Device and method for current measurement

Abstract

Device for measuring current (1) which comprises: a coil (103) provided on a magnetic ring (101), wherein at least one conductor (102) is guided through the magnetic ring described above, carrying the current to be measured; a resistor for sample extraction (104) which is electrically connected to one end of the coil described above; a measuring instrument (105), wherein the measuring instrument (105) described above collects a first signal at the resistor for sample acquisition (104) and measures the current to be measured; an electrical drive voltage source (109) which is electrically connected to the other end of the coil described above, wherein the electrical drive voltage source (109) regulates the electrical drive voltage of the coil described above according to a first signal at the sample extraction resistor (104), a second signal at the internal resistance of the coil (103) and a third signal based on a differential of the first signal described above.

Description

Technical field

[0001] The present invention relates to electronic circuits, in particular a device and a method for measuring current. State of the art

[0002] Magnetic modulation-based methods for measuring alternating and / or direct current are already widely used, in which a conductor carrying the current to be measured is guided through a magnetic ring. A coil located on the magnetic ring is connected to a sample-gathering resistor and an electrical drive voltage source. The electrical drive voltage generated by the electrical drive voltage source alternately switches the operating state of the magnetic ring between the linear region 401 and the non-linear regions 402, 403 of the range shown in Fig. The magnetization curve shown is offset, and the electrical voltage or current is collected across the resistor to obtain a sample and measure the current to be measured.

[0003] In Chinese patent publication CN 1 02 338 822 B, a device and a method for current measurement are disclosed, wherein the electrical drive voltage of the electrical drive voltage source is reversed only when the magnetization curve of the magnetic ring is as close as possible to the actual intersection of the linear and non-linear regions, thus extending the measuring range for the current to be measured while increasing the measurement precision and simultaneously reducing the power consumption during the measurement. Content of the invention

[0004] One of the problems to be solved by a practical embodiment of the present invention is to increase the measurement precision of the magnetic modulation-based method for measuring alternating current and / or direct current and to extend the measurement range.

[0005] According to a practical embodiment of the present invention, a device for current measurement is provided, comprising: a coil provided on a magnetic ring, wherein at least one conductor carrying the current to be measured is guided through the aforementioned magnetic ring; a sample-gathering resistor, which is electrically connected to one end of the aforementioned coil; a measuring instrument, wherein the aforementioned measuring instrument collects a first signal at the sample-gathering resistor and measures the current to be measured;an electrical drive voltage source which is electrically connected to the other end of the coil referred to above, wherein the electrical drive voltage source regulates the electrical drive voltage of the coil referred to above according to a first signal at the sample extraction resistor, a second signal at the internal resistance of the coil and a third signal based on a differential of the first signal referred to above.

[0006] Optionally, the current measurement device in question may also include: a differentiator which performs the differentiation of the first signal at the sample extraction resistor in order to obtain a fourth signal; a comparator which is connected to the electrical drive voltage source and performs a comparison with a previously defined threshold based on the fourth signal and generates the third signal.

[0007] Optionally, the sample acquisition resistor is provided to include a first resistor and a second resistor connected in series, the resistance value of the second resistor corresponding to the internal resistance of the coil, the first signal referred to above being obtained from the sample acquisition resistor, while the second signal referred to above is obtained from the second resistor.

[0008] Optionally, the current measuring device may also include: an amplifier which amplifies the first signal described above to the sum of the first signal and the second signal and transmits it to the electrical drive voltage source.

[0009] Optionally, the previously defined threshold is set as the differential of the first signal when the magnetic ring is located at the inflection point of the non-linear region of the magnetization curve.

[0010] Optionally, the aforementioned electrical drive voltage source includes an adding device, wherein the aforementioned first signal obtained from the sample acquisition resistor, the aforementioned second signal obtained from the second resistor, and the aforementioned third signal are each connected to the input end of the adding device.

[0011] Optionally, the aforementioned electrical drive voltage source includes an adding device, wherein the output of the amplifier and the aforementioned third signal are each connected to the input end of the adding device.

[0012] According to a practical embodiment of the present invention, a method for current measurement is provided, comprising: generating an electrical drive voltage which drives a circuit comprising a sample-gathering resistor and a coil provided on the magnetic ring, wherein at least one conductor carrying the current to be measured is guided through the aforementioned magnetic ring; collecting the first signal generated by the aforementioned electrical drive voltage at the sample-gathering resistor and the second signal generated at the internal resistance of the coil; obtaining a third signal based on a differential of the first signal; regulating the aforementioned electrical drive voltage based on the first signal, the second signal, and the third signal; and measuring the aforementioned current to be measured based on the first signal.

[0013] Optionally, the process step of collecting the first signal generated at the sample acquisition resistor by the aforementioned electrical drive voltage, as well as the second signal generated at the internal resistance of the coil, comprises: the sample acquisition resistor is divided into the first resistor and second resistor connected in series, the resistance value of the second resistor corresponding to the internal resistance of the coil, the aforementioned first signal is collected from the sample acquisition resistor, while the aforementioned second signal is collected from the second resistor.

[0014] Optionally, the process step of collecting the first signal generated at the sample acquisition resistor by the aforementioned electrical drive voltage and the second signal generated at the internal resistance of the coil includes: collecting the aforementioned first signal from the sample acquisition resistor and amplifying the aforementioned first signal to the sum of the first signal and the second signal.

[0015] In the practical embodiments according to the present invention, the electrical drive voltage source regulates the electrical drive voltage of the coil named above according to a first signal at the sample extraction resistor, a second signal at the internal resistance of the coil, and a third signal based on a differential of the first signal named above. The regulation is not solely based on the first signal at the sample extraction resistor and the third signal based on a differential of the first signal named above.In other words, this means that the coil is not considered as an ideal inductance, but rather as having an internal resistance, whereby the effect of the coil's internal resistance is eliminated in order to eliminate deviations in assessing the approximation of the magnetic ring's magnetization curve to the true intersection of the linear and non-linear regions, thereby increasing measurement precision and range. Explanation of the illustrations

[0016] Further features, special characteristics, advantages and positive effects of the present invention can be better illustrated with reference to the accompanying figures and detailed descriptions. At Fig. This is a representation of the device for measuring current 1 according to a practical embodiment of the present invention. At Fig. This is a representation of the device for measuring current 1 according to another practical embodiment of the present invention. At Fig. This is a representation of the device for measuring current 1 according to a further practical embodiment of the present invention. At Fig. This is a representation of the magnetization curve of the magnetic ring. At Fig. This is a description of the process for measuring current 2 according to a practical embodiment of the present invention. Practical examples

[0017] The following is a detailed description of various practical embodiments of the present invention, illustrated by the accompanying figures.

[0018] At Fig. This is a representation of the current measuring device 1 according to a practical embodiment of the present invention. The current measuring device 1 is used to measure any alternating current and / or direct current.

[0019] The current measurement device 1 comprises a coil 103, a sample extraction resistor 104, a measuring instrument 105 and an electrical drive voltage source 109.

[0020] The coil 103 is mounted on a magnetic ring 101, with at least one conductor 102 passing through the magnetic ring carrying the current to be measured. The sample acquisition resistor 104 is electrically connected to one end of the coil. The measuring instrument 105 collects a first signal at the sample acquisition resistor 104 and measures the current to be measured.

[0021] The first signal can be an electrical voltage signal across the sample acquisition resistor 104, or an electrical current signal, etc., across the sample acquisition resistor 104. If the first signal is an electrical voltage signal, the measuring device 105 is a voltage measuring device. If the first signal is an electrical current signal, the measuring device 105 is a current measuring device.

[0022] If the current to be measured, which is carried through the conductor 102, changes, the electromagnetic field of the magnetic ring and coil causes a change in the electric current carried through the coil 103, and a change in the electrical voltage or current of the resistor for sample extraction 104 occurs, and the current to be measured can be calculated.

[0023] If the electrical drive voltage (this is the electrical output voltage of the electrical drive voltage source 109) of the drive of the coil 103 is not controlled, there is no relationship between the electrical drive voltage in question and the current to be measured, which makes controlling the operating state of the magnetic ring very difficult. As stated above, the electrical drive voltage generated by the electrical drive voltage source must cause the operating state of the magnetic ring to alternate between the linear region 401 and the non-linear regions 402, 403 of the Fig. The magnetization curve shown is offset. Only in this way can the method for measuring alternating current and / or direct current based on magnetic modulation technology be used. By collecting the electrical voltage or electrical current across the sample-gathering resistor, the current to be measured is precisely measured. Thus, the electrical drive voltage generated by the electrical drive voltage source causes the magnetization state of the magnetic ring to alternately switch between the linear region 401 and the positive and negative non-linear regions 402, 403 shown in Fig. The magnetization curve BH (B represents the magnetic base density in the magnetic ring. H represents the magnetic field strength in the magnetic ring.) is shown. When the magnetic ring is in the position of the non-linear region of the magnetization curve, approaching the intersection of the linear and non-linear regions, the electrical output voltage of the electrical drive voltage source 109 must be reversed, as this is the only way to extend the measuring range of the current to be measured, increase the measurement precision, and reduce the measurement power consumption.

[0024] Therefore, control of the electrical output voltage of the electrical drive voltage source 109 is necessary. The electrical drive voltage source 109, which is electrically connected to the other end of the coil described above, regulates the electrical drive voltage of the coil described above according to a first signal at the sample extraction resistor 104, a second signal at the internal resistance of the coil 103, and a third signal based on a differential of the first signal described above.

[0025] The second signal could be the electrical voltage, etc., across the internal resistance of coil 103.

[0026] In a practical embodiment, the third signal, based on a differential of the aforementioned first signal, is a square wave signal. This signal is based on a comparison between the differential of the aforementioned first signal and a previously defined threshold. For example, if the differential of the first signal is greater than the previously defined threshold, the square wave signal is positive, while if the differential of the first signal is less than the previously defined threshold, the square wave signal is negative.

[0027] Because the absolute value of the amplitude of the third signal (for example, the positive-negative amplitude of the square wave signal) must be greater than the absolute values ​​of the amplitudes of the first and second signals, the electrical drive voltage generated by the electrical drive voltage source 109, based on the first, second, and third signals, will have the leading amplitude of the third signal. If the third signal (for example, a square wave signal) undergoes a polarity reversal from positive to negative, this normally also leads to a polarity reversal of the electrical drive voltage generated by the electrical drive voltage source 109. The previously defined threshold is set to a differential of the first signal when the magnetic ring is located at the reversal point of the non-linear region of the magnetization curve.The definition of this reversal point is a point within the non-linear region approaching the intersection between the linear and non-linear regions. For example, the setting is defined as the point at which the magnetic flux density B of the magnetic ring within the linear region reaches 1.05 times the magnetic flux density B of the magnetic ring at the intersection of the linear and non-linear regions, as shown in [reference]. Fig. denoted by P and Q. If the differential of the first signal is greater than the previously defined threshold, this indicates that the magnetic ring is in a position within the non-linear region of the magnetization curve where the reversal point has not yet been reached. Therefore, the square wave signal output by the comparator 107 is positive, and there is no reversal of the electrical drive voltage generated by the electrical drive voltage source 109.

[0028] If the differential of the first signal is smaller than the previously set threshold, this indicates that the magnetic ring is in a position within the non-linear region of the magnetization curve where the reversal point has been reached, i.e., approaching the position within the non-linear region near the intersection between the linear and non-linear regions. The square wave signal output by the comparator 107 now becomes negative, and the electrical drive voltage generated by the electrical drive voltage source 109 is reversed.In this way, the requirement is met that when the magnetic ring is in the position within the non-linear region of the magnetization curve near the intersection of the linear region and the non-linear region, a reversal of the electrical output voltage of the electrical drive voltage source 109 must take place in order to extend the measuring range of the current to be measured, increase the measurement precision and reduce the measurement power consumption.

[0029] In a practical embodiment, the current measuring device 1 comprises, as shown in Fig. Also shown is a differentiator 106 and a comparison device 107.

[0030] The differentiator 106 differentiates the first signal across the sample acquisition resistor 104 to obtain a fourth signal. This fourth signal is a differential of the first signal. The electrical voltage applied to the coil 103 is set to i, and the resistance of the sample acquisition resistor 104 is set to R. s . If the first signal at the resistor for sample extraction 104 is the electrical voltage signal i R s The fourth signal is the differential signal i' R, which is located at the resistor for sample extraction 104. S of the relevant electrical voltage signal. The differentiator, for example, is a differentiator circuit.

[0031] The comparator 107 is connected to the electrical drive voltage source 109 and performs a comparison with a predefined threshold based on the fourth signal, generating the third signal. As stated above, the third signal can, for example, be a square wave signal. If the fourth signal is greater than the predefined threshold, the square wave signal is positive. If the fourth signal is less than the predefined threshold, the square wave signal is negative.

[0032] The first signal can be directly input into the electrical drive voltage source 109. If it is as in the Fig. shown in the first signal, an electrical voltage signal at the resistor for sample extraction 104 with a resistance value R sIn this case, the connection end of resistor for sample extraction 104 and coil 103 is directly connected to the electrical drive voltage source, so that the electrical voltage i R s The resistance for sample extraction 104 can be entered into the electrical drive voltage source 109.

[0033] The second signal, the internal resistance of coil 103, cannot be measured directly. For example, if the second signal is the electrical voltage across the internal resistance of coil 103, measuring the electrical voltage at both ends of coil 103 will not provide a representation of the electrical voltage iR. L at the internal resistance R Lthe coil, because part of the electrical voltage at both ends of coil 103 is caused by the inductance L of the coil, namely Li'. Here, i' represents the differential of the current flowing through the coil. However, as in Fig. The possibility of a method to create a resistor 1042, which has the same resistance value as the internal resistance R, has been shown. L the coil 103 exhibits. By measuring the electrical voltage at both ends of the respective resistor 1042, the electrical voltage across the internal resistance of the coil 103 is obtained.

[0034] As in Fig. As shown, the sample extraction resistor 104 comprises a first resistor 1041 and a second resistor 1042 connected in series, the resistance value of the second resistor 1042 corresponding to the internal resistance of the coil 103, namely R LThe connection to the input end of the electrical drive voltage source 109 is made via the junction of the resistor for sample extraction 1041 and the second resistor 1042, thus supplying the electrical voltage i R. L at the second resistor 1042 (identical to the electrical voltage at the internal resistance of the coil 103) into the electrical drive voltage source 109.

[0035] By connecting the output end of the comparator 107 to the input end of the electrical drive voltage source 109, the third signal can be input into the electrical drive voltage source 109.

[0036] The electrical drive voltage source 109 comprises an adding device, wherein the first signal obtained from the sample acquisition resistor 104, the second signal obtained from the second resistor and the third signal are each connected to the input end of the adding device.

[0037] The electrical drive voltage output by the electrical drive voltage source 109 is U e2 . Due to the inductance of the coil 103 caused by the relevant electrical drive voltage, the internal resistance of the coil 103 and the consumption of the resistor for sample extraction 104, the following applies: Ue2=i RL+i Rs+Li'

[0038] Because the electrical drive voltage source 109 includes an adding device whose input is the electrical voltage signal i R transmitted from the connection point of the resistor for sample extraction 104 and the coil 103 s , the electrical voltage signal i R transmitted from the junction of the first resistor 1041 and the second resistor 1042 L and the square wave signal U output by the comparator 107 e1 is, applies Ue2=i RL+i Rs+Ue1

[0039] By comparing equation 1 and equation 2, we obtain i'=Ue1 / L

[0040] The amplitude of the square wave signal U e1is a constant. When the magnetic ring enters the non-linear region (saturation region), the inductance L of the coil rapidly decreases to a low value, causing i' to increase rapidly. In this case, i' is compared to a previously defined threshold value, and an assessment is made as to whether the magnetic ring has reached the reversal point in the magnetization curve. Only the position within the non-linear region near the intersection of the linear and non-linear regions is significant. If Equation 3 is given, i' cannot fully represent the position of the magnetic ring in the magnetization curve, and the comparison with the previously defined threshold value to assess whether the magnetic ring is approaching the intersection of the linear and non-linear regions within the non-linear region becomes meaningless.

[0041] As a comparative example, it should be noted that if in Fig. The connecting line of the connection point between the first resistor 1041 and the second resistor 1042 to the input end of the electrical drive voltage source 109 is not present, or the sample acquisition resistor 104 is divided into the first resistor 1041 and the second resistor 1042, i.e., the electrical drive voltage source 109 regulates the electrical drive voltage of the coil 103 only according to the first signal at the sample acquisition resistor 104 and the third signal based on a differential of the first signal described above, and equation 2 undergoes a change to Ue2=i Rs+Ue1

[0042] Equation 3 undergoes a change to i'=(Ue1−i RL) / L

[0043] Now, i' and L are no longer necessarily inversely proportional, and i' can no longer fully represent the position of the magnetic ring in the magnetization curve. A comparison of i' with the previously defined threshold no longer allows for a reliable assessment of whether the magnetic ring is approaching a position within the non-linear region close to the intersection of the linear and non-linear regions. Therefore, the reversal of the square wave signal output by the comparator 107 does not necessarily correspond to the approach of the magnetic ring's magnetization curve to a position within the non-linear region close to the intersection of the linear and non-linear regions.Reversing the polarity of the electrical drive voltage output by the electrical drive voltage source (109) does not necessarily correspond to the approximation of the magnetization curve of the magnetic ring to the position within the non-linear region near the intersection of the linear and non-linear regions. This means that if the magnetic ring is located within the non-linear region of the magnetization curve near the intersection of the linear and non-linear regions, reversing the electrical drive voltage output by the electrical drive voltage source (109) is necessary, and no further increase in measurement precision or reduction in measurement power consumption can be achieved.

[0044] At Fig. This is a representation of the device for measuring current 1 according to another practical embodiment of the present invention. The difference to Fig. consists in the fact that the connection point of resistor for sample extraction 104 and coil 103 is removed from the Fig. is connected to a connecting line of the input end of the electrical drive voltage source 109 and the connection point of first resistor 1041 and second resistor 1042 is connected to the connecting line of the input end of the electrical drive voltage source 109, so that a connecting line exists between the connection point of resistor for sample acquisition 104 and coil 103 through the amplifier 108 with connection to the connecting line of the electrical drive voltage source 109.

[0045] The amplifier 108 amplifies the first signal at the sample acquisition resistor 104 to the sum of the first signal and the second signal and transmits this to the electrical drive voltage source 109.

[0046] For example, the gain of amplifier 108 (1+R L / R S ). Now, the electrical voltage i R is converted into S The electrical voltage (i R) is measured at the sample extraction resistor 104 after amplification by the amplifier 108. S + i R L ). This is equivalent to the electrical voltage i R transmitted to the electrical drive voltage source 109 via the connecting line between the connection point of the resistor for sample extraction 104 and the coil 103 and the input end of the electrical drive voltage source 109. Sand the electrical voltage i R transmitted to the electrical drive voltage source 109 via the connecting line between the connection point of the first resistor 1041 and the second resistor 1042 and the input end of the electrical drive voltage source 109 L .

[0047] The electrical drive voltage source 109 comprises an adding device. The output of the amplifier 108 and the third signal described above are connected to the input end of the adding device.

[0048] In the example above, the output of amplifier 108 (i R) S + i R L ) and the third signal is a square wave signal of U e1 Therefore, the electrical drive voltage U output by the electrical drive voltage source 109 is e2 still i R L + i R S + U e1 .

[0049] At Fig. This is a representation of the current measurement device 1 according to a further practical embodiment of the present invention. The sample acquisition resistor 104 is not divided into the first resistor 1041 and the second resistor 1042, and the differentiator 106, the comparator 107, and the amplifier 108 are also not required. As in Fig. As shown, only the processing unit 110 is used. All functions of the differentiator 106, comparator 107, and amplifier 108 are implemented via software.

[0050] If the first signal is, for example, still the electrical voltage signal i R S The electrical voltage signal i R is generated at the resistor for sample extraction 104. SThe data is entered into processing unit 110. Processing unit 110 receives the numerical value of the electrical voltage signal through A / D conversion. Processing unit 110 then multiplies this numerical value by (1 + R). L / R S ) and receives the numerical value (i R S + i R L The processing unit 110 performs the differential of the numerical value of the electrical voltage signal i R. S The process compares the result with the previously defined threshold and generates a square wave value converted into a number. The processing unit 110 then adds this square wave value converted into a number with the value converted into a number (i R). S + i R L), performs the D / A conversion of the obtained sum and outputs it to the electrical drive voltage source 109. The signal after the D / A conversion corresponds to the sum of the first signal at the sample acquisition resistor 104, the second signal at the internal resistance of the coil 103, and the third signal based on a differential of the aforementioned first signal.

[0051] At Fig. This is a description of the process for measuring current 2 according to a practical embodiment of the present invention. The current measurement method 2 can be implemented using any current measurement device from the Fig. The procedure can also be carried out using a different current measurement device suitable for carrying out the current measurement procedure 2.

[0052] In step S1, an electrical drive voltage is generated, which drives a circuit comprising a resistor for sample extraction 104 and a coil 103 provided on the magnetic ring 101, S1 wherein at least one conductor 102 is guided through the magnetic ring described above, carrying the current to be measured.

[0053] In step S2, the first signal generated by the aforementioned electrical drive voltage at the resistor for sample acquisition 104 and the second signal generated at the internal resistance of the coil 103 are collected.

[0054] In step S3, a third signal is obtained based on a differential of the first signal.

[0055] In step S4, the regulation of the aforementioned electrical drive voltage takes place based on the first signal, the second signal and the third signal.

[0056] In step S5, the current to be measured, as described above, is measured based on the first signal.

[0057] Optionally, step S2 is provided to include: the sample acquisition resistor 104 is divided into the first resistor 1041 and second resistor 1042 connected in series, the resistance value of the second resistor corresponding to the internal resistance of the coil 103, the first signal referred to above being collected from the sample acquisition resistor 104, while the second signal referred to above is collected from the second resistor.

[0058] Optionally, step S2 is provided to include: collecting the aforementioned first signal from the resistor for sample acquisition 104 and amplifying the aforementioned first signal to the sum of the first signal and the second signal.

[0059] A person skilled in the relevant technical field understands that the various practical embodiments listed above can undergo various modifications and alterations without departing from the essence of the present invention. Therefore, the scope of protection of the present invention is limited by the accompanying claims.

Claims

[1] Current measuring device (1) comprising: a coil (103) provided on a magnetic ring (101), wherein at least one conductor (102) is guided through the magnetic ring described above, carrying the current to be measured; a resistor for sample extraction (104) which is electrically connected to one end of the coil described above; a measuring instrument (105), wherein the measuring instrument (105) described above collects a first signal at the resistor for sample acquisition (104) and measures the current to be measured; an electrical drive voltage source (109) which is electrically connected to the other end of the coil described above, wherein the electrical drive voltage source (109) regulates the electrical drive voltage of the coil described above according to a first signal at the sample extraction resistor (104), a second signal at the internal resistance of the coil (103) and a third signal based on a differential of the first signal described above. [2] Device for measuring current (1) according to claim 1, which further comprises: a differentiator (106) which performs the differentiation of the first signal at the sample extraction resistor (104) in order to obtain a fourth signal; a comparison device (107) which is connected to the electrical drive voltage source (109) and performs a comparison with a previously defined threshold value based on the fourth signal and generates the third signal. [3] Device for current measurement (1) according to claim 1, wherein the sample acquisition resistor (104) comprises a first resistor (1041) and a second resistor (1042) connected in series, wherein the resistance value of the second resistor corresponds to the internal resistance of the coil (103), wherein the first signal described above is obtained from the sample acquisition resistor (104), while the second signal described above is obtained from the second resistor. [4] Device for measuring current (1) according to claim 1, further comprising: an amplifier (108) which amplifies the first signal described above to the sum of the first signal and the second signal and transmits it to the electrical drive voltage source (109). [5] Device for current measurement (1) according to claim 2, wherein the previously determined threshold value is set as the differential of the first signal when the magnetic ring is located at the reversal point of the non-linear region of the magnetization curve. [6] Device for current measurement (1) according to claim 3, wherein the electrical drive voltage source (109) described above comprises an addition device, wherein the first signal described above obtained from the sample acquisition resistor (104), the second signal described above obtained from the second resistor and the third signal described above are each connected to the input end of the addition device. [7] Device for current measurement (1) according to claim 4, wherein the electrical drive voltage source (109) described above comprises an adding device, wherein the output of the amplifier (108) and the third signal described above are each connected to the input end of the adding device. [8] Method for measuring current (2) which includes: Generation of an electrical drive voltage which drives a circuit comprising a resistor for sample extraction (104) and a coil (103) provided on the magnetic ring (101) (S1), wherein at least one conductor (102) is guided through the magnetic ring described above with the current to be measured; Collecting the first signal generated at the sample acquisition resistor (104) by the aforementioned electrical drive voltage and the second signal (S2) generated at the internal resistance of the coil (103); Obtaining a third signal (S3) based on a differential of the first signal; Regulation of the aforementioned electrical drive voltage based on the first signal, the second signal and the third signal (S4); Measuring the aforementioned current to be measured based on the first signal (S5). [9] Method for current measurement (2) according to claim 8, wherein the method step of collecting the first signal generated at the sample acquisition resistor (104) by the aforementioned electrical drive voltage and the second signal (S2) generated at the internal resistance of the coil (103) comprises: the sample acquisition resistor (104) is divided into the first resistor (1041) and second resistor (1042) connected in series, wherein the resistance value of the second resistor corresponds to the internal resistance of the coil (103), wherein the aforementioned first signal is collected from the sample acquisition resistor (104), while the aforementioned second signal is collected from the second resistor. [10] Method for current measurement (2) according to claim 8, wherein the method step of collecting the first signal generated at the sample acquisition resistor (104) by the aforementioned electrical drive voltage and the second signal (S2) generated at the internal resistance of the coil (103) comprises: collecting the aforementioned first signal from the sample acquisition resistor (104) and amplifying the aforementioned first signal to the sum of the first signal and the second signal.

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