Current probe circuit and current probe

Abstract

The embodiment of the invention discloses a current probe circuit and a current probe, and belongs to the technical field of current measurement. In the embodiment of the invention, the current probe circuit comprises a current transformer, a load resistor and a matching resistor, two ends of a primary side coil of the current transformer are detachably connected in series with the to-be-tested element; the dotted terminal of the secondary coil of the current transformer is connected with one end of the load resistor and one end of the matching resistor, and the other end of the matching resistor is connected with the positive electrode of the oscilloscope; the synonym end of the secondary side coil of the current transformer is connected with the other end of the load resistor and the negative electrode of the oscilloscope. The oscilloscope can measure the current flowing through the element to be measured by measuring the voltage between the positive electrode and the negative electrode. The current probe circuit is low in cost and can be used in an over-range mode.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of current measurement, and in particular to a current probe circuit and a current probe. Background Art

[0002] A current probe is a magnetic ring designed based on the Faraday principle to measure interference current signals in a conductor. It is essentially a transformer with 1 turn. A current probe can be used to measure the current flowing through a conductor. Current probes are divided into AC / DC current probes and AC current probes. AC / DC current probes can measure both DC and AC currents, while AC current probes can only measure AC currents.

[0003] Among them, the current flowing through the wire will cause an electromagnetic flux field to be formed around the wire. Existing current probes usually use magnetic induction chips to sense the field strength of the electromagnetic flux field and convert it into a corresponding voltage for measurement using an oscilloscope. However, the cost of magnetic induction chips is relatively high, resulting in a high cost for current probes using magnetic induction chips. Summary of the invention

[0004] The embodiment of the present application provides a current probe circuit and a current probe, and the cost of the current probe circuit is low.

[0005] The embodiment of the present application provides a current probe circuit, including: a current transformer, a load resistor and a matching resistor;

[0006] Both ends of the primary coil of the current transformer are detachably connected in series to the element to be tested;

[0007] The same-name end of the secondary coil of the current transformer is connected to one end of the load resistor and one end of the matching resistor, and the other end of the matching resistor is connected to the positive electrode of the oscilloscope;

[0008] The opposite-name end of the secondary coil of the current transformer is connected to the other end of the load resistor and the negative pole of the oscilloscope.

[0009] Furthermore, the load resistor includes a plurality of chip resistors connected in parallel.

[0010] Furthermore, the coil wire diameters of the primary coil and the secondary coil are 2.5 mm.

[0011] Furthermore, the current measurement range of the current probe circuit is adjusted by adjusting the coil wire diameters of the primary coil and the secondary coil.

[0012] Furthermore, the turns ratio of the primary coil to the secondary coil is 1:100.

[0013] Further, based on the current measurement range of the current probe circuit, determining the measurement sensitivity of the current probe circuit;

[0014] Based on the measurement sensitivity, the turns ratio of the primary coil to the secondary coil and the resistance value of the load resistor are adjusted.

[0015] Furthermore, it also includes: filter resistors and capacitors;

[0016] The filter resistor is connected in series with the capacitor and then connected in parallel to the two ends of the secondary coil.

[0017] Furthermore, it also includes: a first voltage stabilizing diode and a second voltage stabilizing diode;

[0018] The first voltage stabilizing diode and the second voltage stabilizing diode are connected in series in reverse order and then connected in parallel to the two ends of the secondary coil.

[0019] Furthermore, the resistance of the matching resistor is: 50Ω or 1MΩ.

[0020] An embodiment of the present application also provides a current probe, including the current probe circuit described above.

[0021] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0022] In the embodiment of the present application, the current probe circuit includes: a current transformer, a load resistor and a matching resistor; the two ends of the primary coil of the current transformer are detachably connected in series to the component to be measured; the same-name end of the secondary coil of the current transformer is connected to one end of the load resistor and one end of the matching resistor, and the other end of the matching resistor is connected to the positive pole of the oscilloscope; the opposite-name end of the secondary coil of the current transformer is connected to the other end of the load resistor and the negative pole of the oscilloscope. The oscilloscope can measure the current flowing through the component to be measured by measuring the voltage between the positive pole and the negative pole.

[0023] It can be seen that the current probe circuit of the embodiment of the present application does not use a magnetic induction chip. In the current probe circuit: the current transformer, load resistor and matching resistor are all power devices, which have a lower cost than the magnetic induction chip, that is, the cost of the current probe circuit is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0025] Figure 1A schematic diagram of a current probe circuit disclosed in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of another current probe circuit disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] In the description of the embodiments of the present application, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0029] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0030] In the existing current probe, a magnetic induction chip is usually used to sense the field strength of the electromagnetic flux field and convert it into a corresponding voltage for measurement using an oscilloscope. However, the cost of the current probe using the magnetic induction chip is relatively high, and the current probe is difficult to use over a range. Therefore, an embodiment of the present application provides a current probe circuit, which has a low cost and can be used over a range. Figure 1 As shown, the details are as follows:

[0031] In the embodiment of the present application, the current probe circuit includes: a current transformer CT, a load resistor R1 and a matching resistor R2; wherein, the two ends of the coil of the primary coil (primary winding) of the current transformer CT are detachably connected in series with the element to be measured, that is, the primary current of the primary coil is the current flowing through the element to be measured, and the current flowing through the element to be measured can be obtained by measuring the primary current. The same-name end of the secondary coil (secondary winding) of the current transformer CT is connected to one end of the load resistor R1 and one end of the matching resistor R2, and the other end of the matching resistor R2 is connected to the positive pole of the oscilloscope; the opposite-name end of the secondary coil of the current transformer CT is connected to the other end of the load resistor R1 and the negative pole of the oscilloscope (the negative pole of the oscilloscope can be the ground terminal), that is, the two ends of the secondary coil of the current transformer CT are connected in parallel with the load resistor R1, and the load resistor R1 can be 10Ω or 20Ω, which is not specifically limited here; the matching resistor R2 can be 50Ω or 1MΩ, which is not specifically limited here.

[0032] In the embodiment of the present application, the current probe circuit is mainly used to measure alternating current, and the alternating current flowing through the element to be measured is the primary current of the primary coil; generally, the secondary turns N2 of the secondary coil of the current transformer is greater than the primary turns N1 of the primary coil of the current transformer. Based on the conservation of ampere-turns of the primary and secondary sides of the current transformer, it can be known that the primary turns N1*primary current I1=secondary turns N2*secondary current I2, that is, primary current I1: secondary current I2=N2:N1, that is, primary current I1 is greater than secondary current I2, so as to convert the larger primary current I1 into a smaller secondary current I2. Since the two ends of the secondary coil of the current transformer are connected in parallel with the load resistor R1, at this time, it can be obtained that the secondary voltage U2 of the secondary coil: the load resistor R1 = the secondary current I2, and then it can be obtained that the ratio of the secondary voltage to the primary current is: secondary voltage U2: primary current I1 = R1*N1 / N2; this ratio is the measurement sensitivity of the current probe circuit, that is, the measurement sensitivity set by the oscilloscope; wherein, the secondary voltage U2 is the output voltage before the matching resistor R2, and the output impedance of the oscilloscope is consistent with the resistance value of the matching resistor in the current probe circuit, based on the positive and negative voltages measured by the oscilloscope and the measurement sensitivity of the oscilloscope, the primary current (that is, the current flowing through the component to be measured) can be measured on the oscilloscope.

[0033] It can be seen that the current probe circuit in the embodiment of the present application does not use a magnetic induction chip. In the current probe circuit: the current transformer, the load resistor and the matching resistor are all power devices, which have a lower cost than the magnetic induction chip; and the power consumption of the power device is heat power consumption. As long as the heating temperature of the power device does not cause damage to the power device, it can be used over the range, that is, the current probe circuit in the embodiment of the present application can be used over the range.

[0034] The following will be combined Figure 2The current probe circuit of this application is described as follows:

[0035] Furthermore, the load resistor in the current probe circuit may include multiple parallel chip resistors, such as 10 100Ω chip resistors (R101, R102, R103, R104, R105, R106, R107, R108, R109 and R110) in parallel, wherein the 10 100Ω chip resistors are respectively connected in parallel to the two ends of the secondary coil; in this case, the load resistor can be equivalent to a 10Ω resistor. The chip resistor has a low temperature coefficient, an operating temperature range of -55°C to +125°C, and is resistant to high temperatures, so that the current probe circuit can operate in a high temperature environment. At the same time, using multiple chip resistors in parallel to shunt the current can effectively reduce heat generation and improve the safety of the current probe circuit.

[0036] Furthermore, the maximum primary current of the primary coil (i.e., the maximum current that the current probe circuit can measure) is related to the coil wire diameter of the current transformer. The larger the coil wire diameter, the greater the coil impedance, and the greater the maximum current that the coil can withstand. Preferably, the coil wire diameter of the primary coil and the secondary coil is 2.5mm. At this time, the maximum primary current in the current measurement range of the current probe circuit is 30A.

[0037] Furthermore, in the embodiment of the present application, the current measurement range of the current probe circuit can be adjusted. Specifically, the current measurement range of the current probe circuit can be adjusted by adjusting the coil wire diameters of the primary coil and the secondary coil. If the current measurement range needs to be increased, the maximum primary current that can be measured can be increased by increasing the coil wire diameter; if the current measurement range needs to be reduced, the maximum primary current that can be measured can be reduced by reducing the coil wire diameter.

[0038] Further, preferably, the turns ratio of the primary coil turns N1 to the secondary coil turns N2 is 1: 100. When the load resistance R1 is equivalent to 10Ω, the ratio of the secondary voltage to the primary current is R1*N1 / N2=0.1, that is, the measurement sensitivity set by the oscilloscope is 0.1V / A.

[0039] Furthermore, in the embodiment of the present application, the measurement sensitivity of the current probe circuit can be determined based on the current measurement range of the current probe circuit. Generally, the larger the current measurement range of the current probe circuit, the greater the measurement sensitivity of the current probe circuit. For example, when the current measurement range is 0-30A, the measurement sensitivity of the current probe circuit can be: 0.1V / A, and when the current measurement range is 0-300A, in order to meet the measurement requirements of large currents, the measurement sensitivity of the current probe circuit needs to be increased to 0.01V / A.

[0040] The measurement sensitivity of the current probe circuit is: R1*N1 / N2, which is proportional to the turns ratio N1 / N2 of the primary coil and the secondary coil, and proportional to the resistance value of the load resistor R1. That is, the turns ratio of the primary coil and the secondary coil, as well as the resistance value of the load resistor can be adjusted based on the measurement sensitivity. For example, when the measurement sensitivity needs to be increased, the turns ratio of the primary coil and the secondary coil can be increased, or the resistance value of the load resistor can be increased; when the measurement sensitivity needs to be reduced, the turns ratio of the primary coil and the secondary coil can be reduced, or the resistance value of the load resistor can be reduced.

[0041] Furthermore, the current probe circuit also includes: a filter resistor R3 and a capacitor C1; the filter resistor R3 and the capacitor C1 are connected in series and then connected in parallel to the two ends of the secondary coil of the current transformer. The filter resistor R3 and the capacitor C1 are used to perform RC filtering on the secondary voltage.

[0042] Furthermore, the current probe circuit also includes: a first voltage zener diode Z1 and a second voltage zener diode Z2; the first voltage zener diode Z1 and the second voltage zener diode Z2 are connected in reverse series and then connected in parallel to the two ends of the secondary coil. After the two voltage zener diodes are connected in reverse series, they can provide overvoltage protection for the current probe circuit connected in parallel therewith, and can also provide overvoltage protection for the oscilloscope.

[0043] An embodiment of the present application also provides a current probe, including the current probe circuit described above.

[0044] In the present invention, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The term "plurality" refers to two or more, unless otherwise clearly defined.

[0045] The above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, rather than to limit them. Although the embodiments of the present application are described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and description of the embodiments of the present application.

Claims

1. A current probe circuit, characterized in that: include: Current transformer, load resistor and matching resistor; Both ends of the primary coil of the current transformer are detachably connected in series to the element to be tested; The same-name end of the secondary coil of the current transformer is connected to one end of the load resistor and one end of the matching resistor, and the other end of the matching resistor is connected to the positive electrode of the oscilloscope; The opposite-name end of the secondary coil of the current transformer is connected to the other end of the load resistor and the negative pole of the oscilloscope.

2. The current probe circuit according to claim 1, characterized in that: The load resistor includes a plurality of parallel-connected chip resistors.

3. The current probe circuit according to claim 1, characterized in that: The coil wire diameters of the primary coil and the secondary coil are 2.5 mm.

4. The current probe circuit according to claim 1, characterized in that: The current measurement range of the current probe circuit is adjusted by adjusting the coil wire diameters of the primary coil and the secondary coil.

5. The current probe circuit according to claim 1, characterized in that: The turns ratio of the primary coil to the secondary coil is 1:

100.

6. The current probe circuit according to claim 1, characterized in that: Determining a measurement sensitivity of the current probe circuit based on a current measurement range of the current probe circuit; Based on the measurement sensitivity, the turns ratio of the primary coil and the secondary coil, and the resistance value of the load resistor are adjusted.

7. The current probe circuit according to claim 1, characterized in that: Also includes: Filter resistors and capacitors; The filter resistor is connected in series with the capacitor and then connected in parallel to the two ends of the secondary coil.

8. The current probe circuit according to claim 1, characterized in that: Also includes: A first Zener diode and a second Zener diode; The first voltage stabilizing diode and the second voltage stabilizing diode are connected in series in reverse order and then connected in parallel to the two ends of the secondary coil.

9. The current probe circuit according to claim 1, characterized in that: The resistance value of the matching resistor is: 50Ω or 1MΩ.

10. A current probe, characterized in that: The current probe circuit comprises the current probe circuit described in any one of claims 1 to 9.

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