RU52635U1 - ELECTRONIC-ACOUSTIC DEVICE FOR MEASURING THE FLUID LEVEL AND PIPE LENGTH - Google Patents

Abstract

The device relates to instrumentation and can be used to measure the level of liquids in tanks, ponds, non-pressure pipes. The device comprises a radiator 2, the input of which is connected to the output of the pulse generator 1, two receivers of the acoustic signal 4, 5 spaced at a fixed distance, the outputs of which are connected to the device for calculating the speed of sound 6 and to the electronic processing device 7, an indicator 8 and a keyboard 9 characterized in that in the block diagram of the device an additional sensitivity control unit for receivers 14 is introduced, the input of which is connected to a pulse generator 1, and the output to receivers 4,5. By changing the response level of the comparator during the measurement, it is possible to increase the range of measured levels, since with a constant response level of the comparator, a situation arises when the signal reflected from the mill scale, dirt or roughness of the pipe 15 can be at a higher level than the signal reflected from remote border environments

Description

The device relates to instrumentation and can be used to measure the level of liquids in tanks, ponds, non-pressure pipes.

Known electronic-acoustic devices for measuring distances based on fixing the propagation time of the sent and reflected acoustic pulses in the direction of the controlled distance [Gorbatov AA, Rudashevsky G.E. Acoustic methods and means of measuring distances in the air, M., Energy, 1973; RU patent No. 2052768b G 01 B 17/00, 1996; Utility model RU No. 7492, G 01 B 17/00, 1998; Utility model RU 24550 G 01 B 17/00; G 01 F 23/28, 2002]. Level gauges are also known, the principle of which is based on the reflection of an acoustic signal from a controlled fluid [patents SU No. 1530927, G 01 F 23/28, 1989, SU No. 1813203, G 01 F 23/28, b.i. No. 16, 1993]

The prototype of the claimed utility model is an electronic acoustic device [utility model RU 24550 G 01 17/00; G 01 F 23/28, 2002]. The disadvantage of this device is the small range of measured lengths. Indeed, the method of recording the reflected signal using the comparator does not allow high sensitivity: the reflected signal from the scale, dirt or roughness of the pipe located close to the measuring device can be much stronger than the reflection from the more distant boundary of the media of the measured liquid level and can cause a false response of the comparator .

The task is to increase the range of measurement of the liquid level by taking into account the actual propagation conditions of the acoustic signal.

The solution to this problem is achieved by the fact that in the known device containing an emitter, the input of which is connected to the output of the pulse generator and two receivers spaced at a fixed distance, the outputs of which are connected to the electronic processing device, according to the utility model, an additional receiver sensitivity control unit is introduced.

The essence of the utility model is illustrated in Figure 1, which shows the structural diagram of the proposed device. Figure 2 shows the dependence of the received signal power reflected from the media boundary on time t, and Figure 3 shows the diagram of received pulses.

The circuit contains a generator 1 connected to an acoustic emitter 2, connected to the end of the measuring tube (waveguide) 3, which is also connected

the receiver of the reflected signal 4 and the additional receiver of the acoustic signal 5 separated from it by a fixed distance “d”. The outputs of the receivers of the acoustic signal 4 and 5 are connected to a device for calculating the speed of sound in medium 6 and an electronic processing device 7, the output of which is connected to indicator 8. Is controlled the device using the keyboard 9, which is connected to the processing device 7. In the device according to the utility model, a sensitivity control unit for receivers 14 is added, the output of which is connected to the inputs ia sensitivity of receivers. The signal from the generator 1 also enters the blocks 6, 7, 14 to specify the beginning of the propagation time of sound in the waveguide. Devices 1, 2, 4-9, 14 are structurally placed in one housing and form a measuring module 10. The waveguide is installed in the tank or reservoir 11.

Passing along the waveguide, the acoustic signal 12 is reflected from the boundary of the media 13 and returns to receivers 4,5. At the same time, part of the signal is reflected from the scale, dirt or roughness of the pipe 15 and also returns to the receivers. With a close proximity to the obstacle meter 15, the reflection power from the latter can be greater than from the boundary of the media 13, which is located at a considerable distance. Thus, considering with the help of a comparator only the amplitude of the received signal with a wide measurement range, it is impossible to unambiguously determine the boundary of the media.

To determine the boundary of the media in a wide range of measured levels, it is proposed to use a sensitivity control unit 14. The dependence of the power of the received signal P reflected from the boundary of the media 13 on the travel time t, which is directly related to the level of the measured liquid H, has the following form:

where k is the reflection coefficient of power from the boundary of the media

P ₀ - power emitted by the emitter 2

ε is the absorption coefficient of the medium, depending on temperature, humidity, pressure and air composition.

The dependence of the received signal power on time t, which depends on the level H, is shown in Fig. 2 by a bold line. If you change the response level of the comparator, as shown by a dashed line in Figure 2, you can avoid triggering when reflected from false obstacles 15. The sensitivity control unit 14 generates a reference signal for receiver comparators according to the law (1), with a level of less than about 20%, necessary for a clear registration of the pulse reflected from the boundary of the media. Thus, the reflection from the obstacle 15 (U _pr

in Fig. 3) does not cause the comparator to operate, since at the moment of arrival of the pulse, the comparator response level is too high, however, a little later in level the useful signal U _neg will be received.

The measurement process is as follows. A radiating pulse is generated by a generator 1 and a radiator 2, at the same time a sensitivity control unit begins to form a reference voltage (level) for triggering the comparators of the receivers 4, 5, as mentioned above. Given that the coefficients in (1) depend on the environmental conditions by no more than 10%, we can add them to the sensitivity control device as constant coefficients. Also, to significantly simplify the device, you can use several discrete values of the reference voltage of the comparator, sequentially decreasing them over time. At the moment of operation of the emitter, the 2 responses of the receiver comparator are ignored, otherwise the signal immediately received by the device will trigger. The measurement process itself is carried out according to the utility model RU 24550 G 01 17/00; G 01 F 23/28, 2002 or earlier.

The device allows you to expand the range of measurement of liquid level. The use of the device is also effective for measuring pipe lengths.

Claims (1)

An electronic-acoustic liquid level measuring device containing a pulse generator whose output is connected to the emitter, two acoustic signal receivers spaced at a fixed distance, the outputs of which are connected to an electronic processing device and a sound velocity calculating device, an indicator and a keyboard connected to the processing device, characterized in that the receiver sensitivity control unit, the input of which is connected to the impu sov, and an output - to the receivers of the acoustic signal.