CN110006585B - Data acquisition device and method of pressure sensor - Google Patents
Data acquisition device and method of pressure sensor Download PDFInfo
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- CN110006585B CN110006585B CN201910370923.9A CN201910370923A CN110006585B CN 110006585 B CN110006585 B CN 110006585B CN 201910370923 A CN201910370923 A CN 201910370923A CN 110006585 B CN110006585 B CN 110006585B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
- G01L19/08—Means for indicating or recording, e.g. for remote indication
- G01L19/083—Means for indicating or recording, e.g. for remote indication electrical
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
- G05B19/0428—Safety, monitoring
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/26—Pc applications
- G05B2219/2612—Data acquisition interface
Abstract
The application aims to provide a data acquisition device and method of a pressure sensor, wherein the acquisition device comprises a power supply, a microprocessor, a digital-to-analog conversion circuit, a constant current source circuit, the pressure sensor and an analog-to-digital conversion circuit, and a stable voltage reference signal output by the digital-to-analog conversion circuit is determined as a reference voltage through the acquisition device; acquiring the voltage of a converted acquisition point from the analog-to-digital conversion circuit, wherein the acquisition point is a common connection point of the pressure sensor, the constant current source circuit and the analog-to-digital conversion circuit; and determining the current pressure value of the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage. Therefore, the voltage of the output signals of the pressure sensor in different pressure sections can be kept in a relatively stable range, and the data acquisition precision is high.
Description
Technical Field
The application relates to the field of pressure sensors, in particular to a data acquisition device and method of a pressure sensor.
Background
Sensor technology and communication technology, computer technology constitute three major posts of the modern information industry. Among them, sensor technology is a bottleneck industry that is behind relative to communication technology and computer technology. Traditional sensors are gradually eliminated because functions, characteristics, volumes and the like are difficult to meet the requirements of modern computer technology, communication technology on precision, reliability, weather resistance, information processing capability and the like. The film pressure sensor is a novel pressure sensor with excellent performance which is produced along with the development of film technology, adopts high-precision and printing technology, and has the excellent characteristics of high precision, wide working temperature range, good stability and the like. For data acquisition of the film sensor, a set of fixed parameter circuit is generally adopted at present to drive the film sensor, the range of variation of the output result range is larger, the precision is not easy to keep consistent, and the design of a later acquisition circuit is also more complex.
Disclosure of Invention
The application aims to provide a data acquisition device and method of a pressure sensor, which solve the problems of large output result range change, difficult consistency maintenance of precision, complex acquisition circuit design and complex calculation in the data acquisition of a film pressure sensor in the prior art.
According to an aspect of the present application, there is provided a data acquisition device of a pressure sensor, including:
a power supply;
the microprocessor is connected with the power supply;
the digital-to-analog conversion circuit is respectively connected with the microprocessor and the power supply;
the constant current source circuit is respectively connected with the digital-to-analog conversion circuit and the power supply;
the pressure sensor is respectively connected with the constant current source circuit and the power supply;
and the analog-to-digital conversion circuit is respectively connected with the pressure sensor, the microprocessor and the power supply.
Further, the digital-to-analog conversion circuit comprises a digital-to-analog converter and a filter circuit, wherein the digital-to-analog converter is connected with the filter circuit, and the filter circuit is connected with the constant current source circuit.
Further, the filter circuit comprises a first resistor and a first capacitor, wherein the first resistor is respectively connected with the digital-to-analog converter and the first capacitor, and one end of the first capacitor is grounded.
Further, the constant current source circuit includes:
the operational amplifier is connected with the filter circuit;
the field effect tube is respectively connected with the operational amplifier and the pressure sensor;
the sampling resistor is connected with the field effect transistor, and one end of the sampling resistor is grounded;
and the negative feedback circuit is respectively connected with the operational amplifier and the sampling resistor.
Further, the negative feedback circuit comprises a second resistor and a third resistor, wherein the second resistor is connected with the third resistor, and one end of the second resistor is grounded.
According to another aspect of the present application, there is also provided a data acquisition method of a pressure sensor, using the data acquisition device described above, the method comprising:
determining a stable voltage reference signal output by the digital-to-analog conversion circuit as a reference voltage;
acquiring the voltage of a converted acquisition point from the analog-to-digital conversion circuit, wherein the acquisition point is a common connection point of the pressure sensor, the constant current source circuit and the analog-to-digital conversion circuit;
and determining the current pressure value of the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage.
Further, determining a stable voltage reference signal output by the digital-to-analog conversion circuit as a reference voltage includes:
and determining a stable voltage reference signal output by a digital-to-analog converter in the digital-to-analog conversion circuit, and taking the stable voltage reference signal as a reference voltage after high-frequency filtering by the filter circuit.
Further, determining the current pressure value of the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage comprises the following steps:
determining a resistance value corresponding to the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage;
and determining the current pressure value of the pressure sensor according to the corresponding resistance value of the pressure sensor and the preset corresponding relation of the pressure resistance value.
Further, determining a resistance value corresponding to the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage, including:
determining interval information of pressure corresponding to the resistance according to the resistance corresponding to the pressure sensor and a preset pressure resistance corresponding relation;
adjusting the reference voltage to be the reference voltage corresponding to the section information according to the section information of the pressure, and determining the adjusted reference voltage;
re-acquiring the voltage of the converted acquisition point from the analog-to-digital conversion circuit to determine the average voltage of the acquisition point;
and determining the resistance corresponding to the pressure sensor according to the adjusted reference voltage, the average voltage of the acquisition point and the power supply voltage.
Further, the interval information of the pressure includes a first interval, a second interval and a third interval, the first interval corresponds to a first preset reference voltage, the second interval corresponds to a second preset reference voltage, and the third interval corresponds to a third preset reference voltage.
Further, adjusting the reference voltage to the reference voltage corresponding to the section information according to the section information of the pressure, including:
and adjusting the reference voltage to a preset reference voltage corresponding to the interval information according to the interval information of the pressure, wherein the preset reference voltage comprises the first preset reference voltage, the second preset reference voltage and the third preset reference voltage.
Compared with the prior art, the application provides a data acquisition device of a pressure sensor and a method for acquiring data by using the acquisition device, wherein the acquisition device comprises a power supply; the microprocessor is connected with the power supply; the digital-to-analog conversion circuit is respectively connected with the microprocessor and the power supply; the constant current source circuit is respectively connected with the digital-to-analog conversion circuit and the power supply; the pressure sensor is respectively connected with the constant current source circuit and the power supply; and the analog-to-digital conversion circuit is respectively connected with the pressure sensor, the microprocessor and the power supply. Further, the acquisition device is used for determining a stable voltage reference signal output by the digital-to-analog conversion circuit as a reference voltage; acquiring the voltage of a converted acquisition point from the analog-to-digital conversion circuit, wherein the acquisition point is a common connection point of the pressure sensor, the constant current source circuit and the analog-to-digital conversion circuit; and determining the current pressure value of the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage. Therefore, the voltage of the output signal of the film pressure sensor in different pressure sections can be kept in a relatively stable range, the whole measuring interval can be kept to have higher measuring precision, the measured value and the calculation result are in a linear relation, and the calculation is convenient.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:
FIG. 1 illustrates a schematic diagram of a data acquisition device of a pressure sensor provided in accordance with an aspect of the present application;
FIG. 2 is a diagram showing the relationship between the resistance and the pressure of the film pressure sensor according to an embodiment of the application;
FIG. 3 is a schematic circuit diagram of a pressure sensor acquisition device according to an embodiment of the present application;
FIG. 4 is a schematic circuit diagram of a collecting device of another pressure sensor according to an embodiment of the present application;
FIG. 5 is a flow chart of a method for data acquisition of a pressure sensor according to another aspect of the present application;
FIG. 6 is a graph showing the pressure versus resistance of the pressure sensor after dividing the interval according to an embodiment of the present application;
FIG. 7 is a flow chart illustrating the determination of pressure values in an embodiment of the present application.
The same or similar reference numbers in the drawings refer to the same or similar parts.
Detailed Description
The application is described in further detail below with reference to the accompanying drawings.
Fig. 1 shows a schematic structural diagram of a data acquisition device of a pressure sensor according to an aspect of the present application, including a power supply 1; a microprocessor 2, wherein the microprocessor 2 is connected with the power supply 1; the digital-to-analog conversion circuit 3 is respectively connected with the microprocessor 2 and the power supply 1; a constant current source circuit 4, wherein the constant current source circuit 4 is connected with the digital-to-analog conversion circuit 3 and the power supply 1 respectively; the pressure sensor 5 is respectively connected with the constant current source circuit 4 and the power supply 1; the analog-to-digital conversion circuit 6 is respectively connected with the pressure sensor 5, the microprocessor 2 and the power supply 1.
Here, the microprocessor 2 is configured to control the digital-to-analog conversion circuit 3 to output a stable voltage reference signal as a reference voltage; the constant current source circuit 4 is used for controlling the current passing through the pressure sensor 5 to be constant based on the stable voltage reference signal; the analog-to-digital conversion circuit 6 is configured to convert a voltage of an acquisition point, and output the converted voltage of the acquisition point to the microprocessor 2, where the acquisition point is a common connection point of the pressure sensor 5, the constant current source circuit 4 and the analog-to-digital conversion circuit 6; the power supply 1 is connected with the microprocessor 2, the digital-to-analog conversion module 3, the constant current source circuit 4, the pressure sensor 5 and the analog-to-digital conversion module 6 and is used for providing power supply voltage; the microprocessor 2 determines the current pressure value of the pressure sensor according to the reference voltage, the converted voltage of the acquisition point and the power supply voltage. The pressure sensor 5 is a film pressure sensor, and is essentially a variable resistor, the resistance of which changes with different external pressures, and the trend of the resistance change is shown in fig. 2, and the range of the resistance change is larger with the pressure change in a certain pressure range, and the range of the resistance change is smaller after the pressure reaches a certain pressure. As can be seen from FIG. 2, the film pressure sensor has a large resistance variation range and a nonlinear resistance curve, and if a set of fixed parameter circuits is used to drive the film sensor, the variation range of the output result is large, and the resistance variation is small in a region with a large pressure, so that the precision requirement is increased, and the design requirement difficulty of the post-stage data acquisition circuit is increased by the changed curve. Therefore, a circuit for driving the film pressure sensor needs to be adjustable, so that the voltage of the output signal of the film pressure sensor under different pressure sections can be kept in a relatively stable range, thereby ensuring the accuracy of data acquisition.
In an embodiment of the present application, the digital-to-analog converter 3 includes a digital-to-analog converter 31 and a filter circuit 32, the digital-to-analog converter 31 is connected to the filter circuit 32, and the filter circuit 32 is connected to the constant current source circuit 4. The microprocessor 2 is a Micro Control Unit (MCU), the digital-to-analog converter 3 includes a digital-to-analog converter DAC, and the analog-to-digital converter 6 is an analog-to-digital converter ADC. The MCU is used for controlling the DAC circuit of the digital-to-analog converter to output a stable voltage reference signal, stabilizing the voltage reference signal through the constant current source circuit, ensuring that the current passing through the pressure sensor 5 is constant under the condition that the voltage reference signal is unchanged, reading the output voltage of the pressure sensor 5 through the ADC, namely reading the voltage of a sampling point, wherein the read voltage is the voltage converted through the ADC, and determining the current pressure of the pressure sensor through the power output voltage, the reference voltage and the voltage of the sampling point read by the MCU. The filter circuit 32 is configured to perform high-frequency filtering on the stable voltage reference signal output by the digital-to-analog converter 31, and then transmit the filtered stable voltage reference signal to the constant current source circuit 4. The MCU controls the digital-to-analog converter ADC circuit to output a stable voltage reference signal, and filters out high frequency noise in the signal by the filter circuit 32, and then outputs the signal to the subsequent constant current source circuit to stabilize the voltage reference, where the cut-off frequency point of the filter network may be set according to the characteristics of the signal to be measured.
In an embodiment of the present application, the filter circuit 32 includes a first resistor R1 and a first capacitor C1, where the first resistor R1 is connected to the digital-to-analog converter 31 and the first capacitor C1, and one end of the first capacitor C1 is grounded, and an RC filter network is formed by R1 and C1.
In an embodiment of the present application, the constant current source circuit 4 includes an operational amplifier 41, and the operational amplifier 41 is connected to the filter circuit 32; a field effect tube 42, wherein the field effect tube 42 is connected with the operational amplifier 41 and the pressure sensor 5 respectively; the sampling resistor 43 is connected with the field effect tube 42, and one end of the sampling resistor 43 is grounded; and a negative feedback circuit 44, wherein the negative feedback circuit 44 is connected to the operational amplifier 41 and the sampling resistor 43, respectively. Here, the constant current source circuit 4 includes an operational amplifier circuit U2, a field effect transistor Q1, a negative feedback circuit, and a sampling resistor R5; the non-inverting input end of the operational amplifier circuit U2 is connected with the first resistor R1 and the first capacitor C1, the inverting input end of the operational amplifier circuit U2 is connected with the negative feedback circuit, and the output end of the operational amplifier circuit U2 is connected with the grid electrode of the field effect transistor Q1; the source electrode of the field effect tube Q1 is connected with the sampling resistor R5, and the drain electrode of the field effect tube Q1 is connected with the pressure sensor 5. The negative feedback circuit comprises a second resistor R2 and a third resistor R3, the negative feedback circuit comprises the second resistor R2 and the third resistor R3, the second resistor R2 is connected with the third resistor R3, and one end of the second resistor R2 is grounded. Here, one end of the second resistor R2 is grounded, the other end is connected to one end of a third resistor R3 and an inverting input end of the operational amplifier circuit U2, and the other end of the third resistor R3 is connected to the source of the field-effect transistor Q1 and the sampling resistor R5. The specific circuit frame diagram is shown in fig. 3:
the MCU Is connected with the DAC to control the DAC to output a stable voltage reference signal, the DAC Is connected with a filter network formed by a first resistor R1 and a first capacitor C1, wherein the first capacitor C1 Is grounded, a common node of the first resistor R1 and the first capacitor C1 Is connected with a non-inverting input end of the operational amplifier U2, an inverting input end of the U2 Is connected with a negative feedback network formed by a second resistor R2 and a third resistor R3, the second resistor R2 Is grounded, the third resistor R3 Is connected with a sampling resistor R5, an output end of the U2 Is connected with a grid electrode of an N-channel field effect transistor Q1 after passing through a fourth resistor R4, a source electrode of the Q1 Is connected with the sampling resistor R5 and the third resistor R3, a drain electrode of the Q1 Is connected with the film pressure sensor U1 and the ADC, the ADC Is connected with the MCU to convert the voltage of the point A and then transmit the converted voltage to the MCU, the precision circuit Is connected with the MCU by the low noise operational amplifier U2, the N-channel field effect transistor Q2, the negative feedback network R2 and the constant current source circuit can ensure that the sampling voltage of the constant current Is not equal to the constant voltage sensor R1. The point A is a collection point, and the voltage Vout of the point A is a signal to be collected. Therefore, through the circuit designed above, the voltage of the acquisition point is acquired, and then the current pressure value of the film pressure sensor is determined according to the acquired voltage, the power supply voltage and the reference voltage, and the data acquisition device of the pressure sensor in the embodiment can adjust the circuit of the voltage of the film pressure sensor, so that the voltage value of the output signal of the film pressure sensor in different pressure sections can be kept in a relatively stable range, and the accuracy of data acquisition is ensured.
In yet another embodiment of the present application, the constant current source circuit does not include a negative feedback circuit, and an example of a circuit structure is shown in fig. 4, where the MCU is a microprocessor, and is used for operating on data and controlling the DAC and the ADC; the DAC is a digital-to-analog converter, and converts the digital signal given by the MCU to output a corresponding voltage signal Vdac; the ADC is an analog-to-digital converter, and the voltage value Vout at the point A is read through the ADC and the MCU; r1 and C1 form RC filter to filter clutter after DAC output, and adjust R1 and C1 values according to actual condition, if DAC output voltage stability can meet circuit requirement, R1 and C1 can be deleted. R4 is a protection resistor and is used for protecting Q1 and can be deleted. Q1 is an N-channel field effect transistor, and an NPN triode can be used for replacing the N-channel field effect transistor. The operators U2 and Q1, R3, and R5 constitute a constant current amplifying circuit, and can control the current Is flowing through the sensor U1 to be constant, the current value is=vdac/R5. It should be noted that the adjustment capability of the circuit in fig. 4 ranges from 0 to 1200uA depending on the Q1 characteristic. The partial correspondence data of Vdac and Is are given in table 1 for different values of R5.
TABLE 1
Fig. 5 is a schematic flow chart of a data acquisition method of a pressure sensor according to another aspect of the present application, using the data acquisition device described above, the method includes: in the steps S11 to S13,
in step S11, a stable voltage reference signal output by the digital-to-analog conversion circuit is determined as a reference voltage; in step S12, the voltage of the converted sampling point is obtained from the analog-to-digital conversion circuit, where the sampling point is a common connection point of the pressure sensor, the constant current source circuit and the analog-to-digital conversion circuit; in step S13, a current pressure value of the pressure sensor is determined according to the reference voltage, the converted voltage of the collection point, and the power supply voltage. The stable voltage reference signal output by the digital-to-analog conversion circuit Is taken as a reference voltage, and Is marked as Vdac, the voltage of the acquisition point read by the MCU into the ADC Is marked as Vout, the current passing through the pressure sensor Is marked as Is, the resistance value of the pressure sensor Is Rs, and the power supply voltage output voltage Is VCC, and the corresponding relation between the voltage of the acquisition point read by the MCU and the resistance value of the pressure sensor Is as follows: vout=vcc-Is Rs, where Is a constant value with the reference voltage unchanged, and Is in a fixed relationship with the DAC output Vdac, expressed as formula (one): is=f (Vdac), and further, in step S13, determining a resistance value corresponding to the pressure sensor according to the reference voltage, the voltage of the converted collection point, and a power supply voltage; and determining the current pressure value of the pressure sensor according to the corresponding resistance value of the pressure sensor and the preset corresponding relation of the pressure resistance value. Here, the relationship between the voltage at the sampling point and the resistance value of the pressure sensor and the relationship between Is and Vdac are obtained: rs= (VCC-Vout)/f (Vdac), by which it is shown that Rs and Vout are in a linear relationship, thereby facilitating data analysis at a later stage using the linear relationship. The resistance of the pressure sensor can be obtained, and the current pressure value of the pressure sensor can be obtained according to the corresponding relation between the resistance and the pressure.
In an embodiment of the present application, in step S11, a stable voltage reference signal output by a digital-to-analog converter in the digital-to-analog conversion circuit may be determined, and the stable voltage reference signal is subjected to high-frequency filtering by the filtering circuit and then used as a reference voltage. The voltage reference signal output by the digital-to-analog converter is filtered by an RC filter circuit consisting of a first resistor and a first capacitor, high-frequency clutter in the signal is filtered, and the filtered reference voltage signal is used as a reference voltage for adjusting the pressure sensor.
In an embodiment of the present application, as shown in a graph of a pressure versus resistance of a pressure sensor after dividing a section in fig. 6, section information of the pressure includes a first section, a second section, and a third section, where the first section corresponds to a first preset reference voltage, the second section corresponds to a second preset reference voltage, and the third section corresponds to a third preset reference voltage.
In an example of the present application, when Is a fixed value, under the same pressure variation, the variation range of Vout in the area of the first interval (K1) Is larger, and the variation range from the third interval (K3) Is smaller, so that the measurement accuracy in the whole pressure interval will be different. When Is regulated in different intervals, the acquisition range of the voltage of the sampling point Is required to be ensured to be consistent with the sampling interval of the ADC. According to an actual circuit, the values of Vdac1, vdac2 and Vdac3 corresponding to K1, K2 and K3 and the approximate value Vdac0 suitable for the whole interval are measured in advance, so that the ADC can conveniently read Vout. When the pressure value of the pressure sensor is determined, firstly, the range of the section where the pressure value is located can be pre-judged, then the section information where the accurate measurement is carried out by adjusting the corresponding reference voltage, and further the corresponding pressure value is obtained through calculation, so that the finally obtained pressure value is more accurate. The specific implementation mode is as follows:
when the resistance corresponding to the pressure sensor is determined, the interval information of the pressure corresponding to the resistance can be determined according to the resistance corresponding to the pressure sensor and the preset corresponding relation of the pressure resistance; adjusting the reference voltage to be the reference voltage corresponding to the section information according to the section information of the pressure, and determining the adjusted reference voltage; re-acquiring the voltage of the converted acquisition point from the analog-to-digital conversion circuit to determine the average voltage of the acquisition point; and determining the resistance corresponding to the pressure sensor according to the adjusted reference voltage, the average voltage of the acquisition point and the power supply voltage. Specifically, when the reference voltage is adjusted, the reference voltage can be adjusted to a preset reference voltage corresponding to the interval information according to the interval information where the pressure is located, where the preset reference voltage includes the first preset reference voltage, the second preset reference voltage and the third preset reference voltage.
Setting a voltage reference Vdac0 output by the DAC, reading the value of the ADC, judging the interval information that the pressure falls between K1 and K3 according to the output power supply voltage, the voltage of the acquisition point and the reference voltage Vdac0, correspondingly adjusting the output voltage of the DAC to the corresponding Vdac according to the judged interval information, for example, falling to a K1 interval, adjusting the output voltage of the DAC to the Vdac1 corresponding to the K1 interval, re-reading the value of the ADC after adjustment, and obtaining the average value of the Vout according to the value of the ADC read one or more times before according to a formula (II): and Rs= (VCC-Vout)/f (Vdac), determining the resistance corresponding to the pressure sensor, wherein Vdac is the reference voltage when the pressure sensor is regulated last time, and Vout is the average value determined by reading the voltage of the acquisition point in the ADC for a plurality of times. And then obtaining the pressure value corresponding to Rs according to the curve graph of the corresponding relation between the pressure value and the resistance value of the sensor or inquiring the pressure resistance value corresponding table obtained by the pre-test. The measuring accuracy of the whole measuring interval can be kept high by adjusting the Vdac, and the measured value and the calculation result are in a linear relation, so that the calculation is convenient.
In a specific embodiment of the present application, according to the characteristic curve of the pressure and the resistance of the sensor, the sensor may be divided into a plurality of sections for curve fitting, as shown in fig. 6, 3 sections are divided, and each section uses a thicker straight line section for fitting the curve, thereby facilitating calculation without causing too large error. The slopes of the respective sections are defined as K1, K2 and K3, and the corresponding relationship between the resistance Rs and the pressure N is the formula (three): pressure n= -Kn rs+l, where Kn represents K1, K2, K3, is the slope of the fitted line segment; l is a coefficient constant. From the formula (two) and the formula (three), the formula (four) can be derived:
n= -Kn (VCC-Vout)/is+l; according to the formula, by collecting the Vout value in the circuit diagram, the pressure value N can be calculated according to the sensor characteristic curve. By means of the three distinguished areas, linear data acquisition is achieved, and the computational complexity of the processor is reduced.
From the formula (four) and the formula (one), the formula (five) can be obtained:
n= -Kn (VCC-Vout)/(Vdac/R5) +l; from equation (five), the pressure N can be directly calculated from the Vout value read out by the ADC.
The specific implementation mode is as follows: the characteristic curve of the pressure sensor is divided into three fitting line segments (as shown in fig. 6), each line segment is described by a formula (III), the three fitting line segments respectively comprise six constants of K1, K2, K3 and L1, L2 and L3, and the constants Ra and Rb of resistance values of two endpoints of A and B are preset in a program of the microprocessor. And (3) setting a reasonable Is according to a formula (II), so that the measurement result Vout of the ADC Is distributed in the whole measurement range of the ADC in the section of the whole line segment, and the concentration on a certain head of the measurement range Is avoided, thereby obtaining higher measurement precision. After Is set, according to the formula (I), vdac1, vdac2 and Vdac3 corresponding to the three line segments are obtained, and the obtained Vdac1, vdac2 and Vdac3 are preset in a program of the microprocessor. In the actual measurement process, to determine which interval the pressure falls in, the determination may be made by: as shown in fig. 7, different K1, K2 and K3 are set in an attempt one by one, that is, the DAC gives corresponding Vdac1, vdac2 and Vdac3, according to the measurement result, whether Rs falls in the corresponding section is calculated, if not, the different sections are replaced continuously, and if yes, the measurement is performed again for multiple times to average so as to reduce the error, so as to obtain the measurement result.
Through the circuit structure and the acquisition method, the whole measurement interval can be kept to have higher measurement precision by adjusting Vdac, and the measured value and the calculation result are in a linear relationship, so that the calculation is convenient.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
It should be noted that the present application may be implemented in software and/or a combination of software and hardware, e.g., using Application Specific Integrated Circuits (ASIC), a general purpose computer or any other similar hardware device. In one embodiment, the software program of the present application may be executed by a processor to perform the steps or functions described above. Likewise, the software programs of the present application (including associated data structures) may be stored on a computer readable recording medium, such as RAM memory, magnetic or optical drive or diskette and the like. In addition, some steps or functions of the present application may be implemented in hardware, for example, as circuitry that cooperates with the processor to perform various steps or functions.
Furthermore, portions of the present application may be implemented as a computer program product, such as computer program instructions, which when executed by a computer, may invoke or provide methods and/or techniques in accordance with the present application by way of operation of the computer. Program instructions for invoking the inventive methods may be stored in fixed or removable recording media and/or transmitted via a data stream in a broadcast or other signal bearing medium and/or stored within a working memory of a computer device operating according to the program instructions. An embodiment according to the application comprises an apparatus comprising a memory for storing computer program instructions and a processor for executing the program instructions, wherein the computer program instructions, when executed by the processor, trigger the apparatus to operate a method and/or a solution according to the embodiments of the application as described above.
It will be evident to those skilled in the art that the application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is evident that the word "comprising" does not exclude other elements or steps, and that the singular does not exclude a plurality.
Claims (4)
1. A data acquisition method of a pressure sensor, the method being applied to a data acquisition device of the pressure sensor, the method comprising:
determining a stable voltage reference signal output by the digital-to-analog conversion circuit as a reference voltage;
acquiring the voltage of a converted acquisition point from an analog-to-digital conversion circuit, wherein the acquisition point is a common connection point of a film pressure sensor, a constant current source circuit and the analog-to-digital conversion circuit;
determining interval information of pressure corresponding to the resistance value according to the resistance value corresponding to the film pressure sensor and a preset pressure resistance value corresponding relation;
adjusting the reference voltage to the reference voltage corresponding to the section information according to the section information of the pressure, and determining the adjusted reference voltage;
re-acquiring the converted voltage of the acquisition point from the analog-to-digital conversion circuit to determine the average voltage of the acquisition point; determining the resistance value corresponding to the film pressure sensor according to the adjusted reference voltage, the average voltage of the acquisition point and the power supply voltage;
determining the current pressure value of the film pressure sensor according to the corresponding resistance value of the film pressure sensor and the preset corresponding pressure resistance value relation;
the data acquisition device comprises:
a power supply;
the microprocessor is connected with the power supply;
the digital-to-analog conversion circuit is respectively connected with the microprocessor and the power supply;
the constant current source circuit is respectively connected with the digital-to-analog conversion circuit and the power supply;
the film pressure sensor is respectively connected with the constant current source circuit and the power supply; the analog-to-digital conversion circuit is respectively connected with the film pressure sensor, the microprocessor and the power supply;
the microprocessor is used for controlling the digital-to-analog conversion circuit to output a stable voltage reference signal serving as a reference voltage; the constant current source circuit is used for controlling the constant current passing through the film pressure sensor based on the stable voltage reference signal; the analog-to-digital conversion circuit is used for converting the voltage of the acquisition point and outputting the converted voltage of the acquisition point to the microprocessor, wherein the acquisition point is a common connection point of the film pressure sensor, the constant current source circuit and the analog-to-digital conversion circuit; the microprocessor determines interval information of pressure corresponding to the resistance value according to the resistance value corresponding to the film pressure sensor and a preset pressure resistance value corresponding relation, adjusts the reference voltage to the reference voltage corresponding to the interval information according to the interval information of the pressure, determines the adjusted reference voltage, re-acquires the voltage of the converted acquisition point from the analog-to-digital conversion circuit to determine the average voltage of the acquisition point, determines the resistance value corresponding to the film pressure sensor according to the adjusted reference voltage, the average voltage of the acquisition point and the power supply voltage, and determines the current pressure value of the film pressure sensor according to the resistance value corresponding to the film pressure sensor and the preset pressure resistance value corresponding relation;
the digital-to-analog conversion circuit comprises a digital-to-analog converter and a filter circuit, wherein the digital-to-analog converter is connected with the filter circuit, and the filter circuit is connected with the constant current source circuit;
the filter circuit comprises a first resistor and a first capacitor, wherein the first resistor is respectively connected with the digital-to-analog converter and the first capacitor, and one end of the first capacitor is grounded;
the constant current source circuit includes:
the operational amplifier is connected with the filter circuit;
the field effect tube is respectively connected with the operational amplifier and the film pressure sensor; the sampling resistor is connected with the field effect transistor, and one end of the sampling resistor is grounded;
the negative feedback circuit is respectively connected with the operational amplifier and the sampling resistor;
the negative feedback circuit comprises a second resistor and a third resistor, the second resistor is connected with the third resistor, and one end of the second resistor is grounded;
the voltage of the output signal of the film pressure sensor under different pressure sections can be kept in a relatively stable range, so that the whole measuring interval is kept to have higher measuring precision, and the measured value and the calculation result are in a linear relation.
2. The method of claim 1, wherein determining the regulated voltage reference signal output by the digital-to-analog conversion circuit as the reference voltage comprises:
and determining a stable voltage reference signal output by a digital-to-analog converter in the digital-to-analog conversion circuit, and taking the stable voltage reference signal as a reference voltage after high-frequency filtering by the filter circuit.
3. The method of claim 1, wherein the interval information in which the pressure is located includes a first interval, a second interval, and a third interval, the first interval corresponding to a first preset reference voltage, the second interval corresponding to a second preset reference voltage, and the third interval corresponding to a third preset reference voltage.
4. The method of claim 3, wherein adjusting the reference voltage to the reference voltage corresponding to the interval information according to the interval information where the pressure is located comprises:
and adjusting the reference voltage to a preset reference voltage corresponding to the interval information according to the interval information of the pressure, wherein the preset reference voltage comprises the first preset reference voltage, the second preset reference voltage and the third preset reference voltage.
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| CN110567616A (en) * | 2019-08-29 | 2019-12-13 | 北京自动化控制设备研究所 | Signal acquisition circuit for silicon piezoresistive pressure sensor unit |
| CN111056395B (en) * | 2019-12-25 | 2021-09-03 | 武汉科技大学 | Band-type brake fault diagnosis method based on multipoint pressure sensor |
| CN112050975A (en) * | 2020-08-25 | 2020-12-08 | 宇博智能科技(杭州)有限公司 | Signal processing method, module, device and storage medium |
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