WO2020253552A1 - 一种微差法与比例法结合的电阻高精度测量系统与方法 - Google Patents

一种微差法与比例法结合的电阻高精度测量系统与方法 Download PDF

Info

Publication number
WO2020253552A1
WO2020253552A1 PCT/CN2020/094604 CN2020094604W WO2020253552A1 WO 2020253552 A1 WO2020253552 A1 WO 2020253552A1 CN 2020094604 W CN2020094604 W CN 2020094604W WO 2020253552 A1 WO2020253552 A1 WO 2020253552A1
Authority
WO
WIPO (PCT)
Prior art keywords
analog
digital
voltage
microprocessor
converter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2020/094604
Other languages
English (en)
French (fr)
Inventor
陈泽宇
刘少强
李杜林
樊晓平
张熠铭
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Central South University
Original Assignee
Central South University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Central South University filed Critical Central South University
Priority to US17/433,311 priority Critical patent/US11327099B2/en
Publication of WO2020253552A1 publication Critical patent/WO2020253552A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/14—Measuring resistance by measuring current or voltage obtained from a reference source
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/20—Modifications of basic electric elements for use in electric measuring instruments; Structural combinations of such elements with such instruments
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/20—Modifications of basic electric elements for use in electric measuring instruments; Structural combinations of such elements with such instruments
    • G01R1/206—Switches for connection of measuring instruments or electric motors to measuring loads
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/08—Measuring resistance by measuring both voltage and current
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0084—Measuring voltage only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Measuring current only

Definitions

  • the invention relates to the field of sensors and detection technology and instrumentation, in particular to a low-cost and high-precision resistance measurement system and method that combines a differential method and a proportional method.
  • the accurate measurement of resistance is the basis for the high-precision measurement of resistance sensors.
  • Resistive sensors are widely used in practical engineering, and occasions where high-precision measurement of the sensed resistance is required are also common.
  • the high-precision measurement of resistance mostly adopts digital measurement methods, and the measurement devices generally include a microprocessor (CPU), an analog-to-digital converter (ADC), and a signal input circuit.
  • the accuracy of a digital measurement system mainly depends on the accuracy or digits of the ADC. Generally, the more digits, the higher the system resolution and accuracy, but the higher the price.
  • MSP430F series of microcontrollers from TI in the United States as an example.
  • the price of MSP430F5524 with 12-bit ADC is much higher than that of MSP430F5510 with 10-bit ADC.
  • the performance parameters of the two are basically the same, but the price of the former is 1,000 pieces.
  • DACs Digital-to-analog converters
  • 8-bit DACs such as DAC101S101
  • 10-bit DACs such as DAC081S101 are priced at about 0.5$ (the above price data are from the device company Online quotation). It can be seen that the accuracy and cost of the digital measurement system are largely affected by the ADC.
  • the existing automatic detection system generally uses digital electrical measurement technology, and its essence is still achieved by measuring the corresponding voltage change signal that can reflect the resistance change.
  • alternative methods, proportional methods, and differential methods are often used to improve or improve measurement accuracy. Although each method has its own characteristics, there are corresponding technologies. defect:
  • the proportional measurement method (abbreviated as the proportional method) is a method that uses the proportional relationship between the measured and the known quantity to calculate and determine the measured value.
  • the measured resistance is connected in series with a known standard resistance, and the measured resistance value can be obtained by using the proportional relationship between the terminal voltage of the two resistances and the resistance value of the two resistances.
  • the circuit is simple and the cost is low.
  • the advantage of achieving high-precision measurement is that only the current flowing through the series branch of the measured resistance and the reference resistance is stable in a short period of time, but there are no high requirements for specific values.
  • the conditions for achieving high-precision measurement with this method actually include the high-precision requirements for voltage measurement.
  • the differential measurement method (referred to as the differential method) is to compare the measured value with the same quantity or standard quantity of the same property with only a small difference with its known value, by measuring the difference between the two values To determine the measurement method of the measured value.
  • the differential method only the difference between the two is measured, and because the error of the standard quantity is very small, even if the measuring instrument with relatively low accuracy is used, high measurement accuracy can be obtained.
  • the use of relatively low-precision measuring instruments can obtain relatively high-precision measurement results, which is the main advantage of the differential method.
  • this method is limited in practice, because it is not easy to obtain a standard quantity of the same type with a small difference from the measured value, and sometimes it is not available.
  • the present invention provides a resistance measurement system and method combining the differential method and the proportional method, which can realize high-precision resistance measurement while reducing the cost of the measurement system.
  • a high-precision resistance measurement system combining differential method and proportional method, including constant current source, reference resistance, first differential amplifier, programmable gain amplifier, analog-to-digital converter, microprocessor, digital-to-analog converter and tested Resistance interface;
  • the measured resistance interface is used to access the measured resistance
  • the reference resistance and the measured resistance are connected in series to form a series branch, one end of the series branch is connected to the constant current source, and the other end of the series branch is grounded;
  • Two input terminals of the first differential amplifier are respectively connected to two ends of the reference resistor, and an output terminal is connected to the voltage reference terminal of the analog-to-digital converter;
  • the first input terminal is used to connect the single-ended voltage to the ground of the measured resistance, and the second input terminal is controlled to be connected to the analog output terminal of the digital-to-analog converter or one of the ground,
  • the output terminal of the programmable gain amplifier is connected to the analog input terminal of the analog-to-digital converter; the single-ended voltage of the measured resistance to ground corresponds to the potential difference between the two ends of the measured resistance;
  • the present invention uses the reference resistance and the resistance to be measured in series to construct a series branch, and is powered by a constant current source, and then cleverly uses the connection relationship of the first differential amplifier, programmable gain amplifier, analog-to-digital converter and digital-to-analog converter to The proportional method and the differential method are combined to measure the measured resistance, so that the proportional relationship between the voltage and resistance of the two series resistors can be converted into: the proportional relationship between the first differential amplifier and the programmable gain amplifier and analog-to-digital conversion The proportional relationship between the conversion result of the converter and its maximum conversion output value, and then the resistance value of the measured resistance and the resistance value of the reference resistance, the amplification factor of the first differential amplifier, the amplification factor of the programmable gain amplifier and the analog-to-digital converter The relationship is established between the maximum conversion output value of the measured resistance, which can overcome the influence of the measured resistance on the measurement accuracy due to the current change and the influence of the power supply fluctuation on the analog-to-digital conversion result; at
  • the present invention can also effectively reduce the construction cost of the measurement system.
  • the constant current source, the reference resistance, the measured resistance and the ground are connected in sequence to form the series branch; the first input end of the programmable gain amplifier is connected to the non-grounded end of the measured resistance;
  • the system also includes a second differential amplifier.
  • the constant current source, the measured resistance, the reference resistance, and the ground are sequentially connected to form the series branch; the second differential amplifier has two input terminals connected to the measured resistance respectively. The two ends of is connected, the output terminal is connected to the first input terminal of the programmable gain amplifier, and the gain of the second differential amplifier is doubled.
  • the voltage reference terminal of the digital-to-analog converter is connected to the output terminal of the first differential amplifier.
  • control terminal of the programmable gain amplifier is connected to a microprocessor, and the programmable gain amplifier is set by the microprocessor to set an amplification factor.
  • the amplification factor of the programmable gain amplifier satisfies that: the voltage value output by the programmable gain amplifier is smaller than the maximum conversion value of the analog-to-digital converter.
  • the control terminal of the first switching element is connected to the microprocessor, and the second input terminal of the programmable gain amplifier for the microprocessor to control is connected to the analog output terminal of the digital-to-analog converter Or connected to ground; and/or,
  • It also includes a second switch element, the control end of the second switch element is connected to the microprocessor, and the microprocessor controls the on-off between the output end of the first differential amplifier and the voltage reference end of the analog-to-digital converter; and / or,
  • It also includes a third switch element, and the control terminal of the third switch element is connected to the microprocessor for controlling the on-off between the output terminal of the first differential amplifier and the voltage reference terminal of the digital-to-analog converter.
  • a high-precision resistance measurement method combining the differential method and the proportional method includes the following steps:
  • Step 1 Connect the measured resistance to the measured resistance interface of any of the above systems, where the second input terminal of the programmable gain amplifier is connected to ground;
  • Step 2 The microprocessor obtains the analog-to-digital conversion result corresponding to the measured resistance
  • Step 2.1 the programmable gain amplifier amplifies the single-ended voltage U S of the resistance under test by A1 times to obtain the first voltage U S *A1; the analog-to-digital converter performs analog-to-digital conversion on the obtained first voltage U S *A1 Obtain the first voltage digital quantity D1; the microprocessor reads the first voltage digital quantity D1 from the analog-to-digital converter;
  • Step 2.2 the microprocessor calculates and outputs a given voltage digital quantity D1' according to the number of digits of the digital-to-analog converter and sends it to the digital-analog converter.
  • the digital-to-analog converter performs digital-to-analog conversion on the given voltage digital quantity D1'.
  • Step 2.3 switch the second input terminal of the programmable gain amplifier from ground connection to connection with the analog output terminal of the digital-to-analog converter;
  • Step 2.4 the programmable gain amplifier will differentially amplify the measured resistance to the ground single-ended voltage U S and the given voltage U1 by A2 times to obtain the second voltage (U S- U1)*A2;
  • the second voltage (U S -U1)*A2 performs analog-to-digital conversion to obtain the second voltage digital quantity D2;
  • the microprocessor reads the second voltage digital quantity D2 from the analog-digital converter;
  • Step 3 The microprocessor calculates the resistance value R S of the measured resistance according to the following formula:
  • R N represents the resistance of the reference resistor
  • a REF represents the amplification factor of the first differential amplifier
  • D FS is the maximum conversion output number of the analog-to-digital converter.
  • system further includes a first switching element, and the control terminal of the first switching element is connected to the microprocessor;
  • the microprocessor controls the first switching element to connect the second input of the programmable gain amplifier to ground; in step 2.3, the microprocessor controls the first switching element to make the programmable gain amplifier
  • the second input terminal is connected to the analog output terminal of the digital-to-analog converter.
  • system further includes a second switching element and a third switching element, and the control terminals of the second switching element and the third switching element are both connected to the microprocessor;
  • the second switch element is controlled by the microprocessor to connect, so that the output terminal of the first differential amplifier is connected with the voltage reference terminal of the analog-to-digital converter; and after step 3, the second switch is controlled by the microprocessor The disconnection of the element disconnects the output terminal of the first differential amplifier from the voltage reference terminal of the analog-to-digital converter;
  • the microprocessor controls the third switching element to communicate so that the output terminal of the first differential amplifier is connected to the voltage reference terminal of the digital-to-analog converter; and after step 3 includes, the microprocessor controls the third The disconnection of the switching element disconnects the output terminal of the first differential amplifier from the voltage reference terminal of the digital-to-analog converter.
  • the microprocessor sets the amplification factor of the programmable gain amplifier as A1; and after performing step 2.2 and before step 2.4, the microprocessor sets the amplification factor of the programmable gain amplifier as A2.
  • the present invention uses the reference resistance and the resistance to be measured in series to construct a series branch, and is powered by a constant current source, and then cleverly uses the connection relationship of the first differential amplifier, programmable gain amplifier, analog-to-digital converter and digital-to-analog converter to The proportional method and the differential method are combined to measure the measured resistance, so that the proportional relationship between the voltage and resistance of the two series resistors can be converted into: the proportional relationship between the first differential amplifier and the programmable gain amplifier and analog-to-digital conversion The proportional relationship between the conversion result of the converter and its maximum conversion output value, and then the resistance value of the measured resistance and the resistance value of the reference resistance, the amplification factor of the first differential amplifier, the amplification factor of the programmable gain amplifier and the analog-to-digital converter The relationship is established between the maximum conversion output value of the measured resistance, which can overcome the influence of the measured resistance on the measurement accuracy due to the current change and the influence of the power supply fluctuation on the analog-to-digital conversion result; at
  • the present invention can also effectively reduce the construction cost of the measurement system.
  • Figure 1 is a functional block diagram of a measurement system according to the first embodiment of the present invention.
  • Fig. 2 is a design circuit diagram of a constant current source and a reference voltage according to the first embodiment of the present invention
  • FIG. 3 is a design circuit diagram of the measuring device according to the first embodiment of the present invention.
  • Fig. 4 is a functional block diagram of the measurement system according to the second embodiment of the present invention.
  • This embodiment provides a resistance measurement system combining the differential method and the proportional method.
  • the principle block diagram is shown in Fig. 1, and the specific circuit diagram is shown in Fig. 3, including the measured resistance interface, constant current source, reference resistance R N , The first differential amplifier Amp1, the programmable gain amplifier PGA, the analog to digital converter ADC, the microprocessor CPU, the digital to analog converter DAC, the first analog switch I, the second analog switch II, and the third analog switch III.
  • the first end of the reference resistor is connected to the first end of the measured resistance interface, the second end of the reference resistor is connected to the constant current source, and the second end of the measured resistance interface is grounded.
  • the two ends of the reference resistor are respectively connected to the two input terminals of the first differential amplifier Amp1.
  • the output terminal of the first differential amplifier Amp1 is connected to the voltage reference terminal of the analog-to-digital converter through the second analog switch II.
  • the output terminal is connected to the voltage reference terminal of the digital-to-analog converter through the third analog switch III; wherein, the control terminal of the second analog switch II and the control terminal of the third analog switch II are both connected to the microprocessor, and the microprocessor Control on and off.
  • the voltage reference terminals described in this embodiment all refer to the positive terminal voltage reference terminal VREF(+) of the analog-to-digital converter or the digital-to-analog converter, and the negative terminal voltage reference terminal VREF(-) is grounded.
  • the first input end of the programmable gain amplifier is connected to the second end of the measured resistance; the second input end of the programmable gain amplifier is connected to the first analog switch I, and the control end of the first analog switch I is connected to the microprocessor,
  • the second input terminal of the programmable gain amplifier is controlled by the microprocessor to be connected to the analog output terminal of the digital-to-analog converter or connected to ground, and the output terminal of the programmable gain amplifier is connected to the analog input terminal of the analog-to-digital converter;
  • the control end of the gain amplifier is connected with the microprocessor to realize that the programmable gain amplifier is controlled by the microprocessor to increase the amplification factor, and the amplification factor satisfies: the voltage value output by the programmable gain amplifier is smaller than the maximum conversion value of the analog-to-digital converter.
  • the maximum conversion value here can be understood as the critical input value that just reaches the overflow after the analog-to-digital converter is converted.
  • the model of the microprocessor CPU is AT89C51
  • the model of the analog-to-digital converter ADC is 8-digit (binary) ADC0809
  • the digital-to-analog converter DAC is MAX517 with the same digits as the analog-to-digital converter ADC.
  • the programming gain amplifier PGA is composed of instrumentation amplifier AD620, multiplexer CD4051 and resistance elements.
  • the model of the first differential amplifier Amp1 is AD620
  • the model of the second analog switch II and the third analog switch III are ADG821, the first analog switch
  • the model of I is ADG852
  • the voltage reference source is REF2933AIDBZT
  • the reference resistance R N is a 100 ohm manganin resistance.
  • the circuit of the constant current source used in this embodiment is a load-grounded constant current source circuit implementation scheme composed of a commonly used voltage reference source (voltage reference source) device combined with an integrated operational amplifier, as shown in FIG. 2.
  • this embodiment adjusts the output of the constant current source so that the current of the series branch formed by the reference resistance and the measured resistance does not exceed 10 mA; for the measured resistance of 400 to 1000 ohms, make it The current does not exceed 5mA (for a circuit with a working voltage of 5V).
  • the common reference voltage U REF of the analog-to-digital converter and the digital-to-analog converter can eliminate the working current change or value uncertainty due to the measured resistance, and the reference voltage U REF of the analog-to-digital converter and the digital-to-analog converter and its changes Measurement errors caused by differences.
  • the set value of the reference voltage allows the magnitude of the amplitude of the reference resistor R N U N terminal voltage and analog to digital converter and digital to analog converter.
  • this embodiment further uses this system to further explain the method of measuring the measured resistance.
  • the specific measurement method includes the following steps:
  • Step 1 Connect the measured resistance to the measured resistance interface of the resistance high-precision measurement system combining the differential method and the proportional method;
  • the system includes a constant current source, a reference resistor, a first differential amplifier, a programmable gain amplifier, an analog-to-digital converter, a microprocessor, a digital-to-analog converter, and a measured resistance interface;
  • the measured resistance interface is used to access the measured resistance
  • the reference resistance and the measured resistance are connected in series to form a series branch, one end of the series branch is connected to the constant current source, and the other end of the series branch is grounded;
  • Two input terminals of the first differential amplifier are respectively connected to two ends of the reference resistor, and an output terminal is connected to the voltage reference terminal of the analog-to-digital converter;
  • the first input terminal is used to connect the single-ended voltage to the ground of the measured resistance, and the second input terminal is controlled to be connected to the analog output terminal of the digital-to-analog converter or one of the ground,
  • the output terminal of the programmable gain amplifier is connected to the analog input terminal of the analog-to-digital converter; the single-ended voltage of the measured resistance to ground corresponds to the potential difference between the two ends of the measured resistance;
  • step 2 Before performing step 2, it is necessary to confirm whether the second input terminal of the programmable gain amplifier is connected to the ground. If not, the control terminal of the first analog switch I needs to be controlled by the microprocessor to make the second input of the programmable gain amplifier Connect terminal to ground;
  • step 2 it is also necessary to confirm whether the output terminal of the first differential amplifier Amp1 is connected to the voltage reference terminal of the analog-to-digital converter and the voltage reference terminal of the digital-to-analog converter.
  • the voltage reference terminal of one is not connected to the output terminal of the first differential amplifier Amp1, and the control terminal of the corresponding analog switch needs to be controlled by the microprocessor, so that the voltage reference terminal of the analog-to-digital converter and the digital-to-analog converter are both connected to the first
  • the output terminal of the differential amplifier Amp1 is connected to receive the reference voltage U REF provided by the first differential amplifier Amp1;
  • Step 2 The microprocessor obtains resistance calculation data
  • Step 2.1 the programmable gain amplifier amplifies the single-ended voltage U S of the resistance under test by A1 times to obtain the first voltage U S *A1; the analog-to-digital converter performs analog-to-digital conversion on the obtained first voltage U S *A1 Obtain the first voltage digital quantity D1; the microprocessor reads the first voltage digital quantity D1 from the analog-to-digital converter;
  • step 2.1 it also includes setting the amplification factor of the programmable gain amplifier to A1 through the connection between the microcontroller and the control end of the programmable gain amplifier;
  • Step 2.2 The microprocessor calculates and outputs a given voltage digital quantity D1′ according to the number of digits of the digital-to-analog converter according to the first voltage digital quantity D1, and sends it to the digital-to-analog converter.
  • the microprocessor outputs the given voltage digital quantity D1' according to the above formula, which can make the output voltage of the DAC (ie the given voltage U1) and the measured voltage Us (ie the single-ended voltage U S of the measured resistance to ground) close but slightly Smaller, so as to form a slight difference to complete high-precision resistance measurement.
  • Step 2.3 Control the control terminal of the first analog switch I by the microprocessor, and switch the second input terminal of the programmable gain amplifier from ground connection to connection with the analog output terminal of the digital-to-analog converter;
  • Step 2.4 the programmable gain amplifier will differentially amplify the single-ended voltage U S of the resistance under test and the given voltage U1 by A2 times to obtain the second voltage (U S -U1)*A2;
  • the second voltage (U S -U1)*A2 performs analog-to-digital conversion to obtain the second voltage digital quantity D2;
  • the microprocessor reads the second voltage digital quantity D2 from the analog-to-digital converter;
  • step 2.2 after performing step 2.2 and before step 2.4, it also includes that the amplification factor of the programmable gain amplifier controlled by the microprocessor is A2;
  • the amplification factor A1 of the programmable gain amplifier When setting the amplification factor A1 of the programmable gain amplifier, adjust the amplification factor according to the advanced value of the gain gear of the programmable gain amplifier, so that the analog-to-digital conversion result of step 2.1, namely the first voltage digital quantity D1, does not overflow ; At the same time, in order to make the resistance measurement more accurate, the amplification factor A1 of the programmable gain amplifier is required to be as large as possible, so the amplification factor A1 also needs to meet: make the highest bit of the first voltage digital quantity D1 as possible as 1 (for binary analog-to-digital conversion ⁇ ).
  • the amplification factor A1 is adjusted according to the advanced value of the gain gear of the programmable gain amplifier, and when the first voltage digital quantity D1 does not overflow, the larger the amplification factor is, the better. Make the conversion of the analog-to-digital converter no overflow to ensure the accuracy of the analog-to-digital conversion, and to maximize the accuracy of resistance measurement.
  • the PGA amplification factor is adjusted accordingly according to its gain level (binary or decimal), and the output of the PGA does not exceed the input upper limit or number of bits of the ADC.
  • Step 3 The microprocessor calculates the resistance value R S of the measured resistance according to the following formula:
  • R S R N *A REF *(D1′*p2/p1+D2/A2)/D FS ;
  • R N represents the resistance of the reference resistor
  • a REF represents the amplification factor of the first differential amplifier
  • D FS is the maximum conversion output number of the analog-to-digital converter.
  • the resistance value of the measured resistance R S is calculated according to the proportional method of the series branch, and the calculation process is:
  • D FS is the maximum output number of the analog-to-digital converter
  • D FS1 is the maximum input number of the digital-to-analog converter
  • D FS1 1/p2
  • D FS 1/p1.
  • Step 4 Control the control terminal of the first analog switch I by the microprocessor, and connect the second input terminal of the programmable gain amplifier to ground; control the control terminal of the second analog switch II and the control terminal of the third analog switch by the microprocessor
  • the control terminal III disconnects the output terminal of the first differential amplifier Amp1 from the analog-digital sensor and the voltage reference terminal of the digital-analog sensor.
  • the voltage at the common connection end of the measured resistance and the reference resistance is the single-ended voltage to ground corresponding to the potential difference between the two ends of the measured resistance, which can be directly input to The first input of the programmable gain amplifier.
  • the difference from the first embodiment is that this embodiment swaps the positions of the reference resistance and the resistance under test interface, and sets a second differential amplifier between the resistance under test and the programmable gain amplifier, such as Shown in Figure 4.
  • both ends of the measured resistance have potential, it is necessary to set a second differential amplifier Amp-2 with a double gain between the measured resistance and the first input terminal of the programmable gain amplifier.
  • the potential difference between the two ends of the measured resistance is converted into a single-ended voltage to ground, and then input to the programmable gain amplifier for gain amplification calculation. The rest are the same as the solution of the first embodiment, and will not be repeated here.
  • the number of bits of the analog-to-digital converter and the digital-to-analog converter are both 8 bits, that is, the resolution of the two is the same, which is 1/255.
  • the second voltage digital quantity D2 is shown in Table 1 (the values of n in the table are 3,5,6,0,2,9,3,12).
  • the 10-bit DAC device TLC5615 is selected to replace the 8-bit DAC device MAX515 in Example 1. Since its conversion voltage range is 0-2 times the reference voltage, considering that it cannot exceed the power supply voltage, its reference voltage is U REF /2. Do the same test, and the test results are shown in Table 2. It can be seen from Table 2 that there is no need to modify the conversion results of the DAC.
  • the average absolute error of the 8 test points is 0.016 ⁇ , the maximum absolute error does not exceed 0.1 ⁇ , the average relative error is 0.00975%, and the maximum relative error does not exceed 0.05%. It can be seen that the measurement of resistance of the present invention can achieve the purpose of high-precision measurement, and has a relatively good test effect.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Analogue/Digital Conversion (AREA)

Abstract

本发明公开了一种微差法与比例法结合的电阻高精度测量系统与方法，其中系统包括：恒流源、参考电阻、第一差分放大器、可编程增益放大器、模数转换器、微处理器、数模转换器和被测电阻接口；被测电阻接口接入被测电阻；参考电阻与被测电阻串联构成串联支路，连接于恒流源和地之间；第一差分放大器的两个输入端分别与参考电阻两端连接，输出端与模数转换器的电压参考端连接；可编程增益放大器，第一输入端用于接入被测电阻的对地单端电压，第二输入端被控地与数模转换器的模拟输出端或地连接，输出端与模数转换器的模拟输入端连接，模数转换器和数模转换器的数字输出端均与微处理器连接；本发明系统能克服电源波动影响，成本低、测量精度高。

Description

一种微差法与比例法结合的电阻高精度测量系统与方法 技术领域
本发明涉及传感器与检测技术及仪器仪表领域，具体属于一种微差法与比例法结合的低成本高精度电阻测量系统与方法。
背景技术
电阻的准确测量是电阻型传感器实现高精度测量的基础。电阻型传感器在实际工程中应用非常之多，其中需要对传感的电阻进行高精度测量的场合也常见。
在自动检测系统中，对电阻的高精度测量多采用数字化测量方式，测量装置一般都包含有微处理器(CPU)、模数转换器(ADC)、信号输入电路。数字化测量系统的精度则主要取决于ADC的精度或位数，一般位数越多，系统分辨力越高、精度越高，但价格也越高。以美国TI公司MSP430F系列的微控制器为例，含12位ADC的MSP430F5524的价格比含10位ADC的MSP430F5510的价格要高出许多，两者的性能参数基本相同，但前者的千片价格为3.05$，后者为1.70$(两者仅非易失存储器的参数不同，通过比较MSP430G2755和MSP430G2855，易知存储器方面对价格的影响较小)。测量系统中常常需要使用数模转换器(DAC)，但DAC的价格相对ADC而言较为低廉，8位DAC如DAC101S101、10位DAC如DAC081S101价格在0.5$左右(上述价格数据均来自器件公司的网上报价)。由此可见，数字化测量系统的精度、成本很大程度上是受ADC影响。这种情况造成实际应用中对电阻的高精度测量要求受到用户或厂商的低成本要求的制约，因此，如何以低成本实现高性能的问题就成为基于电阻测量的检测系统研发所需要着重解决的一个关键问题。
现有的自动检测系统，一般采用的是数字化电测技术，其实质仍是通过对能反映电阻变化的相应电压变化信号的测量来实现。在传感器与测量技术领域，为了减小或消除测量误差，常常采用替代法、比例法和微差法等方法来提高或改善测量精度，虽然每种方法各有其特点，但均存在相应的技术缺陷：
比例测量法(简称比例法)是利用被测量与已知量的比例关系计算确定被测量的量值的一种方法。应用时将被测电阻与已知标准电阻串联，利用两电阻的端电压和两电阻阻值的比例关系即可求出被测电阻阻值，电路简单，成本较低。以其实现高精度测量的优点是只有保证流过被测电阻与参考电阻串联支路的电流在短期内稳定，对具体数值却没有高要求。另外，以该方法实现高精度测量的条件实际还是包括了对电压测量的高精度要求。
微差测量法(简称微差法)是将被测量与同它只有微小差别的已知其量值的同种量或同性质标准量相比较，通过测量这两个量值之间的差值以确定被测量的量值的测量方法。用这种 方法测量时，只需测量两者的差值，并且由于标准量的误差很小，因此即使采用精度相对低的测量仪表，也能获得高的测量精度。采用精度相对低的测量仪表可以获得精度相对高的测量结果，这是微差法的主要优点。但是该方法在实际中是受到限制的，因为要获得与被测量相差很小的同类标准量是不容易的，有时是得不到的。
因此，单一使用比例法或微差法均很难在实现高精度电阻测量的同时又能降低测量系统的成本。
发明内容
针对上述问题本发明提供一种微差法与比例法结合的电阻测量系统与方法，实现高精度电阻测量的同时又能降低测量系统的成本。
为实现上述技术目的，本发明采用如下技术方案：
一种微差法与比例法结合的电阻高精度测量系统，包括恒流源、参考电阻、第一差分放大器、可编程增益放大器、模数转换器、微处理器、数模转换器和被测电阻接口；
所述被测电阻接口，用于接入被测电阻；
所述参考电阻与被测电阻串联构成串联支路，所述串联支路的一端与所述恒流源连接，所述串联支路的另一端接地；
所述第一差分放大器的两个输入端分别与所述参考电阻的两端连接，输出端与所述模数转换器的电压参考端连接；
所述可编程增益放大器，第一输入端用于接入所述被测电阻的对地单端电压，第二输入端被控地选择连接数模转换器的模拟输出端或地其中之一，可编程增益放大器的输出端与模数转换器的模拟输入端连接；所述被测电阻的对地单端电压，与被测电阻两端的电势差对应；
模数转换器的数字输出端和数模转换器的数字输入端均与微处理器连接。
本发明采用参考电阻与被测电阻串联构建串联支路，并由恒流源供电，然后巧妙地利用第一差分放大器、可编程增益放大器、模数转换器以及数模转换器的连接关系，以采用比例法与微差法相结合对被测电阻进行测量，从而可以将两个串联电阻的电压和电阻的比例关系转化为：第一差分放大器与可编程增益放大器之间的比例关系以及模数转换器的转换结果与其最大转换输出值之间的比例关系，进而将被测电阻的阻值与参考电阻的阻值、第一差分放大器的放大倍数、可编程增益放大器的放大倍数以及模数转换器的最大转换输出值建立关系，从而能克服被测电阻因电流变化对测量精度的影响以及电源波动对模数转换结果的影响；同时可降低对测量系统中模数转换器的精度要求，并且有效提高对被测电阻的测量精度。
正由于本发明对恒流源的精度和稳定性要求低、对模数转换器的位数要求低，因此本发明还可有效降低测量系统的构建成本。
进一步地，所述恒流源、参考电阻、被测电阻和地，依次连接形成所述串联支路；所述可编程增益放大器的第一输入端与被测电阻的非接地端连接；
或者，
所述系统还包括第二差分放大器，所述恒流源、被测电阻、参考电阻和地，依次连接形成所述串联支路；所述第二差分放大器，两个输入端分别与被测电阻的两端连接，输出端与所述可编程增益放大器的第一输入端连接，所述第二差分放大器的增益为一倍。
进一步地，数模转换器的电压参考端与第一差分放大器的输出端连接。
使ADC和DAC的参考电压为同一基准(第一差分放大器的输出电压U REF)，从而消除因被测电阻的工作电流变化或数值不准确、以及ADC与DAC的参考电压及其变化不同所带来的电阻测量误差，即是说可以克服电源波动对被测电阻高精度测量的影响。
进一步地，所述可编程增益放大器的控制端与微处理器连接，且可编程增益放大器由所述微处理器设置放大倍数。
进一步地，所述可编程增益放大器的放大倍数满足：可编程增益放大器输出的电压值小于模数转换器的最大转换值。
进一步地，还包括第一开关元件，所述第一开关元件的控制端与微处理器连接，用于微处理器控制可编程增益放大器的第二输入端与数模转换器的模拟输出端连接或与地连接；和/或，
还包括第二开关元件，所述第二开关元件的控制端与微处理器连接，用于微处理器控制第一差分放大器的输出端与模数转换器的电压参考端之间的通断；和/或，
还包括第三开关元件，所述第三开关元件的控制端与微处理器连接，用于微处理器控制第一差分放大器的输出端与数模转换器的电压参考端之间的通断。
一种微差法与比例法结合的电阻高精度测量方法，包括以下步骤：
步骤1，将被测电阻接入到上述任一系统的被测电阻接口，其中可编程增益放大器的第二输入端与地连接；
步骤2，微处理器获取对应被测电阻的模数转换结果；
步骤2.1，可编程增益放大器将被测电阻的对地单端电压U S放大A1倍，得到第一电压U S*A1；模数转换器对得到的第一电压U S*A1进行模数转换得到第一电压数字量D1；微处 理器从模数转换器读取第一电压数字量D1；
步骤2.2，微处理器按数模转换器位数计算并输出一个给定电压的数字量D1′并发送给数模转换器，数模转换器对给定电压数字量D1′进行数模转换得到给定电压U1；其中，
Figure PCTCN2020094604-appb-000001
表示向下取整，p1是模数转换器的分辨率，p2是数模转换器的分辨率，n为正整数，且n/D1≤σ，σ＝1/10或σ＝1/8；
步骤2.3，将可编程增益放大器的第二输入端从与地连接切换至与数模转换器的模拟输出端连接；
步骤2.4，可编程增益放大器将被测电阻对地单端电压U S和给定电压U1进行差分放大A2倍，得到第二电压(U S-U1)*A2；模数转换器对得到的第二电压(U S-U1)*A2进行模数转换得到第二电压数字量D2；微处理器从模数转换器读取第二电压数字量D2；
步骤3，微处理器按以下公式计算被测电阻的阻值R S：
Figure PCTCN2020094604-appb-000002
式中，R N表示参考电阻的阻值，A REF表示第一差分放大器的放大倍数，D FS为模数转换器的最大转换输出数字。
进一步地，所述系统还包括第一开关元件，所述第一开关元件的控制端与微处理器连接；
在执行步骤2之前，由微处理器控制第一开关元件，使可编程增益放大器的第二输入端与地连接；在步骤2.3时，由微处理器控制第一开关元件，使可编程增益放大器的第二输入端与数模转换器的模拟输出端连接。
进一步地，所述系统还包括第二开关元件和第三开关元件，第二开关元件和第三开关元件的控制端均与微处理器连接；
在步骤2之前，由微处理器控制第二开关元件连通，使第一差分放大器的输出端与模数转换器的电压参考端连通；以及在步骤3之后包括，由微处理器控制第二开关元件的断开，使第一差分放大器的输出端与模数转换器的电压参考端断开；
在执行步骤2之前，由微处理器控制第三开关元件连通，使第一差分放大器的输出端与数模转换器的电压参考端连通；以及在步骤3之后包括，由微处理器控制第三开关元件的断开，使第一差分放大器的输出端与数模转换器的电压参考端断开。
进一步地，在执行步骤2.1之前，由微处理器设置可编程增益放大器的放大倍数为A1；以及在执行步骤2.2之后且步骤2.4之前，由微处理器设置可编程增益放大器的放大倍数为A2。
有益效果
本发明采用参考电阻与被测电阻串联构建串联支路，并由恒流源供电，然后巧妙地利用第一差分放大器、可编程增益放大器、模数转换器以及数模转换器的连接关系，以采用比例法与微差法相结合对被测电阻进行测量，从而可以将两个串联电阻的电压和电阻的比例关系转化为：第一差分放大器与可编程增益放大器之间的比例关系以及模数转换器的转换结果与其最大转换输出值之间的比例关系，进而将被测电阻的阻值与参考电阻的阻值、第一差分放大器的放大倍数、可编程增益放大器的放大倍数以及模数转换器的最大转换输出值建立关系，从而能克服被测电阻因电流变化对测量精度的影响以及电源波动对模数转换结果的影响；同时可降低对测量系统中模数转换器的精度要求，并且有效提高对被测电阻的测量精度。
正由于本发明对恒流源的精度和稳定性要求低、对模数转换器的位数要求低，因此本发明还可有效降低测量系统的构建成本。
附图说明
图1为本发明实施例一的测量系统原理框图；
图2为本发明实施例一的恒流源和参考电压的设计电路图；
图3为本发明实施例一的测量装置的设计电路图；
图4为本发明实施例二的测量系统原理框图。
具体实施方式
下面对本发明的实施例作详细说明，本实施例以本发明的技术方案为依据开展，给出了详细的实施方式和具体的操作过程，对本发明的技术方案作进一步解释说明。
实施例一
本实施例提供一种微差法与比例法结合的电阻测量系统，其原理框图如图1所示，具体电路图如图3所示，包括被测电阻接口、恒流源、参考电阻R N、第一差分放大器Amp1、可编程增益放大器PGA、模数转换器ADC、微处理器CPU、数模转换器DAC、第一模拟开关I、第二模拟开关II和第三模拟开关III。
参考电阻的第一端与被测电阻接口的第一端连接，参考电阻的第二端与恒流源连接，被测电阻接口的第二端接地。
参考电阻的两端分别与第一差分放大器Amp1的两个输入端连接，第一差分放大器Amp1的输出端通过第二模拟开关II与模数转换器的电压参考端连接，第一差分放大器Amp1的输出端通过第三模拟开关III与数模转换器的电压参考端连接；其中，第二模拟开关II的控制端和第三模拟开关II的控制端均与微处理器连接，并由微处理器控制通断。在本实施例中记载的电压参考端，均是指模数转换器或者数模转换器的正端电压参考端VREF(+)，且负端电压参考端VREF(-)接地。
可编程增益放大器的第一输入端与被测电阻的第二端连接；可编程增益放大器的第二输入端与第一模拟开关I连接，第一模拟开关I的控制端与微处理器连接，并由微处理器控制可编程增益放大器的第二输入端与数模转换器的模拟输出端连接或与地连接，可编程增益放大器的输出端与模数转换器的模拟输入端连接；可编程增益放大器的控制端与微处理器连接，实现可编程增益放大器由所述微处理器控制放大倍数，且放大倍数满足：可编程增益放大器输出的电压值小于模数转换器的最大转换值。此处最大转换值，可以理解为，使模数转换器转换后刚好达到溢出的临界输入值。
模数转换器的数字输出端和数模转换器的数字输入端均与微处理器连接。
在本实施例中，微处理器CPU的型号为AT89C51，模数转换器ADC的型号为8位数(二进制)的ADC0809，数模转换器DAC为与模数转换器ADC同位数的MAX517，可编程增益放大器PGA由仪表放大器AD620和多路开关CD4051及电阻元件组合而成，第一差分放大器Amp1的型号为AD620，第二模拟开关II和第三模拟开关III的型号为ADG821，第一模拟开关I的型号为ADG852，电压参考源为REF2933AIDBZT，参考电阻R N选用100欧姆的锰铜电阻。
本实施例采用的恒流源，其电路为常用的电压参考源(电压基准源)器件结合集成运算放大器组成的负载接地恒流源电路实现方案，如图2所示。对于400欧姆以下的被测电阻，本实施例通过调整恒流源的输出，使参考电阻与被测电阻形成的串联支路的电流不超过10mA；对于400～1000欧姆的被测电阻，使其电流不超过5mA(对于工作电压为5V的电路而言)。
另外，本实施例中，第一差分放大器Amp1将参考电阻R N的端电压U N放大A REF倍，并变换为以模拟地电位(即零电位)为参考的单端输出电压，作为提供给模数转换器和数模转换器的共同参考电压U REF，从而可消除因被测电阻的工作电流变化或数值不确定、以及模数转换器和数模转换器的参考电压U REF及其变化不同所带来的测量误差。
其中，第一差分放大器Amp1的放大倍数A REF，根据参考电阻R N的端电压U N的幅值大小和模数转换器以及数模转换器的允许参考电压值进行设置。
相应于上述电阻高精度测量系统，本实施例再进一步使用该系统对被测电阻进行测量的方法进一步解释，其具体测量方法包括以下步骤：
步骤1，将被测电阻接入到微差法与比例法结合的电阻高精度测量系统的被测电阻接口；
所述系统包括恒流源、参考电阻、第一差分放大器、可编程增益放大器、模数转换器、微处理器、数模转换器和被测电阻接口；
所述被测电阻接口，用于接入被测电阻；
所述参考电阻与被测电阻串联构成串联支路，所述串联支路的一端与所述恒流源连接，所述串联支路的另一端接地；
所述第一差分放大器的两个输入端分别与所述参考电阻的两端连接，输出端与所述模数转换器的电压参考端连接；
所述可编程增益放大器，第一输入端用于接入所述被测电阻的对地单端电压，第二输入端被控地选择连接数模转换器的模拟输出端或地其中之一，可编程增益放大器的输出端与模数转换器的模拟输入端连接；所述被测电阻的对地单端电压，与被测电阻两端的电势差对应；
模数转换器的数字输出端和数模转换器的数字输入端均与微处理器连接。
在执行步骤2之前，需确认可编程增益放大器的第二输入端是否与地连接，若否，则需要通过微处理器控制第一模拟开关I的控制端，使可编程增益放大器的第二输入端与地连接；
在执行步骤2之前，还需要确认第一差分放大器Amp1的输出端是否与模数转换器的电压参考端以及数模转换器的电压参考端连接，若模数转换器或数模转换器中任意一个的电压参考端未与第一差分放大器Amp1的输出端连接，均需要通过微处理器控制相应的模拟开关的控制端，使模数转换器和数模转换器的电压参考端均与第一差分放大器Amp1的输出端连通，以接收第一差分放大器Amp1提供的参考电压U REF；
步骤2，微处理器获取阻值计算数据；
步骤2.1，可编程增益放大器将被测电阻的对地单端电压U S放大A1倍，得到第一电压U S*A1；模数转换器对得到的第一电压U S*A1进行模数转换得到第一电压数字量D1；微处理器从模数转换器读取第一电压数字量D1；
在该步骤2.1之前还包括，通过微控制器与可编程增益放大器的控制端之间的连接，设置可编程增益放大器的放大倍数为A1；
步骤2.2，微处理器按数模转换器位数根据第一电压数字量D1计算并输出一个给定电压 数字量D1′，并发送给数模转换器，数模转换器对给定电压数字量D1′进行数模转换得到给定电压U1；其中，
Figure PCTCN2020094604-appb-000003
表示向下取整，p1是模数转换器的分辨率，p2是数模转换器的分辨率，n为正整数，且n/D1≤σ，σ＝1/10或σ＝1/8；；
微处理器按上式输出给定电压数字量D1′，可使得DAC的输出电压(即给定电压U1)与被测电压Us(即被测电阻的对地单端电压U S)接近但略小一点，从而形成微差以完成高精度电阻测量。
步骤2.3，通过微处理器控制第一模拟开关I的控制端，将可编程增益放大器的第二输入端从与地连接切换至与数模转换器的模拟输出端连接；
步骤2.4，可编程增益放大器将被测电阻的对地单端电压U S和给定电压U1进行差分放大A2倍，得到第二电压(U S-U1)*A2；模数转换器对得到的第二电压(U S-U1)*A2进行模数转换得到第二电压数字量D2；微处理器从模数转换器读取第二电压数字量D2；
其中，在执行步骤2.2之后且步骤2.4之前还包括，由微处理器控制可编程增益放大器的放大倍数为A2；
在设置可编程增益放大器的放大倍数A1时，根据可编程增益放大器的增益档位进阶数值调整放大倍数，使得在执行步骤2.1的模数转换结果，即第一电压数字量D1，不产生溢出；同时为使电阻测量更精确，要求可编程增益放大器的放大倍数A1尽量更大，因此放大倍数A1还需满足：使得第一电压数字量D1的最高位尽可能为1(对于二进制模数转换器)。即是说，在本实施例中，根据可编程增益放大器的增益档位进阶数值调整放大倍数A1，在且满足第一电压数字量D1不产生溢出的情况下，放大倍数越大越好，从而使模数转换器的转换无溢出保证模数转换的准确性，而且最大程度提高电阻测量的精度。
同时，在设置可编程增益放大器的放大倍数A2时，根据测量系统对测量准确度的提高，要求所对应的ADC转换数字结果的有效数字位数的增加部分，不超过ADC的自身位数(即不超过ADC的分辨能力)，PGA的放大倍数则按其增益档位进阶数(二进制或十进制)进行相应调整，并保证PGA的输出不超过ADC的输入上限或位数。
步骤3，微处理器按以下公式计算被测电阻的阻值R S：
R S＝R N*A REF*(D1′*p2/p1+D2/A2)/D FS；
式中，R N表示参考电阻的阻值，A REF表示第一差分放大器的放大倍数，D FS为模数转换器的最大转换输出数字。
其中被测电阻R S的阻值根据串联支路按比例法进行推算，其推算过程为：
Figure PCTCN2020094604-appb-000004
式中，
Figure PCTCN2020094604-appb-000005
D FS是模数转换器的最大输出数字，D FS1是数模转换器的最大输入数字，D FS1＝1/p2,D FS＝1/p1。
步骤4，通过微处理器控制第一模拟开关I的控制端，使可编程增益放大器的第二输入端与地连接；通过微处理器控制第二模拟开关II的控制端和第三模拟开关的控制端III，使第一差分放大器Amp1的输出端与模数传感器以及数模传感器的电压参考端断开。
实施例二
在实施例一中，由于被测电阻的一端接地，因此被测电阻与参考电阻的共同连接端的电压，即为与被测电阻两端之间电势差对应的对地单端电压，可直接输入至可编程增益放大器的第一输入端。在本实施例二中，相对于实施例一的区别点在于，本实施例将参考电阻与被测电阻接口交换位置，以及在被测电阻与可编程增益放大器之间设置第二差分放大器，如图4所示。本实施例二中，由于被测电阻的两端均有电势，故需要在被测电阻与可编程增益放大器的第一输入端之间设置一个增益为一倍的第二差分放大器Amp-2，将被测电阻两端之间的电势差转换为对地的单端电压，然后再输入至可编程增益放大器进行增益放大计算。其余均与实施例一的方案相同，在此不再赘述。
在本实施例中，使用本发明测量系统和本发明测量方法，采用的模数转换器和数模转换器的位数均为8位，也即两者的分辨率相同，均为1/255，选择8组不同阻值的被测电阻进行测量，并在proteus7.8软件环境下进行了仿真测试，其中设置A1＝2，A REF＝10，D FS＝255。所测量的电阻值、由DAC转换引起的误差修正量、测量电阻的修正值、测量值的绝对误差、 相对误差、相应的放大增益A2的值以及数字量D1′、第一电压数字量D1、第二电压数字量D2如表1所示(表中n取值依次为：3,5,6,0,2,9,3,12)。
表1
Figure PCTCN2020094604-appb-000006
另外，选择10位DAC器件TLC5615替换实施例1中的8位DAC器件MAX515，由于其转换电压范围为0-2倍参考电压，考虑其不能超过电源电压，使其参考电压为U REF/2,做相同的测试，各测试结果如表2所示。由表2可知，对DAC的转换结果无需修正，这里为了区分分别对应10位和8位DAC的数字量，记CPU给10位DAC的输入数字量为D0，它是按8位DAC对D1”＝(D1-n)/A1变换为10位后取整的数字量
Figure PCTCN2020094604-appb-000007
R S＝R N*A REF*(D0*p2/p1+D2/A2)/D FS,此处p2/p1＝255/1024≈1/4。
由表1和表2得知，8个测试点的平均绝对误差为0.016Ω，最大绝对误差不超过0.1Ω，平均相对误差为0.00975％，最大相对误差不超过0.05％。可以看出本发明对电阻的测量能达到高精度测量的目的，具有较优的测试效果。
表2
Figure PCTCN2020094604-appb-000008
以上实施例为本申请的优选实施例，本领域的普通技术人员还可以在此基础上进行各种变换或改进，在不脱离本申请总的构思的前提下，这些变换或改进都应当属于本申请要求保 护的范围之内。

Claims (9)

  1. 一种微差法与比例法结合的电阻高精度测量系统，其特征在于，包括恒流源、参考电阻、第一差分放大器、可编程增益放大器、模数转换器、微处理器、数模转换器和被测电阻接口；
    所述被测电阻接口，用于接入被测电阻；
    所述参考电阻与被测电阻串联构成串联支路，所述串联支路的一端与所述恒流源连接，所述串联支路的另一端接地；
    所述第一差分放大器的两个输入端分别与所述参考电阻的两端连接，输出端与所述模数转换器的电压参考端连接；数模转换器的电压参考端与第一差分放大器的输出端连接；
    所述可编程增益放大器，第一输入端用于接入所述被测电阻的对地单端电压，第二输入端被控地选择连接数模转换器的模拟输出端或地其中之一，可编程增益放大器的输出端与模数转换器的模拟输入端连接；所述被测电阻的对地单端电压，与被测电阻两端的电势差对应；
    模数转换器的数字输出端和数模转换器的数字输入端均与微处理器连接。
  2. 根据权利要求1所述的系统，其特征在于，所述恒流源、参考电阻、被测电阻和地，依次连接形成所述串联支路；所述可编程增益放大器的第一输入端与被测电阻的非接地端连接；
    或者，
    所述系统还包括第二差分放大器，所述恒流源、被测电阻、参考电阻和地，依次连接形成所述串联支路；所述第二差分放大器，两个输入端分别与被测电阻的两端连接，输出端与所述可编程增益放大器的第一输入端连接，所述第二差分放大器的增益为一倍。
  3. 根据权利要求1所述的系统，其特征在于，所述可编程增益放大器的控制端与微处理器连接，且可编程增益放大器由所述微处理器设置放大倍数。
  4. 根据权利要求1所述的系统，其特征在于，所述可编程增益放大器的放大倍数满足：可编程增益放大器输出的电压值小于模数转换器的最大转换值。
  5. 根据权利要求1所述的系统，其特征在于，还包括第一开关元件，所述第一开关元件的控制端与微处理器连接，用于微处理器控制可编程增益放大器的第二输入端与数模转换器的模拟输出端连接或与地连接；和/或，
    还包括第二开关元件，所述第二开关元件的控制端与微处理器连接，用于微处理器控制第一差分放大器的输出端与模数转换器的电压参考端之间的通断；和/或，
    还包括第三开关元件，所述第三开关元件的控制端与微处理器连接，用于微处理器控制第一差分放大器的输出端与数模转换器的电压参考端之间的通断。
  6. 一种微差法与比例法结合的电阻高精度测量方法，其特征在于，包括以下步骤：
    步骤1，将被测电阻接入到权利要求1-4任一所述系统的被测电阻接口，其中可编程增益放大器的第二输入端与地连接；
    步骤2，微处理器获取对应被测电阻的模数转换结果；
    步骤2.1，可编程增益放大器将被测电阻的对地单端电压U S放大A1倍，得到第一电压U S*A1；模数转换器对得到的第一电压U S*A1进行模数转换得到第一电压数字量D1；微处理器从模数转换器读取第一电压数字量D1；
    步骤2.2，微处理器按数模转换器位数计算并输出一个给定电压的数字量D1′并发送给数模转换器，数模转换器对给定电压数字量D1′进行数模转换得到给定电压U1；其中，
    Figure PCTCN2020094604-appb-100001
    表示向下取整，p1是模数转换器的分辨率，p2是数模转换器的分辨率，n为正整数，且n/D1≤σ，σ＝1/10或σ＝1/8；
    步骤2.3，将可编程增益放大器的第二输入端从与地连接切换至与数模转换器的模拟输出端连接；
    步骤2.4，可编程增益放大器将被测电阻对地单端电压U S和给定电压U1进行差分放大A2倍，得到第二电压(U S-U1)*A2；模数转换器对得到的第二电压(U S-U1)*A2进行模数转换得到第二电压数字量D2；微处理器从模数转换器读取第二电压数字量D2；
    步骤3，微处理器按以下公式计算被测电阻的阻值R S：
    Figure PCTCN2020094604-appb-100002
    式中，R N表示参考电阻的阻值，A REF表示第一差分放大器的放大倍数，D FS为模数转换器的最大转换输出数字。
  7. 根据权利要求6所述的方法，其特征在于，所述系统还包括第一开关元件，所述第一开关元件的控制端与微处理器连接；
    在执行步骤2之前，由微处理器控制第一开关元件，使可编程增益放大器的第二输入端与地连接；在步骤2.3时，由微处理器控制第一开关元件，使可编程增益放大器的第二输入端与数模转换器的模拟输出端连接。
  8. 根据权利要求6所述的方法，其特征在于，所述系统还包括第二开关元件和第三开关元件，第二开关元件和第三开关元件的控制端均与微处理器连接；
    在步骤2之前，由微处理器控制第二开关元件连通，使第一差分放大器的输出端与模数 转换器的电压参考端连通；以及在步骤3之后包括，由微处理器控制第二开关元件的断开，使第一差分放大器的输出端与模数转换器的电压参考端断开；
    在执行步骤2之前，由微处理器控制第三开关元件连通，使第一差分放大器的输出端与数模转换器的电压参考端连通；以及在步骤3之后包括，由微处理器控制第三开关元件的断开，使第一差分放大器的输出端与数模转换器的电压参考端断开。
  9. 根据权利要求6所述的方法，其特征在于，在执行步骤2.1之前，由微处理器设置可编程增益放大器的放大倍数为A1；以及在执行步骤2.2之后且步骤2.4之前，由微处理器设置可编程增益放大器的放大倍数为A2。
PCT/CN2020/094604 2019-06-19 2020-06-05 一种微差法与比例法结合的电阻高精度测量系统与方法 Ceased WO2020253552A1 (zh)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US17/433,311 US11327099B2 (en) 2019-06-19 2020-06-05 High-precision resistance measurement system and method combining micro-differential method and ratiometric method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201910529492.6 2019-06-19
CN201910529492.6A CN110161313B (zh) 2019-06-19 2019-06-19 一种微差法与比例法结合的电阻高精度测量系统与方法

Publications (1)

Publication Number Publication Date
WO2020253552A1 true WO2020253552A1 (zh) 2020-12-24

Family

ID=67625982

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2020/094604 Ceased WO2020253552A1 (zh) 2019-06-19 2020-06-05 一种微差法与比例法结合的电阻高精度测量系统与方法

Country Status (3)

Country Link
US (1) US11327099B2 (zh)
CN (1) CN110161313B (zh)
WO (1) WO2020253552A1 (zh)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110161313B (zh) 2019-06-19 2020-07-24 中南大学 一种微差法与比例法结合的电阻高精度测量系统与方法
CN110780182A (zh) * 2019-09-24 2020-02-11 苏州华兴源创科技股份有限公司 Lcd/oled驱动芯片的检测系统和方法
CN111337747B (zh) * 2020-03-23 2022-03-15 东软睿驰汽车技术（沈阳）有限公司 测量电阻的装置、方法、车载控制器及电动汽车
CN113702710B (zh) * 2020-05-21 2024-11-12 圣邦微电子（北京）股份有限公司 电阻测试电路及电阻测试方法
CN113702711B (zh) * 2020-05-21 2024-11-12 圣邦微电子（北京）股份有限公司 电阻测试电路及电阻测试方法
CN115808653A (zh) * 2021-09-15 2023-03-17 中山市江波龙电子有限公司 采样电阻的电流校准方法、电流采样电路及可读存储介质
CN114036879B (zh) * 2021-11-08 2025-02-14 中国商用飞机有限责任公司北京民用飞机技术研究中心 一种模拟信号采集电路设计方法、采集方法及装置
CN114553222B (zh) * 2022-02-25 2023-03-10 苏州联讯仪器有限公司 一种提高采样保持器增益范围的装置、方法
CN114545086A (zh) * 2022-02-25 2022-05-27 展讯通信（上海）有限公司 待测电阻校准电路、方法和装置
CN114778945B (zh) * 2022-04-28 2025-02-11 深圳市鼎阳科技股份有限公司 一种电阻测量电路、电阻测量方法和数字万用表
CN115694498A (zh) * 2022-10-26 2023-02-03 中国航空工业集团公司西安航空计算技术研究所 高精度模拟量采集电路及方法
FR3147872A1 (fr) * 2023-04-14 2024-10-18 Ateq Dispositif de mesure d’une résistance électrique d’un élément
FR3147873B1 (fr) * 2023-04-14 2025-04-18 Ateq Dispositif de mesure d’une résistance électrique d’un élément
WO2024213382A1 (fr) * 2023-04-14 2024-10-17 Ateq Dispositif de mesure d'une resistance electrique d'un element
CN118483462B (zh) * 2024-02-18 2024-12-31 上海芯诣电子科技有限公司 一种半导体检测电路和方法、半导体检测设备和存储介质
CN118914654B (zh) * 2024-08-02 2025-05-13 成都津研科技有限公司 一种高精度源测量单元
CN119780533B (zh) * 2025-03-11 2025-05-13 聊城大学 一种电阻测量电路及其电阻测量方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4160949A (en) * 1978-03-06 1979-07-10 California Instruments Corporation Auto-zeroed ohmmeter
US5469071A (en) * 1993-12-07 1995-11-21 Kabushiki Kaisha Toshiba Resistor sensor input apparatus
JPH0989952A (ja) * 1995-09-27 1997-04-04 Toshiba Microelectron Corp 抵抗検出回路
CN2702317Y (zh) * 2003-12-02 2005-05-25 赵军 电阻类仪器比例法检定电路
CN102317798A (zh) * 2011-04-13 2012-01-11 华为技术有限公司 电阻检测装置及方法
CN106383272A (zh) * 2015-07-30 2017-02-08 北京电子工程总体研究所 一种高精度小电阻阻值测量电路
CN110161313A (zh) * 2019-06-19 2019-08-23 中南大学 一种微差法与比例法结合的电阻高精度测量系统与方法

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2932568B1 (fr) * 2008-06-11 2010-06-11 Schneider Electric Ind Sas Dispositif de mesure de courant et unite de traitement comportant un tel dispositif
JP2010164358A (ja) * 2009-01-14 2010-07-29 Pulstec Industrial Co Ltd 抵抗測定装置および抵抗測定方法
CN102841260B (zh) * 2012-09-24 2015-06-10 哈尔滨工业大学 直流微电阻测量系统
CN205176136U (zh) * 2015-11-02 2016-04-20 广州开元电子科技有限公司 一种电阻测试装置
DE112017001269T5 (de) * 2016-03-11 2018-11-29 Analog Devices Global Unlimited Company Ausbildbare Hardwareplattform für Messung oder Steuerung
WO2018023080A2 (en) * 2016-07-29 2018-02-01 Apple Inc. Methodology and application of acoustic touch detection
WO2018196986A1 (en) * 2017-04-27 2018-11-01 Advantest Corporation Calibration arrangement and method for deriving a resistance of a resistor
US10935620B2 (en) * 2019-02-26 2021-03-02 Cirrus Logic, Inc. On-chip resonance detection and transfer function mapping of resistive-inductive-capacitive sensors
GB2594668B (en) * 2019-08-02 2022-04-27 Cirrus Logic Int Semiconductor Ltd Detector and method for measuring a resistance of a variable resistance sensor whose resistance varies with respect to a time-varying stimulus

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4160949A (en) * 1978-03-06 1979-07-10 California Instruments Corporation Auto-zeroed ohmmeter
US5469071A (en) * 1993-12-07 1995-11-21 Kabushiki Kaisha Toshiba Resistor sensor input apparatus
JPH0989952A (ja) * 1995-09-27 1997-04-04 Toshiba Microelectron Corp 抵抗検出回路
CN2702317Y (zh) * 2003-12-02 2005-05-25 赵军 电阻类仪器比例法检定电路
CN102317798A (zh) * 2011-04-13 2012-01-11 华为技术有限公司 电阻检测装置及方法
CN106383272A (zh) * 2015-07-30 2017-02-08 北京电子工程总体研究所 一种高精度小电阻阻值测量电路
CN110161313A (zh) * 2019-06-19 2019-08-23 中南大学 一种微差法与比例法结合的电阻高精度测量系统与方法

Also Published As

Publication number Publication date
US11327099B2 (en) 2022-05-10
CN110161313B (zh) 2020-07-24
CN110161313A (zh) 2019-08-23
US20220091169A1 (en) 2022-03-24

Similar Documents

Publication Publication Date Title
CN110161313B (zh) 一种微差法与比例法结合的电阻高精度测量系统与方法
US7812589B2 (en) Modified current source (MCS) with seamless range switching
TW200849830A (en) Analog-to-digital converter offset and gain calibration using internal voltage references
WO2021184740A1 (zh) 一种测试系统中供电通道的电流校准装置及校正方法
CN111855078A (zh) 一种桥梁测力传感器零点自动调节电路及调节方法
CN101498749A (zh) 一种精密电阻测量装置和方法
CN107145182A (zh) 输入电压型模拟电阻器及电阻控制方法
CN205843835U (zh) 应用动态恒流源的铂电阻数字温度表
CN107132417A (zh) 一种抗电路参数漂移的高精度电阻测量方法
CN117607775A (zh) 一种数字示波器模拟通道直流增益现场校准方法
CN101533080A (zh) 数字可调精密直流电阻的系统及检测方法
CN114487984B (zh) 射频电源的校准装置及方法
CN109540313A (zh) 一种基于硅基二极管与ntc热敏电阻的线性测温电路
CN111141406B (zh) 一种pt100测温系统和测温方法
CN113541690A (zh) 一种生产线检测设备的校准方法及模数转换校准系统
CN209486536U (zh) 一种温度传感器校验用恒流源
CN117572321B (zh) 电压比率超量程自校准方法、计算机设备和存储介质
CN107835019A (zh) 一种高精度数模转换器的工厂校准系统及校准方法
CN114660522B (zh) 一种用于校准变压器测试设备的系统
CN101499801B (zh) 一种a/d转换电路及其转换方法
CN108572273B (zh) 低电流测量电路及其测量方法
CN214585670U (zh) 一种高阻抗指针式直流电压表
CN212364401U (zh) 一种测量微弱信号的电阻传感器测量电路
CN208188206U (zh) 一种低阻值电阻测量装置
CN208094531U (zh) 一种高速多通道高精度adda转换电路

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20825718

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

32PN Ep: public notification in the ep bulletin as address of the adressee cannot be established

Free format text: NOTING OF LOSS OF RIGHTS PURSUANT TO RULE 112(1) EPC (EPO FORM 1205A DATED 24.05.2022)

122 Ep: pct application non-entry in european phase

Ref document number: 20825718

Country of ref document: EP

Kind code of ref document: A1