JPS63120226A - Level measuring apparatus - Google Patents

Abstract

PURPOSE:To perform highly reliable measurement, by operating the powder or liquid level in a container on the basis of the frequency peak of the reflected wave of a sonic wave uniformly containing the frequency component of a definite band oscillated in the container. CONSTITUTION:A pulse sound containing an almost uniform frequency component to total frequency in an audible sound band is oscillated in the space part of a hopper 1 through a converter 3. The reflected sonic wave from the space part due to said pulse sound is detected by a pickup 4 and processed by an FFT operation part 6 and an operation part 7 through a data collection part 5 to calculate the frequency peak of the reflected sonic wave and a level is determined from the peak frequency-storage level relation of resonance frequency relation preliminarily calculated. Powder or liquid level measuring reliability is enhanced by the determination based on the resonance frequency changing in accordance with the volume of said space part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a level measuring device used for level measurement in various plants, particularly in hoppers for powder and granular materials.

[Conventional technology]

Many level meters for powder and granular materials that utilize capacitance, microwaves, or radiation have been devised and used. However, these level meters
There was a problem that the contact part of the detection part or υ malfunction could occur.

[Problem that the invention aims to solve]

In addition, in a powder hopper, unlike a liquid hopper, the shape of the particle layer at the top of the hopper is complex, so it has been difficult to accurately determine 1/bell using conventional techniques. In order to solve these problems by extension of the conventional technology, there is a method to increase the number of measurement points and perform calculations based on information from many measurement points to determine the average level, or a method using mechanical scanning. Possible methods include installing a Φ Yana inside a hopper and measuring a large number of points. However, increasing the number of detection units increases the cost, or requires a mechanism to perform calculations on data from multiple points. Furthermore, the inside of the powder hopper is generally not a favorable environment for mechanical mechanisms, resulting in a decrease in reliability.

[Means to resolve the gap]

In other words, the invention includes an oscillating unit that oscillates a sound wave containing substantially uniform frequency components in a certain band within the container.

a receiver for the sound wave; a peak detector for determining the frequency peak of the received sound wave from the power spectrum of the sound wave;
The apparatus includes a calculation section that calculates the level inside the container from the relationship between the volume of the intermediate portion of the container and the frequency peak, which is determined in advance.

[Effect]

In the above configuration, the volume of the middle part of the container changes depending on the level of the stored powder, etc., and the space volume has a unique resonant frequency, which is measured in advance. The relationship between the volume of the middle part of the container and the resonance frequency (frequency peak to be described later) is verified in advance. The sound waves oscillated within the oscillator and the υ container have substantially equal frequency components in a certain band. Therefore, in the sound wave received by the receiver, the resonance frequency component of the sound is magnified.
If the peak detector performs a power spectrum analysis 1-7 of the received sound to find the frequency peak, the resonance frequency is obtained, and the frequency peak is calculated using the second part.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Fig. 1 shows its configuration: 1 is a hopper, 2 is a pulse sound generator, 3 is a converter, 4 is a pickup, 5 is a data collection section, 6 is an FFT (fast Fourier transform) calculation section, 7
Reference numeral 8 indicates a calculation section, 8 a display section, and 9 a control signal line.

A pulse sound generator 2 and a transducer 3 are installed in the hopper 1 to generate an acoustic pulse having an extremely short width, thereby forming an oscillation section. Inside the hopper 1, a pickup 4, for example, a microphone, is further installed as a receiver for detecting the sound resonating inside the hopper 1. When this device starts operating, the pulse sound generator 2
A pulse-like sound is emitted into the hopper 1 from the hopper 1. If the width of a pulse is infinitely short and its amplitude is infinitely large, the pulse has equal energy at all frequencies, that is, it can be considered a unit impulse.

Of course, in reality, pulses with a width of 0" cannot be obtained, but in a relatively low frequency range such as audible sounds, that is, in the range of frequencies necessary for level detection, for practical purposes, it is It is considered that the frequency components are almost uniform for all frequencies.

Simultaneously with the operation, the pulse sound generator 2 sends a start pulse indicating the start of operation to the data collection section 5.

In response to this start pulse, the data acquisition unit 5 captures and stores the signal from the big ara f4 in a binary form. The data acquisition time, acquisition speed, and number of data are determined by the frequency of the target pulse.

The collected data is subjected to FFT calculation in an FFT calculation unit 6 serving as a peak detection device, and is expanded from the time domain to the frequency domain. Here, FFT (Fast Fourier Transform) was used for the transformation to determine the frequency, but other transformation methods,
For example, a Wallace transform or a Hadamard transform may be used.

The data expanded into the frequency domain by the FFT calculation unit 6 is
An amplitude component, that is, a power spectrum, for each frequency is obtained, and a certain frequency peak is determined. Here, the reason why the amplitude is not limited to the maximum frequency peak is because there is a possibility that vibrations associated with the hopper 1 that are unique to various devices may be included.

In any case, the frequency determined here is applied to the next calculation unit 7.
As shown in Figure 2, from the relationship "level of powder = ((peak frequency)",
The level is determined and displayed on the next display section 8. If necessary, it is of course possible to use it not only for display but also for control purposes. This operation is then repeated υ at an appropriate period. This is controlled by a signal on control signal line 9.

FIG. 2 shows an example of the relationship between the powder level and the peak frequency. This is 1. It is necessary to actually measure and store it in the calculation unit 7 in advance.

Note that in small-scale equipment, for example, laboratory-scale equipment, the volume of the hopper is small, so the volume of associated piping cannot be ignored; however, in industrial-scale equipment, such as the one targeted by the present invention, In this case, the influence of piping etc. can be almost ignored.

2, the device of this embodiment does not measure the level by directly detecting the top surface position of powder, etc., but calculates the volume of the remaining space filled with powder, etc., and then calculates the volume of the remaining space filled with powder, etc. It is designed to find the level. Therefore, even if the top surface shape of the powder or the like is, for example, mountain-like or forest-like, the level (volume) can be accurately measured.

In the above embodiment, the pulse sound generator 2 generates a pulse sound so that the sound wave containing frequency components approximately equally in a certain band is received, but the method is not limited to this. For example, a device that oscillates what is called white noise may be used.

〔Effect of the invention〕

As described in detail above, according to the present invention, unlike conventional methods, the method is not based on local information.

It is possible to know the true level by focusing on the volume of powder and granular material in the hopper.
Since the level is determined based on the frequency, it is possible to provide a level measuring device with improved reliability, such as being less affected by, for example, a decrease in the sensitivity of the receiving section.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram showing the configuration, and FIG. 2 is a characteristic diagram illustrating the relationship between the powder level and the peak frequency. 1...Hopper, 2...Pulse sound generator, 3...Converter, 4...Pickup, 5...Data collection section-
6...FFT calculation unit, 7... calculation unit, 8... display unit, 9... control signal line.

Claims (1)

[Scope of Claims] An oscillating means for oscillating a sound wave containing substantially uniform frequency components in a certain band in a space of a container storing powder or liquid, and receiving the sound wave reflected within the space of the container. a receiving means; a peak detecting means for determining the frequency peak of the sound wave from the power spectrum of the sound wave received by the receiving means; and level calculation means for calculating the level of the powder or liquid.