JP3362936B2 - Ultrasonic level measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic level measuring device for measuring the level of a tank, a tank, or a stored material in a container installed in a nuclear power plant or an industrial plant.

[0002]

2. Description of the Related Art Conventionally, in nuclear power plants and industrial / industrial plants, tanks, tanks, and containers for storing substances such as water, oil, and solidification have been installed.
To control the inflow, it is necessary to aim at the level of storage.

As a measuring instrument for measuring the level, a non-contact type level meter for ultrasonic application is applied so as not to directly touch the stored material.

The conventional ultrasonic level meter has an ultrasonic wave transmitter and an ultrasonic wave level meter, and an ultrasonic wave transmission signal is output from a pulse transmission circuit of the ultrasonic wave level meter. The ultrasonic transmitter receives this transmission signal and transmits ultrasonic waves from the ultrasonic transmitter. The ultrasonic wave hits the surface of the storage in the tank and is reflected, and the reflected wave is received by the ultrasonic transmitter. The received wave is then amplified by the preamplifier in the transmitter and sent to the ultrasonic level meter. In the ultrasonic level meter, the reception amplifier 7 removes the influence of noise and noise. Therefore, after the reception amplifier amplifies the signal so that the S / N ratio can be obtained, the trigger circuit catches the reception signal.

When the received wave is caught, the time T from transmission to reception is detected and the distance D is obtained. (Distance D = speed of sound C
Also, since the speed of sound changes depending on the temperature of the medium that propagates ultrasonic waves, a temperature measuring resistor is provided in the ultrasonic transmitter to detect the ambient temperature and perform temperature compensation (sound speed correction). And then seek the level.

The level (= distance) thus obtained is output to the indicator and compared with a high or low set value by a comparison circuit. If the value is abnormal, an alarm is output. It is used as an interlock to stop etc.

[0007]

The conventional ultrasonic level meter corrects the sound velocity by changing the temperature of the propagation medium, but does not process the change in pressure.

For this reason, when pressure fluctuations in the gas phase occur at the time of inflow and outflow of stored products in a closed tank or the like, an output different from the actual water level is output, and in some cases, the received signal is below the trigger level. Then, there may be a problem in operation monitoring such as down-scaling and false trip output.

In such a case, the conventional level output signal is provided with a first-order delay circuit to increase the time constant and suppress the signal change, but there is a problem that the response becomes slow.

In order to solve the above-mentioned problems, the present invention adds a pressure sensor to an ultrasonic transmitter, detects a change in pressure, and detects an ultrasonic level so that the change in pressure does not affect the level output. The purpose is to provide a measuring device.

[0011]

The ultrasonic level measuring device of the present invention transmits ultrasonic waves to a storage object stored in a storage tank and receives a reflected wave reflected by the storage object. An ultrasonic wave transmitter, a preamplifier that amplifies the reflected wave, a receiving amplifier that amplifies a received signal from the preamplifier, and the received signal amplified by the receiving amplifier exceeds a predetermined specified level. A trigger circuit that determines whether or not there is a transmission circuit that transmits the transmission time transmitted from the ultrasonic transmitter, the transmission time transmitted by the transmission circuit and the reflected wave obtained from the trigger circuit. a time detecting circuit for calculating a time difference between the reception time, transfer time difference obtained by the time detection circuit
In the ultrasonic level measuring device, which comprises: a level conversion circuit that calculates a stored material level value by converting the distance from the ultrasonic transmitter to the stored material according to the speed of sound in the seed medium .
Pressure and temperature of the propagation medium present in the storage tank
And a temperature sensor for detecting the degree , a pressure detection circuit and a temperature detection circuit for calculating a propagation medium pressure value and a temperature value by the pressure signal and the temperature signal from the pressure sensor and the temperature sensor , and this pressure A gain adjusting circuit for adjusting the gain of the receiving amplifier according to the pressure value of the propagation medium output from the detecting circuit; and the pressure detecting circuit
The rate of change of the pressure value of the propagating medium output from the
If the conversion rate is too large, the output level of the level conversion circuit is
Change rate determining circuit for holding the level
Of the sound velocity in the propagation medium to obtain the level of
Temperature compensation that corrects according to the temperature value output from the output circuit
A gain adjusting circuit lowers the gain of the amplifier when the propagation medium pressure value rises to lower the noise other than the received signal below the trigger level, and when the propagation medium pressure value falls. The gain of the amplifier is increased to adjust the level of the received signal to be higher than the trigger level. Further, in the present invention, an equivalent temperature compensating circuit for converting the propagation medium temperature from the propagation medium pressure value output by the pressure detection circuit and correcting the stored material level value may be used.

[0012]

In the ultrasonic level measuring apparatus of the present invention , the storage tank is
The ultrasonic wave is transmitted to the stored material inside the battery, the reflected wave reflected by the stored material is received, and the reflected wave is received by the preamplifier.
Amplify and receive the signal amplified by this preamplifier.
The received signal is amplified by the receiving amplifier, and this received signal is determined in advance.
The trigger circuit determines if the specified level is exceeded.
Set. This trigger circuit allows reception of waves that exceed the specified level.
The timing at which the signal is received is the reception time of the reflected wave,
Calculate the time difference from the ultrasonic wave transmission time with a time detection circuit
To do. This time difference is converted into a distance by the speed of sound in the propagation medium.
Calculate the distance from the ultrasonic transmitter to the stored product
Calculate the level. At this time, the propagation medium in the storage tank
The pressure and temperature are detected, and the reception medium
The gain of the sound is adjusted and the speed of sound is compensated by the temperature of the propagation medium.
To correct. In addition, the change in pressure is too large, and the gain adjustment
If it cannot respond, the level signal should be adjusted so that it does not change.
Holds the output of the converter circuit. These results, storage
Unaffected by pressure and temperature changes of the propagation medium in the tank
The storage level can be measured accurately and stably.
It The temperature of the propagation medium is converted from the pressure of the propagation medium.
You may use the value.

[0013]

EXAMPLE An example of the ultrasonic level measuring apparatus of the present invention will be described below. In FIG. 1, reference numeral 3 denotes an ultrasonic wave transmitter that transmits an ultrasonic wave to a stored object stored in a storage tank and receives a reflected wave reflected by the stored object, 4 is a preamplifier for amplifying the reflected wave, Reference numeral 7 is a reception amplifier for amplifying the reception signal from the preamplifier 4, 8 is a trigger circuit for judging whether or not the reception signal amplified by the reception amplifier 7 exceeds a predetermined level, and 6 is an ultrasonic wave. Originator 3
A transmission circuit for transmitting the transmission time transmitted from the device, 9 is a time detection circuit for calculating the time difference between the transmission time transmitted by the transmission circuit 6 and the reception time of the reflected wave obtained from the trigger circuit 8, and 12 is the time detection The level conversion circuit 5 for converting the time difference obtained by the circuit 9 into the distance from the ultrasonic wave transmitter 3 to the stored material and calculating the stored material level value, detects the temperature of the propagation medium interposed in the storage tank. Temperature detector,
Temperature detection circuit for calculating a propagation medium temperature by the temperature signal from the temperature detector 5 is 10, a temperature compensation circuit for correcting the reservoir level value output from the level converting circuit 12 by the temperature value from the temperature detection circuit 10 is 11 Reference numeral 15 is a pressure sensor for detecting the pressure of the propagation medium interposed in the storage tank, 16 is a pressure detection circuit for calculating the pressure value of the propagation medium based on the pressure signal of the pressure sensor 15, and 17 is the pressure detection circuit 1.
According to the pressure value of the propagation medium output from 6, the reception amplifier 7
This is a gain adjustment circuit that adjusts the gain of a level meter that measures the level of stored items in a tank using ultrasonic waves, and detects the pressure of the medium in which ultrasonic waves propagate, and the level of the received wave due to pressure changes. It is an ultrasonic level meter characterized by automatically correcting fluctuations.

That is, in this embodiment, an ultrasonic wave transmitter 3 for transmitting an ultrasonic wave and receiving a reflected wave and a preamplifier 4 for amplifying a signal are used.
It is composed of an ultrasonic transmitter 1 having a resistance temperature detector 5 and a pressure sensor 15 built-in, and an ultrasonic level meter 2 for processing signals from the transmitter.

The inside of the ultrasonic level meter 2 is further composed of the following circuits. A transmission circuit 6 that issues a command signal for transmitting an ultrasonic wave to the ultrasonic transmitter 1, a reception amplifier 7 that amplifies the received signal from the ultrasonic transmitter 1, a trigger circuit 8 that determines whether the received signal is at or above a specified level, There is a time detection circuit 9 that detects the time from transmission to reception, and a level conversion circuit 12 that converts the time from the sound speed to the level.

A temperature detecting circuit 10 and a temperature compensating circuit 11 for correcting the sound velocity in the propagation medium are also provided. Further, a circuit 17 for adjusting the gain of the receiving amplifier according to the pressure change and a circuit 18 for judging the pressure change rate are added to prevent the level signal from changing.

The level signals obtained by these circuits are output to the indicator 13 and compared with the alarm level by the comparison circuit 14, and when the level is above or below the set value, an alarm output (interlock signal depending on the system) is output. A circuit for outputting is provided.

The operation of the ultrasonic level meter having the above structure will be described below.

In an ultrasonic level meter, the influence of pressure fluctuations in the atmosphere in which the oscillator is mounted does not cause a change in sound velocity, but it has the following phenomenon.

When the pressure of the atmosphere rises, the density of the gas becomes thicker and the characteristic acoustic impedance of the gas increases. As a result, the electro-acoustic conversion efficiency of the transmitter, the propagation loss of ultrasonic waves, and the overall sensitivity of the reflection coefficient on the water surface increase, and the unwanted reflected waves that were caught as noise during steady operation increase, reaching the trigger level and reaching the water level. The level signal changes as the value becomes higher.

On the other hand, when the pressure of the atmosphere decreases, the specific acoustic impedance of the gas decreases, the overall sensitivity decreases, the normal reception wave signal decreases, the trigger level is not reached, the level signal decreases, and finally downscale occurs. The phenomenon occurs. Expressing these phenomena in a mathematical relationship, it is known that the received voltage signal V of the level meter is proportional to the square of the atmospheric pressure P.

Therefore, in the present invention, a pressure sensor 15 is added to the ultrasonic transmitter 1 to detect the pressure of the atmosphere in which the transmitter is attached. For the pressure signal, the pressure detection circuit 16 of the ultrasonic level meter 2 obtains a gain inversely proportional to the square of the pressure,
Change the gain of the receiving amplifier.

That is, when the pressure rises, the amplifier gain is lowered to lower the level of the unwanted received signal which is regarded as noise so that the trigger level is not caught. If the pressure drops, increase the gain and increase the attenuated received voltage so that it is above the trigger level.

As a result, the normal reception wave is detected at the trigger level, and the level signal conversion processing that is not affected by the pressure fluctuation is performed.

Further, a pressure change rate determination circuit 18 is provided,
If the rate of change is too large to be dealt with by the above gain adjustment, the hold circuit 19 is set so that the level signal does not change.
Therefore, the output is held.

As another embodiment of the present invention, although the pressure sensor and the temperature sensor are separately installed in the ultrasonic level transmitter in the above-mentioned embodiment, they are integrated as a composite sensor.

That is, since the pressure of the medium changes due to the temperature change, a circuit for converting the output change of the pressure sensor into the temperature change is provided in the ultrasonic level meter 2 to detect the temperature for sound velocity correction. . This can reduce the number of sensors installed in the transmitter.

Since the propagation medium temperature can be converted from the propagation medium pressure value output by the pressure detection circuit 16 ,
The level change to obtain the storage level value from this converted temperature value
Also using the equivalent temperature compensation circuit for temperature compensation of the circuit
Yes.

[0029]

As an effect of the present invention, the level signal is not affected even if there is a pressure fluctuation generated during the operation of the plant system (discharge of the stored material, inflow of the stored material, etc.), so that the actual level is accurately monitored. Also, stable measurement and monitoring are possible, and stable operation is also possible. Further, when the output signal of the ultrasonic level meter is used in a system having an interlock such as an alarm or a pump trip, the present invention eliminates unnecessary fluctuations in the level signal, so that a false alarm or a false trip signal is eliminated. Is no longer output, the shock given to the device is alleviated.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultrasonic level measuring apparatus showing an embodiment.

[Explanation of symbols]

16 Pressure detection circuit 17 Gain adjustment circuit 18 Change rate judgment circuit 19 Hold circuit

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01F 23/28 B65G 43/08 G01S 15/08

Claims (2)

(57) [Claims] 1. An ultrasonic wave transmitter that transmits an ultrasonic wave to a stored material stored in a storage tank and receives a reflected wave reflected by the stored material, and a preamplifier that amplifies the reflected wave. A reception amplifier that amplifies the reception signal from the preamplifier, a trigger circuit that determines whether the reception signal amplified by the reception amplifier exceeds a predetermined level, and the ultrasonic wave transmission A transmission circuit for transmitting a transmission time transmitted from the child, a time detection circuit for calculating a time difference between the transmission time transmitted by the transmission circuit and a reception time of the reflected wave obtained from the trigger circuit, and Time difference obtained by the time detection circuit
In the ultrasonic level measuring device, a level conversion circuit that calculates a stored material level value by converting the distance from the ultrasonic transmitter to the stored material according to the speed of sound in the propagation medium, in the storage tank. The pressure of the intervening propagation medium and
And temperature sensor for detecting temperature and temperature, and pressure signal and temperature from this pressure sensor and temperature sensor
A pressure detection circuit and a temperature detection circuit for calculating a propagation medium pressure value and a temperature value by a signal , a gain adjustment circuit for adjusting the gain of the receiving amplifier by the propagation medium pressure value output from the pressure detection circuit, and the pressure detection
The rate of change of the pressure value of the propagation medium output from the circuit is detected.
If the rate of change is too large, the output of the level conversion circuit
Change rate judgment circuit for holding level and level conversion
The speed of sound in the propagation medium for determining the level of the circuit
Temperature corrected by the temperature value output from the temperature detection circuit
A compensating circuit , wherein the gain adjusting circuit lowers the gain of the amplifier when the propagation medium pressure value rises, lowers noise other than the received signal below the trigger level, and lowers the propagation medium pressure value. 2. An ultrasonic level measuring device, characterized in that the gain of the amplifier is increased and the level of the received signal is adjusted to be higher than a trigger level. Wherein converting the propagation medium temperature from the propagation medium pressure value output by the pressure detecting circuit, characterized by comprising the equivalent temperature compensation circuit for correcting the reservoir level value 請 Motomeko 1 Symbol placement of the ultrasonic level measurement device.