A method for measuring ultra-high precision current from micro-ampere to kilo-ampere

Abstract

The application belongs to the field of current sensor, and particularly relates to a super-high-precision current measurement method from micro-ampere level to kilo-ampere level. The current sensor comprises a large-current detection system, a small-current detection system, a T3 magnetic core, a comparator U1 and a MOS tube Q1. The large-current detection system comprises a first measurement coil group, a first magnetic core group and a large-current magnetic flux detection module which are electrically connected. The small-current detection system comprises a second measurement coil group, a second magnetic core group and a small-current magnetic flux detection module which are electrically connected. The T3 magnetic core is a shielded magnetic core and is used for magnetic shielding. The comparator U1 and the MOS tube Q1 are arranged between the small-current magnetic flux detection module and the large-current magnetic flux detection module and are connected in series with the small-current magnetic flux detection module and the large-current magnetic flux detection module. Compared with the prior art, the minimum measurement current recognition capability can be reduced to uA level under the condition that the highest range is several hundred amperes, and the two sets of detection systems realize automatic switching of large and small currents and large and small ranges without manual selection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of current sensor, more particularly, it relates to a kind of from microampere to kiloampere ultra-high precision current measurement method. BACKGROUND

[0002] The current sensor on the market for high-precision detection of large current, basically all use closed-loop fluxgate scheme, it has high precision, low temperature drift, low noise, and small interference to primary current.

[0003] Generally, the resolution of the closed-loop fluxgate current sensor of several hundred ampere range is generally in tens of mA (i.e. measurement error can only be accurate to mA level), and the precision can reach 10~100ppm;But due to the inductive capacity of the magnetic core material and the offset of the circuit components, there is a very low zero drift, and there is no way to distinguish the uA level of small current fluctuation, which cannot achieve perfect compensation and accurate measurement of uA level current change. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a kind of from microampere to kiloampere ultra-high precision current measurement method for solving the above technical problems.

[0005] To achieve the above purpose, the present application provides the following technical scheme:

[0006] 1. A kind of from microampere to kiloampere ultra-high precision current measurement method, the current sensor applied includes large current detection system, small current detection system, T3 magnetic core, comparator U1 and MOS tube Q1,

[0007] The large current detection system includes electrically connected first measurement coil group, first magnetic core group and large current magnetic flux detection module,

[0008] The small current detection system includes electrically connected second measurement coil group, second magnetic core group and small current magnetic flux detection module,

[0009] T3 magnetic core is shielded magnetic core and is used for magnetic shielding, T3 magnetic core is matched with first measurement coil group, first magnetic core group, second measurement coil group, second magnetic core group,

[0010] Comparator U1 and MOS tube Q1 are placed between small current magnetic flux detection module and large current magnetic flux detection module and are connected in series with small current magnetic flux detection module and large current magnetic flux detection module.

[0011] Further, the first measurement coil group comprises N1 winding, N2 winding, N3 winding and N4 winding, the first magnetic core group comprises T1 magnetic core and T2 magnetic core, the second measurement coil group comprises N5 winding, N6 winding and N7 winding, the second magnetic core group comprises T5 magnetic core and T6 magnetic core, the N1 winding, the N2 winding, the N5 winding and the N6 winding correspond to the T1 magnetic core, the T2 magnetic core, the T5 magnetic core and the T6 magnetic core respectively,

[0012] The T1 magnetic core and the T2 magnetic core are used for sensing the direct current signal of the primary current Ip, the N1 winding and the N2 winding are connected in reverse series to offset the interference of the oscillation on the primary current Ip, the N3 winding is a mutual inductance coil and is used for detecting the alternating current signal of the primary Ip, the N4 winding is a compensation coil and is used for outputting a compensation current, the T3 magnetic core is a shielding magnetic core and is used for magnetic shielding, the N5 winding and the N6 winding are connected in reverse series, the N5 winding and the N6 winding are both used for detecting the magnetic field signal generated by a small current, and the N7 winding is a compensation winding of the detected small current signal,

[0013] The N1 winding and the N2 winding are connected with a large current magnetic flux detection module, the N5 winding and the N6 winding are connected with a small current magnetic flux detection module, and the comparator U1 is arranged between and connected in series with the small current magnetic flux detection module and the large current magnetic flux detection module.

[0014] Further, when the primary side passes through a current Ip, the magnetic flux in the coil is not zero, and the large current magnetic flux detection module can capture the duty cycle change of the N1 winding and the N2 winding, and output a compensation signal to the rear end for reverse compensation. At this time, the comparator U1 outputs a high level, and the MOS tube Q1 is cut off to prevent the output of the small current magnetic flux detection signal.

[0015] Further, when the large current compensation is completed, the duty cycle returns to a level close to 50%, the comparator U1 outputs a low level, and the MOS tube Q1 is turned on to drive the small current magnetic flux detection module to work. Although the large current has been compensated at this time, it is not completely symmetrical compensation, and there is not completely zero magnetic flux. At this time, the N5 winding and the N6 winding start to detect the magnetic field of the residual current and drive the rear compensation.

[0016] Further, the current sensor further comprises a resistance R2 connected with the N4 winding and a resistance R12 connected with the N7 winding. When the whole compensation process is completed, the voltage division of the resistances R2 and R12 is measured, the compensation currents in the two coils are obtained through Icomp=U / R, and the corresponding two primary currents are added to obtain the final primary current size through Ip=Icomp*N / Np.

[0017] By adopting the above technical scheme, the application has the following beneficial effects:

[0018] 1. The measurement accuracy can be improved to the level of one millionth.

[0019] 2. In the case of the highest range of several hundred amperes, the minimum measurement current recognition ability can be reduced to the order of uA;

[0020] 3. Large and small currents are automatically switched in large and small ranges, without manual selection. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of a current measurement circuit of a traditional closed-loop fluxgate current sensor.

[0022] Figure 2 It is a schematic diagram of a current measurement circuit of a closed-loop fluxgate current sensor of the present application.

[0023] Figure 3 It is a schematic diagram of a large-current flux detection module. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0026] As shown in Figure 1 , the traditional closed-loop fluxgate current sensor only has one large-current detection system, the magnetic head part of which is composed of four windings and three magnetic cores. N1 and N2 are windings on magnetic cores T1 and T2, respectively, which are used to sense the direct-current signal of the primary current Ip, and are connected in opposite directions in series to offset the interference of oscillation on the primary current Ip. When the primary current Ip passes through, the duty cycle of the oscillation waveform of N1 and N2 is changed, and the change in duty cycle is captured by the current flux detection module to drive the subsequent stage to perform reverse compensation. N3 is a mutual inductor coil used to detect the alternating-current signal of the primary current Ip. N4 is a compensation coil used to output a compensation current. T3 is a shielding magnetic core used for magnetic shielding to avoid internal and external interference.

[0027] As shown in Figure 2 , compared with Figure 1The traditional closed-loop fluxgate current sensor shown, which adds a linkage of small current detection system, namely adding a N5 winding, T5 magnetic core, N6 winding, T6 magnetic core, N7 winding and a small current magnetic flux detection module, N5, N6 are winding on the magnetic core T5, T6 and used for detecting the magnetic field signal generated by small current, N7 is the compensation winding of the detected small current signal.

[0028] When the primary side passes through a current Ip, the magnetic flux in the coil is not zero, at this time the large current magnetic flux detection module captures the duty cycle change of N1, N2, and outputs a compensation signal to the rear end for reverse compensation; at this time the comparator U1 outputs low level, preventing the small current magnetic flux detection module from working.

[0029] When the large current compensation is completed, U1 outputs high level, driving the small current magnetic flux detection module to work. Although the large current has been compensated at this time, it is not completely symmetrical compensation, there is not completely zero magnetic flux, at this time the two windings N5, N6 start to detect the magnetic field of the remaining current and push the rear compensation.

[0030] When the entire compensation process is completed, the voltage division of R2 and R12 resistors is measured, the compensation current in the two coils is obtained through Icomp=U / R, and the corresponding two primary side currents are added to obtain the final primary side current size through Ip=Icomp*N / Np.

[0031] In combination Figure 3 , the working principle of the large current magnetic flux detection module is described:

[0032] ①. When the operational amplifier comparator A1 outputs high level, the fixed voltage of the magnetic core T1 is the voltage division on the resistor R4, and the winding N2 at this time starts to charge as an inductor, the voltage of the magnetic core T2 is low, the voltage of the magnetic core T1 is higher than that of the magnetic core T2, and the output of the comparator A1 is still high level;

[0033] ②. When the winding N2 is fully charged, the inductive reactance is reduced and is approximately short-circuited, the voltage of the magnetic core T2 is instantaneously raised and exceeds that of the magnetic core T1, at this time the output of the comparator A1 is inverted to low level;

[0034] ③. Repeating the above ① and ② processes can make the operational amplifier comparator A1 continuously output square wave, and the winding N2 continuously charges and discharges, and the coil generates oscillation;

[0035] ④. When the magnetic flux is zero, the duty cycle of the oscillation is 50%; when the current passes through, the magnetic flux changes, which increases or decreases the duty cycle;

[0036] ⑤. The winding N1 and the winding N2 are opposite in the same name end, and generate opposite oscillation waveforms, which can offset each other to reduce the external radiation interference;

[0037] Similarly, the large current magnetic flux detection module and the small current magnetic flux detection module have the same principle, except that the low inductance core is used in the small current detection, and the small magnetic field generated by the small current is more sensitive to the induction.

[0038] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application, and any common change and replacement within the technical scheme range of the present application should be included in the protection range of the present application.

Claims

1. A super-precision current measurement sensor from micro-ampere to kilo-ampere, characterized in that, The current sensor comprises a large current detection system, a small current detection system, a T3 magnetic core, a comparator U1 and a MOS tube Q1, The large current detection system comprises a first measurement coil group, a first magnetic core group and a large current magnetic flux detection module connected electrically, The small current detection system comprises a second measurement coil group, a second magnetic core group and a small current magnetic flux detection module connected electrically, The T3 magnetic core is a shielded magnetic core and is used for magnetic shielding, and the T3 magnetic core is matched with the first measurement coil group, the first magnetic core group, the second measurement coil group and the second magnetic core group correspondingly, The comparator U1 and the MOS tube Q1 are arranged between and connected in series with the small current magnetic flux detection module and the large current magnetic flux detection module. The first measurement coil group comprises N1 winding, N2 winding, N3 winding and N4 winding, the first magnetic core group comprises T1 magnetic core and T2 magnetic core, the second measurement coil group comprises N5 winding, N6 winding and N7 winding, the second magnetic core group comprises T5 magnetic core and T6 magnetic core, and the N1 winding, the N2 winding, the N5 winding and the N6 winding correspond to the T1 magnetic core, the T2 magnetic core, the T5 magnetic core and the T6 magnetic core respectively, The T1 magnetic core and the T2 magnetic core are used for sensing the direct current signal of the primary current Ip, the N1 winding and the N2 winding are connected in reverse series to offset the interference of oscillation on the primary current Ip, the N3 winding is a mutual inductance coil and is used for detecting the alternating current signal of the primary Ip, the N4 winding is a compensation coil and is used for outputting a compensation current, the N5 winding and the N6 winding are connected in reverse series, and the N5 winding and the N6 winding are both used for detecting the magnetic field signal generated by a small current, and the N7 winding is a compensation winding of the detected small current signal, The N1 winding and the N2 winding are connected with the large current magnetic flux detection module, and the N5 winding and the N6 winding are connected with the small current magnetic flux detection module.

2. The measuring method of the ultra-high precision current measuring sensor from microampere level to kiloampere level according to claim 1, characterized in that, When the primary passes through a current Ip, the magnetic flux in the coil is not zero, and the large current magnetic flux detection module can capture the duty cycle change of the N1 winding and the N2 winding, and output a compensation signal to the rear end for reverse compensation; at this time, the comparator U1 outputs a high level, the MOS tube Q1 is cut off, and the small current magnetic flux detection module is prevented from working.

3. The measuring method of a microampere to kiloampere ultra-high precision current measuring sensor according to claim 2, characterized in that, When the large current compensation is completed, the duty cycle returns to a level close to 50%, at this time, the comparator U1 outputs a low level, the MOS tube Q1 is turned on to drive the small current magnetic flux detection module to work; although the large current has been compensated at this time, it is not completely symmetrical compensation, and there is no complete zero magnetic flux, at this time, the N5 and N6 windings start to detect the magnetic field of the remaining current and drive the rear compensation.

4. The measurement method of the ultra-high precision current measurement sensor from microampere to kiloampere according to claim 3, characterized in that, The current sensor further comprises a resistance R2 connected with the N4 winding and a resistance R12 connected with the N7 winding, After the completion of the whole compensation process, the voltage division of the resistances R2 and R12 is measured, the compensation currents in the two coils are obtained through Icomp=U / R, and the corresponding two primary currents are added to obtain the final primary current size through Ip=Icomp*N / Np.

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