JPS642905B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a method for arranging a transmitter and a receiver facing each other with a certain distance apart, and the time it takes for an ultrasonic pulse sent from the transmitter to reach the receiver. The present invention relates to a device that measures the propagation time of ultrasonic waves used in devices that measure intervals and calculate wind speed, flow speed, etc. based on the counting results.

Here, the propagation time of ultrasound is measured by counting the clock pulses included in the time from transmitting the ultrasound pulse to receiving it, but at the beginning and end of counting, the time is extremely short. This requires advanced design technology, which is not only economically disadvantageous but also extremely complicated to manufacture.

In view of this point, the present invention incorporates a means for expanding the time interval as simple as possible to perform processing in a time expanded by an arbitrary m times, thereby ensuring reliable measurement and improving measurement accuracy. .

Next, an explanation will be given based on drawings showing examples.

FIG. 1 is a block diagram of the embodiment, and FIG. 2 is an explanatory diagram of the operation, and the parts indicated by symbols in FIG. 1 are shown corresponding to each other.

In FIG. 1, 1 and 2 are set-reset flip-flop circuits, 3 is an AND gate circuit,
4 is an up counter, 5 is a subtracter, 6 is an OR circuit, 7 is an integrator, and 8 is an analog-to-digital converter.

P indicates a transmitting pulse input terminal, R indicates a receiving pulse input terminal, and CLK indicates a clock pulse input terminal.

The transmitted pulse P ₁ (see FIG. 2 A) entering the terminal P and the received pulse R ¹ from the terminal R (see FIG. 2 B) are connected to the set terminal S and the reset terminal of the first flip-flop circuit 1, respectively. When the voltage is applied to the terminal R, the output of the circuit 1 is turned ON between the transmission pulse P ₁ and the reception pulse R ₁ as shown in FIG. 2C, and this output is applied to one terminal of the AND gate circuit 3.

A clock pulse from terminal CLK is applied to the other terminal of circuit 3, and the output of circuit 3 is as shown in FIG. Count the number A of clock pulses.

On the other hand, the transmitting pulse _P1 and the receiving pulse _R1 are applied to the set terminal S of the second flip-flop circuit 2 via the OR circuit 6, while the clock pulse is applied to the reset terminal R, and the output is the first one. As shown in Figure 2E, the output is ON for t ₁ hour starting from the rising edge of the transmitting pulse _P1 and ending at the rising edge of the first clock pulse following the transmitting pulse _P1 , and the output is ON for the receiving pulse _R1 . Even if the received pulse R ₁
up to the rising edge of the first clock pulse following
t Outputs that are ON for ₂ hours are obtained, and these outputs become the inputs of the integrator 7. After both outputs are integrated, the analog value is converted to a digital value by the analog-to-digital converter 8, and then sent to the subtracter 5. Apply.

If the resolution of the analog-to-digital converter 8 is selected appropriately, when the outputs at times t ₁ and t ₂ detected by the second flip-flop circuit 2 are integrated and digitized, the resolution will be reduced. The data can be processed with a magnification factor determined by the calculation, for example, m times, that is, t ₁ and t ₂ are multiplied by m.

On the other hand, since the output of the first flip-flop circuit 1 (see FIG. 2 C) is applied to the subtracter 5, the output of the subtracter 5 is the digital value B corresponding to mt ₁ hour and the digital value B corresponding to mt ₂ hours. The difference between the digital values C of B-
C is obtained.

Count values A and (B-C) obtained in this way
By performing the following arithmetic processing on , it is possible to obtain a calculated value that indicates the correct time interval from the transmitted signal to the received signal.

If the scale of the A/D converter is set to m, and the time interval corresponding to 1 count obtained in A is set to full scale, the value of 1 bit obtained in (B-C) will be 1/ Since it has a weight of time interval m, in order to convert both to the same time unit, the count value of A must be multiplied by m, or (B
- It is necessary to set the count value of C) to 1/m. In other words, when m values of (B-C) are gathered, they become the same time unit as A.

Therefore, the time interval t between transmission and reception is as shown in the following formula. That is, time interval t = [A x m + (B-C)] x time equivalent to one wavelength of the clock/m or = [A + 1/m (B-C)] x (time equivalent to one wavelength of the clock) Although we will not discuss the calculation methods in detail, we will use digital calculations, conversion to analog values, etc.
A well-known calculation method may be used.

The present invention is as explained above. Conventionally, only the count value of A mentioned above was obtained and this count value was used as the time interval between transmission and reception.
Errors could not be avoided because parts below the wavelength cannot be counted, but by using a time interval expansion circuit, it is now possible to measure parts that are one wavelength away from the clock pulse, allowing accurate time intervals to be measured. It is extremely advantageous not only in terms of manufacturing but also economically, as it eliminates the need to raise the clock pulse frequency unnecessarily high to improve accuracy, and the counter does not need to be particularly high-class. Therefore, the practical effect is great.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment. FIG. 2 is an explanatory diagram of the operation of FIG. 1. 1, 2...Flip-flop circuit, 3...AND gate circuit, 4...Up counter, 5...
Subtractor, 6...OR circuit, 7...Integrator, 8...
Analog to digital converter.

Claims (1)

[Claims] 1. A device that measures the propagation time of ultrasonic waves by counting clock pulses included in the time from when the ultrasonic pulses are transmitted to when they are received. , from sending to receiving
A first flip-flop circuit that is turned ON; a gate circuit to which the output of the circuit and clock pulses are applied; and an up counter to which the output of the gate circuit is applied and counts the number A of clock pulses included in the output. , the transmitting pulse and the receiving pulse sent through the OR circuit, and the clock pulse are applied, starting from the rising edge of the transmitting pulse and the receiving pulse, respectively, and arriving after the transmitting pulse and the receiving pulse, respectively. a second flip-flop circuit that detects a pulse that is ON only during times _t1 and _t2 up to the rising edge of the clock pulse; an integrating circuit to which the output of the circuit is applied; an analog-to-digital converter that digitizes at a magnification of m times ₁ and _t2 ; the output of the analog-to-digital converter and the output of the first flip-flop circuit are applied;
detected at the output of the analog-to-digital converter.
Digital value B corresponding to the time of mt ₁ and mt ₂
It is equipped with a subtracter that calculates the difference between the digital numerical value C corresponding to (B-C), and the value of the time interval t between transmission and reception as t=
1. An ultrasonic propagation time measuring device characterized in that the ultrasonic propagation time is determined as [A+1/m(B-C)]×(time corresponding to one wavelength of a clock).