JPH05825Y2 - - Google Patents

Description

[Detailed explanation of the idea] a Industrial application field The present invention relates to a checker for an ultrasonic current meter.

b. Conventional technology Ultrasonic waves are actually emitted into a propagation medium (for example, water, ebonite, acrylic resin) whose sound speed, dimensions, etc. are known, and the ultrasonic waves propagated through the propagation medium are detected, and an ultrasonic current meter is used. This is a checker for the ultrasonic current meter to confirm whether it is operating normally.

c. Problems to be Solved by the Invention Since the checkers of conventional ultrasonic current meters actually use ultrasonic propagation media such as water and ebonite, the propagation time is fixed for each propagation medium. Therefore, it has been impossible to check the operation due to changes in propagation time due to changes in flow velocity or changes in propagation time depending on the transmission direction.

Furthermore, since it uses an ultrasonic transducer, it is expensive.

An object of the present invention is to provide a checker for an ultrasonic current meter that generates a pseudo received signal delayed by a predetermined time with respect to a transmitted signal without using an actual ultrasonic transducer.

d Means for solving the problem The above problem is solved by the comparison circuit that binarizes the ultrasonic transmission signal, the ultrasonic propagation time setting means that presets a numerical value corresponding to the ultrasonic propagation time, and the ultrasonic frequency. an oscillation circuit that oscillates at a higher frequency; a first counter circuit that counts the output signal of the oscillation circuit and generates a load signal when the counted value reaches a predetermined number; A second counter circuit that presets the value set by the time setting means and counts the output signal of the oscillation circuit, and a write address specified by the output signal of the first counter circuit using the output of the oscillation circuit as a clock signal. This problem was solved by an ultrasonic current meter checker equipped with a static RAM that alternately writes the output of the comparator circuit and reads the contents of the read address specified by the output signal of the second counter circuit.

e Effect The read address of the static RAM is specified by the output of the first counter circuit,
The output of the comparison circuit is stored at the write address.

The count content of the first counter and the count content of the second counter differ by the value set in the ultrasonic propagation time setting means, and the readout specified by the content of the second counter is different. The address has a certain difference from the above write address.
The above static RAM uses the output of the above oscillation circuit as a clock pulse.
The signal written in the RAM is read out with a delay corresponding to the numerical difference between the above addresses.

Since the output of the static RAM has the same waveform as the output of the comparison circuit and has a predetermined time delay, it can be used as a pseudo reception signal of the signal propagated in the medium.

When the ultrasonic propagation time setting means is composed of a plurality of numerical value setting means and a multiplexer, and the numerical values for the forward/reverse directions of the ultrasonic propagation time are independently set with respect to the flow velocity, the values selected by the multiplexer can be set independently. The obtained value is preset in the second counter.

f Example Fig. 1 is a block diagram of an embodiment of a checker for an ultrasonic anemometer according to the present invention, Fig. 2 is a block diagram of an embodiment of an ultrasonic anemometer to which the checker of Fig. 1 is connected, and Fig. 3 is a block diagram of an embodiment of an ultrasonic anemometer checker according to the present invention. The figure is a time chart of the checker signal of FIG. 1.

The ultrasonic current meter shown in FIG. 2 operates as follows during measurement. Part of the output of main oscillator 1 is
The output of the counter 2 and the output of the main oscillator 1 are input to the NAND gate 3. The output of the NAND gate 3 is
The power is amplified by the transmitting circuit T and sent to one of the ultrasonic transducers US1 and US2 via a changeover switch 4 controlled by the output of the counter 2. The ultrasonic waves transmitted from one of the ultrasonic transducers propagate through the fluid at a flow velocity V and are detected by the other ultrasonic transducer. The signal detected by the ultrasonic transducer reaches the receiving circuit R via the changeover switch. The output signal of the receiving circuit R is amplified by the amplifier circuit 5, passed through the measurement/check switch 6, transformed into a rectangular wave by the rectangular wave converting circuit 7, and then converted into a rectangular wave by the second counter circuit 8.
is counted down and becomes one input of the phase difference detection circuit 9. The other input signal of the phase difference detection circuit 9 is obtained from the first counter circuit. The output of the phase difference detection circuit 9 corresponding to the phase difference between the transmitted signal and the received signal is converted into a voltage signal by the phase/voltage conversion circuit 10. The voltage signal is sampled and held in one of the sample and hold units. Two sample and hold circuits are provided and are switched by a sample and hold changeover switch 12 controlled by a monostable flip-flop circuit 11 which is synchronized with the changeover switch 4. For example, the sample and hold circuit S/H ₁ converts the output of the phase/voltage conversion circuit 10 when the ultrasonic propagation direction is in the forward direction with respect to the flow velocity, and the sample and hold circuit S/H ₂ converts the phase/voltage when the direction of ultrasonic propagation is in the opposite direction. The output of the circuit 10 is sampled and held.

A subtraction circuit 13 calculates the difference between the contents held in the sample and hold circuits S/H ₁ and S/H ₂ , and an addition circuit 14 calculates the sum. The above-mentioned sum is negatively fed back to the main oscillation circuit 1 so that the value becomes a constant value, thereby compensating for the dependence of the flow velocity measurement value on the sound velocity in the fluid. Note that the above difference corresponds to the flow velocity V.

On the other hand, when checking the function of the ultrasonic current meter, switch the measurement/check changeover switch 6 to the check mode, send the output of the transmitting circuit T to the input terminal of the checker 15, create a pseudo reception signal in the checker, and then The output is sent to the rectangular wave converting circuit 7. The signal processing after the rectangular wave converting circuit 7 is the same as in the assumed mode.

In contrast to the transmitted ultrasound transmitted from the transducer (Fig. 3a), the ultrasound received by the transducer has an ultrasound propagation time determined by the distance L between the ultrasound transducers, the sound velocity C, and the flow velocity V. It is delayed by φ (Fig. 3b). The values φ ₁ and φ ₂ of the ultrasonic propagation time φ when the flow velocity direction and the ultrasonic direction are forward or backward are given by the following equations.

φ ₁ = L/C+V...(1) φ ₂ = L/C-V...(2) The input signal of the checker of the ultrasonic current meter shown in FIG. 1 is the signal in FIG. 3 a. At this time, the signal shown in FIG. 2b, which is a pseudo received signal, is generated as an output signal.

The checker shown in FIG. 1 binarizes the transmission signal from the transmitting circuit 4 shown in FIG.
17, read the signal from the 1-bit static RAM 17 after a predetermined period of time has elapsed,
It is sent out via the D flip-flop circuit 18 and the level shift circuit 19.

The write address and read address of the static RAM 17 are specified by the counts of the first counter circuit CNT1 and the second counter circuit CNT2, respectively. The above first counter circuit
Contents of CNT1 and the above second counter circuit CNT2
The contents of are sent to the address terminal of the 1-bit static RAM 17 via the first multiplexer MPX1. Since the write address terminal and the read address terminal are common, writing and reading are selected by the W control terminal of the 1-bit static RAM.

The first and second counters CNT1 and CNT2 count the output signals of the oscillation circuit OSC. Note that the input signal to the W control terminal is the output signal of the OSC via the delay circuit DL. The delay circuit DL can sometimes be omitted. The above first counter circuit
When CNT1 reaches a predetermined count value N (for example, N=100), the load signal is sent to the second counter circuit CNT2.
send to The second counter circuit CNT2 presets a numerical value n, which is an output signal of a second multiplexer MPX2, which will be described later, every time it receives the load signal. Therefore, the first counter circuit
CNT1 and the second counter circuit CNT2 operate the oscillation circuit while keeping the difference between their counts at a constant value n.
Count the output of OSC. Note that the second counter circuit CNT2 counts the output of the oscillation circuit OSC via the inverting circuit 20. As a result, the contents of both counter circuits CNT1 and CNT2 alternately change every half cycle of the output of the oscillation circuit OSC. oscillation circuit
Counter circuit CNT1, CNT for each pulse of OSC
Since the contents of 2 change by 1, the above 1 bit
The write address and read address of the static RAM also change one by one. At this time, since the difference between the write address and the read address is a numerical value n, the signal input to the input terminal of the 1-bit static RAM 17 is sent out from the output terminal with a delay of a time corresponding to the numerical value n. The signal sent from the output terminal is sent to the rectangular wave converting circuit 7 in FIG. 2 via a D flip-flop circuit and a level shift circuit 19. The D flip-flop 18 is used to remove the influence when the output of the static RAM 17 is temporarily in a floating state.
It may not be necessary depending on the type of RAM.

a second multiplexer MPX that sends a preset value n to the second counter circuit CNT2;
Two data setting means DS1 and DS2 (for example, a dip switch) are connected to 2. In the data setting means DS1 and DS2, numerical values n 1 corresponding to the ultrasonic propagation time φ ₁ =L/C+V φ ₂ =L/C-V when the flow velocity and the ultrasonic traveling direction are forward/reverse, _{respectively.} , n ₂ . The above numerical value n ₁ ,
_n2 becomes a numerical value n which is alternately selected by the control signal cs (for example, a 10 Hz rectangular wave) of the second multiplexer MPX2 and preset in the second counter circuit CNT2. The signal of the counter circuit 2 which controls the changeover switch 4 in FIG. 2 can be used as the control signal cs.

Variables C, V, L in the formula giving φ ₁ and φ ₂ above
By arbitrarily changing , it is possible to conduct a simulation test of flow velocity measurement almost freely.

g Effect It is possible to check whether the operation of the flow rate measuring device is normal or abnormal without actually flowing the fluid.

Can be checked without using an actual ultrasound transducer.

It is possible to simulate the case where the ultrasound propagation direction is forward/reverse to the flow velocity.

It can be conveniently used during initial installation on site and maintenance services.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of a checker for an ultrasonic anemometer according to the present invention, Fig. 2 is a block diagram of an embodiment of an ultrasonic anemometer to which the checker of Fig. 1 is connected, and Fig. 3 is a block diagram of an embodiment of an ultrasonic anemometer checker according to the present invention. This is a time chart of the checker signal in Figure 1. 1... Main oscillation circuit, 2... First counter, 3
...HAND gate, 4...Switch switch, 5
...Amplification circuit, 6...Measurement/check changeover switch, 7...Square wave conversion circuit, 8...Second counter, 9...Phase difference detection circuit, 10...Phase/voltage conversion circuit, 11... Monostable flip-flop circuit, 12...sample hold changeover switch,
13... Subtraction circuit, 14... Addition circuit, 15...
Checker, 16... Comparison circuit, 17... Static RAM, 18... D flip-flop circuit, 19... Level shift circuit, 20... Inverting circuit. CNT1, CNT2...Counter circuit,
DL... delay circuit, DS1, DS2... ultrasonic propagation time setting means, MPX1, MPX2... multiplexer circuit, OSC... oscillation circuit, R... receiving circuit,
SH ₁ , SH ₂ ... Sample hold circuit, T ... Transmission circuit, US1, US2 ... Ultrasonic transducer.

Claims (1)

[Claims for Utility Model Registration] (1) A comparison circuit that binarizes the ultrasonic transmission signal, an ultrasonic propagation time setting means that presets a value corresponding to the ultrasonic propagation time, and a frequency higher than the ultrasonic frequency. an oscillation circuit that oscillates, a first counter circuit that counts the output signal of the oscillation circuit and generates a load signal when the counted value reaches a predetermined number; and a first counter circuit that generates a load signal when the count reaches a predetermined number; a second counter circuit that presets the numerical value set by the means and counts the output signal of the oscillation circuit, and a write address specified by the output signal of the first counter circuit using the output of the oscillation circuit as a clock signal. A checker for an ultrasonic current meter, comprising a static RAM that alternately writes the output of the comparison circuit and reads the contents of the read address specified by the output signal of the second counter circuit. (2) Utility model registration claim 1, characterized in that the ultrasonic propagation time setting means comprises two data setting means and a multiplexer MPX2 that selects the numerical value set in the data setting means. Checker for the ultrasonic current meter described. (3) The checker for an ultrasonic current meter according to claim 2, wherein the data setting means is a dip switch.