JP3198904B2 - Conductor length measuring device and 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 apparatus for measuring the length of a conductor such as a metal rod electrode or a carbon electrode, and an apparatus for measuring the level of a molten metal using the measurement technique.

[0002]

2. Description of the Related Art Conventionally, as a technique for measuring the length of a conductor, for example, there is TDR (Time Domain Reflectometry) for measuring the length of a communication line. TDR is a technique that is generally used to detect the failure position of a communication line. A high-frequency pulse signal is input from one end of a communication line such as a coaxial cable, and the pulse signal propagates through the communication line and proceeds. It is detected that the signal is reflected from a point where the propagation impedance changes due to a line disconnection or short circuit and returns to the signal input terminal. The time (real time) from the input time of the pulse signal to the detection of the reflected wave and the distance from the propagation speed of the signal to the point where the propagation impedance changes are measured.

As an example of a technique for measuring the level of molten metal having electrical conductivity, two electrodes are inserted into the molten metal, a pulse signal is input from one electrode, and the input signal is applied to one electrode. When a signal that propagates through the molten metal from a contact portion between the electrode and the molten metal and propagates through the other electrode from a contact portion between the molten metal and the other electrode is detected as an output, the pulse signal is input. There is one that measures the time from the time to the time when the output signal is detected, and calculates the level of the molten metal corresponding to the measured time.

[0004]

However, the conventional T
In the method of measuring the length of a coaxial cable or the like by the DR method, since the real time from the signal input time to the reflected signal detection time is measured, the measurement accuracy (resolution) of the length is several tens to several tens. Bad with 100mm. Further, since the signal propagation speed is high, it is difficult to measure a short distance, and there is a problem that the length of a short electrode cannot be accurately measured. Also, if the frequency of the signal to be propagated to the device under test is increased to improve the measurement accuracy, if the signal is input to a conductor such as an unbalanced conductor that is not a coaxial cable, the signal that propagates along the conductor will be attenuated. And the waveform distortion is very large, which makes it difficult to perform measurement based on the detection of the reflected signal.

In the method of measuring the level of a molten metal by inserting two electrodes into the molten metal, it is necessary to always maintain good electrical conduction at a contact portion between the two electrodes and the molten metal. In addition, there is a problem that measurement cannot be performed if the electrical continuity of the contact portion is poor due to fluctuations in the surface of the molten metal, slugs, or the like. In addition, since two electrodes are required for level measurement, there are also restrictions on the installation such that the electrode installation space may not be sufficient. The present invention has been made in order to solve the above problems, and provides a highly accurate measuring device for the length of a conductor such as a metal rod electrode or a carbon electrode, and a molten metal level measuring device utilizing this technology. The purpose is to:

[0006]

According to a first aspect of the present invention, there is provided a conductor length measuring device for generating a first pseudo-random signal synchronized with a first clock frequency; Means for synchronizing to a slightly different second clock frequency to generate a second pseudo-random signal having the same pattern as the first pseudo-random signal; and generating the first pseudo-random signal and a second pseudo-random signal. First multiplying means for multiplying the generated random signal by the random signal;
A pseudorandom signal is input from one end of the conductor to be measured as an electromagnetic wave, and the input signal is propagated along the length direction of the conductor, and the input signal is propagated along the length direction of the conductor, Means for separating and detecting the reflected signal reflected from the other end and returning to the input end from the input signal, and a second multiplication for multiplying the detected reflected signal by the generated second pseudo-random signal Means, first integration means and second integration means for integrating and outputting the multiplication results of the first and second multiplication means, respectively, and
Means for measuring the time between the time at which the maximum amplitude value of the output signal of the integrating means is detected and the time at which the maximum amplitude value of the output signal of the second integrating means is detected. Means for measuring the length of the conductor from the signal input end to the signal reflection end. As a result, the first and second clock frequencies are respectively set to f ₁ ,
Assuming that f ₂ is f ₂ and the difference between f ₁ and f ₂ is Δf, the time measured is f _1, which is the time actually required for propagation and reflection of electromagnetic waves.
Since the magnification is / Δf times, extremely accurate length measurement is possible.

According to a second aspect of the present invention, there is provided a level measuring device for generating a first pseudo-random signal synchronized with a first clock frequency, and a second clock slightly different from the first clock frequency. Means for generating a second pseudo-random signal having the same pattern as the first pseudo-random signal in synchronism with the frequency, and multiplying the generated first pseudo-random signal by a second pseudo-random signal. Multiplication means of 1 and the generated first pseudo-random signal as an electromagnetic wave, one end of which is inserted into the molten metal and input from the other end of the immersed rod-shaped electrode, and the input signal is input to the length of the rod-shaped electrode. Means for propagating along the direction, and separating the reflected signal propagating along the length direction of the rod-shaped electrode and reflected from the tip or the contact portion between the electrode and the molten metal and returned to the input end from the input signal. Means for multiplying the detected reflected signal and the generated second pseudo-random signal, and a multiplication result of the first and second multiplication means. A first integration means and a second integration means for integrating and outputting, respectively, a time at which a maximum amplitude value of an output signal of the first integration means is detected, and
Means for measuring the time between the time when the maximum amplitude value of the output signal of the integrating means is detected, and measuring the length from the signal input end of the rod-shaped electrode to the signal reflection position based on the measured time. And a means for measuring the level of the molten metal based on the measured length from the signal input end of the rod-shaped electrode to the signal reflection position. As a result, the first and second clock frequencies are respectively set to f
_1, and f _2, when the difference between f ₁ and f ₂ and Delta] f, since the time to the measurement becomes an enlarged actually the time required for the reflection and propagation of electromagnetic waves in f ₁ / Delta] f times, very high Accuracy level measurement becomes possible.

According to a third aspect of the present invention, in the level measuring apparatus according to the second aspect, a rod-shaped electrode parallel to and adjacent to a rod-shaped electrode for transmitting and reflecting an electromagnetic wave by the first pseudo random signal. An electrode is additionally provided, and one end of the additionally provided rod-shaped electrode is inserted and immersed in the molten metal, and the other end is grounded. With the above structure, the rod-shaped electrode that propagates and reflects the electromagnetic wave and the rod-shaped electrode adjacent to the rod-like electrode perform the same operation as the parallel line, and the state of propagation and reflection of the electromagnetic wave (microwave) is simply Compared with the case where one electrode is used, the occurrence of signal attenuation and waveform distortion is suppressed, so that measurement over a long span and stable operation and level measurement with high accuracy can be performed.

According to a fourth aspect of the present invention, in the level measuring apparatus according to the second aspect of the present invention, a concentric cylindrical shape is provided outside a rod-shaped electrode for transmitting and reflecting an electromagnetic wave by the first pseudorandom signal. And one end of the additionally provided concentric cylindrical electrode is inserted and immersed in the molten metal, and the other end is grounded. The rod-shaped electrode that propagates and reflects the electromagnetic wave and the concentric cylindrical electrode outside the rod-shaped electrode perform the same operation as the coaxial cable, and the state of propagation and reflection of the electromagnetic wave (microwave) is as follows. As compared with the case of a single electrode or two parallel electrodes, the occurrence of signal attenuation and waveform distortion is further suppressed, and high-accuracy level measurement with more stable operation can be performed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a diagram showing a configuration of a conductor length measuring device according to Embodiment 1 of the present invention. In FIG.
Are first and second clock signal generators respectively, 3 and 4 are first and second pseudo random signal generators respectively, 5, 6 are first and second multipliers respectively, 7 is a directional coupler, 8 , 9
Are the first and second low-pass filters (LPF), 1
Reference numeral 0 denotes a measurement operation unit, 11 denotes a conductor length measuring device constituted by each of the devices 1 to 10, 12 denotes a coaxial cable connecting the directional coupler 7 and the electrode 13, and 13 denotes an object to be measured having a length. There is a rod-shaped electrode. In this example, electrode 1
As 3, a metal rod (iron bar) having a diameter of 5 mm and a length of about 1 m was used. The first and second clock signal generators 1 and 2 have frequencies of 1500.005 MHz and 1500.00, respectively.
A clock signal of 0 MHz is generated, and the first and second pseudo-random signal generators 3 and 4 generate M-sequence signals M ₁ and M ₂ having a code length of 127, respectively. Note that a pseudo random signal such as a Barker code other than the M-sequence signal may be generated.

FIG. 2 is a waveform diagram for explaining the operation of FIG. 1. The operation of FIG. 1 will be described with reference to FIG. Frequency f ₁ = 150 output from first clock signal generator 1
The 0.005 MHz clock signal is supplied to the first pseudo-random signal generator 3, and the first pseudo-random signal generator 3
Is, M-sequence signal M ₁ in synchronization with the clock frequency f ₁
Is generated and output. Similarly, the second clock signal generator 2
Clock signal of frequency f ₂ = 1500.000MHz output is supplied to the second pseudo random signal generator 4, the second pseudo random signal generator 4 a M-sequence signal M ₂ in synchronization with the clock frequency f ₂ Generate and output.

Here, the difference between two clock frequencies (Δf =
f ₁ −f ₂ ) is very small,
The M-sequence signals M ₁ and M ₂ output from the second pseudo-random signal generators 3 and 4, respectively, have slightly different periods, but have the same code (same pattern) with a code length of one period of 127. Signal. Also, this M-sequence signal M ₁ ,
M ₂ is, when the sign of the M-sequence code "1", respectively positive voltage (+ E), when the "0" is output as a voltage signal of a negative voltage (-E). Therefore, the first and second pseudo-random signal generators 3 and 4 output the cyclic circulating signal having the amplitude of the positive / negative voltage and being repeated every code length 127 of one cycle. Then, the clock frequency in this example is about 1.
Since the 5-GHz M-sequence signals M ₁ and M ₂ are microwaves generally called L-band, a microwave transmission line or a processor is used for transmission and processing of these signals.

An M-sequence signal M ₁ output from the first pseudo-random signal generator 3 is supplied to a multiplier 5 and a directional coupler 7, and an M-sequence signal M ₂ output from a second pseudo-random signal generator 4 Is supplied to the multiplier 5 and the multiplier 6. Multiplier 5
Multiplies the two input M-sequence signals M ₁ and M ₂ and supplies the multiplication result to the first low-pass filter 8. Note that the M-sequence signals M ₁ ,
Since M ₂ is a microwave of about 1.5 GHz, a frequency mixer for microwaves can be used for the multipliers 5 and 6. Here, the two M-sequence signals M ₁ and M ₂ are positive / negative signals having the same sign and have slightly different circulating periods. Therefore, the phases of the signal patterns of the two signals gradually change over time. When the two signals have the same sign (that is, both signals are both positive voltages or both negative voltages), the result of the multiplication is a positive voltage, and the opposite sign (that is, one of the two signals is a positive voltage and the other is a negative voltage). In the case of (voltage), the result of the multiplication is a negative voltage, and the positive voltage is continuous when the two signal patterns substantially match (see (a) of FIG. 2).

The first and second low-pass filters 8, 9 respectively remove high-frequency components from the input signal and pass only low-frequency components. As a result, the low-pass filters 8, 9 integrate the input signal. The output signal becomes a smooth signal (a signal close to a DC signal) obtained by integrating the input signal. When an output signal of the multiplier 5 as shown in FIG. 2A is input, the first low-pass filter 8 outputs a waveform close to a triangular wave as shown in FIG. It is supplied to the measurement calculation unit 10. The measurement calculation unit 10 detects a peak value (maximum amplitude value) of a waveform close to a triangular wave supplied from the first low-pass filter 8 and detects the detection time t _a (the time t _a shown in FIG. 2D).
_a )). For example, the amplitude value of the triangular waveform is sampled for each unit time, and the previous sampled value and the current sampled value are compared with each other. As shown in (d), one pulse may be generated, and the generation time of this pulse may be stored. And a correlation signal peak value detection time t _a when there is no time delay due to the transmission of the M-sequence signal M ₁ and the reference time of the time measurement.

As the directional junction device 7, a commercial product for the L band used in radars and the like can be used. First
The M-sequence signal M ₁ output directly from the pseudo-random signal generator 3 or via a power amplifier (not shown) is input to the left side of the directional coupler 7 using a microwave transmission line such as a coaxial cable. This input signal is output from the right side of the directional coupler 7 as an electromagnetic wave only to the coaxial cable 12 side, and is not output to the multiplier 6 (lower side). Further, the directional coupler 7 operates so that the reflected signal input from the coaxial cable 12 is output only to the multiplier 6 side and not output to the first pseudo random signal generator 3 side. The M-sequence signal M ₁ as an electromagnetic wave output from the first pseudo-random signal generator 3 and passed through the directional coupler 7 is
It is supplied to one end of the electrode 13 through the coaxial cable 12. Here, it is assumed that the length of the electrode 13 is _Lx, and this _Lx is measured.

Here, the M-sequence signal M ₁ has the frequency of about 1.
It is a microwave of 5 GHz, and the coaxial cable 12 is known as a microwave transmission path. The length L ₀ of the coaxial cable 12 is calibrated in advance, and the calibration value L ₀ is input to the measurement calculation unit 10 before measurement and stored. The electrode 13 has a diameter of 5 m as described above in this example.
m, an iron bar having a length of about 1 m, one end of which is connected to the core wire of one end of the coaxial cable 12 and the other end is open (op
en), and no other electrical conductor is provided in addition to the electrode 13.

In such a structure, the electrode 13 has a structure close to that of a rod antenna. However, since the radiation efficiency is low as an antenna radiator, the energy of the microwave radiated from the electrode 13 into the atmosphere is small, and the signal is low. It propagates along the electrode 13 as an electromagnetic wave. As a result, the electrode 13 operates as a signal propagation path composed of a nearby electric conductor or ground (a conductor having the same function as the outer conductor of the coaxial cable). Therefore, the electromagnetic wave propagated along the electrode 13 is
The light is reflected based on a change in propagation impedance due to the other end being opened. Electrode 1 as described above
If a second electric conductor adjacent to and parallel to 3 is provided, or if the electrode 13 is held close to and parallel to the ground, the measurement operation is further stabilized.

The M-sequence signal M ₁ reflected from the tip of the electrode 13 in this manner is again input to the directional coupler 7 through the coaxial cable 12, and the directional coupler 7 extracts only the reflected signal. And input to the multiplier 6.
Here, the M-sequence signal M ₁ reflected from the tip of the electrode 13 and input to the multiplier 6 is compared with the M-sequence signal M ₁ directly input to the multiplier 5 from the first pseudo-random signal generator 3. , The total length of the coaxial cable 12 and the electrode 13
R> (L ₀ + L _x ), which is a signal delayed by the time required for the microwave to propagate and reciprocate.

[0019] The M-sequence signal M ₁ delayed reflected from the electrode 13 and the M-sequence signal M ₂ is directly input from the second pseudo random signal generator 4 are multiplied by a multiplier 6,
The result of the multiplication is input to the second low-pass filter 9.
The second low-pass filter 9 operates similarly to the first low-pass filter 8, outputs a waveform close to a triangular wave as shown in FIG. The measurement calculation unit 10 detects a peak value (maximum amplitude value) of a waveform close to a triangular wave input from the second low-pass filter 9 as in the case of the input signal from the first low-pass filter 8,
The detection time, for example, in FIG. 2 one pulse as shown in (e) occurs, stores the occurrence time t _b of the pulse. And a correlation signal peak value detection time t _b which is delayed in accordance with the transmission distance of the M-sequence signal M ₁ and signal detection time, measures the time T _D from the reference time t _a up signal detection time t _b (FIG. see T _D indicated in the 2 (e)).

Next, a method of calculating the length or the distance from the measurement time T _D will be described. The repetition frequency of the first pseudo-random signal is f ₁ , the repetition frequency of the second pseudo-random signal is f _2, and the pattern of each pseudo-random signal is the same. Here, it is assumed that f ₁ > f ₂ . The period at which the reference signal obtained by correlating the transmitted first pseudo-random signal with the second pseudo-random signal (a correlation signal is obtained by the multiplication and integration processes) is T,
_B When (see the indicated T _B in the FIG. 2 (d)), the first pseudo random signal and the wave number of exactly one cycle difference in wave number of the second pseudo random signal contained between the T _B N
(Same as the code length). That _{T B T B · f 1 =} T B · f 2 + N Rearranging the above given by the following equation (1). _{T B = N / (f 1} -f 2) ... (1) i.e. as the difference between the two clock frequencies is small, the period T _B of the reference signal becomes the maximum value is larger.

Next, the first pseudo-random signal has a length x
(In this example, x = L ₀ + L _x ), and the signal reflected back from the tip of this propagation path and the second signal
When the detection signal obtained by taking the correlation between the pseudo random signal of time t _b and the reference signal having the largest value is the time T _D between time t _a which is a maximum value, occurs between T _D wavenumber of the second pseudo random signal, from the wave number of the first pseudo random signal generated between T _D, the first occurring to the actual time required for propagation and reflection of the first pseudo random signal τ Since the number is smaller by the wave number of the pseudo-random signal, the following equation holds. _{T D · f 2 = T D} · f 1 -τ · f 1 and rearranging the above equation T _D is given by the following equation (2). T _D = τ · f ₁ / (f ₁ −f ₂ ) (2) Here, the propagation time τ of the microwave is represented by v;
Assuming that the propagation distance is x, since τ = 2 × x / v, the following equation (3) is obtained from the equation (2).

[0022]

(Equation 1)

Therefore, the two clock frequencies f ₁ , f
_2, by previously inputting the propagation velocity v of the microwaves, the previously measured calculating unit 10 the value of the length L ₀ of the calibrated coaxial cable, measurement computation unit 10 measures the time T _D,
The propagation distance x is calculated from the equation (3). In the example of FIG. 1, since x = (L ₀ + L _x ), the length L _x of the electrode 13 can be obtained by subtracting the length L ₀ of the coaxial cable 12 from _x .

In this example, the frequency f _{1 of} the first pseudo-random signal is 150.005 MHz, the frequency f _{2 of} the second pseudo-random signal is 150.000 MHz,
Since the wave number N of one cycle is set to 127, substituting these values into the equation (1) results in a repetition cycle T _{B of the} time reference signal (and the detection signal) of T _B = 25.4 msec. In addition, the measurement time T _D is given by f
₁ / (f ₁ −f ₂ ), the measurement time T _D becomes 3 times the real time τ by substituting the above values in this example.
As a result of being enlarged by a factor of 00,000, highly accurate measurement is possible.

In this example, the measurement calculation unit 10 sets the output signal of each of the first and second low-pass filters 8 and 9 as shown in FIGS. 2B and 2C at a sampling period of 10 μsec. / sequential read amplitude data D conversion, the time t _a which each signal is the maximum amplitude value, detecting a t _b, the two time t _a, measured time T _D between t _b, performs calculation length Was. Sampling cycle 10 μse in this case
c is 10 μsec / real time in real time from the time expansion rate.
This corresponds to 300,000 = 3.33 psec, which means that the signal sampling is performed at 0.5 mm in terms of distance, and the length of the electrode 13 can be measured with high accuracy. Further, the main measurement operation unit 10 can measure the electrode length with an accuracy of 1 mm by averaging a plurality of measurement data.

The reflected signal from the device under test may contain noise, but since this noise component has no correlation with the pseudo-random signal, the result of the correlation processing by the multiplier 6 and the second low-pass filter is obtained. In the signal output, noise is suppressed, and signal detection with improved SN ratio and high sensitivity becomes possible. Further, in this example, a metal rod is used as a measurement target, but various conductive materials through which a pseudo random signal propagates can also be used as a measurement target. For example, the length can be obtained by measuring a carbon electrode, a steel material, a carbon block, and the like.

Embodiment 2 FIG. FIG. 3 is a diagram showing a level measuring device using the device of FIG. 1 according to the second embodiment of the present invention. FIG. 3 (a) is a diagram of a measurement target viewed from a side, and FIG.
Is a view of the same measurement target viewed from directly above. In FIG. 3, 20 is a coaxial cable, 21 is an electrode, 22 is a conductor length measuring device, 23 is a signal processing device for level measurement, 24 is an electrode holding device, 25 is a mold, 26 is a tundish,
27 is a nozzle, 28 is molten steel, and 29 is a dummy bar.
In this example, the electrode 21 was a metal bar (iron bar) having a diameter of 3 mm, and the same conductor length measuring device 22 as that shown in FIG. 1 was used. In the example of FIG. 3, the electrode 21 which is a metal rod is vertically inserted into the molten metal mold 25, and its tip is immersed in the molten steel 28 in the mold 25 to measure the level of the molten steel in the mold 25. Things.

The operation of FIG. 3 will be described. An electromagnetic wave based on the M-sequence signal M ₁ sent from the conductor length measuring device 22 is input to one end of the electrode 21 via the coaxial cable 20,
The light propagates in the length direction along the electrode 21. in this case,
As described with reference to FIG. 1, the light propagates through a signal propagation path including the electrode 21 and a nearby electric conductor (in this case, the nozzle 22, the mold 25, or the molten steel 28). The change in the propagation impedance at the contact position between the electrode 21 and the molten steel 28 (the propagation due to the transition of the propagation surface from the rod to the flat surface and the presence of electrical resistance when the electrical conduction at the contact portion is poor). Impedance change) causes reflection,
The electromagnetic wave of the M-sequence signal M ₁ reflected from the contact position returns to the semiconductor length measuring device 22 through the coaxial cable 20 again. Conductive body length measuring apparatus 22 calculates the length of the electrode 21 based on the measurement of the time T _D as described in FIG. The signal processing device 23 stores pre-calibrated correspondence data between the length of the electrode 21 and the molten steel level, and based on the length data of the electrode 21 supplied from the conductor length measurement device 22 and the correspondence data, molds Calculate the inner molten steel level.

In this example, since a metal rod is used as the electrode 21, the electrode 21 melts when immersed in molten steel. However, by using a high melting point conductive material such as tungsten for the electrode 21, continuous level measurement for a long time becomes possible. Further, even with the electrode 21 of a metal rod, it is possible to measure an increase in the level of molten steel in the mold at the start of casting. Furthermore, in the measurement when the molten steel level in the mold fluctuates, by using a long electrode rod and providing an automatic supply means of the electrode rod for continuously inserting the electrode rod into the mold, the electrode and the molten steel can be measured. The continuous measurement can be performed while always maintaining the contact. FIG. 3 shows an example in which the level of molten steel in a mold of a continuous casting facility is measured. However, the level measuring device can be applied to other levels of molten metal.

Embodiment 3 FIG. 4 is a diagram illustrating an example of level measurement using two electrodes in the apparatus of FIG. 3 according to the third embodiment of the present invention. In FIG. 4A, two electrodes, that is, a first electrode 21A and a second electrode 21B are held in parallel and adjacent to each other. The first electrode 21A is connected to the core wire of the coaxial cable 20 as a signal electrode, to perform the propagation and reflection of M-sequence signal M ₁ by electromagnetic waves, the second electrodes 21B are used to ground as a ground electrode. Therefore, the state of microwave propagation and reflection is more stable than when a single electrode is used, and signal attenuation and waveform distortion are suppressed, so that measurement and operation over a long span are stable. Level measurement with high accuracy becomes possible. The other measurement operations are the same as those in FIG. 3, and the description thereof is omitted.

FIG. 4B shows the structure of two electrodes and their connection. A second electrode 21B having a concentric cylindrical shape is provided outside the first electrode 21A, and the first electrode 21A is coaxial. The second electrode 21 </ b> B is connected to the outer conductor of the coaxial cable 20 while being connected to the core wire of the cable 20.
1B is grounded. With such a structure, the two electrodes 21A and 21B have a structure similar to that in which the coaxial cable 20 is directly extended and inserted into the molten steel 28, and performs a signal propagation operation similar to that of the coaxial cable. Wave) and the state of reflection
Compared to the case of the parallel electrodes, the occurrence of signal attenuation and waveform distortion is further suppressed, and high-accuracy level measurement with more stable operation can be performed. Also, two electrodes 21A, 21B
Has a structure that looks like a single electrode, and therefore requires less space when inserted into the mold 25.
It also has the feature of a structure convenient for measurement.

[0032]

As described above, according to the first aspect of the present invention, the means for generating the first pseudo-random signal synchronized with the first clock frequency and the second means slightly different from the first clock frequency are provided. Means for generating a second pseudo-random signal having the same pattern as the first pseudo-random signal in synchronization with the second clock frequency, and generating the first pseudo-random signal and the second pseudo-random signal. First multiplying means for multiplying, and inputting the generated first pseudo-random signal as an electromagnetic wave from one end of the conductor to be measured,
Means for propagating the input signal along the length of the conductor, and propagating along the length of the conductor;
Means for separating and detecting the reflected signal reflected from the other end and returning to the input end from the input signal, and a second multiplication for multiplying the detected reflected signal by the generated second pseudo-random signal Means, first integration means and second integration means for integrating and outputting the multiplication results of the first multiplication means and second multiplication means, respectively, and a maximum amplitude of an output signal of the first integration means. Means for measuring the time between the time at which the value is detected and the time at which the maximum amplitude value of the output signal of the second integrating means is detected, and from the signal input terminal of the conductor based on the measured time. Means for measuring the length to the signal reflection end is provided to measure the length of the conductor, so that the first and second clock frequencies are respectively set to f
_1, and f _2, when the difference between f ₁ and f ₂ and Delta] f, since the time to be measured will be an enlarged actually the time required for the reflection and propagation of electromagnetic waves in f ₁ / Delta] f times, extremely high accuracy Length measurement becomes possible. In addition, even if the signal is attenuated or the waveform is distorted by inputting the signal to a single conductor, not a coaxial cable, the signal can be detected with high sensitivity by using a pseudo random signal, and the length of the single conductor can be detected. Can be measured.

Further, in the invention according to claim 2, means for generating a first pseudo-random signal synchronized with the first clock frequency, and a second clock frequency slightly different from the first clock frequency. Means for synchronizing and generating a second pseudo-random signal having the same pattern as the first pseudo-random signal; and a first multiplying means for multiplying the generated first pseudo-random signal by a second pseudo-random signal. Multiplying means, the first pseudo-random signal generated as an electromagnetic wave, one end of which is inserted into the molten metal and input from the other end of the immersed rod-shaped electrode, and the input signal is applied in the longitudinal direction of the rod-shaped electrode. Means for propagating along the length of the rod-shaped electrode, and separating the reflected signal returned from the input end, which is reflected from the tip or the contact portion of the electrode and the molten metal, from the input signal by separating it from the input signal Output means; second multiplying means for multiplying the detected reflected signal by the generated second pseudo-random signal; and multiplying results of the first and second multiplying means. A first integrating means and a second integrating means for integrating and outputting, a time at which a maximum amplitude value of an output signal of the first integrating means is detected, and a maximum amplitude value of an output signal of the second integrating means. A means for measuring a time between the detected time and a means for measuring a length from a signal input end of the rod-shaped electrode to a signal reflection position based on the measured time; and Means for measuring the level of the molten metal on the basis of the length from the signal input end to the signal reflection position, so that the level of the molten metal is measured. _1, and f _2, and f ₁ The difference between the _{2 Δf}
Then, the time for the measurement is obtained by expanding the time required for the propagation and reflection of the electromagnetic wave by f ₁ / Δf times, so that the level measurement with extremely high accuracy is possible. Also,
By inserting and immersing one rod-shaped electrode in the molten metal, level measurement is possible and the installation space can be reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, a rod-shaped electrode parallel to and adjacent to a rod-shaped electrode for transmitting and reflecting an electromagnetic wave by the first pseudo-random signal is added. One end of the additionally provided rod-shaped electrode is inserted and immersed in the molten metal,
Since the other end is grounded, the rod-shaped electrode for transmitting and reflecting the electromagnetic wave and the rod-shaped electrode adjacent to the rod-like electrode perform the same operation as the parallel line, and the propagation of the electromagnetic wave (microwave) In the state of reflection, the occurrence of signal attenuation and waveform distortion is suppressed as compared with the case where a single electrode is used, so that measurement over a long span and highly accurate level measurement with stable operation can be performed.

According to a fourth aspect of the present invention, in the second aspect of the present invention, a concentric cylindrical electrode is added outside a rod-shaped electrode for transmitting and reflecting an electromagnetic wave by the first pseudorandom signal. One end of the additionally provided concentric cylindrical electrode is inserted into the molten metal,
Since the electrode is immersed and the other end is grounded, the rod-shaped electrode for transmitting and reflecting the electromagnetic wave and the concentric cylindrical electrode outside the rod-shaped electrode perform the same operation as the coaxial cable, and the electromagnetic wave (microwave ) Propagation and reflection states
Compared with the case of a single electrode or two parallel electrodes, the occurrence of signal attenuation and waveform distortion is further suppressed, and high-accuracy level measurement with more stable operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a conductor length measuring device according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a diagram showing a level measurement device using the device of FIG. 1 according to the second embodiment of the present invention.

FIG. 4 is a diagram showing an example of measurement using two electrodes in the apparatus of FIG. 3 according to the third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st clock signal generator 2 2nd clock signal generator 3 1st pseudorandom signal generator 4 2nd pseudorandom signal generator 5, 6 Multiplier 7 Directional coupler 8 1st low pass filter 9 2nd low pass filter Reference Signs List 10 Measurement calculation unit 11 Conductor length measurement device 12 Coaxial cable 13 Electrode

Claims (4)

(57) [Claims] A means for generating a first pseudo-random signal synchronized with a first clock frequency; a first pseudo-random signal synchronized with a second clock frequency slightly different from said first clock frequency; Means for generating a second pseudo-random signal having the same pattern as the signal; first multiplying means for multiplying the generated first pseudo-random signal by a second pseudo-random signal; Means for inputting the pseudo-random signal of one as an electromagnetic wave from one end of the conductor to be measured, and propagating the input signal along the length direction of the conductor; Means for separating and detecting the reflected signal reflected from the other end and returned to the input end from the input signal; and a second means for multiplying the detected reflected signal and the generated second pseudo-random signal. Multiplying means; first integrating means and second integrating means for integrating and outputting the multiplication results of the first multiplying means and second multiplying means, respectively; and a maximum of an output signal of the first integrating means. Means for measuring the time between the time when the amplitude value is detected and the time when the maximum amplitude value of the output signal of the second integrating means is detected, and based on the measured time, the signal input terminal of the conductor. Means for measuring the length from the signal to the signal reflection end. 2. A means for generating a first pseudo-random signal synchronized with a first clock frequency, wherein said first pseudo-random signal is synchronized with a second clock frequency slightly different from said first clock frequency. Means for generating a second pseudo-random signal having the same pattern as the signal; first multiplying means for multiplying the generated first pseudo-random signal by a second pseudo-random signal; A means for inputting one pseudorandom signal as an electromagnetic wave from the other end of the rod-shaped electrode having one end inserted into and immersed in the molten metal, and propagating the input signal along the length direction of the rod-shaped electrode; Means for separating and detecting a reflected signal which propagates along the length direction of the electrode and is reflected from the tip or the contact portion between the electrode and the molten metal and returned to the input end, separately from the input signal; and Second multiplying means for multiplying the signal by the generated second pseudo-random signal; first integrating means for integrating and outputting the multiplication results of the first multiplying means and the second multiplying means, respectively; And second integrating means, and measuring a time between a time when the maximum amplitude value of the output signal of the first integrating means is detected and a time when the maximum amplitude value of the output signal of the second integrating means is detected. Means for measuring the length from the signal input end of the rod-shaped electrode to the signal reflection position based on the measured time; and the length from the signal input end of the measured rod-shaped electrode to the signal reflection position. Means for measuring the level of the molten metal based on the level. 3. An additional rod-shaped electrode parallel and adjacent to a rod-shaped electrode for transmitting and reflecting an electromagnetic wave by the first pseudo-random signal is provided, and one end of the additionally provided rod-shaped electrode is placed in the molten metal. 3. The level measuring device according to claim 2, wherein the level measuring device is inserted and immersed in the device, and the other end is grounded. 4. A concentric cylindrical electrode is additionally provided outside a rod-shaped electrode for transmitting and reflecting an electromagnetic wave by the first pseudorandom signal, and one end of the additionally provided concentric cylindrical electrode is provided. 3. The level measuring device according to claim 2, wherein the level measuring device is inserted and immersed in the molten metal, and the other end is grounded.