CN114859097A - Current sensor and current detection method - Google Patents
Current sensor and current detection method Download PDFInfo
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- CN114859097A CN114859097A CN202210652392.4A CN202210652392A CN114859097A CN 114859097 A CN114859097 A CN 114859097A CN 202210652392 A CN202210652392 A CN 202210652392A CN 114859097 A CN114859097 A CN 114859097A
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- G01—MEASURING; TESTING
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- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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Abstract
The invention discloses a current sensor and a current detection method, wherein the current sensor comprises an excitation source unit, a first fluxgate detection unit and an expansion module, wherein the expansion module comprises a second fluxgate detection unit, a switch unit and a detected coil; the excitation source unit is respectively connected with the first fluxgate detection unit and the second fluxgate detection unit; the current output end of the first fluxgate detection unit is connected with the input end of the switch unit; the input end of the tested coil is connected with the input end of the switch unit; the conducting state of the switch unit is determined based on the target precision and the target measuring range of the current sensor; the current detection method is based on the current sensor and calculates the current to be detected through compensating current. The problem that the current sensor cannot keep a high signal-to-noise ratio when the large dynamic range of the current to be measured changes is solved, and the high precision of current measurement is guaranteed.
Description
Technical Field
The invention relates to the field of sensors, in particular to a current sensor and a current detection method.
Background
The current sensor is a single-range proportional transformation device, and because the secondary coil of the current sensor is solidified in the sensor, the current sensor has a single range, and the measurement accuracy is influenced due to the existence of the signal-to-noise ratio. The signal-to-noise ratio of the current sensor is not consistent according to different application scene requirements, especially in the high-energy physical field, the dynamic range of the measured signal is large, and the current sensor with a single measuring range cannot generally guarantee a high signal-to-noise ratio in a large dynamic range, namely accuracy in the large dynamic range.
In the prior art, an excitation source excites a magnetic core to saturation through an excitation coil according to a periodic signal with a certain frequency, and when a current to be measured IP =0, the magnetic core keeps magnetic balance. If the current to be measured IP = x, the current to be measured breaks magnetic balance, the demodulator detects the balance, and the servo source IS driven to generate compensation current IS to be applied to the magnetic core, so that the magnetic core IS restored to be balanced; the number of turns of the current to be measured IS marked as WP, the number of turns of the secondary compensation coil IS marked as WS, and then WP + IP = WS + IS; namely the current to be measured IP = WS/WP IS.
Once the current sensor IS determined, the WS/WP which works simultaneously IS a constant, the large dynamic change of the current to be measured IP causes the large dynamic change of the secondary current IS, but the system noise basically does not change along with the current to be measured IP, so the signal-to-noise ratio of the secondary current IS IS reduced along with the reduction of the current to be measured, and the measurement accuracy IS lost.
If WP/WS =1/4000, when the current to be measured IP =4000A, IS =1A, and assuming that the system noise IS 10uA, the signal-to-noise ratio IS 100 dB;
when the current to be measured IP =40A, IS =10mA, the signal-to-noise ratio IS 60dB, and the measurement accuracy IS reduced.
If WP/WS =1/400, since there is only one proportional coil, if IP =4000A, then the current sensor output data is invalid and the sensor enters an overload state, and there is a risk of saturating the sensor core, since there is no 10A current output due to the limitation of the output capability of the servo source.
Disclosure of Invention
The invention aims to solve the problem that a current sensor cannot keep a higher signal-to-noise ratio when the current to be measured changes in a large dynamic range, and provides a current sensor.
In order to solve the above problems, the present invention adopts the following technical means.
A current sensor comprises an excitation source unit, a first fluxgate detection unit and an expansion module, wherein the expansion module comprises a second fluxgate detection unit, a switch unit and a coil to be detected;
the excitation source unit is respectively connected with the first fluxgate detection unit and the second fluxgate detection unit;
the first fluxgate detection unit is used for detecting a current to be detected, generating a first compensation current according to the current to be detected, and outputting the first compensation current from a current output end of the first fluxgate detection unit; the current output end of the first fluxgate detection unit is connected with the input end of the switch unit, and the output end of the switch unit is grounded;
the input end of the tested coil is connected with the input end of the switch unit, and the output end of the tested coil is grounded;
the second fluxgate detection unit is configured to detect a current in the coil to be detected, and output a second compensation current from a current output terminal of the second fluxgate detection unit, wherein an on state of the switch unit is determined based on a target accuracy and a target measurement range of the current sensor.
In some embodiments, the first and second fluxgate detection units each include: the device comprises an excitation coil, an excitation magnetic core, a decoupling coil, a decoupling magnetic core, a detection coil, a detection magnetic core, a compensation coil, a demodulator, a power amplifier, a first resistor and a second resistor; the output end of the excitation source unit is respectively connected with the input end of the decoupling coil, the input end of the excitation coil and the input end of the demodulator, the output end of the excitation coil, the output end of the decoupling coil and the output end of the detection coil are respectively connected with the input end of the demodulator, the output end of the decoupling coil is connected with one end of the first resistor, and the other end of the first resistor is grounded; the output end of the exciting coil is connected with one end of the second resistor, and the other end of the second resistor is grounded; the input end of the detection coil is grounded; the output end of the demodulator is connected with the input end of the power amplifier, the output end of the power amplifier is connected with the input end of the compensating coil, and the output end of the compensating coil is connected with the coil to be detected; the demodulator in the first fluxgate detection unit is connected to the switching unit.
In the above embodiments, the excitation coil, the excitation core, the decoupling coil, the decoupling core, the detection coil, the detection core, the compensation coil, the demodulator, the power amplifier, the first resistor, and the second resistor are only named functionally, and the first fluxgate detection unit and the plurality of second fluxgate detection units may have different sizes, dimensions, and specifications.
In some embodiments, the first and second fluxgate detection units further include a third resistor and an operational amplifier; the input end of the operational amplifier is connected with the output end of the compensation coil and one end of the third resistor, the other end of the third resistor in the first fluxgate detection unit is connected with the input end of the coil to be detected, and the other end of the third resistor in the second fluxgate detection unit is grounded.
The third resistor is used for converting the first compensation current or the second compensation current into voltage, and the operational amplifier is used for adjusting the voltage to a standard output range; the third resistor and the operational amplifier are only named functionally, and the first fluxgate detection unit and the plurality of second fluxgate detection units may have different sizes and dimensions.
In some embodiments, the excitation core and the decoupling core are magnetically identical, and the number of excitation coil turns is equal to the number of decoupling coil turns.
In some embodiments, the expansion module further comprises a range state interface, wherein an input end of the range state interface is connected with an output end of the switch unit, and the range state interface is used for monitoring and controlling the use of the expansion module by workers; the switch unit further comprises a monitoring interface, wherein the monitoring interface comprises one or a group of LED lamps.
In some of these embodiments, the excitation source unit includes an oscillation unit, a frequency allocation unit, a flip-flop unit, a power driving unit, and an output coupling unit;
the output end of the oscillation unit is connected to the input end of the frequency distribution unit, and the oscillation unit is used as a clock source of the frequency distribution unit to provide a basic clock for normal operation of the sensor;
the output end of the frequency distribution unit is connected to the input end of the trigger unit, and the frequency distribution unit provides an excitation clock of a magnetic core and a demodulation clock of a demodulator according to preset configuration;
the output end of the trigger unit is connected to the input end of the power driving unit, and the trigger unit inverts the excitation clock so as to output two excitation clock signals with opposite polarities at different ports;
the output end of the power driving unit is connected to the input end of the output coupling unit, and the power driving unit enhances the loading capacity of two excitation clock signals with opposite polarities so as to excite the magnetic core to saturation;
the output coupling unit is used for filtering the direct current signal output by the oscillation unit.
In some embodiments, the number of the expansion modules is N, and the N expansion modules are cascaded in sequence; the input end of the switch unit of the nth-stage expansion module is connected with the current output end of the second fluxgate detection unit of the nth-1-stage expansion module, where N is an integer greater than or equal to 2.
A circuit detection method based on the current sensor comprises the following steps:
determining a conduction state of the switching unit based on a target accuracy and a target range of the current sensor;
determining the current to be measured based on the first compensation current when the switch unit is turned on;
determining the current to be measured based on the second compensation current with the switching unit turned off.
A current detection method based on the current sensor comprises the following steps:
determining the conducting state of the switch unit of each expansion module based on the target precision and the target range of the current sensor;
under the condition that a switch unit of a first-stage expansion module is conducted, determining the current to be measured based on the first compensation current;
under the condition that the switch unit of the N-th-stage expansion module is switched on and the switch units of the previous N-1-stage expansion module are switched off, determining the current to be measured based on a second compensation current output by the N-1-stage expansion module;
and under the condition that the switch units of the 1 st-Nth-stage expansion modules are all switched off, determining the current to be measured based on the second compensation current output by the Nth-stage expansion module.
The primary extension current sensor comprises an excitation source unit, a first fluxgate detection unit and an extension module, wherein the extension module comprises a second fluxgate detection unit, a switch unit and a detected coil;
the excitation source unit is respectively connected with the first fluxgate detection unit and the second fluxgate detection unit, outputs a current signal IE to the first fluxgate detection unit and the second fluxgate detection unit, and receives the current signal IE and keeps magnetic balance;
the first fluxgate detection unit IS configured to detect a current to be detected, generate a first compensation current IS from a current to be detected IP according to a certain proportion (WP/WS), and output the first compensation current IS from a current output end of the first fluxgate detection unit, where current change proportions (WP/WS) of the second fluxgate detection units in the plurality of expansion modules are different; the current output end of the first fluxgate detection unit is connected with the input end of the switch unit, and the output end of the switch unit is grounded;
the input end of the tested coil is connected with the input end of the switch unit, and the output end of the tested coil is grounded;
the second fluxgate detection unit is configured to detect a current in the coil to be detected, and output a second compensation current from a current output terminal of the second fluxgate detection unit, wherein an on state of the switch unit is determined based on a target accuracy and a target measurement range of the current sensor.
The multistage extended current sensor is based on the one-stage extended current sensor, wherein the number of the extended modules is N, and the N extended modules are sequentially cascaded; an input end of the switch unit of the nth stage of the expansion module is connected with a current output end of the second fluxgate detection unit of the nth-1 stage of the expansion module, where N is an integer greater than or equal to 2.
The application provides a current detection method based on a primary extension current sensor, which comprises the following steps:
determining a conduction state of the switching unit based on a target accuracy and a target range of the current sensor;
determining the current to be measured based on the first compensation current when the switch unit is turned on;
determining the current to be measured based on the second compensation current with the switching unit turned off.
The application provides a current detection method based on a multistage extended current sensor, which comprises the following steps:
determining the conducting state of the switch unit of each expansion module based on the target precision and the target range of the current sensor;
under the condition that a switch unit of a first-stage expansion module is conducted, determining the current to be measured based on the first compensation current;
determining the current to be measured based on a second compensation current output by the expansion module of the Nth stage under the condition that the switch unit of the expansion module of the Nth stage is switched on and the switch units of the expansion module of the first N-1 stage are switched off, wherein N is an integer greater than or equal to 2;
and under the condition that the switch units of the 1 st-Nth-stage expansion modules are all disconnected, determining the current to be measured based on the second compensation current output by the Nth-stage expansion module.
Therefore, the invention has the following beneficial effects:
(1) the expansion module provides more transformation ratios existing at the same time, is more flexible to use, can cover current change in a large dynamic range, and ensures high accuracy of current measurement in the large dynamic range;
(2) by using the operational amplifier, the detected signal is smaller and has larger signal output, the signal-to-noise ratio of the system is improved, and the accuracy of the system is improved;
(3) compared with the current sensor for switching the turns of the secondary winding, the current sensor has basically no switching response time; in the prior art, short-term output invalidation can be caused due to switching gaps, and the risk of saturating a magnetic core of a sensor exists.
Drawings
In order to more clearly illustrate the embodiments of the present application or technical solutions in related arts, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a block diagram of a first-stage expansion structure of a current sensor provided by the present invention;
FIG. 2 is a topology diagram of a first stage expansion circuit of the current sensor provided by the present invention;
FIG. 3 is a block diagram of an excitation source module of the current sensor provided by the present invention;
FIG. 4 is a block diagram of a two-stage expansion structure of the current sensor provided by the present invention;
FIG. 5 is a two-stage expanded circuit topology of the current sensor provided by the present invention;
FIG. 6 is a schematic flow chart of a current detection method based on a primary extended current sensor provided by the present invention;
fig. 7 is a schematic flow chart of a current detection method based on a multi-stage extended current sensor provided by the invention.
Description of reference numerals:
1. an excitation source unit; 11. an oscillation unit; 12. a frequency allocation unit; 13. trigger unit, 14, power drive unit; 15. an output coupling unit; 2. a first fluxgate detection unit; 3. an expansion module; 31. a second fluxgate detection unit; 32. a switch unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. All other examples, which can be obtained by a person skilled in the art without making creative efforts based on the examples in the present application, belong to the protection scope of the present application.
It is obvious that the drawings in the following description are only examples or embodiments of the application, from which the application can also be applied to other similar scenarios without inventive effort for a person skilled in the art. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.
Unless otherwise defined, technical or scientific terms used in the claims and the specification should have the ordinary meaning as understood by those of ordinary skill in the art to which this application belongs. The use of the terms "a" and "an" and "the" and similar referents in the context of describing and claiming the application are not to be construed as limiting in any way, but rather as indicating the singular or plural. The word "comprise" or "comprises", and the like, means that the element or item listed before "comprises" or "comprising" covers the element or item listed after "comprising" or "comprises" and its equivalent, and does not exclude other elements or items. "connected" or "coupled" and similar terms are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. As used in the specification and claims of this application, "a plurality" means two or more. The terms "first", "second" and "third" are used only for distinguishing different objects, and have no practical meaning. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone.
Example 1: as shown in fig. 1, the present embodiment provides a current sensor including an excitation source unit 1, a first fluxgate detection unit 2, and an expansion module 3, and the expansion module 3 includes a second fluxgate detection unit 31, a switching unit 32, and a coil under test. The output end of the excitation source unit 1 is respectively connected with the input end of the first fluxgate detection unit 2 and the input end of the second fluxgate detection unit 31, the output end of the first fluxgate detection unit 2 is respectively connected with the input end of the switch unit 32 and the input end of the coil to be detected, the first fluxgate detection unit 2 is used for detecting a current to be detected, generating a first compensation current according to the current to be detected and outputting the first compensation current from the current output end of the first fluxgate detection unit 2; the second fluxgate detection unit 31 is configured to detect a current in the coil under test and output a second compensation current from a current output terminal of the second fluxgate detection unit 31; the on state of the switching unit 32 is determined based on the target accuracy and the target range of the current sensor.
As shown in fig. 2, the excitation coil includes an excitation coil W3 and an excitation coil W3', the excitation core includes an excitation core C3 and an excitation core C3', the decoupling coil includes a decoupling coil W2 and a decoupling coil W2', the decoupling core includes a decoupling core C2 and a decoupling core C2', the detection coil includes a detection coil W1 and a detection coil W1', the detection core includes a detection core C1 and a detection core C1', the compensation coil includes a compensation coil WS and a compensation coil WS ', the demodulator includes a first demodulator and a second demodulator, and the power amplifier includes a first power amplifier and a second power amplifier; the first resistor comprises a first resistor R1 and a first resistor R1', the second resistor comprises a second resistor R2 and a second resistor R2', the third resistor comprises a third resistor RS and a third resistor RS ', and the operational amplifier comprises an operational amplifier AS and an operational amplifier AS'.
The first fluxgate detecting unit 2 includes an excitation coil W3, an excitation core C3, a decoupling coil W2, a decoupling core C2, a detection coil W1, a detection core C1, a compensation coil WS, a first demodulator, a first power amplifier, a first resistor R1, a second resistor R2, a third resistor RS, and an operational amplifier AS; the excitation magnetic core C3 and the decoupling magnetic core C2 have the same magnetic performance, and the number of turns of the excitation coil W3 is equal to that of the decoupling coil W2; the output end of the excitation source unit 1 is respectively connected with the input end of a decoupling coil W2, the input end of an excitation coil W3 and the input end of a first demodulator, the output end of an excitation coil W3, the output end of a decoupling coil W2 and the output end of a detection coil W1 are respectively connected with the input end of the first demodulator, the output end of a decoupling coil W2 is connected with one end of a first resistor R1, and the other end of the first resistor R1 is grounded; the output end of the excitation coil W3 is connected with one end of a second resistor R2, and the other end of the second resistor R2 is grounded; the input end of the detection coil W1 is grounded; the output end of the first demodulator is connected with the input end of the first power amplifier, the output end of the first power amplifier is connected with the input end of the compensating coil WS, the output end of the compensating coil WS is connected with the input end of the operational amplifier AS and one end of the third resistor RS, the other end of the third resistor RS is connected with the input end of the tested coil, and the first demodulator is connected with the switch unit 32; the third resistor RS is used to convert the first compensation current into a voltage, and the operational amplifier AS is used to adjust the voltage to a standard output range.
The exciting source unit 1 outputs a current IE to excite the exciting core C3 to saturation through an exciting coil W3 by a periodic signal with a certain frequency, the first demodulator identifies the magnetic flux change condition of the exciting core C3 through the voltage change on a second resistor R2 connected with the exciting coil W3 in series, if the total magnetic flux IS not 0 (namely the current IP to be measured IS not zero, magnetic potential IS generated), the magnetic potential which IS equal to the magnetic potential generated by the current IP to be measured and IS opposite to the magnetic potential generated by the current IP to be measured IS generated by controlling the first power amplifier to output the current IS to the compensating coil WS until the total magnetic flux in the exciting core C3 IS zero, and closed-loop control IS completed. At this time:
IP=WS/WP*IS。
the second fluxgate detecting unit 31 includes an excitation coil W3', an excitation core C3', a decoupling coil W2', a decoupling core C2', a detection coil W1', a detection core C1', a compensation coil WS ', a second demodulator, a second power amplifier, a first resistor R1', a second resistor R2', a third resistor RS ', and an operational amplifier AS '; the excitation magnetic core C3 'and the decoupling magnetic core C2' have consistent magnetic performance, and the number of turns of the excitation coil W3 'is equal to that of the decoupling coil W2'; the output end of the excitation source unit 1 is respectively connected with the input end of a decoupling coil W2', the input end of an excitation coil W3' and the input end of a second demodulator, the output end of the excitation coil W3', the output end of the decoupling coil W2' and the output end of a detection coil W1 'are respectively connected with the input end of the second demodulator, the output end of the decoupling coil W2' is connected with one end of a first resistor R1', and the other end of the first resistor R1' is grounded; the output end of the excitation coil W3' is connected with one end of a second resistor R2', and the other end of the second resistor R2' is grounded; the input end of the detection coil W1' is grounded; the output end of the second demodulator is connected with the input end of a second power amplifier, the output end of the second power amplifier is connected with the input end of a compensating coil WS ', the output end of the compensating coil WS ' is connected with the input end of an operational amplifier AS ' and one end of a third resistor RS ', and the other end of the third resistor RS ' is grounded; the third resistor RS 'is used to convert the second compensation current to a voltage, and the operational amplifier AS' is used to adjust the voltage to a standard output range.
The input end of a measured coil WP 'is connected with the output end of a third resistor RS and the output end of the switch unit 32 respectively, a compensation coil WS is connected with the measured coil WP' in series, currents in the compensation coil WS and the measured coil WP 'are consistent, the output end of the measured coil WP' is connected with the output end of the switch unit 32 and is grounded, the expansion module 3 is provided with a range state interface SE1, and the range state interface SE1 is connected with the output end of the switch unit 32; the switch unit 32 is provided with a monitoring interface which is provided with a group of LED lamps, a range state interface SE1 is used for monitoring and controlling the use of the expansion module 3, and a user can freely switch between a basic range and an expansion range by matching with the monitoring interface; the input end of the switch unit 32 is connected with the output end of the first demodulator, the output end of the switch unit 32 is respectively connected with the output end of the compensation coil WS and the input end of the detected coil WP ', the first demodulator outputs a signal to the switch unit 32, and the switch unit 32 controls whether the detected coil WP' of the expansion module 3 is short-circuited or not according to the size of the output signal of the first demodulator.
The exciting source unit 1 outputs current IE ' to excite the exciting magnetic core C3' to saturation through an exciting coil W3' by a periodic signal with a certain frequency, the second demodulator identifies the magnetic flux change condition of the second exciting magnetic core C3' through the voltage change on a resistor R2' connected with the exciting coil W3' in series, if the total magnetic flux IS not 0 (namely the current IS to be measured IS not zero, magnetic potential IS generated), magnetic potential which IS equal to the magnetic potential generated by the current IS to be measured in magnitude and opposite to the magnetic potential generated by the current IS to be measured IS generated by controlling the second power amplifier output current IS ' to a compensating coil WS ' until the total magnetic flux in the exciting magnetic core C3' IS zero, and closed-loop control IS completed. At this time:
IS =WS'/WP'*IS'；
IP=WS/WP*IS=WS/WP*WS'/WP'*IS'。
as shown in fig. 3, the excitation source unit 1 includes an oscillation unit 11, a frequency distribution unit 12, a trigger unit 13, a power driving unit 14 and an output coupling unit 15, an output end of the oscillation unit 11 is connected to an input end of the frequency distribution unit 12, and the oscillation unit 11 serves as a clock source of the frequency distribution unit 12 to provide a basic clock for normal operation of the sensor; the output end of the frequency distribution unit 12 is connected to the input end of the trigger unit 13, and the frequency distribution unit 12 provides the excitation clock of the magnetic core and the demodulation clock of the demodulator according to the preset configuration; the output end of the flip-flop unit 13 is connected to the input end of the power driving unit 14, and the flip-flop unit 13 inverts the excitation clock to output two excitation clock signals with opposite polarities at different ports; the output end of the power driving unit 14 is connected to the input end of the output coupling unit 15, the power driving unit 14 enhances the loading capacity of the two excitation clock signals with opposite polarities so as to excite the magnetic core to saturation, and the output coupling unit 15 is used for filtering the direct current signal output by the oscillating unit 11.
When the current sensor of the present embodiment measures the current,
(a) if IP =400A to 4000A, the expansion module 3 disables: WS =4000, WP =1, WS ' =100, WP ' =0, IS =0.1A to 1A, IS ' = 0A; RS =0.5R, AS gain is 20, then
VS=1V～10V；
The system ratio at this time was 4000A/10V. If the system noise is 10uV, the signal-to-noise ratio of the measuring range is 100dB to 120 dB.
(b) If IP =40A to 400A, the extension module 3 disables: WS =4000, WP =1, IS = 0.01A-0.1A, IS' = 0A; RS =0.5R, AS gain is 20, then
VS=0.1V～1V；
The system ratio at this time was 400A/1V. If the system noise is 10uV, the signal-to-noise ratio of the measuring range is 80dB to 100 dB.
The expansion module 3 enables: WS =4000, WP =1, WS ' =100, WP ' =1000, IS = 0.01A-0.1A, IS ' = 0.1A-1A; RS '=0.5R, AS' gain is 20, then output from VS
VS'=1V～10V；
The system ratio at this time was 400A/10V. If the system noise is 10uV, the signal-to-noise ratio of the measuring range is 100dB to 120 dB.
The basic range 1/4000 of the present embodiment is always valid, and the extension module 3 controls the switch unit 32 to enable the tested coil WP' according to the output signal of the first demodulator, and the enabling point is about IP = 440A. When the IP IS from 40A (VS ': 1V, VS: 0.1V) to 440A (VS ': 11V, VS: 1.1V) of the extended range, the range state interface SE1 changes from low level to high level, the current sensor outputs through VS ', the switching unit 32 controls the tested coil WP ' to be short-circuited, then IP ' = IS, no overload exists; when the IP is reduced from 4000A (VS ': 0V, VS: 10V) to 440A (VS': 11V, VS: 1.1V), the span state interface SE1 is changed from high level to low level, the current sensor outputs through VS ', and the switching unit 32 releases the short-circuit switch of the coil WP' to be tested.
Through the flexible configuration of the routine state interface SE1 and VS' and VS, the flexible switching without data loss can be realized, and the signal-to-noise ratio of the current IP to be measured in the range of 40A to 4000A is ensured to be larger than 100 dB.
Therefore, the use of the expansion module 3 improves the signal-to-noise ratio of the system and improves the low-range precision of the sensor.
Example 2: as shown in fig. 4, the present embodiment provides a current sensor, which includes an excitation source unit 1, a first fluxgate detection unit 2, and an expansion module 3, where the expansion module 3 includes a first expansion module 3 and a second expansion module 3, and the first expansion module 3 and the second expansion module 3 are communicated in structure and connection, but the sizes, dimensions, and specifications of the components are different; the output end of the excitation source unit 1 is respectively connected with the input end of the first fluxgate detection unit 2, the input end of the first expansion module 3 and the input end of the second expansion module 3, the output end of the first fluxgate detection unit 2 is respectively connected with the input end of the switch unit 32 in the first expansion module 3 and the input end of the detected coil in the first expansion module 3, and the output end of the second fluxgate detection unit 31 in the first expansion module 3 is respectively connected with the input end of the switch unit 32 in the second expansion module 3 and the input end of the detected coil in the second expansion module 3.
As shown in fig. 5, the exciting coil includes an exciting coil W3, an exciting coil W3' and an exciting coil W3 ″, the exciting core includes an exciting core C3, an exciting core C3' and an exciting core C3 ″, the decoupling coil includes a decoupling coil W2, a decoupling coil W2' and a decoupling coil W2 ″, the decoupling core includes a decoupling core C2, a decoupling core C2' and a decoupling core C2 ″, the detection coil includes a detection coil W1, a detection coil W1' and a detection coil W1 ″, the detection core includes a detection core C1, a detection core C1' and a detection core C1 ″, the compensation coil includes a compensation coil WS, a compensation coil WS ' and a compensation coil WS ″, the demodulator includes a first demodulator, a second demodulator and a second demodulator, and includes a first power amplifier, a second power amplifier and a second power amplifier; the first resistor comprises a first resistor R1, a first resistor R1 'and a first resistor R1' ', the second resistor comprises a second resistor R2, a second resistor R2' and a second resistor R2'', the third resistor comprises a third resistor RS, a third resistor RS 'and a third resistor RS' ', the operational amplifier comprises an operational amplifier AS, an operational amplifier AS' and an operational amplifier AS '', and the span state interface comprises a span state interface SE1 and a span state interface SE 2.
The first fluxgate detection unit 2, the first expansion module 3 and the second expansion module 3 have the same structure as that of the embodiment 1, the connection relationship between the first fluxgate detection unit 2 and the first expansion module 3 is the same as that of the embodiment 1, the input end of the coil to be measured WP ″ in the second expansion module 3 is respectively connected with the output end of the third resistor RS ' in the first expansion module 3 and the output end of the switch unit 32 in the second expansion module 3, the compensation coil WS ' in the first expansion module 3 is connected in series with the coil to be measured WP ″ in the second expansion module 3, the compensation coil WS ' in the first expansion module 3 is consistent with the current in the coil to be measured WP ″ in the second expansion module 3, the output end of the coil to be measured WP ″ in the second expansion module 3 is connected with the output end of the switch unit 32 in the second expansion module 3 and grounded, the second expansion module 3 is provided with a range state interface SE2, the range state interface SE2 is connected with the output end of the switch unit 32 in the second expansion module 3; the switch unit 32 is provided with a monitoring interface which is provided with a group of LED lamps, the range state interface SE2 is used for monitoring and controlling the use of the second extension module 3, and a user can freely switch between the first-stage extension range and the second-stage extension range by matching with the monitoring interface; the input end of the switch unit 32 in the second expansion module 3 is connected to the output end of the second demodulator in the first expansion module 3, the output end of the switch unit 32 in the second expansion module 3 is connected to the output end of the compensation coil WS' in the first expansion module 3 and the input end of the tested coil WP ″ in the second expansion module 3, respectively, the second demodulator in the first expansion module 3 outputs a signal to the switch unit 32 in the second expansion module 3, and the switch unit 32 in the second expansion module 3 controls whether the tested coil WP ″ of the second expansion module 3 is short-circuited or not according to the magnitude of the output signal of the second demodulator in the first expansion module 3.
In this embodiment, WP IP = WS IS,
WP'*IS=WS'*IS'，
WP ' = WS ' = IS ', therefore, current to be measured
IP=WS/WP*IS
=WS/WP*WS'/WP'*IS'
=WS/WP*WS'/WP'*WS''/WP''*IS''。
Based on the method, more embodiments can be generated by continuous cascade connection, so that the current change under a large dynamic range can be covered, and the high precision of current measurement under the large dynamic range is ensured.
The invention provides a current detection method based on a primary extended current sensor, as shown in fig. 6, the steps include:
determining the on state of the switching unit 32 based on the target accuracy and the target range of the current sensor;
determining a current to be measured based on the first compensation current in a case where the switching unit 32 is turned on;
with the switching unit 32 open, the current to be measured is determined based on the second compensation current.
Referring to embodiment 1, when the switch unit 32 is turned on, the coil WP' to be measured is short-circuited, and at this time, the expansion module 3 is in a non-operating state, and the current to be measured can be determined by the first compensation current, that is:
IP=WS/WP*IS。
under the condition that the switch unit 32 is turned off, the coil WP' to be tested normally works, and the extension module 3 is in a working state, at this time, the first compensation current is: IS = WS '/WP '/IS ';
the current to be measured can be determined through the second compensation current, namely:
IP=WS/WP*IS=WS/WP*WS'/WP'*IS'。
the invention provides a current detection method based on a multistage extended current sensor, as shown in fig. 7, the steps include:
determining the conducting state of the switch unit 32 of each expansion module 3 based on the target precision and the target range of the current sensor;
determining the current to be measured based on the first compensation current under the condition that the switch unit 32 of the first-stage expansion module 3 is turned on;
under the condition that the switch unit 32 of the Nth-stage expansion module 3 is switched on and the switch units 32 of the previous N-1-stage expansion module 3 are switched off, determining the current to be measured based on the second compensation current output by the N-1-stage expansion module 3;
under the condition that the switch units 32 of the 1 st-Nth-stage expansion modules 3 are all switched off, the current to be measured is determined based on the second compensation current output by the Nth-stage expansion module 3.
Referring to embodiment 2, when the switch unit 32 in the first expansion module 3 is turned on, the coil WP' to be tested in the first expansion module 3 is short-circuited, and at this time, both the first expansion module 3 and the second expansion module 3 are in a non-operating state, and the current to be tested can be determined by the first compensation current, that is:
IP=WS/WP*IS。
when the switch unit 32 in the second expansion module 3 is turned on and the switch unit 32 in the first expansion module 3 is turned off, the coil WP' to be measured in the first expansion module 3 normally works, the coil WP ″ to be measured in the second expansion module 3 is short-circuited, at this time, the first expansion module 3 is in a working state, the second expansion module 3 is in a non-working state, at this time, the first compensation current is: IS = WS '/WP '/IS '; the current to be measured can be determined by the second compensation current output by the first expansion module 3, that is:
IP=WS/WP*IS=WS/WP*WS'/WP'*IS'。
when the switch unit 32 in the first expansion module 3 and the switch unit 32 in the second expansion module 3 are both turned off, the coil WP' to be measured in the first expansion module 3 and the coil WP ″ to be measured in the second expansion module 3 both work normally, and at this time, the first expansion module 3 and the second expansion module 3 are both in a working state, and at this time, the first compensation current is: IS = WS '/WP '/IS '; the second compensation current output by the first expansion module 3 is: IS' = WS "/WP". IS "; the current to be measured can be determined by the second compensation current output by the second expansion module 3, that is:
IP=WS/WP*WS'/WP'*WS''/WP''*IS''。
It is obvious that the invention is not restricted to the details of the embodiments presented above, but that there are numerous specific embodiments in which the invention can be implemented, including the essential features of the invention. Accordingly, the present embodiments are to be considered as illustrative and not restrictive. Any changes or modifications of the technical solution of the present invention by those skilled in the art without departing from the scope of the claims of the present invention are covered in the claims of the present invention.
Claims (9)
1. A current sensor is characterized by comprising an excitation source unit (1), a first fluxgate detection unit (2) and an expansion module (3), wherein the expansion module (3) comprises a second fluxgate detection unit (31), a switch unit (32) and a coil to be detected;
the excitation source unit (1) is respectively connected with the first fluxgate detection unit (2) and the second fluxgate detection unit (31);
the first fluxgate detection unit (2) is configured to detect a current to be detected, generate a first compensation current according to the current to be detected, and output the first compensation current from a current output end of the first fluxgate detection unit (2); the current output end of the first fluxgate detection unit (2) is connected with the input end of the switch unit (32), and the output end of the switch unit (32) is grounded;
the input end of the coil to be tested is connected with the input end of the switch unit (32), and the output end of the coil to be tested is grounded;
the second fluxgate detection unit (31) is configured to detect a current in the coil under test and output a second compensation current from a current output terminal of the second fluxgate detection unit (31), wherein a conduction state of the switching unit (32) is determined based on a target accuracy and a target measurement range of the current sensor.
2. The current sensor according to claim 1, wherein the first fluxgate detection unit (2) and the second fluxgate detection unit (31) each comprise: the device comprises an excitation coil, an excitation magnetic core, a decoupling coil, a decoupling magnetic core, a detection coil, a detection magnetic core, a compensation coil, a demodulator, a power amplifier, a first resistor and a second resistor; the output end of the excitation source unit (1) is respectively connected with the input end of the decoupling coil, the input end of the excitation coil and the input end of the demodulator, the output end of the excitation coil, the output end of the decoupling coil and the output end of the detection coil are respectively connected with the input end of the demodulator, the output end of the decoupling coil is connected with one end of the first resistor, and the other end of the first resistor is grounded; the output end of the exciting coil is connected with one end of the second resistor, and the other end of the second resistor is grounded; the input end of the detection coil is grounded; the output end of the demodulator is connected with the input end of the power amplifier, the output end of the power amplifier is connected with the input end of the compensating coil, and the output end of the compensating coil is connected with the coil to be detected; the demodulator in the first fluxgate detection unit (2) is connected to the switching unit (32).
3. The current sensor according to claim 1, wherein the first fluxgate detection unit (2) and the second fluxgate detection unit (31) further comprise a third resistor and an operational amplifier; the input end of the operational amplifier is connected with the output end of the compensation coil and one end of the third resistor, the other end of the third resistor in the first fluxgate detection unit (2) is connected with the input end of the coil to be detected, and the other end of the third resistor in the second fluxgate detection unit (31) is grounded.
4. The current sensor of claim 1, wherein the excitation core and the decoupling core are magnetically identical, and wherein the number of excitation coil turns is equal to the number of decoupling coil turns.
5. The current sensor according to claim 1, characterized in that the expansion module (3) further comprises a span status interface, the span status interface input end is connected with the switch unit (32) output end, the span status interface is used for monitoring and controlling the use of the expansion module (3) by staff; the switch unit (32) further comprises a monitoring interface comprising one or a group of LED lamps.
6. The current sensor according to claim 1, characterized in that the excitation source unit (1) comprises an oscillation unit (11), a frequency allocation unit (12), a trigger unit (13), a power drive unit (14) and an output coupling unit (15);
the output end of the oscillation unit (11) is connected to the input end of the frequency distribution unit (12), and the oscillation unit (11) is used as a frequency distribution unit clock source to provide a clock for normal operation of the sensor;
the output end of the frequency distribution unit (12) is connected to the input end of the trigger unit (13), and the frequency distribution unit (12) provides an excitation clock of a magnetic core and a demodulation clock of a demodulator according to a preset configuration;
the output end of the trigger unit (13) is connected to the input end of the power driving unit (14), and the trigger unit (13) inverts the excitation clock so as to output two excitation clock signals with opposite polarities at different ports;
the output end of the power driving unit (14) is connected to the input end of the output coupling unit (15), and the power driving unit (14) enhances the loading capacity of two excitation clock signals with opposite polarities so as to excite a magnetic core to saturation;
the output coupling unit (15) is used for filtering the direct current signal output by the oscillation unit.
7. The current sensor according to any one of claims 1 to 6, characterized in that the number of said expansion modules (3) is N, N of said expansion modules (3) being cascaded in sequence; wherein, the input end of the switch unit (32) of the nth stage of the expansion module (3) is connected with the current output end of the second fluxgate detection unit (31) of the nth-1 stage of the expansion module (3), where N is an integer greater than or equal to 2.
8. A circuit detection method based on the current sensor of claim 1, comprising:
determining a conducting state of the switching unit (32) based on a target accuracy and a target range of the current sensor;
determining the current to be measured based on the first compensation current when the switching unit (32) is turned on; and
-determining the current to be measured based on the second compensation current in case the switching unit (32) is open.
9. A current detection method based on the current sensor of claim 7, comprising:
determining the conducting state of the switch unit (32) of each expansion module (3) based on the target precision and the target measuring range of the current sensor;
determining the current to be measured based on the first compensation current under the condition that a switch unit (32) of a first-stage expansion module (3) is conducted;
under the condition that the switch unit (32) of the expansion module (3) of the Nth stage is turned on and the switch units (32) of the expansion module (3) of the previous N-1 stages are all turned off, determining the current to be measured based on a second compensation current output by the expansion module (3) of the Nth-1 stage;
and under the condition that the switch units (32) of the 1 st-Nth-stage expansion modules (3) are all disconnected, determining the current to be measured based on the second compensation current output by the Nth-stage expansion module (3).
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