CN115951276A - Fluxgate sensor, digital sampling system, digital sampling method and controller - Google Patents
Fluxgate sensor, digital sampling system, digital sampling method and controller Download PDFInfo
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Abstract
The invention provides a fluxgate sensor, a digital sampling system, a digital sampling method and a controller, the fluxgate sensor comprising: the excitation source generating circuit is provided with an external input interface; the excitation source generating circuit is connected with the controller through an external input interface and is also connected with an excitation winding in the fluxgate sensor; the excitation source generating circuit receives an excitation source driving signal output by the controller; and the excitation source generating circuit generates a corresponding excitation input signal according to the excitation source driving signal, outputs the excitation input signal to the excitation winding and excites the excitation winding. In the invention, the external input interface and the excitation source generating circuit are arranged in the fluxgate sensor, and the excitation source generating circuit is utilized to generate the excitation signal according to the externally input excitation source driving signal, so that the excitation signal is adjusted, the interference of the excitation signal in the sampling process is avoided, and the acquisition precision is improved.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a fluxgate sensor, a digital sampling system, a digital sampling method and a controller.
Background
The fluxgate sensor can realize superior measurement performance through zero-magnetic-flux closed-loop control due to the unique magnetic modulation technology, and is particularly characterized by fast response time, superior temperature drift characteristics, capability of measuring alternating current and direct current signals, wide measurement range and wide application in high-precision and high-performance current measurement application occasions.
The earliest fluxgate sensors were relatively simple single core structures, but the output signal of the single core modulator contained odd harmonics with large amplitudes due to the influence of its excitation winding. In order to improve the measurement accuracy, double-magnetic core modulation can be adopted, so that the amplitude of the excitation signals on the two excitation windings at any moment is equal and the phases are opposite, odd harmonics contained in output signals are mutually offset, even harmonics are mutually added, and the influence brought by the excitation windings can be eliminated so as to further improve the measurement accuracy. On the basis, in order to further improve the measurement bandwidth of the sensor, an alternating current magnetic core and a winding are additionally arranged so as to improve the measurement capability of the sensor on alternating current signals.
Although the fluxgate with double-core winding can theoretically eliminate odd harmonics caused by the excitation current and further reduce the sampling error of the sensor, for a digital sampling system with high sampling rate and high precision, because the data acquisition rate is very high (100 ksps level or even Msps level), referring to fig. 1, the excitation signal of the fluxgate sensor is generated by an oscillation signal output by a fluxgate oscillator, and the oscillation signal and the corresponding excitation signal are signals with fixed frequency and fixed phase. The sampling time is always the excitation time of the sensor inevitably, and the disturbance of the jump point of the excitation signal is still inevitably coupled to the secondary side output current at the positive and negative jump time of the excitation signal. Therefore, under the condition of high sampling rate, the sampling time of the sampling device always partially overlaps with the excitation time of the sensor, so that finally acquired data contains noise components of excitation frequency, and for a micro-current high-precision sampling system (uA-10 mA level), the noise components account for a very heavy weight, and the sampling precision is greatly influenced.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
The invention mainly aims to provide a fluxgate sensor, a digital sampling system, a digital sampling method and a controller, and aims to solve the technical problem that the acquisition precision is reduced due to the noise of excitation frequency in the prior art.
To achieve the above object, the present invention provides a fluxgate sensor comprising: the excitation source generating circuit is provided with an external input interface;
the excitation source generating circuit is connected with the controller through the external input interface and is also connected with an excitation winding in the fluxgate sensor;
the excitation source generating circuit is used for receiving the excitation source driving signal output by the controller;
the excitation source generating circuit is further configured to generate a corresponding excitation input signal according to the excitation source driving signal, output the excitation input signal to the excitation winding, and excite the excitation winding.
Optionally, the excitation source generating circuit comprises: the first to the second diodes, the first to the second switch tubes, the first capacitor and the first to the second resistors;
the anode of the first diode is connected with the positive output end of the driving signal of the controller excitation source, the cathode of the first diode is connected with the control end of a first switch tube, the input end of the first switch tube is connected with a positive power supply, the output end of the first switch tube is connected with the first end of a first resistor, the second end of the first resistor is connected with the first end of a first capacitor, and the second end of the first capacitor is connected with the excitation winding;
the anode of the second diode is connected with the negative electrode output end of the driving signal of the controller excitation source, the cathode of the second diode is connected with the control end of the second switch tube, the input end of the second switch tube is connected with the negative power supply, the output end of the second switch tube is connected with the first end of the second resistor, and the second end of the second resistor is connected with the first end of the first capacitor.
Optionally, the fluxgate sensor further comprises: a signal demodulation circuit;
the signal demodulation circuit is respectively connected with the controller and a detection winding in the fluxgate sensor;
the signal demodulation circuit is used for receiving a reference signal output by the controller and an excitation output signal output by the detection winding;
the signal demodulation circuit is further configured to compare the excitation output signal with the reference signal to obtain a phase difference, and feed back the phase difference to the controller, so that the controller adjusts the excitation source driving signal according to the phase difference.
Optionally, the fluxgate sensor further comprises: a third diode and a third switching tube;
the anode of the third diode is connected with the controller, the cathode of the third diode is connected with the control end of the third switching tube, and the input end and the output end of the third switching tube are both connected with the signal demodulation circuit.
In addition, to achieve the above object, the present invention also provides a digital sampling system, comprising: the device comprises a controller, a sampling chip, a signal conditioning circuit and the fluxgate sensor;
the controller is respectively connected with the sampling chip and an excitation source generating circuit in the fluxgate sensor, and the sampling chip is connected with the fluxgate sensor through a signal conditioning circuit;
the controller is used for generating a sampling signal and an excitation source driving signal, sending the sampling signal to the sampling chip and sending the excitation source driving signal to the excitation source generating circuit; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal from the excitation source driving signal is inversely proportional to the integer multiple;
and the sampling chip is used for outputting a current signal to the fluxgate sensor according to the sampling signal when receiving the sampling signal.
Optionally, the digital sampling system further comprises: an overcurrent detection circuit;
the overcurrent detection circuit is respectively connected with the controller and a primary winding of the fluxgate sensor;
the overcurrent detection circuit is used for detecting a current signal passing through the primary winding and outputting an overcurrent signal to the controller when the current value of the current signal is greater than a preset current value;
the controller is further configured to stop outputting the sampling signal to the sampling chip when receiving the over-current signal.
Optionally, the over-current detection circuit includes: the third resistor, the fourth resistor, the sixth resistor, the fourth switch tube and the first comparator;
the first end of the third resistor is connected with the primary winding, the second end of the third resistor is connected with the first end of the fourth resistor and the first end of the fifth resistor, the second end of the fourth resistor is connected with the positive input end of the first comparator, the second end of the fifth resistor is grounded, the reverse input end of the first comparator is connected with a preset current source, the output end of the first comparator is connected with the control end of the fourth switching tube, the input end of the fourth switching tube is connected with the first end of the sixth resistor, the output end of the fourth switching tube is grounded, and the second end of the sixth resistor is connected with the controller.
In addition, to achieve the above object, the present invention further provides a digital sampling method, including:
generating a sampling signal and an excitation source driving signal when starting sampling; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal from the excitation source driving signal is inversely proportional to the integer multiple;
outputting the excitation source driving signal to a fluxgate sensor so that the fluxgate sensor generates a corresponding excitation signal to excite the excitation winding;
and outputting the sampling signal to a sampling chip so that the sampling chip collects the current parameter output by the fluxgate sensor according to the sampling signal.
Optionally, after the step of outputting the sampling signal to a sampling chip to enable the sampling chip to collect the current parameter output by the fluxgate sensor according to the sampling signal, the method further includes:
generating a reference signal according to the excitation source driving signal;
outputting the reference signal to a signal demodulation circuit in the fluxgate sensor, so that the signal demodulation circuit compares a second harmonic signal with the reference signal and feeds back a phase difference; the second harmonic signal is a signal obtained by superposing and demodulating an external current magnetic field signal output by the detection winding and the excitation signal;
adjusting the excitation source drive signal according to the phase difference;
detecting a current signal through the primary winding;
and when the current value of the current signal is greater than a preset current value, disconnecting the connection between the equipment to be detected and the fluxgate sensor.
In addition, in order to achieve the above object, the present invention further provides a controller, wherein the controller is connected to the sampling chip and the fluxgate sensor;
the controller is used for implementing the digital sampling method.
The invention provides a fluxgate sensor, a digital sampling system, a digital sampling method and a controller, the fluxgate sensor comprising: the excitation source generating circuit is provided with an external input interface; the excitation source generating circuit is connected with the controller through the external input interface and is also connected with an excitation winding in the fluxgate sensor; the excitation source generating circuit is used for receiving the excitation source driving signal output by the controller; the excitation source generating circuit is further configured to generate a corresponding excitation input signal according to the excitation source driving signal, output the excitation input signal to the excitation winding, and excite the excitation winding. In the invention, the external input interface and the excitation source generating circuit are arranged in the fluxgate sensor, and the excitation signal is generated by the excitation source generating circuit according to the externally input excitation source driving signal, so that the excitation signal is adjusted, the interference of the excitation signal in the sampling process is avoided, and the acquisition precision is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic structural view of a fluxgate sensor in the related art;
fig. 2 is a schematic structural view of a fluxgate sensor according to a first embodiment of the present invention;
FIG. 3 is a diagram illustrating the sampling time and the excitation time of a digital sampling system according to the prior art;
FIG. 4 is a block circuit diagram of the interface connections of the controller according to the present invention;
fig. 5 is a schematic structural diagram of a digital sampling system according to the present invention;
fig. 6 is a schematic diagram of the sampling time and the excitation time of the digital sampling system according to the present invention;
FIG. 7 is a flowchart illustrating a first embodiment of a digital sampling method according to the present invention;
fig. 8 is a flowchart illustrating a digital sampling method according to a second embodiment of the present invention.
The reference numbers illustrate:
the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as upper, lower, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the motion situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions in the embodiments may be combined with each other, but must be based on the realization of the technical solutions by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the technical solutions should be considered that the combination does not exist, and the technical solutions are not within the protection scope of the present invention.
Referring to fig. 2, fig. 2 is a schematic structural view of a fluxgate sensor according to a first embodiment of the present invention. A first embodiment of the fluxgate sensor of the present invention is proposed based on fig. 2.
In this embodiment, the fluxgate sensor includes: the excitation source generating circuit 10, the excitation source generating circuit 10 is provided with an external input interface;
the excitation source generating circuit 10 is connected to the controller through the external input interface, and the excitation source generating circuit 10 is further connected to an excitation winding in the fluxgate sensor.
It should be understood that in fig. 1, the fluxgate sensor generally includes a fixed-frequency oscillator, a power amplifier of a driving source, an exciting winding W1, a primary winding W2, a detecting winding W3, a compensating winding W4, a signal demodulation, an integration, a power amplification, and the like. Wherein the oscillator outputs an oscillating signal of a fixed frequency. Referring to fig. 3, when the fluxgate sensor collects a current signal, a start sampling time of the sampling signal may occur simultaneously with a rising edge of an excitation signal generated by an oscillation signal output by the oscillator, and the collected current signal may be interfered by the rising edge of the excitation signal, resulting in a great reduction in collection accuracy.
In the present embodiment, the excitation source generating circuit 10 is a circuit for generating an excitation signal. The signal frequency of the driving signal output from the stimulus generation circuit 10 can be adjusted within a certain range.
The excitation source generating circuit 10 includes an external input interface 101, the external input interface 101 can directly receive a signal input by the controller, and when the frequency or phase of the signal input by the controller changes, the frequency or phase of the excitation signal generated by the excitation source generating circuit 10 changes correspondingly.
In a specific implementation, the stimulus source generation circuit 10 may receive a stimulus source driving signal output by the controller through the external input interface 101; and then generating a corresponding excitation input signal according to the excitation source driving signal, outputting the excitation input signal to the excitation winding, and exciting the excitation winding.
The excitation source driving signal is generated by a controller, the sampling frequency is an integral multiple relation between the driving frequency of the excitation source driving signal and the sampling frequency of the sampling signal, and the phase difference between the excitation source driving signal and the sampling signal is inversely proportional to the integral multiple. The stimulus source drive signal may be used to drive the stimulus source generation circuit 10 such that the stimulus source generation circuit 10 outputs a corresponding stimulus signal. The excitation source drive signal and the excitation signal are both PWM signals. The excitation signal is the same frequency and phase as the excitation source drive signal.
The present embodiment provides a fluxgate sensor comprising: the excitation source generating circuit is provided with an external input interface; the excitation source generating circuit is connected with the controller through the external input interface and is also connected with an excitation winding in the fluxgate sensor; the excitation source generating circuit is used for receiving the excitation source driving signal output by the controller; the excitation source generating circuit is further configured to generate a corresponding excitation input signal according to the excitation source driving signal, output the excitation input signal to the excitation winding, and excite the excitation winding. In the embodiment, the external input interface and the excitation source generating circuit are arranged in the fluxgate sensor, and the excitation source generating circuit is used for generating the excitation signal according to the externally input excitation source driving signal, so that the excitation signal is adjusted, the interference of the excitation signal in the sampling process is avoided, and the acquisition precision is improved.
A second embodiment of the fluxgate sensor of the present invention is proposed based on the first embodiment of the fluxgate sensor described above.
Referring to fig. 4, in the present embodiment, the excitation source generating circuit 10 includes: the circuit comprises first to second diodes, first to second switching tubes, a first capacitor C1 and first to second resistors;
the anode of the first diode D1 is connected with the positive output end PWM + of the driving signal of the controller excitation source, the cathode of the first diode D1 is connected with the control end of the first switch tube Q1, the input end of the first switch tube Q1 is connected with the positive power supply + VCC, the output end of the first switch tube Q1 is connected with the first end of the first resistor R1, the second end of the first resistor R1 is connected with the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected with the primary winding;
the positive pole of second diode D1 with controller excitation source drive signal's negative pole output PWM-is connected, the negative pole of second diode D1 with second switch tube Q2's control end is connected, second switch tube Q2's input is connected with negative power supply VCC, second switch tube Q2's output with the first end of second resistance R2 is connected, the second end of second resistance R2 with the first end of first electric capacity C1 is connected.
It should be understood that the excitation signal received by the excitation winding needs to include a forward voltage and a reverse voltage that are switched with each other to form a magnetic flux change on the excitation winding, and thus the forward voltage and the reverse voltage are required in forming the excitation signal.
Note that the positive power supply + VCC is a power supply for outputting a positive voltage, and the negative power supply-VCC is a power supply for outputting a negative voltage. The controller can output PWM signals with opposite phases through two different interfaces, so that the positive power supply + VCC and the negative power supply-VCC are controlled to output corresponding voltages at respective corresponding moments. The first switch tube Q1 and the second switch tube Q2 are on-off devices with control ends, such as a controllable switch, a triode, a MOS transistor, and the like.
In one embodiment, the controller may output a PWM signal from the positive output terminal and a PWM signal from the negative output terminal having the same frequency and amplitude but completely opposite phase. When the first PWM signal is in a high level state, the first switching tube Q1 can be controlled to be turned on, and at this time, the positive power supply + VCC can output a positive voltage to the excitation winding through the first switching tube Q1 and the first resistor R1. When the second PWM signal is in a high level state, the second switch Q2 can be controlled to be turned on, and the negative power supply-VCC can output a negative voltage to the excitation winding through the second switch Q2 and the second resistor R2.
In addition, the first diode D1 and the second diode D2 can prevent the positive voltage or the negative voltage output by the positive power supply + VCC or the negative power supply-VCC from flowing back to the controller, so as to protect the controller.
Further, referring to fig. 1 and 2, in the present embodiment, the fluxgate sensor further includes: a signal demodulation circuit;
the signal demodulation circuit is respectively connected with the controller and the detection winding W3 in the fluxgate sensor.
It should be understood that the magnetic field signal output through the detection winding W3 needs to be demodulated to obtain a corresponding current signal. The signal demodulation circuit is a circuit for demodulating a magnetic field signal. In this embodiment, the signal demodulation circuit is further connected to the PI integration and power amplification device, so as to output a more accurate current signal.
It should be noted that, when the fluxgate sensor collects a current signal, after the electromagnetic changes of the primary winding W2, the excitation winding W1, etc., a certain phase difference may exist between an actual current signal demodulated by the signal demodulation circuit and a theoretically output current signal, so that the collected current signal is inaccurate.
It is emphasized that the signal demodulation circuit of fig. 1 is used to demodulate the excitation output signal output by the detection winding W3, and does not need to establish a connection with the controller. The signal demodulation circuit in this embodiment, i.e. the signal demodulation circuit in fig. 2, is also connected to the controller, and can receive the reference signal input by the controller. The reference signal may be used to determine whether the phase of the excitation output signal output by the detection winding is disturbed. The reference signal may be a PWM signal corresponding to a double frequency stimulus drive signal of the stimulus drive signal.
In order to avoid the occurrence of phase deviation of the current signal, in this embodiment, the controller may further output a reference signal to the signal demodulation circuit; the signal demodulation circuit superposes and demodulates the external current magnetic field signal output by the detection winding and the excitation signal to obtain a second harmonic signal; then comparing the second harmonic signal with the reference signal to obtain a phase difference between the second harmonic signal and the reference signal, and feeding the phase difference back to the controller; the controller may further adjust the excitation source driving signal according to the phase difference, so that the second harmonic signal output by the signal demodulation circuit has the same phase as the excitation signal.
The second harmonic signal is a harmonic signal obtained by superposing an external current magnetic field signal and an excitation signal. The second harmonic signal is subjected to PI integration and power amplification to obtain an acquired current signal. The reference signal is a signal output by the controller for determining whether or not a phase change occurs in the demodulated second harmonic signal. The reference signal may be a PWM signal that is a double frequency of the excitation source drive signal.
The fluxgate sensor further includes: a third diode D3 and a third switching tube Q3;
the anode of the third diode D3 is connected to the controller, the cathode of the third diode D3 is connected to the control end of the third switching tube Q3, and the input end and the output end of the third switching tube Q3 are both connected to the signal demodulation circuit.
Referring to fig. 4, the controller may output a PWM signal through the reference signal output terminal CLK-IN to control the on/off state of the third switching tube Q3, so that the frequency-multiplied PWM signal is input to the demodulation circuit as a reference signal.
In the embodiment, the external input interface and the excitation source generating circuit are arranged in the fluxgate sensor, and the excitation source generating circuit is used for generating the excitation signal according to the externally input excitation source driving signal, so that the excitation signal is adjusted, the interference of the excitation signal in the sampling process is avoided, and the acquisition precision is improved. In addition, the signal demodulation circuit is connected with the controller, and the driving signal of the excitation source can be adjusted through the phase difference between the reference signal and the second harmonic, so that the interference of the excitation signal in the sampling process can be more accurately avoided.
To achieve the above object, the present invention also provides a digital sampling system, including: the fluxgate sensor comprises a controller 400, a sampling chip 300, a signal conditioning circuit 200 and the fluxgate sensor 100;
the controller 400 is respectively connected with the sampling chip 300 and the excitation source generating circuit 10 in the fluxgate sensor 100, and the sampling chip 300 is connected with the fluxgate sensor 100 through the signal conditioning circuit 200;
the controller 400 is configured to generate a sampling signal and an excitation source driving signal, send the sampling signal to the sampling chip 300, and send the excitation source driving signal to the excitation source generating circuit; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple;
the sampling chip 300 is configured to output a current signal to the fluxgate sensor according to the sampling signal when receiving the sampling signal.
It should be noted that the controller 400 is a device for controlling processes of signal acquisition, excitation, and the like of the fluxgate sensor 100. The controller 400 may be composed of an FPGA or other control chip having the same function. The stimulus source generation circuit 10 is a circuit for generating a stimulus source. The stimulus generation circuit 10 may output different stimulus signals depending on the input drive signal. The excitation source generating circuit 10 may be connected to the controller 400 through an excitation source control interface to receive the driving signal output by the controller 400. Wherein, the signal frequency of the driving signal output by the excitation source generating circuit 10 can be adjusted within a certain range. The sampling chip 300 is a chip for sampling according to a current signal output from the fluxgate sensor 100. The sampling chip 300 may be an ADC sampling chip. At the time corresponding to the sampling signal, the sampling chip 300 may output the current signal conditioned by the signal conditioning circuit 200, thereby completing the current sampling process. The signal conditioning circuit 200 is configured to condition the current signal output by the fluxgate sensor 100 into a corresponding voltage signal.
In a specific implementation, the controller 400 may generate a sampling signal and an excitation source driving signal when sampling is started, where a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, a phase difference between the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple, and then send the sampling signal to the sampling chip 300, and simultaneously send the excitation source driving signal to the excitation source generating circuit 10; the excitation source generating circuit 10 may generate a corresponding excitation signal according to the excitation source driving signal, and output the excitation signal to the excitation winding to excite the excitation winding; the sampling chip 300 may collect the current parameter output by the fluxgate sensor when receiving the sampling signal, where the sampling signal and the excitation signal may refer to fig. 6, and there is no mutual interference between the sampling signal and the excitation signal.
The sampling signal is a signal for controlling the fluxgate sensor 100 to collect current. The sampling signal is a high frequency PWM signal. In order to avoid that the excitation signal triggers simultaneously with the sampling signal, the signal frequencies and phases of the excitation signal and the sampling signal may be defined. In the process of generating the sampling signal and the excitation source driving signal, one signal can be generated firstly, and then the frequency and the phase of the other signal are adjusted by taking the signal generated firstly as a reference, so that the interference of the excitation signal to the sampling signal is avoided.
In this embodiment, a digital sampling system is provided, which includes: the controller 400, the fluxgate sensor 100, the signal conditioning circuit 200 and the sampling chip 300; the controller 400 is connected with a sampling chip 300 and an excitation source generating circuit in the fluxgate sensor 100, and the sampling chip is connected with the fluxgate sensor 100 through a signal conditioning circuit 200; the controller 400 is configured to generate a sampling signal and an excitation source driving signal when sampling is started, send the sampling signal to the sampling chip, and send the excitation source driving signal to the excitation source generating circuit; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple; and the sampling chip is used for outputting a current signal to the fluxgate sensor according to the sampling signal when receiving the sampling signal. In the invention, the frequency and phase relation of the sampling signal and the excitation signal is limited when the sampling signal and the excitation source driving signal are generated, so that the interference of the excitation signal does not exist at each sampling moment in the sampling process, and the acquisition precision is improved.
Based on the first embodiment of the digital sampling system described above, a second embodiment of the digital sampling system of the present invention is presented.
Referring to fig. 4 and 5, in the present embodiment, the digital sampling system further includes: an over-current detection circuit 500;
the over-current detection circuit 500 is respectively connected to the controller 400 and the primary winding W2 of the fluxgate sensor 100.
It should be understood that during the current collection process of the fluxgate sensor 100, there may be a case where the current input to the primary winding is too large, resulting in a current process in the fluxgate sensor 100, causing damage to the sensor.
Therefore, when the fluxgate sensor 100 collects the current, the current in the fluxgate sensor 100 may also be collected to ensure that the current inside the sensor is not too large to damage the sensor. Wherein the overcurrent detecting circuit 500 is a circuit for confirming a current value in the fluxgate sensor 100. When the current value is too large, the process detection circuit can output a corresponding overcurrent signal, so that the overcurrent state of the sensor is prompted.
In a specific implementation, the over-current detection circuit 500 may detect a current signal passing through the primary winding W2, and output an over-current signal to the controller 400 when a current value of the current signal is greater than a preset current value; the controller 400 outputs a sampling cut-off signal to the sampling chip when receiving the over-current signal; and when the sampling chip receives the sampling cut-off signal, the connection between the equipment to be detected and the primary winding W2 is disconnected.
In addition, the over-current detection circuit 500 may also directly output the over-current signal to control the indicator light on the fluxgate sensor 100 to light up, so as to indicate that the fluxgate sensor 100 is in the over-current state.
The over-current signal is a signal output by the over-current detection circuit 500 when the sensor is in an over-current state. The preset current value is a preset maximum current that the fluxgate sensor 100 can pass. The sampling cut-off signal is a signal for controlling the primary winding W2 of the fluxgate sensor 100 to be disconnected from the device to be detected.
Referring to fig. 4, in the present embodiment, the over-current detection circuit 500 includes: the third to sixth resistors, the fourth switching tube Q4 and the first comparator A1;
a first end of a third resistor R3 is connected to the primary winding W2, a second end of the third resistor R3 is connected to a first end of a fourth resistor R4 and a first end of a fifth resistor R5, a second end of the fourth resistor R4 is connected to a forward input end of the first comparator A1, a second end of the fifth resistor R5 is grounded GND, a reverse input end of the first comparator A1 is connected to a preset current source Vref, an output end of the first comparator A1 is connected to a control end of the fourth switching tube Q4, an input end of the fourth switching tube Q4 is connected to a first end of the sixth resistor R6, an output end of the fourth switching tube Q4 is grounded GND, and a second end of the sixth resistor R6 is connected to the controller 400.
Referring to fig. 4, the preset current source is a preset current source for providing a preset current value. After the current in the fluxgate sensor 100 is input to the positive input terminal of the first comparator A1 through the third to sixth resistors, the current value of the current signal is compared with the preset current value through the first comparator A1, when the current value of the current signal is greater than the preset current value, the first comparator A1 outputs a low level signal, the fourth switching tube Q4 is turned off, and the overcurrent terminal STATU of the controller 400 is not directly grounded and is in a high resistance state; when the current value of the current signal is smaller than the preset current value, the fourth switching tube Q4 is turned on, and the overcurrent end of the controller 400 is grounded through the sixth resistor R6 and is in a low level state. The controller 400 may determine whether the fluxgate sensor 100 is in the overcurrent state according to the state of the overcurrent pin, and control the fluxgate sensor 100 to stop operating in the overcurrent state. The controller 400 may also output the sampling signal or the sampling off signal through the sampling signal output terminal ADC.
Referring to fig. 7, fig. 7 is a flowchart illustrating a digital sampling method according to a first embodiment of the present invention; the present invention also provides a digital sampling method, which includes:
step S10: generating a sampling signal and an excitation source driving signal when starting sampling; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal from the excitation source driving signal is inversely proportional to the integer multiple;
step S20: outputting the excitation source driving signal to a fluxgate sensor so that the fluxgate sensor generates a corresponding excitation signal to excite the excitation winding;
step S30: and outputting the sampling signal to a sampling chip so that the sampling chip collects the current parameter output by the fluxgate sensor according to the sampling signal.
It should be understood that the fluxgate sensor generally includes a fixed frequency oscillator, a power amplifier of the excitation source, a winding, a signal demodulation, an integration, a power amplification, and so on. Wherein the oscillator outputs a PWM signal of a fixed frequency. When the fluxgate sensor collects the current signal, the inspiration sampling moment of the sampling signal may appear simultaneously with the rising edge of the PWM signal output by the oscillator, and the collected current signal may be interfered by the rising edge of the PWM signal, resulting in greatly reduced collection precision.
Note that, in this embodiment, a controller may be used as an execution main body. The controller is a device for controlling the processes of signal acquisition, excitation and the like of the fluxgate sensor. The controller can be composed of an FPGA or other control chips with the same functions.
The excitation source generating circuit in the fluxgate sensor is a circuit for generating an excitation source. The excitation source generating circuit can output different excitation signals according to different input driving signals. The excitation source generating circuit may be connected to the controller through an excitation source control interface to receive the driving signal output by the controller. The signal frequency of the driving signal output by the excitation source generating circuit can be adjusted within a certain range. The fluxgate sensor may include a primary winding, an excitation winding, a detection winding, a compensation winding, and a structure of an iron core. The sampling chip is a circuit used for collecting current signals of the fluxgate sensor.
In a specific implementation, the controller may generate a sampling signal and an excitation source driving signal when starting sampling, the sampling frequency of the sampling signal is an integer multiple of the driving frequency of the excitation source driving signal, and the phase difference between the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple, and then send the sampling signal to the sampling chip while sending the excitation source driving signal to the excitation source generating circuit; the excitation source generating circuit can generate a corresponding excitation signal according to the excitation source driving signal, output the excitation signal to the excitation winding and excite the excitation winding; the sampling chip can collect the current parameters output by the fluxgate sensor when receiving the sampling signal.
The sampling signal is a signal for controlling the sampling signal to collect the current output by the fluxgate sensor. The sampling signal is a high frequency PWM signal. The stimulus source drive signal may be used to drive the stimulus source generation circuit 10 such that the stimulus source generation circuit 10 outputs a corresponding stimulus signal. In order to avoid that the excitation signal triggers simultaneously with the sampling signal, the signal frequencies and phases of the excitation signal and the sampling signal may be defined. In the process of generating the sampling signal and the excitation source driving signal, one signal can be generated firstly, and then the frequency and the phase of the other signal are adjusted by taking the signal generated firstly as a reference, so that the interference of the excitation signal to the sampling signal is avoided.
Generating a sampling signal and an excitation source driving signal when starting sampling, and specifically comprising the following steps: and when sampling is started, generating a sampling signal according to the sampling requirement. And acquiring an initial excitation source driving signal, and adjusting the initial excitation source driving signal according to the frequency and the phase of the sampling signal to generate an excitation source driving signal.
It will be appreciated that the sampling requirement is a condition of the current sampling setting of the fluxgate sensor. The sampling requirements may include sampling frequency, sampling time, and the like. In determining the sampling requirement, the controller may generate a corresponding sampling signal according to the sampling requirement.
It should be noted that the initial excitation source driving signal is a frequency and phase adjustment-free driving signal. Interference may exist between the excitation signal generated by the initial excitation source driving signal through the excitation source generating circuit and the sampling signal.
In a specific implementation, after the sampling signal is confirmed, the initial excitation source driving signal is adjusted by taking the sampling signal as a reference to generate a corresponding excitation source driving signal; of course, when determining the excitation source driving signal, the corresponding sampling signal may be generated by adjusting the excitation source driving signal as a reference. Since the adjustment of the excitation source driving signal and the sampling signal are both in a small range, the adjustment mode can be determined according to the specific adjustment range during specific adjustment.
The present embodiment provides a digital sampling method, including: generating a sampling signal and an excitation source driving signal when starting sampling; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple; outputting the excitation source driving signal to a fluxgate sensor so that the fluxgate sensor generates a corresponding excitation signal to excite the excitation winding; and outputting the sampling signal to a sampling chip so that the sampling chip collects the current parameter output by the fluxgate sensor according to the sampling signal. In the invention, the frequency and phase relation of the sampling signal and the excitation signal is limited when the sampling signal and the excitation source driving signal are generated, so that the interference of the excitation signal does not exist at each sampling moment in the sampling process, and the acquisition precision is improved.
Referring to fig. 8, fig. 8 is a flow chart of a digital sampling method according to a second embodiment of the present invention; a second embodiment of the digital sampling method of the present invention is proposed based on the above-described first embodiment.
In this embodiment, after the step S30, the method further includes:
step S40: generating a reference signal according to the excitation source driving signal;
step S50: outputting the reference signal to a signal demodulation circuit in the fluxgate sensor, so that the signal demodulation circuit compares a second harmonic signal with the reference signal and feeds back a phase difference;
step S60: adjusting the excitation source drive signal according to the phase difference.
It should be understood that the magnetic field signal output by the sensing winding needs to be demodulated to obtain a corresponding current signal. The signal demodulation circuit is a circuit for demodulating a magnetic field signal. In this embodiment, the signal demodulation circuit is further connected to the PI integration and power amplification device, so as to output a more accurate current signal.
It should be noted that, when the fluxgate sensor collects a current signal, after electromagnetic changes of the primary winding, the excitation winding, and the like, a certain phase difference may exist between an actual current signal demodulated by the signal demodulation circuit and a theoretically output current signal, so that the collected current signal is inaccurate.
In order to avoid the occurrence of phase deviation of the current signal, in this embodiment, the controller may further output a reference signal to the signal demodulation circuit; the signal demodulation circuit superposes and demodulates the external current magnetic field signal output by the detection winding and the excitation signal to obtain a second harmonic signal; then comparing the second harmonic signal with the reference signal to obtain a phase difference between the second harmonic signal and the reference signal, and feeding the phase difference back to the controller; the controller may further adjust the excitation source driving signal according to the phase difference, so that the second harmonic signal output by the signal demodulation circuit has the same phase as the excitation signal.
The second harmonic signal is a harmonic signal obtained by superposing an external current magnetic field signal and an excitation signal. The second harmonic signal is subjected to PI integration and power amplification to obtain an acquired current signal. The reference signal is a signal output by the controller for determining whether or not a phase change occurs in the demodulated second harmonic signal. The reference signal may be a PWM signal that is a double frequency of the excitation source drive signal.
In this embodiment, step S60 is followed by:
step S70: a current signal through the primary winding is detected.
Step S80: and when the current value of the current signal is greater than a preset current value, disconnecting the device to be detected from the fluxgate sensor.
It should be understood that, during the current collection process of the fluxgate sensor, there may be a situation that the current input to the primary winding is too large, which causes the current in the fluxgate sensor to be too large, and damages to the sensor.
Therefore, when the fluxgate sensor collects the current, the current in the fluxgate sensor can be collected, so that the sensor is ensured not to be damaged due to overlarge current in the sensor. The over-current detection circuit is a circuit for confirming a current value in the fluxgate sensor. When the current value is too large, the process detection circuit can output a corresponding over-current signal, so that the over-current state of the sensor is prompted.
In a specific implementation, the over-current detection circuit may detect a current signal passing through the primary winding, and output an over-current signal to the controller when a current value of the current signal is greater than a preset current value; the controller outputs a sampling cut-off signal to the sampling chip when receiving the overcurrent signal; and when the sampling chip receives the sampling cut-off signal, the connection between the equipment to be detected and the primary winding is disconnected.
In addition, the overcurrent detection circuit can also directly output the overcurrent signal to control the indicator light on the fluxgate sensor to be lightened, so that the fluxgate sensor is indicated in an overcurrent state.
The over-current signal is a signal output by the over-current detection circuit when the sensor is in an over-current state. The preset current value is the maximum current which can be passed by the preset fluxgate sensor. The sampling cut-off signal is a signal for controlling the disconnection between the primary winding in the sensor and the equipment to be detected.
In addition, in order to achieve the above object, the present invention further provides a controller, wherein the controller is connected to the sampling chip and the fluxgate sensor;
the controller is used for implementing the digital sampling method. Because the digital sampling methods all use the controller as an execution main body, the controller can realize the digital sampling method and has the corresponding beneficial effects of the digital sampling method.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A fluxgate sensor characterized in that the fluxgate sensor comprises: the excitation source generating circuit is provided with an external input interface;
the excitation source generating circuit is connected with the controller through the external input interface and is also connected with an excitation winding in the fluxgate sensor;
the excitation source generating circuit is used for receiving the excitation source driving signal output by the controller;
the excitation source generating circuit is further configured to generate a corresponding excitation input signal according to the excitation source driving signal, output the excitation input signal to the excitation winding, and excite the excitation winding.
2. The fluxgate sensor according to claim 1, wherein the excitation source generating circuit comprises: the first to the second diodes, the first to the second switch tubes, the first capacitor and the first to the second resistors;
the anode of the first diode is connected with the positive output end of the driving signal of the controller excitation source, the cathode of the first diode is connected with the control end of a first switch tube, the input end of the first switch tube is connected with a positive power supply, the output end of the first switch tube is connected with the first end of a first resistor, the second end of the first resistor is connected with the first end of a first capacitor, and the second end of the first capacitor is connected with the excitation winding;
the anode of the second diode is connected with the cathode output end of the driving signal of the controller excitation source, the cathode of the second diode is connected with the control end of the second switch tube, the input end of the second switch tube is connected with the negative power supply, the output end of the second switch tube is connected with the first end of the second resistor, and the second end of the second resistor is connected with the first end of the first capacitor.
3. The fluxgate sensor according to claim 1, wherein the fluxgate sensor further comprises: a signal demodulation circuit;
the signal demodulation circuit is respectively connected with the controller and a detection winding in the fluxgate sensor;
the signal demodulation circuit is used for receiving a reference signal output by the controller and an excitation output signal output by the detection winding;
the signal demodulation circuit is further configured to compare the excitation output signal with the reference signal to obtain a phase difference, and feed back the phase difference to the controller, so that the controller adjusts the excitation source driving signal according to the phase difference.
4. The fluxgate sensor of claim 3, wherein the fluxgate sensor further comprises: a third diode and a third switching tube;
the anode of the third diode is connected with the controller, the cathode of the third diode is connected with the control end of the third switching tube, and the input end and the output end of the third switching tube are both connected with the signal demodulation circuit.
5. A digital sampling system, comprising: a controller, a sampling chip, a signal conditioning circuit and the fluxgate sensor of any one of claims 1 to 4;
the controller is respectively connected with the sampling chip and an excitation source generating circuit in the fluxgate sensor, and the sampling chip is connected with the fluxgate sensor through a signal conditioning circuit;
the controller is used for generating a sampling signal and an excitation source driving signal, sending the sampling signal to the sampling chip and sending the excitation source driving signal to the excitation source generating circuit; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple;
and the sampling chip is used for outputting a current signal to the fluxgate sensor according to the sampling signal when receiving the sampling signal.
6. The digital sampling system of claim 5, further comprising: an overcurrent detection circuit;
the overcurrent detection circuit is respectively connected with the controller and a primary winding of the fluxgate sensor;
the overcurrent detection circuit is used for detecting a current signal passing through the primary winding and outputting an overcurrent signal to the controller when the current value of the current signal is greater than a preset current value;
the controller is further configured to stop outputting the sampling signal to the sampling chip when receiving the over-current signal.
7. The digital sampling system of claim 6, wherein the over-current detection circuit comprises: the third resistor, the fourth resistor, the sixth resistor, the fourth switch tube and the first comparator;
the first end of the third resistor is connected with the primary winding, the second end of the third resistor is connected with the first end of the fourth resistor and the first end of the fifth resistor, the second end of the fourth resistor is connected with the positive input end of the first comparator, the second end of the fifth resistor is grounded, the reverse input end of the first comparator is connected with a preset current source, the output end of the first comparator is connected with the control end of the fourth switching tube, the input end of the fourth switching tube is connected with the first end of the sixth resistor, the output end of the fourth switching tube is grounded, and the second end of the sixth resistor is connected with the controller.
8. A digital sampling method for use in a controller in a digital sampling system, the digital sampling method comprising:
generating a sampling signal and an excitation source driving signal when starting sampling; wherein a sampling frequency of the sampling signal is an integer multiple of a driving frequency of the excitation source driving signal, and a phase difference of the sampling signal and the excitation source driving signal is inversely proportional to the integer multiple;
outputting the excitation source driving signal to a fluxgate sensor so that the fluxgate sensor generates a corresponding excitation signal to excite the excitation winding;
and outputting the sampling signal to a sampling chip so that the sampling chip collects the current parameter output by the fluxgate sensor according to the sampling signal.
9. The digital sampling method according to claim 8, wherein after the step of outputting the sampling signal to a sampling chip so that the sampling chip collects the current parameter output by the fluxgate sensor according to the sampling signal, the method further comprises:
generating a reference signal according to the excitation source driving signal;
outputting the reference signal to a signal demodulation circuit in the fluxgate sensor, so that the signal demodulation circuit compares a second harmonic signal with the reference signal and feeds back a phase difference; the second harmonic signal is a signal obtained by superposing and demodulating an external current magnetic field signal output by a detection winding and the excitation signal;
adjusting the excitation source drive signal according to the phase difference;
detecting a current signal through the primary winding;
and when the current value of the current signal is greater than a preset current value, disconnecting the connection between the equipment to be detected and the fluxgate sensor.
10. The controller is characterized in that the controller is connected with a sampling chip and a fluxgate sensor;
the controller is used for implementing the digital sampling method of any one of claims 8 to 9.
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| CN202211668969.7A CN115951276A (en) | 2022-12-23 | 2022-12-23 | Fluxgate sensor, digital sampling system, digital sampling method and controller |
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