JP5012142B2 - Electrical resistance measurement method and apparatus - Google Patents

Description

  The present invention relates to an electrical resistance measurement method and apparatus for measuring the electrical resistance of an object having good conductivity, such as metal.

Conventionally, as a method of measuring the electrical resistance of an object to be measured such as a carbon brick used in a blast furnace, generally, four electrodes are installed on the object to be measured, and the electric resistance of the object to be measured is measured. In many cases, a four-terminal method is used.
In this four-terminal method, first, a pair of current application electrodes connected to a current generation source is installed on the object to be measured, and a pair of voltage detection electrodes connected to a voltmeter is connected to a pair of current application electrodes. Install them at regular intervals.

The current generated by the current generation source is applied to the object to be measured via the pair of current application electrodes, and the voltage generated at the pair of voltage detection electrodes is detected by a voltmeter, and the current is detected according to Ohm's law. This is a method for obtaining the electrical resistance of a measurement object. In this method, the measurement accuracy of electrical resistance improves as the contact electrical resistance between the object to be measured and each electrode decreases.
When measuring the electrical resistance of an object to be measured using such a method, if the electrical resistance of the object to be measured is low, the voltage detected by the voltmeter is also reduced, so that the measurement accuracy of the electrical resistance is improved. Therefore, it is necessary to increase the current value applied to the object to be measured.

However, for example, when measuring the electrical resistance of a metal, a direct current is applied to detect a voltage generated in the metal by this current. If the current value is large, the metal is heated by Joule heat, and a partial current is detected. There is a risk of generating a thermoelectromotive force due to a temperature difference.
When the thermoelectromotive force is generated, a noise voltage is generated in the signal component due to the thermoelectromotive force, and it is difficult to distinguish the noise voltage from the signal component. In particular, when the electrical resistance of the object to be measured varies greatly depending on the temperature, such as when the object to be measured is a metal, there may be a problem that accurate measurement of the electrical resistance becomes more difficult.

Therefore, in order to distinguish between the noise voltage generated by the thermoelectromotive force and the signal component, it can be considered that the current applied to the object to be measured is an alternating current. In this case, since the signal component is alternating current (sinusoidal wave) and the thermoelectromotive force is direct current, it is possible to detect only the signal component as distinguished from the thermoelectromotive force.
However, since the current generates a magnetic flux, when the current applied to the object to be measured is a sine wave, the magnetic flux changes according to time, and this temporal change of the magnetic flux may generate an induced electromotive force. .

In addition, since the induced electromotive force increases as the current value applied to the object to be measured increases, the voltage detected is reduced when measuring the electric resistance of the object to be measured, such as metal, which has a low electric resistance. The electromotive force and the detected voltage may be the same or different values. For this reason, there exists a possibility that the problem that exact measurement of an electrical resistance becomes difficult may arise.
In addition, when a low current is used so that the influence of the magnetic flux is smaller than the resolution of the apparatus, an amplifier must be used in order to sufficiently secure the S / N ratio of the detected voltage. However, since an amplifier capable of amplifying a low voltage is relatively expensive, the use of such an amplifier may increase the cost.

In order to solve such a problem, for example, an electrical resistance measurement method described in Patent Document 1 is used.
In the electrical resistance measurement method described in Patent Document 1, first, a pseudo-random signal is used as an application signal to be applied to the current application electrode, and the voltage generated between the voltage detection electrodes is converted into a voltage signal converted from the current signal. At the same time, it is input to the signal processing means.
The signal processing means performs a process of excluding inductive noise generated when the pseudo random signal is switched on the current waveform and the voltage waveform, and further performs a correlation calculation process between the current waveform and the voltage waveform.

Since the maximum value (peak value) in the obtained correlation waveform is the voltage generated between the electrodes, the electric resistance of the object to be measured is obtained by dividing this voltage by the current value based on Ohm's law. It is a method to measure.
JP 2006-177699 A

However, in the electrical resistance measurement method described in Patent Document 1, when the object to be measured is a high-temperature molten metal or a low electrical resistor such as a heated metal, the inside of the object to be measured is used. Since the temperature distribution becomes uneven, there is a risk that thermal noise or thermoelectromotive force may occur in the object to be measured.
When thermal noise or electromotive force is generated in the device under test, noise voltage such as white noise or drift noise is generated in the detected signal component due to these effects, and the measurement accuracy of the electrical resistance is lowered. There is a risk of problems.

Further, in the electrical resistance measurement method described in Patent Document 1, when the object to be measured is an electrically grounded structure, drift noise is added to the detected signal component due to the influence of stray current noise or induced noise. There is a possibility that a noise voltage including
If a noise voltage including drift noise is generated in the detected signal component, it is difficult to accurately measure the voltage value or the electric resistance value, which may cause a problem that the measurement accuracy of the electric resistance is lowered.
The present invention has been made paying attention to the above-described problems, and even when the electrical resistance of the object to be measured is low, the electrical resistance of the object to be measured can be accurately measured. It is an object to provide a resistance measuring method and an apparatus therefor.

In order to solve the above-mentioned problem, the invention described in claim 1 of the present invention applies a current modulated by a binary reference signal having the same absolute value and different signs to the object to be measured. A voltage generated in the object to be measured by the measured current, correlatively calculating the detected voltage and the reference signal, and based on a result of the correlation calculating process, an electric resistance of the object to be measured An electrical resistance measurement method for measuring
Said reference signal, and the pulse width and the time that the even equal the shortest pulse width pseudo-random signal, and switches the order of the pulse code, unlike according to the sign of the pseudo-random signal,
Rukoto performs correlation operation with respect to the reference signals for several cycles, calculates an average of the maximum value of the correlation function in each cycle, to calculate the electrical resistance of the mean the object to be measured using the maximum value thus calculated It is characterized by.

According to the present invention, binary reference signals having the same absolute value but different signs are set to a time obtained by dividing the pulse width by an even number of the shortest pulse width of the pseudo-random signal, and the switching order of the pulse codes is set to pseudo. Different depending on the sign of the random signal.
For this reason, even when a noise voltage is generated in the detected signal component, it is possible to suppress the influence of the noise voltage, and thus it is possible to accurately measure the electrical resistance of the object to be measured. Become.

Next, the invention described in claim 2 is the invention described in claim 1, wherein an induced electromotive force component and a signal component which are noise components in measurement are temporally separated from the detected voltage, and the signal component is temporally separated. Only a signal component is extracted, a conductive voltage signal of a signal component obtained by separating the noise component is generated, and the correlation calculation process is performed using the generated conductive voltage signal and the reference signal. .
According to the present invention, a voltage generated in an object to be measured is detected, a conductive voltage signal of a signal component obtained by separating a noise component is generated from the detected voltage, and the generated conductive voltage signal and the reference signal are used. Perform correlation calculation processing.
For this reason, it becomes possible to measure the electrical resistance of the object to be measured with a high S / N ratio, and it is possible to accurately measure the electrical resistance of the object to be measured.

Next, among the present inventions, the invention described in claim 3 is a binary pulse train having the same absolute value and different signs, and the pulse width is a time obtained by equally dividing the shortest pulse width of the pseudo-random signal. And a signal processing means for generating a reference signal consisting of a pulse train whose pulse code switching order is different depending on the code of the pseudo-random signal;
A current applying means for applying a current modulated by the generated reference signal by means of a pair of current applying electrodes installed on the object to be measured;
Voltage detecting means for detecting a voltage generated in the object to be measured by the applied current by a voltage detecting electrode;
A signal processing means for performing a correlation calculation process on the detected voltage and the reference signal, and calculating an electric resistance of the object to be measured based on a result of the correlation calculation process ;
The signal processing means performs correlation calculation processing on the reference signal of several cycles, calculates an average of the maximum value of the correlation function in each cycle, and uses the average of the calculated maximum values to It is an electrical resistance measuring device characterized by calculating resistance .

According to the present invention, the correlation detection process is performed on the voltage detected by the voltage detection unit and the reference signal having a pulse train that differs according to the sign of the pseudo-random signal, and the object to be measured is based on the result of the correlation calculation process. The electrical resistance is calculated.
For this reason, even when a noise voltage is generated in the detected signal component, it is possible to suppress the influence of the noise voltage, and thus it is possible to accurately measure the electrical resistance of the object to be measured. Become.

Next, the invention described in claim 4 is the invention described in claim 3, wherein the signal processing means includes:
Clock generating means for outputting binary pulses having the same absolute value and different signs of the time width of the shortest pulse;
Pseudo-random signal generating means for outputting binary pseudo-random signals having the same absolute value and different signs;
Multiplying operation means for generating the reference signal by multiplying the pulse output from the clock generating means and the pseudorandom signal output from the pseudorandom signal generating means, To do.
According to the present invention, the signal processing means includes multiplication operation means for generating a reference signal by multiplying the pulse output from the clock generation means by the pseudo random signal output from the pseudo random signal generation means. ing.
For this reason, it becomes possible to measure the electrical resistance of the object to be measured with a high S / N ratio, and it is possible to accurately measure the electrical resistance of the object to be measured.

Next, the invention described in claim 5 is the invention described in claim 3 or 4, wherein the object to be measured is at least one of a low electrical resistor and an electrically grounded object. ,
A plurality of the voltage detection electrodes are provided between the pair of current application electrodes.
According to the present invention, even when the object to be measured is a low electric resistance element such as a high-temperature molten metal or a heated metal, the electric resistance of the object to be measured is reduced. It becomes possible to measure accurately.
Further, according to the present invention, even when the object to be measured is a structure that is electrically grounded, such as a carbon brick blast furnace, the electrical resistance of the object to be measured is accurately measured. It becomes possible to do.

  According to the present invention, even when the electrical resistance of the object to be measured is low, the measurement accuracy of the electrical resistance of the object to be measured can be improved, and therefore the electrical resistance of the object to be measured is accurately measured. It becomes possible.

Next, embodiments of the present invention will be described with reference to the drawings.
First, the configuration of the electrical resistance measurement apparatus according to the present embodiment will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a configuration of an electrical resistance measurement apparatus 1 according to the present embodiment.
As shown in FIG. 1, the electrical resistance measuring apparatus 1 of the present embodiment includes a signal generating unit 2, a pair of current application electrodes 4 a and 4 b, a pair of voltage detection electrodes 6 a and 6 b, and a correlation calculation unit 8. For example, it is used when measuring the electrical resistance of the object to be measured 10 such as a carbon brick blast furnace.

The signal generation means 2 includes a pseudo random signal generation means 12, a pulse generation means 14, and a signal processing means 16, and a pair of current application electrodes 4a via two current application cables 18a and 18b. , 4b.
The pseudo-random signal generator 12 is connected to an oscillator (not shown), generates a pseudo-random signal S1 based on frequency control by the oscillator, and generates the pseudo-random signal S1 as a signal processing unit 16. The function to output to. In the present embodiment, a case where an M-sequence signal is used as the pseudo random signal S1 will be described as an example.

FIG. 2 is a diagram showing a pseudo random signal S1 generated by the pseudo random signal generating means 12 used in the present invention.
As shown in FIG. 2, the pseudo random signal S1 generated by the pseudo random signal generating means 12 has a positive and negative binary code having the same absolute value, and the positive code of the binary codes is “+1”. ”And the negative sign is“ −1 ”. FIG. 2 shows a case where the code length of the pseudo random signal S1 is 127 as an example.

  The pulse generating means 14 repeatedly generates a pulse signal S2 having a pulse period of an evenly divided period with respect to the minimum period of the pulses output from the pseudo random signal generating means 12, and the generated pulse signal S2 is generated. In addition, it has a function of outputting to the signal processing means 16 in synchronism with the pseudo-random signal S1 (the pulse rise and fall timings coincide). In the present embodiment, as an example, a case will be described in which the pulse period is divided into two equal parts with respect to the minimum period of the pulses output from the pseudo-random signal generator 12.

When the pseudo random signal S1 and the pulse signal S2 are input, the signal processing means 16 multiplies these signals to generate a reference signal S3, and applies the generated reference signal S3 to two currents. It has a function of applying to the DUT 10 from the pair of current application electrodes 4a and 4b via the cables 18a and 18b.
Here, when the generated reference signal S3 is applied from the pair of current application electrodes 4a and 4b to the device under test 10, the reference signal S3 is digitally converted using a known D / A converter (not shown). The signal is converted into an analog signal, and is output from the signal processing means 16 to the pair of current application electrodes 4a and 4b via the two current application cables 18a and 18b.

FIG. 3 is a diagram showing a procedure for generating the reference signal S3. 3A shows a part of the pseudo-random signal S1, FIG. 3B shows a part of the pulse signal S2, and FIG. 3C shows the reference signal S3. It is a figure which shows a part of.
In the signal processing means 16, a pseudo random signal S1 having a minimum pulse width Wmin as shown in FIG. 3A and a pulse width obtained by dividing the minimum pulse width Wmin into two equal parts as shown in FIG. And a reference signal S3 as shown in FIG. 3C is generated.

At this time, the cycle of the pulse signal S2 is Wmin / 2, and synchronization is performed so that the code switching timing of the pulse signal S2 coincides with the code switching timing of the pseudo-random signal S1.
Therefore, by multiplying the pseudo random signal S1 and the pulse signal S2, a reference signal S3 as shown in FIG. 3C is generated. Specifically, when the code of the pseudo random signal S1 is “+1”, the code of the pseudo random signal S1 is evenly divided in time in the order of “+1” to “−1”. On the other hand, when the code of the pseudo-random signal S1 is “−1”, the code of the pseudo-random signal S1 is evenly divided in time in the order of “−1” to “+1”.

  In FIG. 3C, there is a portion with a long pulse width. This is because the sign of the pseudo-random signal S1 changes from “+1” to “−1” or from “−1” to “+1”. This is the timing point. This is because, when the pseudo random signal S1 and the pulse signal S2 are multiplied at the timing at which the code of the pseudo random signal S1 changes, the same code is continuous.

  When the reference signal S3 generated by the signal generating means 2 is applied to the pair of current application electrodes 4a and 4b via the two current application cables 18a and 18b, a current is supplied to the device under test 10. Flowing. When a current flows through the device under test 10, a voltage corresponding to the electrical resistance of the device under test 10 is generated inside the device under test 10, and the generated voltage is detected by the pair of voltage detection electrodes 6a and 6b. Is done.

Here, the pair of current application electrodes 4a and 4b is directly connected to the device under test 10 so that the contact electrical resistance with the device under test 10 is lower than the device under test 10 whose electrical resistance is to be measured. They are connected or installed using a highly conductive adhesive or the like.
In addition, the pair of voltage detection electrodes 6a and 6b is in contact with the device under test 10 with respect to the device under test 10 between the pair of current application electrodes 4a and 4b, like the current application electrode 4. It is directly connected to the object to be measured 10 or installed using a highly conductive adhesive or the like so that the electric resistance is lowered.

The correlation calculation means 8 is formed by, for example, a computer, and includes a signal extraction unit 20, a correlation calculation unit 22, and a resistance calculation unit 24. A pair of voltage detection cables 26a and 26b are used as a pair. The voltage detection electrodes 6a and 6b are connected.
When the voltage detected by the pair of voltage detection electrodes 6a and 6b is input via the two voltage detection cables 26a and 26b, the signal extraction unit 20 receives the conductive voltage signal and the transient induction noise. Whether or not is included is determined. When the voltage detected by the pair of voltage detection electrodes 6a and 6b includes a conduction voltage signal and transient induction noise, the conduction voltage of the conduction voltage signal and the transient induction noise included in the voltage is included. Only the signal is temporally separated and extracted, and the extracted conductive voltage signal is output to the correlation calculation unit 22.

The voltage detected by the voltage detection electrode 6 includes a conductive voltage signal and transient inductive noise when the current value applied to the current application electrode 4 is large or there is a metal around the object to be measured 10. This often occurs when a manufactured structure is present.
Hereinafter, a procedure for temporally separating and extracting only the conductive voltage signal from the voltage detected by the voltage detection electrode 6 will be described.
When the voltage detected by the voltage detection electrode 6 is V ₀ (t), the conductive voltage signal is S, and the transient induction noise is N ₀ , the voltage V ₀ (t) is calculated by the following equation (1). Is done.

  The conductive voltage signal S is calculated by the following equation (2).

In addition, r shown in Formula (2) is an electrical resistance of the DUT 10 and i is a current applied to the current application electrode 4.
Further, the transient induction noise N ₀ is calculated by the following equation (3).

Note that φ shown in Equation (3) is a magnetic flux penetrating the entire measurement system including the current application cable 18 and the voltage detection cable 26.
Hereinafter, the processing in the signal extraction unit 20 will be described with reference to FIG.
FIG. 4A is a diagram illustrating an example of a waveform of a voltage detected by the voltage detection electrode 6.
As shown in FIG. 4A, the transient induction noise generated in the voltage detected by the voltage detection electrode 6 is generated at the moment when the sign of the detected voltage is switched, as shown in FIG. 4B. The absolute value of the time change rate ΔV / Δt of the voltage becomes a very large value at the moment when the sign is switched, and gradually decreases to a value close to 0V.

At this time, a threshold value is set for the absolute value of the detected voltage time change rate ΔV / Δt, and a time interval in which the absolute value of ΔV / Δt is larger than the threshold value is set as an induction noise interval, and ΔV A time interval in which the absolute value of / Δt is small is set as a signal component interval.
The time for which transient induced noise is attenuated is determined by the configuration of the detection system when performing measurement, so the time for which transient induced noise is attenuated is the same for each symbol unless the configuration of the detection system cable or electrode is changed. It appears for the same time after the sign change. In such a case, as shown in FIG. 4, even if the absolute value of the voltage time change rate ΔV / Δt is not compared with a threshold value, the induced noise and the signal component are changed at the time from the time of switching the sign. The section can be distinguished.

Therefore, as shown in FIG. 5 (a), the fixed time To of the set induction noise interval is removed from the switching point of each sign in the voltage waveform detected by the voltage detection electrode 6, and corresponds to the signal component interval. The detected voltage to be extracted is extracted as a signal component, and the extracted signal component is used as a conductive voltage signal. In this case, in order to facilitate the correlation calculation process described later, the voltage in the induction noise section is set to 0V. In addition, the number of data n where the voltage in the induction noise section is 0 V is counted and recorded. FIG. 5B is a waveform diagram showing the voltage of the signal component after removing the noise component.
The correlation calculation unit 22 uses the reference signal S3 applied to the current application electrode 4 as a reference signal, performs a correlation calculation process between the reference signal and the detection voltage signal, and outputs the processing result to the resistance calculation unit 24. have.

Hereinafter, a procedure for performing correlation calculation processing between the reference signal and the detection voltage signal will be described.
First, the total period of the signal component section and the induction noise section, that is, the number of voltage data detected (sampled) in one cycle of the pseudo-random signal S1 is N, and from this data number N, the signal extraction unit 20 sets 0V The number n of recorded data is subtracted to calculate N−n number of data for correlation calculation. Also, the reference signal S3 is set to 0V in the section corresponding to the data set to 0V in the induced noise section of the detection voltage.

Thereafter, both the detection voltage signal and the reference signal are removed from the 0V section, and the correlation calculation process is performed as a signal obtained by combining the remaining signals. Therefore, as shown in FIG. 5C, the detection voltage signal is a signal in which only the conduction voltage signal is connected.
At this time, assuming that the i-th data of the calculated reference signal waveform is f (i) and the i-th data in the voltage waveform of the conductive voltage signal is g (i), the correlation function V (j) is as follows. Calculated by equation (4).

In this equation (4), when j becomes a value corresponding to the current propagation path, V (j) becomes the maximum value, and the maximum value corresponds to the voltage value. However, since the paths through which the current propagates are various and it is difficult to specify the distance, it is calculated which value the correlation value will be by changing the value of j.
Therefore, the maximum value of the correlation function V (j) when the integer j is changed between 0 and (N−n) is a voltage necessary for calculating the electrical resistance of the DUT 10.

The resistance calculation unit 24 has a function of measuring the electrical resistance of the DUT 10 based on the result of the correlation function processing in the correlation calculation unit 22. Specifically, when the maximum value of the correlation function V (j) when the integer j is changed between 0 and (N−n) is input, the correlation function V (j) of this maximum value is converted into a voltage. Based on this voltage and the current of the reference signal, the electrical resistance of the DUT 10 is calculated.
Here, correlation calculation processing is performed on the reference signal (reference signal S3) of several cycles, the average of the maximum values of the correlation function V (j) in each cycle is calculated, and the average of the calculated maximum values is used. Further, it is possible to further improve the S / N ratio.

Thereafter, the signal processing means 16 multiplies the pseudo random signal S1 and the pulse signal S2 to generate a reference signal S3, and the generated reference signal S3 is applied to the pair of current application electrodes 4a and 4b. The reason will be described with reference to FIG.
When the reference signal S3 generated in the signal processing means 16 is applied to the current application electrode 4, the voltage detected by the voltage detection electrode 6 has an amplitude proportional to the current value of the reference signal S3. A waveform having the same pattern as the current waveform of the reference signal S3 appears.

However, when the object to be measured 10 is a low electric resistance value such as a carbon brick, the voltage generated inside the object to be measured 10 is reduced due to the current flowing through the object 10 to be detected. A lot of noise is superimposed on the waveform of the voltage.
Here, as noise generated in the waveform of the detected voltage, white noise, drift noise, 1 / f noise, and the like can be cited when the DUT 10 is a high temperature low electrical resistor. These noises are generated due to thermal noise and thermoelectromotive force.
Further, when the DUT 10 is a structure that is electrically grounded, examples of noise generated in the detected voltage waveform include stray noise and induction noise. These noises are caused by the current flowing from the grounded part of the structure.

  When only the pseudo-random signal S1 is applied to the current application electrode 4 without multiplying the pseudo-random signal S1 and the pulse signal S2, white noise or 1 / f noise is generated in the detected voltage waveform. It becomes possible to suppress. However, when only the pseudo-random signal S1 is applied to the current application electrode 4, noise that drifts in the waveform over time, such as drift noise, occurs in the waveform of the detected voltage. It is impossible to suppress. Therefore, it is difficult to accurately measure the electrical resistance of the DUT 10.

On the other hand, in the electrical resistance measuring apparatus 1 of this embodiment, since the reference signal S3 is applied to the current application electrode 4, not only white noise and 1 / f noise can be obtained by performing correlation function processing. Also, it is possible to suppress the occurrence of a detected voltage waveform even with respect to drift noise.
This is because the total number of clocks (code length) corresponding to one period of the pseudo-random signal S1 is an odd number, whereas the reference signal S3 is evenly divided in time by each clock (each code). This is because the total number of clocks (code length) is an even number.

Here, the waveform of the m ₀ of the pseudo-random signal S1 (t), is detected when a pseudo-random signal S1 is applied, the waveform of the voltage noise caused by the _m'0 (t), noise in addition to drift noise Let V ₀ (t) be the waveform of the voltage where the occurrence of δ and δ (t) the drift noise. It is assumed that the drift noise δ (t) changes within one period T of the pseudo random signal S1.
When the above definition is applied, the waveform m ′ ₀ (t) of the voltage in which noise occurs is calculated by the following equation (5).

Moreover, the correlation function between the waveform _m'0 (t) the waveform m ₀ (t) and the voltage noise occurs pseudo random signal S1 [Phi (tau) is calculated by equation (6) shown below.

Note that T shown in Equation (6) is the period of the pseudo-random signal S1 (M-sequence signal), and τ is the delay time .

Pseudo case of applying only the random signal S1 to the current supply electrode 4, since the total clock pseudorandom signal S1 is an odd number, it is the number of positive and negative signs are different from each other, that the noise term may remain without disappearing It becomes.

On the other hand, in the reference signal S3, as shown in FIG. 6, each clock is evenly divided in time, so that the total number of clocks is even. For this reason, when the positive and negative signs are the same and the correlation function Φ (τ) is calculated by the above equation (6), the same positive and negative values of the reference signal S3 to be locally referred to and the drift noise δ (t) The drift noise δ (t) can be canceled over one period. FIG. 6 is a diagram showing the relationship between the reference signal and the voltage signal detected by the voltage detection electrode 6, and a part of the reference signal and a part of the voltage signal detected by the voltage detection electrode 6. FIG. 6 is a diagram illustrating a correspondence relationship in correlation calculation with drift noise among noises generated in detected voltage.
Therefore, by applying the reference signal S3 generated by the signal processing means 16 to the current application electrode 4, it is possible to suppress the influence of drift noise, so that the accurate electrical resistance of the DUT 10 can be reduced. It becomes possible to measure.

FIG. 7 is a diagram illustrating an example of a result of performing the correlation calculation processing in this way.
FIG. 7 shows a correlation calculation result when the voltage detected by the voltage detection electrode 6 is temporally coincident with the waveform of the reference signal S3 without time delay. (Τ) has a maximum value at time τ = 0, and its value is “+1”. Note that when both waveforms are shifted by the time τa and coincide (for example, the detected voltage waveform is delayed by the time τa), the correlation function Φ (τa) = 1.

That is, when the current applied to the current application electrode 4 (corresponding to the reference signal) is 1A (ampere) and the binary values “+ 1A” and “−1A” are used as the reference signal of the reference signal S3, If the electrical resistance of the device under test 10 is 1Ω, the maximum value Φ (τa) of the correlation function is 1V (volt) based on Ohm's law.
However, in the actual measurement of the low electric resistance body, the detected voltage is low, and the waveform of the noise voltage is often superimposed on the waveform. Therefore, it is preferable that the applied current has a value larger than 1A. . In this case, the maximum value of the calculated correlation function is I × V when the applied current (reference signal) is I (A) and the detection voltage (detection signal) is V (V). Therefore, the voltage value V is obtained by dividing the maximum value IV of the correlation function by the current value I, and when this voltage value V is further divided by the current value I, the electric resistance R (Ω) of the DUT 10 is calculated. The Rukoto.

Note that the two current application cables 18a and 18b as described above allow the reference signal S3 generated by the signal generation means 2 to be applied to the pair of current application electrodes 4a and 4b installed on the DUT 10. A current applying unit is configured to apply and apply a current to the DUT 10.
In addition, the two voltage detection cables 26a and 26b as described above are configured so that a voltage generated in the device under test 10 when a current flows through the device under test 10 is placed between the pair of current application electrodes 4a and 4b. Thus, voltage detecting means for detecting via the plurality of voltage detecting electrodes 6 is constructed.

Next, based on FIGS. 1 to 7, the operation and effect of the method for measuring the electrical resistance of the DUT 10 using the electrical resistance measuring device 1 of the present embodiment will be described with reference to FIG. 8. .
FIG. 8 is a flowchart showing a method of measuring the electrical resistance of the DUT 10 using the electrical resistance measurement device 1 of the present embodiment (hereinafter referred to as “electrical resistance measurement method”).
In the flowchart of FIG. 8, the pseudo-random signal S1 is generated in the pseudo-random signal generating means 12, the pulse signal S2 is generated in the pulse generating means 14, and these signals are multiplied in the signal processing means 16, that is, The process starts from the point where the signal generating means 2 generates the reference signal S3 (step S10).

When the reference signal S3 is generated in the signal generating means 2, the generated reference signal S3 is applied to the pair of current application electrodes 4a and 4b via the two current application cables 18a and 18b. Then, a current flows through the device under test 10 (step S20).
In step S20, the reference signal S3 generated by the signal generator 2 is output to the correlation calculation unit 22 (steps S50 and S60).

When a current flows through the device under test 10, a voltage corresponding to the electrical resistance of the device under test 10 is generated inside the device under test 10, and the generated voltage is detected by the pair of voltage detection electrodes 6a and 6b. (Step S30).
The voltages detected by the pair of voltage detection electrodes 6a and 6b are input to the signal extraction unit 20 via the two voltage detection cables 26a and 26b. In the signal extraction unit 20, the voltage detection electrode 6 detects the voltage detection electrodes 6a and 6b. It is determined whether or not transient induced noise is included in the measured voltage (step S40).

If it is determined in step S40 that the voltage detected by the voltage detection electrode 6 includes transient induction noise, the process proceeds to step S42.
In step S42, a threshold value is set for the absolute value of the detected voltage change rate ΔV / Δt, and a time interval in which the absolute value of ΔV / Δt is larger than the threshold value is set as an induction noise interval. The time interval in which the absolute value of ΔV / Δt is small is set as the signal component interval, that is, the induced noise interval and the signal component interval are separated, and the process proceeds to step S46.

In step S46, the fixed time of the induction noise section set in step S42 is removed from the switching time of each code in the voltage waveform detected by the voltage detection electrode 6. Then, the detection voltage corresponding to the signal component section is extracted as a signal component, and the extracted signal component is output as a conductive voltage signal to the correlation calculation unit 22, and the process proceeds to step S48.
In step S50, the reference signal S3 generated by the signal generating means 2 is estimated to be a signal having the same pattern as the conductive voltage signal, and the section corresponding to the data set to 0 V by the conductive voltage signal is used as the reference signal. In S3, the voltage is set to 0 V, and the number of data n recorded in the signal extraction unit 20 as the number of data signals for correlation calculation is excluded from the total number of data N of the signal component section and the induction noise section, and the process proceeds to step S48. .

In step S48, based on the calculated reference signal waveform data and the data in the voltage waveform of the conductive voltage signal, a voltage required for calculating the electrical resistance of the DUT 10 is calculated, and the process proceeds to step S70. To do.
On the other hand, when it is determined in step S40 that the voltage detected by the voltage detection electrode 6 does not include transient induction noise, the process proceeds to step S44.
In step S44, the voltage detected by the voltage detection electrode 6 is input, the input voltage signal is output to the correlation calculation unit 22, and the process proceeds to step S60.
In step S60, based on the calculated reference signal waveform data and the data in the voltage waveform detected by the voltage detection electrode 6, the voltage required for calculating the electrical resistance of the DUT 10 is calculated. Control goes to step S70.

In step S70, the electrical resistance of the device under test 10 is calculated based on the voltage calculated in step S48 or step S60, and the process ends.
Therefore, according to the electrical resistance measurement method of the present embodiment, the reference signal S3 is converted to the pseudo random signal S1 having positive and negative binary signs having the same absolute value, in the order from positive to negative or from negative to positive. They are generated evenly in time.
Further, the order in which the sign of the pseudo-random signal S1 is evenly divided in time when the sign of the pseudo-random signal S1 is positive and negative is different from each other.
For this reason, even when a noise voltage is generated in the detected signal component, it is possible to suppress the influence of the noise voltage, and thus it is possible to accurately measure the electrical resistance of the object to be measured. Become.

As a result, even if the electrical resistance of the device under test 10 is low, the measurement accuracy of the electrical resistance of the device under test 10 can be improved, so the electrical resistance of the device under test 10 is accurately measured. It becomes possible.
In the electrical resistance measurement method of the present embodiment, as the correlation calculation process, only the conductive voltage signal S is temporally separated from the detected voltage and extracted, and the reference signal S3 is extracted as the reference signal. Correlation calculation processing between the conductive voltage signal and the reference signal is performed.

As a result, it is possible to measure the electrical resistance of the device under test with a high S / N ratio, and it is possible to improve the measurement accuracy of the electrical resistance of the device under test 10. Can be measured accurately.
Furthermore, in the electrical resistance measurement method of the present embodiment, the positive sign is “+1” and the negative sign is “−1” among the binary codes constituting the reference signal S3. It is possible to easily divide the sign of S3 into even numbers in time.

In the electrical resistance measurement method of the present embodiment, the object to be measured 10 is a low electrical resistance body such as a high-temperature molten metal or a heated metal. However, the electrical resistance of the DUT 10 can be accurately measured.
In the electrical resistance measurement method of the present embodiment, even if the device under test 10 is a structure that is electrically grounded, such as a carbon brick used in a blast furnace, for example, It becomes possible to accurately measure the electric resistance of 10.

  In the electrical resistance measurement method of the present embodiment, the reference signal S3 is an even number in time in the order of the sign from “+1” to “−1” when the sign of the pseudo random signal S1 is “+1”. On the other hand, when the code of the pseudo-random signal S1 is “−1”, the code is evenly divided in time in the order of “−1” to “+1”, but is not limited thereto. It is not something. That is, when the code of the pseudo random signal S1 is “+1”, the reference signal S3 is equally divided in time in the order of “−1” to “+1”, while the pseudo random signal S1. If the code of “−1” is “−1”, the code may be evenly divided in time in the order of “+1” to “−1”. In short, when the sign of the pseudo-random signal S1 is positive, the order of equally dividing the sign of the pseudo-random signal S1 in time and the pseudo-random signal S1 when the sign of the pseudo-random signal S1 is negative The order in which the codes are evenly divided is only required to be different from each other.

  The electrical resistance measuring device 1 used in the electrical resistance measuring method of the present embodiment has a configuration including a pair of voltage detection electrodes 6 a and 6 b, that is, a configuration including two voltage detection electrodes 6. However, the present invention is not limited to this. That is, for example, three or more voltage detection electrodes 6 are provided, and these voltage detection electrodes 6 are all installed on the DUT 10 between the pair of current application electrodes 4a and 4b. Also good. The point is that a plurality of voltage detection electrodes 6 are provided, and these voltage detection electrodes 6 may be configured to be installed on the DUT 10 between the pair of current application electrodes 4a and 4b.

  Furthermore, in the electrical resistance measurement method of the present embodiment, the positive and negative binary signs having the same absolute value in the reference signal S3 are “+1” and “−1”, but the present invention is not limited to this. is not. That is, the positive and negative binary codes having the same absolute value in the reference signal S3 may be “+ I” and “−I”, which are current values actually applied to the current application electrode 4.

In the electrical resistance measurement method of the present embodiment, when a reference signal S3 generated by software inside the computer is applied to the pair of current application electrodes 4a and 4b, a known D / A converter is used. The reference signal S3 is output from the signal processing means 16 to the pair of current application electrodes 4a and 4b via the two current application cables 18a and 18b. However, the present invention is not limited to this. That is, for example, a pseudo-random signal S1 generated by an electric circuit and a rectangular wave having a frequency obtained by dividing the clock frequency corresponding to the shortest pulse width of the pseudo-random signal S1 into two equal parts are mixed (multiplication operation) with matching timings of code switching )
In the electrical resistance measurement method of the present embodiment, the M-sequence signal is used as the pseudo-random signal S1, but the present invention is not limited to this, and a signal other than the M-sequence signal may be used as the pseudo-random signal S1. Good.

  Hereinafter, in the blast furnace, the experimental results of measuring the electrical resistance in the plating bath provided in the hot dip galvanizing line using the electrical resistance measuring device similar to the electrical resistance measuring device 1 used in the electrical resistance measuring method of the present embodiment, The experimental results of measuring electrical resistance are shown respectively. In both experiments, an M-sequence signal was used as a pseudo-random signal, as in the electrical resistance measurement method of the present embodiment.

First, the experimental results of measuring the electrical resistance in the plating bath will be described.
FIG. 9 is a diagram for explaining measurement of electrical resistance in the plating bath.
As shown in FIG. 9, in this experiment, a probe 30 for measuring electrical resistance is installed in the plating bath 28.
The plating bath 28 is filled with molten zinc at about 450 ° C.

In the hot dip galvanizing line including such a plating bath 28, Fe eluted from the steel plate in the plating bath 28 is alloyed with Al or Zn to become dross such as FeZn ₇ and is deposited on the bottom of the plating bath 28. A bottom dross is generated. When the bottom dross becomes large, when the steel plate is passed through the plating bath 28, the bottom dross is rolled up, the bottom dross adheres to the steel plate passing through the plating bath 28, and the steel plate is rolled. Therefore, it is necessary to manage the amount of bottom dross in the plating bath 28.

The probe 30 includes a pair of current application electrodes 4a and 4b and four voltage detection electrodes 6a, 6b, 6c and 6d disposed between the pair of current application electrodes 4a and 4b, that is, all six electrodes. It consists of electrodes.
Each of the current application electrode 4 and each voltage detection electrode 6 has an electric wire serving as an electrode passing through the heat-resistant insulating case 32 and the tip projecting to the outside, and each tip portion 34 is an insulating layer such as a coating film. Is immersed in a plating bath containing molten zinc, bottom dross, and the like in the plating bath 28 in a state where it can be removed and conducted.

Further, each current application electrode 4 and each voltage detection electrode 6 are arranged along the depth direction of the plating bath 28, and the electrode arranged above the pair of current application electrodes 4a and 4b is Installed in the vicinity of a preset upper limit of the height at which a problem occurs due to accumulation of bottom dross. In FIG. 9, the electrode disposed above the pair of current application electrodes 4a and 4b is described as the current application electrode 4a.
When measuring the electrical resistance in the plating bath 28 using such an electrical resistance measuring device, by observing the electrical resistance calculated based on the voltage detected by each voltage detection electrode 6, When the electrical resistance exceeds a certain value, it is determined that the amount of bottom dross accumulated in the plating bath 28 has exceeded the upper limit of the height at which the problem occurs.

The reason will be described below.
FIG. 10 is a diagram showing the relationship between the zinc component existing between the voltage detection electrodes 6 and the amount of bottom dross deposited in the plating bath 28. The vertical axis in the figure represents the electric resistance R (unit: 10 ⁻⁷ Ωm), and the horizontal axis in the figure represents the ratio of molten zinc in the bottom dross deposited in the plating bath 28.
As shown in FIG. 10, when the ratio in the plating bath existing between the voltage detection electrodes 6 is almost only the bottom dross, the ratio in the plating bath is almost equal to that in the case of molten zinc. The electrical resistance value is more than five times larger. The electric resistance value in the plating bath varies depending on the ratio of bottom dross and molten zinc in the plating bath.

Therefore, since the magnitude of the electrical resistance is clearly different between the case where the ratio of molten zinc and the percentage of bottom dross are large in the plating bath existing between the voltage detection electrodes 6, the calculated electrical resistance is constant. When the value is exceeded, it may be determined that the amount of bottom dross accumulated in the plating bath 28 has reached the upper limit of the height at which the problem occurs.
Further, in this experiment, when each current application electrode 4 generates a thermoelectromotive force, the generated thermoelectromotive force becomes drift noise. Therefore, by using an M-sequence signal as a pseudo-random signal, the influence of drift noise is reduced. Suppressed. Here, the M-sequence signal used as the pseudo-random signal has a total clock number (code length) of 127 and a clock frequency of 0.5 Hz.

  When the code of the M-sequence signal is “+1”, the M-sequence signal is generated as a rectangular wave whose frequency is 1 Hz and whose sign is changed from “−1” to “+1”. When the code of the sequence signal is “−1”, a rectangular wave whose frequency is 1 Hz and whose sign changes in the order of “+1” to “−1” is generated. As a result, the processed signal has a total clock number of 254 and a clock frequency of 1 Hz. The M-sequence signal before processing was generated inside the computer, and the generated M-sequence signal was also processed inside the computer.

FIG. 11 is a diagram showing the waveform of the current applied to each current application electrode 4 and the voltage waveform detected by each voltage detection electrode 6 in this experiment, and FIG. A part of the waveform is shown, and FIG. 11B shows a part of the voltage waveform.
As shown in FIG. 11 (a), when a current having a sign of ± 1A is applied to each current application electrode 4, the waveform of the voltage detected by each voltage detection electrode 6 is shown in FIG. 11 (b). The waveform is as shown.

In the detected voltage waveform, drift noise caused by the thermoelectromotive force is generated, but since an M-sequence signal is used as a pseudo-random signal, as shown in FIG. The impact is suppressed.
Here, as in the region X shown in FIG. 11B, when the influence of the transient induction noise appears in the detected voltage waveform, the correlation calculation is performed in the same manner as the electrical resistance measurement method of the present embodiment. Processing by means (processing in steps S42 to S48 in the flowchart of FIG. 8) may be performed.

As a result of measuring the electric resistance in the plating bath by such an electric resistance measuring method, when the molten zinc occupies between the voltage detection electrodes 6, the measured value of the electric resistance is 3.2 (μΩ). It became. On the other hand, when the bottom dross occupies between the voltage detection electrodes 6, the measured value of the electrical resistance was 11.2 (μΩ).
Therefore, it is confirmed that the difference in the magnitude of the electric resistance is clearly different depending on the ratio of the molten zinc and the bottom dross existing between the voltage detecting electrodes 6, and when the measured electric resistance exceeds a certain value, the plating is performed. It was confirmed that it was effective to determine that the amount of bottom dross accumulated in the bath 28 reached the upper limit of the height at which the problem occurred.

Next, experimental results of measuring electrical resistance in a blast furnace will be described.
In this experiment, a probe for measuring electrical resistance is installed at the bottom of the blast furnace.
The probe is composed of a pair of current application electrodes and a pair of voltage detection electrodes arranged between the pair of current application electrodes, that is, all four electrodes.
Each current application electrode and each voltage detection electrode are arranged in a straight line along the vertical direction in the lower part of the furnace, and are opened to the iron skin and stamp material (refractory), and the tip thereof The part is in contact with the furnace wall brick.

Of the pair of current application electrodes, the electrode disposed above and the pair of voltage detection electrodes are disposed below the tuyere of the blast furnace and above the outlet, The electrode arranged below among the electrodes is installed on the side surface of the furnace bottom.
In the electrical resistance measurement apparatus used in this experiment, the current value applied to the current application electrode is 4 A, and the voltage detection electrode is configured as a correlation calculation means via a known AD converter. Connected to a computer.

Further, in this experiment, the M-sequence signal used as the pseudo-random signal has a total clock number (code length) of 127 and a clock frequency of 3 Hz. Then, this M-sequence signal is processed, and when the sign of the M-sequence signal is “+1”, a rectangular wave is generated at a frequency of 6 Hz and the sign changes in the order of “−1” to “+1”, When the sign of the M-sequence signal is “−1”, a rectangular wave with a frequency of 6 Hz and a sign that changes in order from “+1” to “−1” is generated. As a result, the processed reference signal has a total clock number of 254 and a clock frequency of 6 Hz. The M-sequence signal before processing was generated inside the computer, and the generated M-sequence signal was also processed inside the computer.
Here, as an M-sequence signal before processing, an M-sequence signal having a long period such as 511 or 2047 may be used when there is a margin in measurement time. Further, the clock frequency may be determined with reference to the attenuation rate of transient induction noise.

FIG. 12 is a diagram showing a part of the waveform of the voltage detected by the voltage detection electrode in this experiment.
As shown in FIG. 12, offset noise occurs in the waveform of the voltage detected by the voltage detection electrode. This offset noise changes with time depending on the environment around the blast furnace. In FIG. 12, the average value of the voltage waveform is indicated by a broken line, and offset noise is represented by the difference between the broken line and a line indicating a voltage of 0 mV.
FIG. 13 is a diagram illustrating a correlation calculation processing result between the waveform of the voltage detected by the voltage detection electrode and the waveform of the reference signal.

  As shown in FIG. 13, the correlation calculation processing result between the waveform of the voltage detected by the voltage detection electrode and the waveform of the reference signal is represented by the waveform, and this waveform represents the maximum value of the correlation function, Divided by the current value. Therefore, the maximum value of the waveform shown in FIG. 13 was taken as the voltage value, and this voltage value was divided by the current value to calculate the electrical resistance of the blast furnace. When calculating the voltage value, it is possible to measure with higher accuracy by taking a plurality of cycles of the waveform of the detected voltage and averaging the maximum values appearing in each cycle.

Since the detected voltage waveform shows the influence of transient induced noise, the transient induced noise is removed by performing processing by the correlation calculation means, as in the electrical resistance measurement method of the present embodiment. Went. At this time, the threshold regarding the absolute value of the time change rate of the voltage was set to 1 (V / sec).
As a result of measuring the electric resistance of the blast furnace by such an electric resistance measuring method, the measured value of the electric resistance was 12.3 (μΩ). The temporal transition of the electrical resistance at the bottom of the blast furnace is considered to represent the residual level in the furnace, but in this experiment, the M series signal used as a pseudo-random signal was processed, and this processed M series Since the signal is applied to the current application electrode, it is possible to suppress the influence of offset noise that changes with time depending on the environment around the blast furnace.

It is a figure which shows the structure of the electrical resistance measuring apparatus of this embodiment. It is a figure which shows the pseudo random signal generated by the pseudo random signal generation means. FIG. 3A is a diagram illustrating a procedure for generating a reference signal, FIG. 3A is a diagram illustrating a part of a pseudo-random signal, FIG. 3B is a diagram illustrating a part of a pulse signal, and FIG. FIG. 4 is a diagram showing a part of a reference signal. It is a figure showing the setting method of an induction noise area and a signal component area. It is a wave form diagram which shows the voltage of the signal component after removing a noise component. It is a figure showing the correspondence of a reference signal and the voltage signal detected by the electrode for voltage detection. It is a figure which shows an example of the correlation calculation result of a reference signal and a voltage signal. It is a flowchart which shows an electrical resistance measuring method. In an Example, it is a figure explaining the measurement of the electrical resistance in a plating bath. In an Example, it is a figure which shows the relationship between the ratio of the molten zinc in a plating bath, and the electrical resistance at that time. In an Example, it is a figure which shows the waveform of the electric current applied to each electrode for current application, and the waveform of the voltage detected by each electrode for voltage detection, Fig.11 (a) is a part of waveform of the applied current FIG. 11B shows a part of the voltage waveform. In an Example, it is a figure which shows a part of waveform of the voltage detected by the electrode for voltage detection. In an Example, it is a figure which shows the correlation calculation process result of the waveform of the voltage detected by the electrode for voltage detection, and the waveform of a reference signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrical resistance measuring device 2 Signal generation means 4 Current application electrode 6 Voltage detection electrode 8 Correlation calculation means 10 Measured object 12 Pseudorandom signal generation means 14 Pulse generation means 16 Signal processing means 18 Current application cable 20 Signal extraction section 22 Correlation Calculation Unit 24 Resistance Calculation Unit 26 Voltage Detection Cable 28 Plating Bath 30 Probe 32 Heat-resistant Insulation Case 34 Tip S1 Pseudorandom Signal S2 Pulse Signal S3 Reference Signal

Claims (5)

A current modulated by binary reference signals having the same absolute value and different signs is applied to the device under test, a voltage generated in the device under test by the applied current is detected, and the detected voltage and An electrical resistance measurement method for performing a correlation calculation process on the reference signal and measuring an electrical resistance of the object to be measured based on a result of the correlation calculation process,
Said reference signal, and the pulse width and the time that the even equal the shortest pulse width pseudo-random signal, and switches the order of the pulse code, unlike according to the sign of the pseudo-random signal,
Rukoto performs correlation operation with respect to the reference signals for several cycles, calculates an average of the maximum value of the correlation function in each cycle, to calculate the electrical resistance of the mean the object to be measured using the maximum value thus calculated An electrical resistance measuring method characterized by the above. From the detected voltage, an induced electromotive force component and a signal component that are noise components in measurement are temporally separated to extract only the signal component, and a conductive voltage signal of the signal component obtained by separating the noise component is generated, The electrical resistance measurement method according to claim 1, wherein the correlation calculation process is performed using the generated conductive voltage signal and the reference signal. It is a binary pulse train having the same absolute value and different signs, and the pulse width is set to a time evenly divided by the shortest pulse width of the pseudo-random signal, and the switching order of the pulse codes is the code of the pseudo-random signal. And a signal processing means for generating a reference signal consisting of different pulse trains,
A current applying means for applying a current modulated by the generated reference signal by means of a pair of current applying electrodes installed on the object to be measured;
Voltage detecting means for detecting a voltage generated in the object to be measured by the applied current by a voltage detecting electrode;
A signal processing means for performing a correlation calculation process on the detected voltage and the reference signal, and calculating an electric resistance of the object to be measured based on a result of the correlation calculation process ;
The signal processing means performs correlation calculation processing on the reference signal of several cycles, calculates an average of the maximum value of the correlation function in each cycle, and uses the average of the calculated maximum values to An electrical resistance measuring device that calculates resistance. The signal processing means includes
Clock generating means for outputting binary pulses having the same absolute value and different signs of the time width of the shortest pulse;
Pseudo-random signal generating means for outputting binary pseudo-random signals having the same absolute value and different signs;
Multiplying operation means for generating the reference signal by multiplying the pulse output from the clock generating means and the pseudorandom signal output from the pseudorandom signal generating means, The electrical resistance measuring device according to claim 3. The object to be measured is at least one of a low electrical resistance body and an electrically grounded object,
5. The electrical resistance measuring apparatus according to claim 3, wherein a plurality of the voltage detection electrodes are installed between the pair of current application electrodes. 6.

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