transducer 14 to become a transmitter, the transducer 13 to become a receiver, and the oscillator element 1 to switch from the oscillator 12 to the synchronizing pulse generating circuit 2 and the counter 3. The gate circuit 6 is controlled so that the output signal of the transmitting circuit 5 is guided to the transducer 14 and the output signal of the transducer 13 is guided to the receiving circuit 7.

Therefore, the backward propagation time Tb when the ultrasonic pulse is emitted in the opposite direction to the flow of the fluid to be measured by the same operation as described above is replaced by the oscillation frequency of the oscillator 12. Thus, the measurement of the backward propagation time is completed. The difference between the oscillation frequencies of the oscillators 11 and 12 is taken out by a reversible counter 17 as a frequency difference proportional to the flow velocity, and the display circuit 18
It is displayed as flow rate or flow velocity. by the way,
Since ultrasonic waves are susceptible to various disturbances depending on the conditions of the propagation path, it is necessary to sufficiently monitor whether or not propagation is occurring normally.

The present invention has been made in view of these points, and when measuring the forward propagation time and the backward propagation time alternately, the forward ultrasonic pulse and the backward ultrasonic pulse or the backward ultrasonic pulse The ultrasonic measuring device is designed to be able to determine that the propagation of ultrasonic pulses is normal only when two consecutive ultrasonic pulses, i.e., forward ultrasonic pulses, and forward ultrasonic pulses are propagated normally. According to the invention, such an object is to provide a measuring device of the type mentioned at the beginning, in which the time difference (counting time and propagation time) when an ultrasonic pulse is emitted in the forward direction is determined. It is detected whether or not a first voltage signal corresponding to the time difference) and a second voltage signal corresponding to the time difference when emitted in the opposite direction are within a predetermined voltage width, and the first voltage signal Alternately and continuously output a first information signal representing whether or not the voltage signal is within the predetermined voltage range, and a second information signal representing whether or not the second voltage signal is within the predetermined voltage range. a comparator that receives the first information signal and the second information signal from this comparator alternately and consecutively, stores the previously applied information signal, and stores the stored information signal and the information signal immediately after the first information signal and the second information signal from the comparator. and the information signal given to This is accomplished by comprising a logic circuit that emits an output signal indicating that two consecutive ultrasound pulses, a sonic pulse or a backward ultrasound pulse and a forward ultrasound pulse, are propagated together normally. .

Next, embodiments of the present invention will be described in detail based on the drawings.

FIG. 3 is a block diagram of one embodiment of the present invention.

In FIG. 3, parts having the same functions as those in FIG. 1 are given the same reference numerals. In the present invention, an abnormality monitoring circuit 21 is provided that determines whether the propagation of ultrasonic waves is normal or abnormal. This abnormality monitoring circuit 21 is a RAM when emitting ultrasonic pulses in the forward direction.
a comparator 22 that detects whether the value R1 of the output signal R of the P circuit and the value R2 of the output signal R of the RAMP circuit when emitted in the opposite direction are within predetermined voltage widths;
A logic circuit 23 detects whether the values R, , R2 are continuously within the predetermined voltage range. As shown in FIG. 4, the comparator 22 is composed of a first comparator 221 and a second comparator 222, and each of the comparators 221 and 222 has resistors R39R49R5 and R6 (however, the resistor R49R5 is a variable resistor). Setting voltages E5, E52 are set by the power supply E5 and the power supply E5, respectively.
This set voltage E5l is set at a potential slightly higher than the reference voltage E5O in FIG. 0.1V). What is particularly noteworthy about the present invention is that in order to determine whether the propagation of sound waves is normal or abnormal, attention is paid to the output signal R of the RAMP circuit of the time difference detection circuit 7 in FIG. The comparator circuit 22 is led to the remaining inputs of the comparators 221 and 222.
1 is "1" when the output signal R is below the set voltage E5l.
On the other hand, the comparator 222 continues to emit the 6F signal if its output signal R exceeds the set voltage E52. On the other hand, the logic circuit 23 outputs the output N of the comparator 221 and the AND circuit 2 from which output N2 is derived
35 and D to which the output M of this AND circuit 235 is given.
- a flip-flop 231 and a D-flip-flop 232 to which the output Q of this D-flip-flop is applied;
and the outputs Ql of the D-flip-flops 231 and 232,
It mainly consists of an AND circuit 233 from which Q2 is derived, and a sampling pulse T is applied to the T inputs of D-flip-flops 231 and 232, respectively. D-flip-flops 231 and 232 constitute a serial shift register, and in this case, the sampling pulse T becomes the shift pulse of the shift register. In addition,
234 is a NOT circuit, which is used when the abnormal signal U is desired to be in positive logic. Next, the operation of the above configuration will be explained with reference to FIG.

Note that, based on the transmission of the synchronization signal pulse L, the transmission circuit 5
The transmission pulse is transmitted from , and the individual pulses of this synchronizing signal pulse L are subscripts 1, 2, . . . to this L.
will be expressed as Ll, L2, . . . As can be understood from the output signal R of the RAMP circuit in FIG.
When L2, L4, L5, L7, L9, the RAMP
The value of the output signal R of the circuit is within a predetermined voltage range (E52 to E5l) of the set voltages E5l and E52, which means that the ultrasonic wave propagated normally. direction,
When the synchronizing signal pulse L3, L6, L8, the value R
does not fall between the set voltages E5l and E52. Therefore,
Ultrasonic pulse propagation is forward/reverse or backward/
The synchronizing signal pulse L is continuous and normal in both forward directions.
, -L2 and L4-L5, and therefore the propagation of one ultrasonic wave is normal only in this section.A signal W is transmitted from the logic circuit 23 after a certain time delay.On the other hand, the pulse L2-L3? L3-L4 la L5-L
In the continuous sections of 62L6-L7, L7-L8, and L8-L9, the signal W is not transmitted because the propagation of the two ultrasonic pulses is not normal. In this way, in the present invention, two ultrasonic pulses (a continuous forward ultrasonic pulse and a backward ultrasonic pulse, or a continuous backward ultrasonic pulse and a forward ultrasonic pulse) are Only when it is normal can a signal W indicating the normality be obtained. FIG. 6 is a circuit diagram of another embodiment of the abnormality monitoring circuit 21.

In this embodiment, the logic circuit 23 includes a comparator 221
NAN from which the output N1 and sampling pulse T are derived
D circuit 236, a NAND circuit 237 to which the output N2 of the comparator 222 and the sampling pulse T are guided, and both NA
E to which the outputs Ml and M2 of the ND circuits 236 and 237 are derived
xcl-UsiveOR circuit 238 and this Excl
A monostable multivibrator 239 that is triggered or can be triggered by the output M3 of the siveOR circuit 238
It is composed of. The set output pulse width ΔT of this monostable multivibrator 239 is set longer than the sum of the forward direction measurement period and the reverse direction measurement period. In other words, it is equal to or more than two cycles of the sampling pulse T. FIG. 7 shows the waveforms of the output signals in each section when measurements are carried out under the same conditions as in FIG. 5 and the same output signal R appears. As shown in FIG. 7, since the monostable multivibrator 239 can be triggered, if the propagation of ultrasonic pulses is abnormal continuously or every other time, the monostable multivibrator 239 will continue to propagate. An abnormal signal is sent. Note that the embodiment shown in FIG.
Compared to the embodiment shown in FIG. 4, the set time ΔT, that is, the duration of the abnormality signal can be arbitrarily adjusted, which is convenient when a long-term abnormality warning is required. FIG. 8 is a circuit diagram of another embodiment of the present invention.

In this embodiment, the difference △f (= f1 - F2
) and this modulator 2
an F/V converter 29 that converts the output signal of 8 into a voltage signal, and a differential amplifier 24 to which the output of this converter 29 is guided to one input and the output of an integrator 26 to be described later is guided to the other input. and this differential amplifier 24 via the switch circuit 25.
The V/I converter 27 includes an integrator 26 to which the output of the integrator 26 is guided, and a V/I converter 27 that converts the voltage output of the integrator 26 into a current signal. The switch circuit 25 is composed of, for example, a field effect transistor Q3, and is controlled from 0N to 0FF by the output signal U of the abnormality monitoring circuit 21. In other words, when the signal U (or σ) is a "1" signal (that is, the propagation of the sound wave is abnormal), the transistor Q3 is controlled to 0N, and the output of the differential amplifier 24 is supplied to the integrator 26. be prevented from being done. Therefore, in this embodiment, when the propagation of sound waves is abnormal,
The previous indicated value is retained. Note that the LED is a light emitting diode. As explained above, in the present invention, since the normality or abnormality of ultrasonic propagation is determined for each measurement in the forward and reverse directions, the response to abnormality determination is quick.
Therefore, it has the effect of ensuring that there is no omission in abnormality detection.Moreover, only when the propagation of the ultrasonic pulse is normal in two consecutive directions, such as in the forward direction and reverse direction, or in the reverse direction and forward direction, the propagation is detected. This is very desirable from a measurement point of view because it sends out a signal indicating that it is normal.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional ultrasonic flow rate measuring device, Fig. 2 is a circuit diagram of its time difference detection circuit, Fig. 3 is a circuit diagram of an embodiment of the present invention, and Fig. 4 shows its main parts. A circuit diagram of the embodiment, Fig. 5 is a waveform diagram of output signals of each part to explain its operation, Fig. 6 is a circuit diagram of another embodiment of the main part, and Fig. 7 explains its operation. FIG. 8 is a circuit diagram of another embodiment of the present invention. 1: Oscillator element, 2: Synchronous pulse generation circuit, 3: Counter, 4: Delay element, 5: Transmission circuit , 6... Gate circuit, 7... Receiving circuit, 8... Time difference detection circuit, 9... Switch, 11, 12...
... Oscillator, 21 ... Abnormality monitoring circuit, 22.
...Comparator, 23...Logic circuit.

Claims (1)

[Claims] 1. The counter detects the time difference between the counting time required for counting the oscillation output of the oscillator up to a set value and the propagation time required for the ultrasonic pulse to propagate in the fluid to be measured, and Based on the signal, the oscillation frequency of the oscillator is changed so that the time difference becomes a predetermined value, and thus ultrasonic pulses are emitted alternately in the forward direction and the reverse direction with respect to the flow of the fluid to be measured. The ultrasonic pulse is emitted in the forward direction, and the flow velocity or flow rate of the fluid to be measured is measured from the difference between the oscillation frequency when emitted in the forward direction and the oscillation frequency when emitted in the reverse direction. detecting whether or not a first voltage signal corresponding to the time difference when emitted in the opposite direction and a second voltage signal corresponding to the time difference when emitting in the opposite direction are each within a predetermined voltage width; A first information signal indicating whether the first voltage signal is within the predetermined voltage width and a second information signal indicating whether the second voltage signal is within the predetermined voltage width are alternately and continuously transmitted. and a comparator that outputs the first information signal and the second information signal from this comparator alternately and continuously, stores the previously applied information signal, and outputs the stored information signal. and an information signal given immediately thereafter, and if both of the information signals are information signals indicating that each of the voltage signals is within the predetermined voltage width, it is determined that the forward ultrasonic pulse is a forward ultrasonic pulse. A logic circuit that emits an output signal indicating that two consecutive ultrasonic pulses, that is, a backward ultrasonic pulse or a backward ultrasonic pulse and a forward ultrasonic pulse, are propagated normally. Ultrasonic measuring device. 2 The counter detects the time difference between the counting time required for the oscillator's oscillation output to the set value and the propagation time required for the ultrasonic pulse to propagate in the fluid under test, and based on this difference signal, The oscillation frequency of the oscillator is changed so that the time difference becomes a predetermined value, and the ultrasonic pulses are emitted alternately in the forward direction and in the reverse direction with respect to the flow of the fluid to be measured, and the ultrasonic pulses are emitted in the forward direction. The time difference when the ultrasonic pulse is emitted in the forward direction, in which the flow velocity or flow rate of the fluid to be measured is measured from the difference between the oscillation frequency when the ultrasonic pulse is emitted in the forward direction and the oscillation frequency when the ultrasonic pulse is emitted in the opposite direction. and a second voltage signal corresponding to the time difference when emitted in the opposite direction are each within a predetermined voltage width. a comparator that alternately and continuously outputs a first information signal representing whether the voltage signal falls within the voltage width and a second information signal representing whether the second voltage signal falls within the predetermined voltage width; The first information signal and the second information signal are alternately and continuously applied from this comparator, and the previously applied information signal is stored, and this stored information signal and the second information signal are applied immediately after. When both information signals are information signals indicating that each of the voltage signals is within the predetermined voltage width, a forward ultrasonic pulse and a reverse ultrasonic pulse or a logic circuit for generating an output signal indicating that two successive ultrasonic pulses, a backward ultrasonic pulse and a forward ultrasonic pulse, are propagated together normally; and an oscillation in the forward direction obtained from the oscillator; A modulator that forms a difference between the oscillation frequency in the opposite direction, an F/V converter that converts the output signal of this modulator into a voltage signal, and the output of this F/V converter is guided to one input. comprising a differential amplifier and an integrator to which the output of the differential amplifier is guided through a switch, the output of the integrator being guided to the other input of the differential amplifier;
The switch is turned on and off based on the output of the register.
An ultrasonic measuring device characterized in that the output of the integrator is used as a measure of the flow velocity or flow rate of the fluid to be measured.