CN114719730A - Automatic calibration inductance displacement sensor detection circuit - Google Patents
Automatic calibration inductance displacement sensor detection circuit Download PDFInfo
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- CN114719730A CN114719730A CN202210235452.2A CN202210235452A CN114719730A CN 114719730 A CN114719730 A CN 114719730A CN 202210235452 A CN202210235452 A CN 202210235452A CN 114719730 A CN114719730 A CN 114719730A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
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Abstract
The invention discloses a detection circuit for automatically calibrating an inductance displacement sensor, which is used for detecting the inductance displacement sensor and comprises a controlled excitation source, a built-in coil of the inductance displacement sensor to be detected is equivalent to an internal resistance rc and an inductance L which are connected in series, the controlled excitation source is controlled by a control and operation unit and is simultaneously connected with the inductance displacement sensor to be detected, a standard resistance and an amplifier A3, and the other end of the inductance displacement sensor is simultaneously connected with a switch I and a switch II; the other end of the standard resistor is connected to the first switch and the second switch at the same time; the output of the first switch is connected, and the other end of the sampling resistor and the output end of the amplifier A1 are connected with the amplifier A1; the switch I is connected with the negative input end of the amplifier A2; the output end of the amplifier A1 is connected with the positive input end of the amplifier A2; the output terminal SB of the switch II is connected with the negative input end of the amplifier A3; the output end of the amplifier A2 is connected to the control and operation unit; the output of the amplifier a3 is connected to the control and arithmetic unit.
Description
Technical Field
The invention relates to the technical field of inductive displacement sensors, in particular to a detection circuit for automatically calibrating an inductive displacement sensor.
Background
In order to meet the use requirements under severe environment, various detection technologies are successively developed by inductive proximity sensor suppliers, wherein the detection technologies comprise a pulse charging and discharging detection circuit based on a time domain; a low-frequency oscillating circuit based on differential coil compensation; impedance analysis circuitry based on the frequency domain. However, these sensors and their detection circuits can only be calibrated before the product leaves the factory, and once a certain component is changed in performance state during use, the detection circuit cannot automatically complete compensation, which eventually results in performance degradation and even function loss in the application link. The maintenance personnel can not determine the fault position quickly and accurately even, and can only detect and calibrate the equipment regularly, which brings great inconvenience to the maintenance and guarantee link.
Although calibration can be achieved by simply introducing a switching circuit into the circuit, the switches used are of the relay mechanical contact type and also of the analog switch electronic contact type. The mechanical contact switch has the reliability problems of contact arc noise, poor contact and the like after the working frequency is increased; the analog switch electronic contact has on-resistance which has large dispersity and large uncertain temperature drift, and uncertain factors can be introduced into a measuring loop, so that the significance of calibration is lost.
Disclosure of Invention
The invention aims to: the automatic calibration inductive displacement sensor detection circuit can be used for detecting an inductive displacement sensor.
In order to achieve the purpose, the invention adopts the following technical scheme:
a detection circuit for automatically calibrating an inductance displacement sensor comprises a controlled excitation source, a built-in coil of the inductance displacement sensor to be detected, a standard resistor, a first switch, a second switch, a sampling resistor, an amplifier A1, an amplifier A2, an amplifier A3 and a control and operation unit, wherein the built-in coil of the inductance displacement sensor to be detected is equivalent to an internal resistance rc and an inductance L which are connected in series, the controlled excitation source is controlled by the control and operation unit and is simultaneously connected with the inductance displacement sensor to be detected, the standard resistor and a positive input end of the amplifier A3, and the other end of the inductance displacement sensor is simultaneously connected with an SA1 terminal of the first switch and an SB1 terminal of the second switch; the other end of the standard resistor is simultaneously connected to the SA2 terminal of the first switch and the SB2 terminal of the second switch; an output terminal SA of the first switch is connected with a negative input end of a sampling resistor and an amplifier A1, and the other end of the sampling resistor is connected with an output end of an amplifier A1; the output terminal SA of the first switch is connected with the negative input end of an amplifier A2; the output end of the amplifier A1 is connected with the positive input end of an amplifier A2; the output terminal SB of the second switch is connected with the negative input end of the amplifier A3; the output end of the amplifier A2 is connected to a control and operation unit; the amplifier a3 output is connected to a control and arithmetic unit.
On the basis of the above scheme and as a preferable scheme of the scheme: the control and operation unit is a digital signal processor DSP, a singlechip MCU, a programmable logic device CPLD/FPGA, a RISC microprocessor ARM, a hardware multiplier and a divider.
On the basis of the above scheme and as a preferable scheme of the scheme: the controlled excitation source is an oscillator circuit, a digital signal processor DSP, a single chip microcomputer MCU, a single chip digital frequency synthesis chip DDS, a programmable logic device CPLD/FPGA and a RISC microprocessor ARM.
On the basis of the above scheme and as a preferable scheme of the scheme: the amplifiers a1, a2, and A3 are dedicated amplifiers, amplifier circuits each formed by combining independent operational amplifiers, and amplifier circuits each formed by combining discrete semiconductors.
On the basis of the above scheme and as a preferable scheme of the scheme: the first switch and the second switch are switch circuits which are realized by an analog multiplexer, a single-channel analog switch, a multi-channel analog switch, a relay and various switches.
The invention has the beneficial effects that: the detection circuit for automatically calibrating the inductive displacement sensor can be used for detecting the inductive displacement sensor, can implement calibration steps before measurement by building a simple circuit and a reasonably designed signal extraction and calibration method, improves the precision of the detection circuit, and can effectively solve the problem that the existing detection technology cannot accurately isolate the inductive displacement sensor and the detection circuit. Meanwhile, a synchronous fully differential structure can be adopted, so that the problems of switch contact and uncertain influence of on-resistance are avoided.
Drawings
FIG. 1 is a schematic diagram of a detection circuit and a detection method according to the present invention;
FIG. 2 is an auto-calibration equivalent schematic of the present invention;
fig. 3 is an equivalent schematic diagram of the inductive displacement sensor of the present invention.
In the figure:
the device comprises a controlled excitation source-1, an inductive displacement sensor-2, a standard resistor-3, a switch I-4, a switch II-5, a sampling resistor-6, a control and operation unit-7, an amplifier-A1, an amplifier-A2 and an amplifier-A3.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings, 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.
Referring to fig. 1-3, a detection circuit for automatically calibrating an inductance displacement sensor is shown in fig. 1, and includes a controlled excitation source 1, a built-in coil of an inductance displacement sensor 2 to be measured, which is equivalent to series connection of an internal resistance rc and an inductance L, a standard resistor 3, a switch one 4, a switch two 5, a sampling resistor 6, an amplifier a1, an amplifier a2, an amplifier A3, and a control and operation unit 7, wherein the controlled excitation source 1 is controlled by the control and operation unit 7 and is simultaneously connected to positive input ends of the inductance displacement sensor 2 to be measured, the standard resistor 3 and the amplifier A3, and the other end of the inductance displacement sensor 2 is simultaneously connected to an SA1 terminal of the switch one 4 and an SB1 terminal of the switch two 5; the other end of the standard resistor 3 is connected to the SA2 terminal of the switch I4 and the SB2 terminal of the switch II 5 simultaneously; an output terminal SA of the first switch 4 is connected with a sampling resistor 6 and a negative input end of an amplifier A1, and the other end of the sampling resistor 6 is connected with an output end of an amplifier A1; the output terminal SA of the first switch 4 is connected with the negative input end of an amplifier A2; the output end of the amplifier A1 is connected with the positive input end of an amplifier A2; the output terminal SB of the second switch 5 is connected with the negative input end of the amplifier A3; the output end of the amplifier A2 is connected to a control and operation unit; the amplifier a3 output is connected to a control and arithmetic unit.
The control and operation unit is a digital signal processor DSP, a single chip microcomputer MCU, a programmable logic device CPLD/FPGA, a RISC microprocessor ARM, a hardware multiplier and a divider.
The controlled excitation source is an oscillator circuit, a digital signal processor DSP, a single chip microcomputer MCU, a single chip digital frequency synthesis chip DDS, a programmable logic device CPLD/FPGA and a RISC microprocessor ARM.
The amplifiers a1, a2, and A3 are dedicated amplifiers, amplifier circuits each formed by combining independent operational amplifiers, and amplifier circuits each formed by combining discrete semiconductors.
The first switch and the second switch are switch circuits which are realized by an analog multiplexer, a single-channel analog switch, a multi-channel analog switch, a relay and various switches.
The application and working method of the detection circuit for the automatic calibration inductive displacement sensor comprises the following steps:
(1) the control and operation unit controls the controlled excitation source to output a periodic signal of the excitation test circuit;
(2) the control and operation unit controls the connection of a terminal SA2 of the first switch and the terminal SA, and at the same time, the control unit controls the connection of a terminal SB2 of the second switch and the terminal SB so as to connect the standard resistor into the measuring loop;
(3) the amplifier A2 extracts the differential voltage at the two ends of the sampling resistor and outputs a voltage Us, and at the same moment, the amplifier A3 extracts the differential voltage at the two ends of the calibration resistor and outputs a voltage Uz;
(4) the control and operation unit synchronously samples Us and Uz in the step (3) for n times according to a certain sampling interval delta t and filters the sampled Us and Uz to obtain two signal sequences (Us, delta t, n), (Uz, delta t, n);
(5) the control and operation unit operates the two signal sequences in the step (4) to obtain a calculated value of the standard resistor;
(6) the control and operation unit compares the calculated value in the step (5) with the rated value of the standard resistor to obtain a gain coefficient Ks of the measurement loop;
(7) the control and arithmetic unit controls the first switch to be connected to the terminal SA 1. At the same time, the control unit controls a terminal SB1 of the second switch to be connected with the terminal SB, and the inductance displacement sensor to be measured is connected into the measurement loop;
(8) the amplifier A2 extracts the differential voltage of the two ends of the sampling resistor, the output voltage Us 'is at the same time, the amplifier A3 extracts the differential voltage of the two ends of the inductance displacement sensor to be detected, and the output voltage Uz';
(9) the control and operation unit synchronously samples Us 'and Uz' in the step (8) for n times according to a certain sampling interval delta t and filters the samples to obtain two signal sequences (Us ', delta t, n), (Uz', delta t, n);
(10) and (4) controlling and calculating the two signal sequences in the step (9) to obtain an impedance calculation value of the inductive displacement sensor, and calibrating according to the gain coefficient Ks in the step (6) to obtain the impedance of the inductive displacement sensor.
Further, the steps (1) to (10) are repeated continuously, and the periodic automatic calibration, the impedance measurement and the fault diagnosis isolation are completed.
The method for completing the periodic automatic calibration, the impedance measurement and the fault diagnosis isolation comprises the following steps that in the step (6), when the gain coefficient Ks exceeds a preset reasonable distribution range, a fault of the test circuit is reported, the current-period measurement is terminated, and the self-test function of the test circuit is realized; when the gain coefficient Ks is distributed in a preset range, the test circuit is normal, and the next measurement is carried out;
in the step (10), the impedance of the calibrated inductance displacement sensor is compared with a preset reasonable distribution range. When the calculated value exceeds a preset reasonable distribution range, reporting the fault of the inductive displacement sensor; when the current period measurement is ended, the health test function of the inductive displacement sensor is realized;
in the step (10), the impedance of the inductance displacement sensor is calibrated to obtain the corresponding relation between the impedance and the displacement of the inductance displacement sensor, a lookup table is established, after the impedance measurement of the inductance displacement sensor is completed, the current displacement state of the inductance displacement sensor is obtained through the lookup table, and quantitative displacement information is output.
The measurement principle of the invention is as shown in fig. 1, controlling and calculating the conduction of SA2 of the switch 1 and the SA terminal through the CT terminal of the switch, and connecting the standard resistor Ra into the measurement loop. While SB2 of switch 2 is conductive with the SB terminal. The equivalent circuit of the measuring loop is shown in fig. 2.
The control and operation unit controls the controlled excitation source OSC to output an excitation signal. Similarly, the current Iz flowing through the standard resistor Ra and the switch on-resistance rw1 and the current Is flowing through the standard resistor Rs satisfy the following relationship:
Iz＝Is
is flows through a sampling resistor Rs and Is differentiated to Us by an amplifier A2. Iz flows through the standard resistor Ra, and under the action of the switch 2, the amplifier a3 only differentiates the standard resistor Ra to obtain a differential voltage Uz, and at this time, the on-resistance rw1 of the switch 1 is isolated out of the amplifier differential loop. It has been described above that the amplifier input leakage current is negligible small, the current consumed at the on-resistance rw2 of the switch 2 is negligible, and by designing the switching circuit, the influence of the switch on-resistance is isolated, so Us, Uz satisfy the following relationship:
the calculated value of the standard resistance Ra is obtained through finishing:
assuming that the rated resistance value of the standard resistor Ra is Re, the gain coefficient Ks of the measuring loop is obtained as follows:
uz and Us in the formula are obtained by sampling and are known quantities; the standard resistance Rs is a known quantity, and the standard resistance rated value Re is a known quantity; it is obvious from the above derivation that the on-resistance rw1 of the switch 1 and the on-resistance rw2 of the switch 2 are unknown quantities, but do not participate in the measurement and calculation of the calibration link, so that the influence of the on-resistance is avoided, and the obtained gain coefficient Ks is determined and reliable. Judging the health state of the detection circuit according to the size of the Ks, judging the fault of the detection circuit once the Ks exceeds a reasonable distribution range, and stopping the measurement of the current period; if the Ks is distributed in a reasonable range, the detection circuit is judged to be normal, and the measurement is continued.
The control and operation unit controls the A1 of the switch 1 to be conducted with the SA terminal through the CT terminal of the switch, and the inductance displacement sensor to be measured is connected into the measurement loop. While SB1 of switch 2 is conductive with the SB terminal. The equivalent circuit of the measurement loop is shown in fig. 3.
As described above
Iz'＝Is'
The amplifier A2 obtains the differential voltage Us 'at the two ends of the sampling resistor Rs, the amplifier A3 obtains the differential voltage Uz' at the two ends of the inductance displacement sensor to be detected, and the following relations are satisfied:
the method comprises the following steps:
and according to the gain coefficient Ks obtained in the previous step, revising the measurement result:
uz 'and Us' in the formula are obtained by sampling and are known quantities; the sampling resistor Rs is a known quantity, and the standard resistor rated value Re is a known quantity; similarly, it can be clearly seen that the on-resistance rw1 'of the switch 1 and the on-resistance rw 2' of the switch 2 are unknown quantities, but do not participate in the measurement operation of the to-be-measured inductive displacement sensor. Calculating the impedance Z of the inductance displacement sensor to be measured according to the formulaLAnd final calibration is performed. And judging the health condition of the inductance displacement sensor to be measured according to the calibration result. When Z isLExceeding the reasonable distribution range, judging the fault of the inductive displacement sensor, and when Z isLWhen distributed in a reasonable range according to ZLAnd judging the displacement state of the target according to the size of the displacement, and finishing displacement detection.
The invention provides a detection circuit for automatically calibrating an inductive displacement sensor and a detection method thereof, which are characterized in that a simple circuit is built, a signal extraction and calibration method with reasonable design is adopted, and a calibration step is carried out before measurement, so that the precision of the detection circuit is improved, and the problem that the existing detection technology cannot accurately isolate the inductive displacement sensor and the detection circuit from faults is effectively solved. Meanwhile, due to the adoption of a synchronous fully differential structure, the problems of switch contact and uncertain influence of on-resistance are avoided.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (5)
1. An automatic calibration inductance displacement sensor detection circuit which characterized in that: the device comprises a controlled excitation source (1), a built-in coil of an inductance displacement sensor (2) to be tested, a standard resistor (3), a switch I (4), a switch II (5), a sampling resistor (6), an amplifier A1, an amplifier A2, an amplifier A3 and a control and operation unit (7), wherein the built-in coil is equivalent to an internal resistance rc and an inductance L which are connected in series, the controlled excitation source (1) is controlled by the control and operation unit (7) and is simultaneously connected with positive input ends of the inductance displacement sensor (2) to be tested, the standard resistor (3) and the amplifier A3, and the other end of the inductance displacement sensor (2) is simultaneously connected with an SA1 terminal of the switch I (4) and an SB1 terminal of the switch II (5); the other end of the standard resistor (3) is simultaneously connected to the SA2 terminal of the switch I (4) and the SB2 terminal of the switch II (5); an output terminal SA of the first switch (4) is connected with a sampling resistor (6) and a negative input end of an amplifier A1, and the other end of the sampling resistor (6) is connected with an output end of an amplifier A1; the output terminal SA of the first switch (4) is connected with the negative input end of an amplifier A2; the output end of the amplifier A1 is connected with the positive input end of an amplifier A2; the output terminal SB of the second switch (5) is connected with the negative input end of the amplifier A3; the output end of the amplifier A2 is connected to a control and operation unit; the amplifier a3 output is connected to a control and arithmetic unit.
2. The self-calibrating inductive displacement sensor detection circuit of claim 1, wherein: the control and operation unit is a digital signal processor DSP, a singlechip MCU, a programmable logic device CPLD/FPGA, a RISC microprocessor ARM, a hardware multiplier and a divider.
3. The self-calibrating inductive displacement sensor detection circuit of claim 1, wherein: the controlled excitation source is an oscillator circuit, a digital signal processor DSP, a single chip microcomputer MCU, a single chip digital frequency synthesis chip DDS, a programmable logic device CPLD/FPGA and a RISC microprocessor ARM.
4. The self-calibrating inductive displacement sensor detection circuit of claim 1, wherein: the amplifiers a1, a2, and A3 are dedicated amplifiers, amplifier circuits each formed by combining independent operational amplifiers, and amplifier circuits each formed by combining discrete semiconductors.
5. The self-calibrating inductive displacement sensor detection circuit of claim 1, wherein: the first switch and the second switch are switch circuits which are realized by an analog multiplexer, a single-channel analog switch, a multi-channel analog switch, a relay and various switches.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210235452.2A CN114719730A (en) | 2022-03-10 | 2022-03-10 | Automatic calibration inductance displacement sensor detection circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210235452.2A CN114719730A (en) | 2022-03-10 | 2022-03-10 | Automatic calibration inductance displacement sensor detection circuit |
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| CN114719730A true CN114719730A (en) | 2022-07-08 |
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| CN202210235452.2A Pending CN114719730A (en) | 2022-03-10 | 2022-03-10 | Automatic calibration inductance displacement sensor detection circuit |
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- 2022-03-10 CN CN202210235452.2A patent/CN114719730A/en active Pending
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