JPH07159221A - Ultrasonic level measuring apparatus - Google Patents

Abstract

PURPOSE:To eliminate the influence of pressure variation on the ultrasonic level by providing an ultrasonic oscillator with a pressure sensor for detecting the pressure variation. CONSTITUTION:An ultrasonic oscillation unit 1 comprises an ultrasonic oscillator 3 for oscillating an ultrasonic wave and receiving the reflected wave, a preamplifier 4, a temperature measuring resistor 5, and a pressure sensor 15 for detecting the atmospheric pressure of the oscillation unit 1. The pressure detecting circuit 16 in an ultrasonic level meter 2 determines a gain reverse proportional to the square of pressure for a pressure signal and alters the gain of a receiving amplifier 7. In other words, when the pressure increases, the gain of the amplifier 7 is decreased to lower the signal level of undesired receiving wave being captured as noise thus avoiding the trigger level. When the pressure decreases, the gain is increased to amplify the damped receiving wave voltage over the trigger level. Consequently, a normal receiving wave is detected at the trigger level and the level signal processing is effected regardless of the pressure variation.

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]

SUMMARY OF THE INVENTION An ultrasonic level measuring apparatus of the present invention is an ultrasonic level measuring apparatus for transmitting ultrasonic waves to a storage object stored in a storage tank and receiving reflected waves reflected by the storage object. Sound wave transmitter, preamplifier that amplifies the reflected wave, receiving amplifier that amplifies the received signal from the preamplifier, and determine whether the received signal amplified by the receiving amplifier exceeds a specified level A trigger circuit, a transmission circuit that transmits the transmission time transmitted from the ultrasonic transmitter, and time detection that calculates the time difference between the transmission time transmitted by the transmission circuit and the reception time of the reflected wave obtained from the trigger circuit. An ultrasonic level measuring device comprising a circuit and a level conversion circuit for calculating a stored product level value by converting a time difference obtained by a time detection circuit into a distance from an ultrasonic transmitter to a stored product. In addition, a pressure sensor that detects the pressure of the propagation medium interposed in the storage tank, a pressure detection circuit that calculates the propagation medium pressure value from the pressure signal from the pressure sensor, and a propagation medium pressure value that is output from the pressure detection circuit. And a gain adjusting circuit for adjusting the gain of the receiving amplifier. The ultrasonic level measuring device according to claim 2 further includes a change rate determining circuit that determines whether the propagation medium pressure value output from the pressure detecting circuit exceeds a predetermined pressure set value, and a change rate. When the result determined by the determination circuit is less than or equal to the pressure set value, a holding circuit for holding the stored material level value output from the level conversion circuit is provided. The ultrasonic level measuring device according to claim 3 further comprises an equivalent temperature compensation 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. And

[0012]

In the ultrasonic level measuring apparatus of the present invention, ultrasonic waves are transmitted to the stored material stored in the storage tank, the reflected wave reflected by the stored material is received, and the reflected wave is amplified. , Amplifies the received signal from the preamplifier, determines whether the received signal amplified by the receiving amplifier exceeds a predetermined level, and transmits the transmission time transmitted from the ultrasonic transmitter. , Calculates the time difference between the transmission time transmitted by the transmission circuit and the reception time of the reflected wave obtained from the trigger circuit, and converts the time difference obtained by the time detection circuit into the distance from the ultrasonic transmitter to the stored object. The pressure level of the propagating medium intervening in the storage tank is detected, the propagating medium pressure value is calculated from the pressure signal from the pressure sensor, and the propagating medium pressure value output from the pressure detection circuit is calculated. Therefore adjusting the gain of the receiving amplifier. Further, in the ultrasonic level measuring device according to claim 2, it is determined whether or not the propagation medium pressure value output from the pressure detection circuit exceeds a predetermined pressure set value, and the change rate determination circuit determines. If the result is less than the pressure set value, the stored level value output from the level conversion circuit is held. Further, in the ultrasonic level measuring device according to the third aspect, the propagation medium temperature is converted from the propagation medium pressure value output by the pressure detection circuit to correct the stored material level 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,
Reference numeral 10 is a temperature detection circuit for calculating the propagation medium temperature based on the temperature signal from the temperature detector 5, and 11 is a temperature compensation circuit for correcting the stored level value output from the level conversion circuit 12 according to the temperature value from the pressure detection circuit 10. 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 to hold the output so that the level signal does not change when the change rate is too large and cannot be dealt with by the gain adjustment.

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.

In the ultrasonic level measuring apparatus according to the second aspect, 18 is a change rate judging circuit for judging whether or not the propagation medium pressure value output from the pressure detecting circuit exceeds a predetermined pressure set value. , 19 is a hold circuit for holding the stored material level value output from the level conversion circuit 12 when the result determined by the change rate determination circuit 18 is less than or equal to the pressure set value. The sound wave level measuring device is characterized by including an equivalent temperature compensating circuit that converts the propagation medium temperature from the propagation medium pressure value output by the pressure detection circuit and corrects the stored level value.

[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 determination circuit 19 Hold circuit

Claims (3)

[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 An ultrasonic level measurement comprising: a level conversion circuit for converting the time difference obtained by the time detection circuit into a distance from the ultrasonic transmitter to the stored material to calculate a stored material level value. In the apparatus, a pressure sensor for detecting the pressure of the propagation medium interposed in the storage tank, a pressure detection circuit for calculating a pressure value of the propagation medium by a pressure signal from the pressure sensor, and an output from the pressure detection circuit. And a gain adjustment circuit that adjusts the gain of the reception amplifier according to the pressure value of the propagation medium. 2. A change rate determination circuit for determining whether or not the propagation medium pressure value output from the pressure detection circuit exceeds a predetermined pressure set value, and a result determined by the change rate determination circuit. Is less than the pressure setting value,
An ultrasonic level measuring device, comprising: a hold circuit that holds a stored-material level value output from the level conversion circuit. 3. The equivalent temperature compensating circuit for converting the propagation medium temperature from the propagation medium pressure value output by the pressure detection circuit to correct the stored material level value. The ultrasonic level measuring device described in 1.