JPS6026462B2 - Angle correction method of radio current meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting changes in flow velocity due to angles of deflection and declination of a radio beam with respect to a fluid surface when measuring with a radio current meter. It can be applied to a measurement system that compares the incident wave and reflected wave to determine the Doppler shift frequency.

Conventionally, methods such as the propeller method using a Price current meter, the float method, or the thermal diffusion method have been used to measure the flow velocity in rivers, waterways, etc.

Price current meters are available, but the float type has the disadvantage that continuous measurement is difficult and requires a large number of people to measure, while the thermal diffusion method can detect changes in water temperature, water surface height, and river and waterway conditions. The disadvantage is that changes can cause large measurement errors. There is also a flow velocity measurement method that uses underwater ultrasonic propagation, but measurements may not be possible due to the distribution of water temperature, the height of the water surface, and especially the content of sediment during floods. These conventional measurement methods require that the detection unit or a portion thereof be constantly in contact with flowing water, and are directly affected by changes in river conditions, making it difficult to continuously obtain flow velocity data. On the other hand, a radio current meter measures the flow velocity by injecting a radio wave beam onto the surface of flowing water and measuring the Doppler shift frequency of the reflected wave and the incident wave. This is an excellent flow velocity measurement method that can continuously and automatically measure flow velocity, especially during floods. However, regarding this method,
The calculation means for angle correction as introduced in Section 5 is complicated digital multiplexing using a microprocessor, which has the drawback of being too expensive. The purpose of the present invention is to set the Dobbler shift frequency measured as a correction calculation using the forward angle and the declination angle in a reversible counter in order to obtain the true flow velocity, and then to set it in a reversible counter, which is then proportional to the product of the cosines of the elongation angle and the declination angle. A simple and inexpensive calculation method that subtracts the Doppler shift frequency using a pulse train of the same frequency, creates a time gate from the start of the subtraction until it becomes zero, and measures the flow velocity by counting the reference clock pulses between these gates. The purpose of this paper is to provide an angle correction method for a radio current meter. Embodiments of the invention will be described with reference to the drawings.

FIG. 1 is a diagram explaining the principle of a radio current meter. In FIG. 1, a radio current meter comprising an antenna 1 and a current velocity measuring device 2 is installed on the bank of a river flowing in the direction of arrow A between the two banks marked with diagonal lines. At the antenna 1, a radio wave beam with a frequency of 0 is incident on a point B on the surface of the flowing water, and a reflected wave of a frequency of 2 is received. Frequency n d is the Doppler shift frequency of the reflected wave that is proportional to the velocity of the flowing water surface. If the extension angle at the point of incidence B of the radio wave beam on the flowing water surface is 0 and the declination angle is 0, and the vector BC is represented by the flow velocity V at point B, then
Vector BD indicates the flow velocity component V・cos0 in the declination direction, and vector BE further indicates the flow velocity component V・cos◇ in the declination direction.
- Indicates cos8. The radio waves that are reflected from the radio waves with the frequency 〆 which are incident at point B have the frequency 〆10〆d, but when the radio wave beams are incident on the flowing water in the direction of the arrow A, the reflected waves are 〆10〆d. It has a frequency d, and arrow A
When it is incident in the same direction as the beam direction, it has a frequency of nerve d. In any case, the flow rate measuring device 2 detects only the Doppler shift frequency pd. As is well known, this n d is expressed by the following equation. 〆d=2na-V℃
. Customer 8-heart OS? ...[11 However, in the formula '1-, C represents the propagation speed of radio waves in the air. (1} Rewriting the equation with respect to the flow velocity V, C.〆d
...■V=2〆-COS8-COS〇.

As is clear from the formula {2), the propagation speed C of the radio wave, the frequency N of the radio wave, and the angle 8 of the radio wave beam, the angle of declination ? Since V is known and given by a constant, the flow velocity V can be immediately determined by measuring the deviation frequency d. FIG. 2 is a block system diagram showing one embodiment of a conventional radio current meter.

The case where microwaves are used as the incident radio waves is shown. In the figure, reference numeral 3 denotes an oscillator, which oscillates microwaves using elements such as Gunn diodes and impact diodes. A directional coupler 4 is coupled to the output end of the oscillator 3 via a three-dimensional line such as a waveguide.

A circulator 5 is connected to the output end of the directional coupler 4 and supplies microwaves to the antenna 1.The microwaves are incident on the flowing water surface from the antenna 1, and the reflected waves are Doppler-modulated and received by the antenna 1 again. Output to the output terminal.

A mixer 6 is connected to the output end of the circulator 5 and the output end of the directional coupler 4, respectively, and outputs a Doppler shift frequency 〆d by homodyne detection.

Reference numeral 7 denotes a band filter, which has a passband width of a frequency within the range of the flow velocity to be measured, and removes the influence of unnecessary reflected waves, radio waves, etc.

8 is a limit amplifier which amplifies and limits the sine wave to shape the waveform into a rectangular wave.

9 is a counter connected to the output terminal of limit amplifier 8,
Count the output square waves.

A time generator 10 is connected to the counter 9 and outputs a timing signal at regular intervals to reset the counter 9.

11 is an antenna angle sensor, which is a driving part of antenna 1 (
(not shown) and the extension angle 8 and declination angle ◇ of the antenna 1.
Output.

For example, a digital resolver or the like is used. 12 is a coefficient unit connected to the output terminal of the antenna angle sensor 11,
Using step angle 8 and declination angle, C/2〆・cos8・cos
◇ Outputs the calculated value.

The coefficient unit 12 is an arithmetic unit or a microprocessor, and the values of C and N are stored in advance in a ROM (memory for logic output) or the like. 13 is a multiplier, with a counter 9 and a coefficient unit 12 at the multiplier input terminal and the multiplicand input terminal, respectively.
The output end of is connected to output a signal corresponding to the flow velocity V.

A display 14 is connected to the output end of the balance calculator 13 and displays the flow velocity V digitally or analogously with a meter.

Furthermore, it can also be recorded on recording paper or the like. Next, the operation of the radio current meter shown in FIG. 2 will be explained. The transmitted wave of the frequency oscillated by the oscillator 3 is sent to the directional coupler 4 and the circulator 5.
from the antenna 1 through the desired angle 8 and declination angle? is incident on the surface of the flowing water. The reflected wave of frequency 〆〆d which is Doppler modulated by the flowing water velocity V is received by antenna 1,
It is input to a mixer 6 via a circulator 5. On the other hand, the transmitted wave is inputted to the mixer 6 via the directional coupler 4, and mixed with the reflected wave and subjected to homodyne detection to extract a signal having a Doppler shift frequency nad. This signal is processed into a counter 9 as a rectangular pulse wave that is amplified and limited by a limit amplifier 8 after cutting off unnecessary frequency components by an Obishiro filter 7.
added to. The counter 9 is reset at regular time intervals by the timing signal 0 from the time generator 8. For example, if the period of the timing signal is set to 1 second, the count immediately before reset represents the frequency n. On the other hand, the deflection angle 8 and the deflection angle ◇ of the antenna 1 are selected to optimize the reflected power of the reflected wave and the Doppler shift frequency according to the surface conditions of the flowing water, the conditions of the installation location of the antenna 1, etc. It is detected by an antenna angle sensor 11 that is linked to the antenna angle sensor 11, and is added to a coefficient multiplier 12. These expansion angle a and deviation angle ◇ are added as digital angle signals when a digital resolver is used. The coefficient multiplier 12 calculates the microwave transmission frequency N and propagation speed C.
According to C. ．． ．． ...'3;2 na-
Perform the calculation COS8-COS◇.

[The result of equation 3' is the Doppler shift frequency na d of counter 9.
And multiplier 13 calculates C. nad.
...(412 na・coso-COS○), and the formula [4} matches the formula [2}.

The flow velocity V thus obtained is displayed or recorded by the display 14. Changes in the angle a and the declination angle are automatically calculated and the flow velocity is automatically corrected, so the flow velocity measurement is performed continuously. However, this method has the disadvantage that the coefficient unit 12 and the multiplier 13 perform complex digital multiplexing as their calculation means, requiring a considerable amount of expense. FIG. 3 is a block system diagram showing one embodiment of the radio current meter according to the present invention. In this figure, blocks having the same functions as those shown in FIG. 2 are designated by the same reference numerals and their explanations will be omitted. FIG. 4 is a timing chart of important waveforms indicated by lower case letters in FIG. 3, and will be explained in conjunction with FIG. 3. 20 is a gate circuit connected to the output terminal of the limit amplifier 8, and a fixed time (for example, 1 second) is supplied from the time generator 10.
It receives a reference gate signal b on the other side, performs time selection of a measurement signal a having a Doppler shift frequency na d from the limit amplifier 8, and outputs an addition input signal c.

A reversible counter 21 has an addition input terminal connected to the gate circuit 20, and adds the addition input signal c.

It goes without saying that if the gate period of the reference gate signal b is set for exactly 1 second, the frequency pd itself is added. The subtraction input terminal is connected to the gate circuit 29 and subtracts the subtraction input signal f from the measurement gate signal c. 22 is a zero detector consisting of a comparator, which is connected to the reversible counter 21 and outputs a reset signal when it detects that the output becomes zero as a result of addition and subtraction.

23 is an R.S flip-flop connected to the zero detector 22 and one time generator, inputs a reset signal and a set signal, and outputs a measurement gate signal e.

A reference oscillator 26 outputs a reference clock signal g.

A gate circuit 27 is connected to the reference oscillator 26 and the R.S flip-flop 23 and outputs a display input signal h within the measurement gate signal e.

A counter 28 is connected to the gate circuit 27, counts the display input signal h, and outputs the result to the display 14.

24 is an antenna angle sensor consisting of potentiometers s and s2 and a DC intensifier p, and the potentiometers S and S are connected to changes in the angle and declination of the antenna, respectively.
When the notch of 2 and 2 is switched, the DC multiplier p consisting of an arithmetic multiplier uses the reference voltage proportional to the cos as the input voltage, and increases with the degree of multiplication proportional to the cos.
)×(cos◇).

If the notch is replaced with a cosine potentiometer, continuous values can be obtained. A V/F converter 25 is connected to the antenna angle sensor 24 and converts the input voltage into a frequency pulse train.

That is, a V/F converter output d consisting of a pulse train proportional to (cos8)×(cosgu) is obtained. A gate circuit 29 is connected to the V/F converter 25 and the R/S flip-flop 23 and outputs a subtraction input signal f within the measurement gate signal e.

Next, the operation of the radio current meter shown in FIG. 3 will be explained. However, since the parts up to the limit amplifier 8 are the same as the conventional one, their explanation will be omitted. The measurement signal a having the Doppler shift frequency 〆d is input to the gate circuit 20 and becomes the addition input signal C after being time-selected by the reference gate signal b.

For example, if the gate width of the reference gate signal b is selected to be exactly 1 second, the addition input signal C will be a pulse train of the same number as the Doppler shift frequency 〆d. The addition input signal C is input to the addition input terminal of the reversible counter 21, and the reversible counter 21 is set to nad.

On the other hand, from the antenna angle sensor 24 (cos8) x (c
The output voltage proportional to osg) enters the V/F converter 25 and becomes the V/F converter output signal d, and the frequency of the pulse train is proportional to (cos8)×(cos◇). For example, 8=450, J=4? When setting the antenna angle sensor 24 so that the proportionality constant is 100, V/F
The frequency of converter output signal d is 100・COSa・C
OS◇=100・COS450・cos450 = Z on the same day.

The V/F converter output signal d enters the gate circuit 29,
The time is selected by the measurement gate signal and becomes the subtraction input signal f, which enters the subtraction input terminal of the reversible counter 21 and is subtracted. The reversible counter 21 is set to d, and then when nd is subtracted and zero is detected by the drop detector, a reset signal is sent to the R/S flip-flop 23, which has already been set from the time generator 10. The measurement gate signal e, which is set when subtraction starts, is reset by the signal. Therefore, the gate width T of the measurement gate signal e is the period from when the reversible counter 21 starts subtracting d numbers to zero, and the frequency 50 of the above-mentioned V/F converter output signal d.
It is equal to the period of teaching d pulses on day 2. In other words, NadT=〆d-High.

=・oo-'s S450 Shinka 4? - Nad
...(51100・COS8・CO
S? holds true.

The reference oscillator 26 oscillates a reference clock signal g, and its oscillation frequency is set to be proportional to C/2. For example, if the proportionality constant is 10,000 and a microwave of 1 Hz is used, the oscillation frequency 〆s can be written as follows. Na S publication oo.

・Nose = Koki obi. =・5oHZ・…−・■ The reference clock signal g having such a frequency enters the gate circuit 27, and the time is selected by the measurement gate signal e having the gate width T, and becomes the display input signal h, which is output to the counter 28.
The result of counting is displayed on the display 19.

However, the counting results are displayed at the end of the display input signal h, but since these timing signals are well known, they are not shown in FIG. Next, the frequency of the display input signal h, that is, the counting result, can be written as follows using equations '4}, [5}, and '6). The value of 10 tones of the true flow velocity V thus subjected to angle correction, i.e., unit arc/S
The flow velocity shown by is calculated.

From the '5} and '7} expressions, Nas. 〆d l/50=100.
For example, if nad=100, the display will show 3.
0 ratio ne'S is displayed. In the above explanation, the gate width of the reference gate signal b was set to 1 second, but this is set to 1 second, 6 seconds.
It is also easy to display the average value instead of sand. Further, in this embodiment, a case has been described in which measured values are displayed on a display, but as is well known, it is easy to record them on a recorder or to have both display and record. Furthermore, in this embodiment, the potentiometers S and S2 were moved in conjunction with the antenna 1, but once the antenna is installed, it is hardly moved. and s2 may be manually set to the measured values.

As described above, the present invention provides an inexpensive angle angle radio current meter that can perform correction calculations for the angle and declination of a radio beam simply by using a reversible counter and a gate circuit without performing complicated digital multiplexing. This provides a correction method.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of a radio current meter, Fig. 2 is a block system diagram showing one embodiment of a subordinate radio current meter, and Fig. 3 is a block diagram showing an embodiment of the radio current meter according to the present invention. System diagram,
FIG. 4 is a timing chart of key waveforms indicated by lower case letters in FIG. 1... Antenna, 2... Current velocity measuring device, 3... ...Oscillator, 4...Directional coupler,
5...Circulator, 6...Mixer, 7...Band filter, 8...Limit amplifier, 9 and 28...Counter, 10... ...Time generator, 11 and 24...Antenna angle sensor,
12... Coefficient calculator, 13... Chicken calculator, 1
4...Display unit, 20, 27 and 29...
Gate circuit, 21... Reversible counter, 22... Zero detector, 23... R/S flip-flop, 25... V
/F converter, 26...Reference oscillator. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Set the depression angle and declination angle of the radio wave beam incident on the fluid surface in advance, and compare the incident wave and reflected wave of this radio wave beam to find the Doppler shift frequency. Correct the above depression angle and declination angle to find the true flow velocity. In a radio current meter that measures , the measured Doppler shift frequency is set in a reversible counter, and then the Doppler shift frequency is subtracted by a pulse train with a frequency proportional to the product of the cosines of the depression angle and the declination angle. An angle correction method for a radio current meter, which is characterized in that a measurement gate is created from the start of subtraction to zero, and the flow velocity is measured by counting reference clock pulses between these gates.