CN113189172B - PH value transmitting circuit for automatic temperature compensation based on thin-film platinum thermal resistor - Google Patents

PH value transmitting circuit for automatic temperature compensation based on thin-film platinum thermal resistor Download PDF

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CN113189172B
CN113189172B CN202110411576.7A CN202110411576A CN113189172B CN 113189172 B CN113189172 B CN 113189172B CN 202110411576 A CN202110411576 A CN 202110411576A CN 113189172 B CN113189172 B CN 113189172B
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管力明
陈德传
马雪晴
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Xi'an Huaqi Zhongxin Technology Development Co ltd
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Hangzhou Dianzi University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/302—Electrodes, e.g. test electrodes; Half-cells pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K15/00—Testing or calibrating of thermometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
    • G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/36—Glass electrodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit

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Abstract

The invention belongs to the field of industrial measurement and control, relates to a circuit, in particular to a pH value transmitting circuit for carrying out automatic temperature compensation based on a thin-film platinum thermal resistor, and is suitable for various application occasions needing to detect the pH value (pH value) of liquid. The invention comprises a film thermal resistor TD1, a composite electrode GE1, an amplifier IC1, a signal operational amplifier IC2, a compensation operational amplifier IC3, a reference source IC4, an inverse operational amplifier IC5, a V/I operational amplifier IC6, a follower IC7, a compensation potentiometer RP1, a reference potentiometer RP2 and the like. According to the relationship between the output signal of the glass electrode and the temperature of the liquid to be measured and the operational relationship of the circuit gain, the invention adopts a circuit scheme taking an operational amplifier as a main part to carry out automatic temperature full compensation, and takes a power operational amplifier as an output stage to output an industrial standard current signal which is in direct proportion to the pH value to be measured. The invention has the advantages of simple and reliable circuit, strong anti-interference capability, low cost and easy product production.

Description

PH value transmitting circuit for carrying out automatic temperature compensation based on thin film platinum thermal resistor
Technical Field
The invention belongs to the field of industrial measurement and control, relates to a circuit, in particular to a pH value transmitting circuit for carrying out automatic temperature compensation based on a thin-film platinum thermal resistor, and is suitable for various application occasions needing to detect the pH value (pH value) of liquid.
Background
The application range of the on-line detection and control of the liquid pH value (pH value) is very wide, and the on-line detection and control of the liquid pH value (pH value) is in various industries, wherein the most used detection scheme is based on the composite glass electrode, but the output signal of the composite glass electrode is greatly influenced by the temperature of the detected liquid, so how to solve the temperature compensation problem becomes a key technical problem in the pH value detection based on the composite glass electrode. At present, the pH value on-line detection technology mainly adopts MCU (single chip microcomputer, DSP and the like) as a core, armored platinum resistors as temperature measuring elements and a software algorithm for temperature compensation, and has the following defects: the detection device has high cost, long development period and high anti-interference requirement, and in addition, the armored platinum resistor has large volume and is difficult to be integrally installed with the glass electrode, thereby limiting the use environment condition. With the emergence of the film type thermal resistor, the integration with the glass electrode becomes possible, and based on the integration, the invention provides a full-circuit type automatic temperature compensation pH value transmitting circuit, which has important practical significance and product value.
Disclosure of Invention
The invention aims to provide a pH value transmitting circuit with automatic temperature compensation based on a composite glass electrode, a thin film platinum thermal resistor as a detection element and an operational amplifier as a core, aiming at the defects in the prior art. The core of the invention is that according to the relation between the output signal of the glass electrode and the temperature of the liquid to be measured and the operational relation of the circuit gain, a circuit scheme mainly comprising an operational amplifier is adopted to carry out automatic temperature full compensation, and a power operational amplifier is used as an output stage to output an industrial standard current signal which is in direct proportion to the pH value to be measured. The invention has the advantages of simple and reliable circuit, strong anti-interference capability, low cost and easy product production.
A pH value transmitting circuit for automatic temperature compensation based on a thin-film platinum thermal resistor comprises: a thin film thermal resistor TD1, a composite electrode GE1, an amplifier IC1, a signal operational amplifier IC2, a compensation operational amplifier IC3, a reference source IC4, an inverse operational amplifier IC5, a V/I operational amplifier IC6, a follower IC7, a compensation potentiometer RP1, a reference potentiometer RP2, an input resistor R1, a bias resistor R2, an amplification resistor R3, a reference resistor R4, an inverse resistor R5, an upper voltage-dividing resistor R6, a lower voltage-dividing resistor R7, a reference resistor R8, a detection resistor R9, a detection resistor R10, a left voltage-dividing resistor R11, a right voltage-dividing resistor R12, a compensation resistor R13, an operational resistor R13, a positive terminal resistor R13, a negative terminal resistor R13, a positive feedback resistor R13, a negative feedback resistor R13, a follower resistor R13, a sampling resistor R13, a load resistor RL, a filter capacitor C13, a TD 13, a thermal resistor 13, a signal output terminal of the other terminal of the TD 13 is connected with an output terminal of the compensation resistor R13, and an output terminal of the thin film thermal amplifier IC 13, the negative end Eph-end of the composite electrode GE1 is grounded, the positive end Eph + end of the composite electrode GE1 is connected with one end of an input resistor R1, the other end of the input resistor R1 is connected with one end of a filter capacitor C1 and the positive input end IN + end of an amplifier IC1, the other end of the filter capacitor C1 is grounded, the positive power source end + V end of a reference source IC4 is connected with the positive power source end + VCC end of the circuit, the ground end GND end of the reference source IC4 is grounded, the output end OUT end of the reference source IC4 is connected with one end of a bias resistor R2, one end of a reference resistor R4 and one end of an upper voltage-dividing resistor R6, the other end of the reference resistor R4 is connected with one end of an inverting resistor R5 and the positive input end IN-end of an inverting operational amplifier IC5, the other end of the inverting resistor R5 is connected with one end of a lower voltage-dividing resistor R7, the output end OUT end of the inverting operational amplifier IC5 and one end of a left voltage-dividing resistor R11, and the inverting operational amplifier IC5 is grounded, the positive power terminal + V terminal of the inverting operational amplifier IC5 is connected with the positive power terminal + VCC terminal of the circuit, the negative power terminal-V terminal of the inverting operational amplifier IC5 is connected with the negative power terminal-VSS terminal of the circuit, the other end of the left divider resistor R11 is connected with one end of the right divider resistor R12 and one end of the negative terminal resistor R16, the other end of the right divider resistor R12 is grounded, the other end of the lower divider resistor R7 is connected with the right end of the reference potentiometer RP2, the left end of the reference potentiometer RP2 is connected with the other end of the upper divider resistor R6, the center terminal of the reference potentiometer RP2 is connected with one end of the reference resistor R8, the other end of the bias resistor R2 is connected with one end of the amplifying resistor R3 and the negative input terminal IN-terminal of the amplifier IC1, the other end of the amplifying resistor R3 is connected with one end of the output terminal OUT terminal of the amplifier IC1 and one end of the detection resistor R9, the positive power terminal of the amplifier IC1 is connected with the positive power terminal + VCC terminal of the circuit, the negative power supply end-V end of the amplifier IC1 is connected with the negative power supply end-VSS end of the circuit, the negative input end IN-end of the signal operational amplifier IC2 is connected with the other end of the reference resistor R8, the other end of the detection resistor R9 and the other end of the output resistor R10, the positive input end IN + end of the signal operational amplifier IC2 is grounded, the positive power supply end + V end of the signal operational amplifier IC2 is connected with the positive power supply end + VCC end of the circuit, the negative power supply end-V end of the signal operational amplifier IC2 is connected with the negative power supply end-VSS end of the circuit, the other end of the compensation resistor R13 is connected with one end of the operational resistor R14 and the negative input end IN-end of the compensation operational amplifier IC3, the other end of the operational resistor R14 is connected with one end of the compensation potentiometer RP1, the other end and the center end of the compensation potentiometer RP1 are both connected with the output end OUT end of the compensation operational amplifier IC3 and one end of the positive resistor R15, the positive input end IN + end of the compensation operational amplifier IC3 is grounded, the positive power terminal + V terminal of the compensation operational amplifier IC3 is connected with the positive power terminal + VCC terminal of the circuit, the negative power terminal-V terminal of the compensation operational amplifier IC3 is connected with the negative power terminal-VSS terminal of the circuit, the other end of the positive resistor R15 is connected with one end of the positive feedback resistor R17 and the positive input terminal IN + terminal of the V/I operational amplifier IC6, one end of the positive feedback resistor R17 is connected with one end of the sampling resistor R20 and one end of the load resistor RL, the other end of the load resistor RL is grounded, the negative input terminal IN-terminal of the V/I operational amplifier IC6 is connected with the other end of the negative resistor R16 and one end of the negative feedback resistor R18, the output terminal OUT terminal of the V/I operational amplifier IC6 is connected with the other end of the sampling resistor R20 and one end of the following resistor R19, the positive power terminal + V terminal of the V/I operational amplifier IC6 is connected with the positive power terminal + V terminal of the positive power terminal of the circuit, the negative power terminal-V terminal of the V/I operational amplifier IC6 is connected with the negative power terminal-VSS terminal of the circuit, the positive input end IN + end of the follower IC7 of the follower operational amplifier is connected with the other end of the follower resistor R19 and one end of the follower capacitor C2, the other end of the follower capacitor C2 is grounded, the negative input end IN-end and the output end OUT-end of the follower IC7 are both connected with the other end of the negative feedback resistor R18, the positive power source end + V end of the follower IC7 is connected with the positive power source end + VCC end of the circuit, and the negative power source end-V end of the follower IC7 is connected with the negative power source end-VSS end of the circuit.
The invention has the following beneficial effects:
the invention adopts a simple circuit scheme mainly comprising an operational amplifier to realize automatic temperature full compensation of the output signal of the glass electrode, and outputs an industrial standard current signal which is in direct proportion to the measured pH value by taking a power operational amplifier as an output stage. The invention has the advantages of simple and reliable circuit, strong anti-interference capability, low cost, easy productization, wide application range and industrialization prospect.
Drawings
Fig. 1 is a circuit diagram of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
A pH value transmitting circuit for automatic temperature compensation based on a thin film platinum thermistor as shown in fig. 1, comprising: a thin film thermal resistor TD1, a composite electrode GE1, an amplifier IC1, a signal operational amplifier IC2, a compensation operational amplifier IC3, a reference source IC4, an inverse operational amplifier IC5, a V/I operational amplifier IC6, a follower IC7, a compensation potentiometer RP1, a reference potentiometer RP2, an input resistor R1, a bias resistor R2, an amplification resistor R3, a reference resistor R4, an inverse resistor R5, an upper voltage-dividing resistor R6, a lower voltage-dividing resistor R7, a reference resistor R8, a detection resistor R9, a detection resistor R10, a left voltage-dividing resistor R11, a right voltage-dividing resistor R12, a compensation resistor R13, an operational resistor R13, a positive terminal resistor R13, a negative terminal resistor R13, a positive feedback resistor R13, a negative feedback resistor R13, a follower resistor R13, a sampling resistor R13, a load resistor RL, a filter capacitor C13, a TD 13, a thermal resistor 13, a signal output terminal of the other terminal of the TD 13 is connected with an output terminal of the compensation resistor R13, and an output terminal of the thin film thermal amplifier IC 13, the negative end Eph-end of the composite electrode GE1 is grounded, the positive end Eph + end of the composite electrode GE1 is connected with one end of an input resistor R1, the other end of the input resistor R1 is connected with one end of a filter capacitor C1 and the positive input end IN + end of an amplifier IC1, the other end of the filter capacitor C1 is grounded, the positive power source end + V end of a reference source IC4 is connected with the positive power source end + VCC end of the circuit, the ground end GND end of the reference source IC4 is grounded, the output end OUT end of the reference source IC4 is connected with one end of a bias resistor R2, one end of a reference resistor R4 and one end of an upper voltage-dividing resistor R6, the other end of the reference resistor R4 is connected with one end of an inverting resistor R5 and the positive input end IN-end of an inverting operational amplifier IC5, the other end of the inverting resistor R5 is connected with one end of a lower voltage-dividing resistor R7, the output end OUT end of the inverting operational amplifier IC5 and one end of a left voltage-dividing resistor R11, and the inverting operational amplifier IC5 is grounded, the positive power supply terminal + V terminal of the inverting operational amplifier IC5 is connected with the positive power supply terminal + VCC terminal of the circuit, the negative power supply terminal-V terminal of the inverting operational amplifier IC5 is connected with the negative power supply terminal-VSS terminal of the circuit, the other end of the left voltage-dividing resistor R11 is connected with one end of the right voltage-dividing resistor R12 and one end of the negative terminal resistor R16, the other end of the right voltage-dividing resistor R12 is grounded, the other end of the lower voltage-dividing resistor R7 is connected with the right end of the reference potentiometer RP2, the left end of the reference potentiometer RP2 is connected with the other end of the upper voltage-dividing resistor R6, the center terminal of the reference potentiometer RP2 is connected with one end of the reference resistor R8, the other end of the bias resistor R2 is connected with one end of the amplifying resistor R3 and the negative input terminal IN-terminal of the amplifier IC1, the other end of the amplifying resistor R3 is connected with the output terminal OUT terminal of the amplifier IC1 and one end of the detection resistor R9, the positive power supply terminal 1 is connected with the positive power supply terminal of the circuit, the negative power supply end-V end of the amplifier IC1 is connected with the negative power supply end-VSS end of the circuit, the negative input end IN-end of the signal operational amplifier IC2 is connected with the other end of the reference resistor R8, the other end of the detection resistor R9 and the other end of the output resistor R10, the positive input end IN + end of the signal operational amplifier IC2 is grounded, the positive power supply end + V end of the signal operational amplifier IC2 is connected with the positive power supply end + VCC end of the circuit, the negative power supply end-V end of the signal operational amplifier IC2 is connected with the negative power supply end-VSS end of the circuit, the other end of the compensation resistor R13 is connected with one end of the operational resistor R14 and the negative input end IN-end of the compensation operational amplifier IC3, the other end of the operational resistor R14 is connected with one end of the compensation potentiometer RP1, the other end and the center end of the compensation potentiometer RP2 are both connected with the output end OUT end of the compensation operational amplifier IC3 and one end of the positive resistor R15, the positive input end IN + end of the compensation amplifier IC3 is grounded, the positive power source terminal + V terminal of the compensation operational amplifier IC3 is connected with the positive power source terminal + VCC terminal of the circuit, the negative power source terminal-V terminal of the compensation operational amplifier IC3 is connected with the negative power source terminal-VSS terminal of the circuit, the other terminal of the positive terminal resistor R15 is connected with one terminal of the positive feedback resistor R17 and the positive input terminal IN + terminal of the V/I operational amplifier IC6, one terminal of the other terminal of the positive feedback resistor R17 is connected with one terminal of the sampling resistor R20 and one terminal of the load resistor RL, the other terminal of the load resistor RL is grounded, the negative input terminal IN-terminal of the V/I operational amplifier IC6 is connected with the other terminal of the negative terminal resistor R16 and one terminal of the negative feedback resistor R18, the output terminal OUT terminal of the V/I operational amplifier IC6 is connected with the other terminal of the sampling resistor R20 and one terminal of the following resistor R19, the positive power source terminal + V terminal of the V/I operational amplifier IC6 is connected with the positive power source terminal + VCC terminal of the circuit, the negative-V/I operational amplifier IC6 is connected with the negative power source terminal VSS-VSS terminal of the circuit, the positive input end IN + end of the follower IC7 of the follower operational amplifier is connected with the other end of the follower resistor R19 and one end of the follower capacitor C2, the other end of the follower capacitor C2 is grounded, the negative input end IN-end and the output end OUT-end of the follower IC7 are both connected with the other end of the negative feedback resistor R18, the positive power source end + V end of the follower IC7 is connected with the positive power source end + VCC end of the circuit, and the negative power source end-V end of the follower IC7 is connected with the negative power source end-VSS end of the circuit.
All devices used by the invention, including a thin film thermal resistor TD1, an amplifier IC1, a signal operational amplifier IC2, a compensation operational amplifier IC3, a reference source IC4, a reverse phase operational amplifier IC5, a V/I operational amplifier IC6, a follower IC7 and the like, adopt existing mature device products and can be obtained through the market. For example: the thin film thermal resistor TD1 adopts a thin film Pt1000, an amplifier, a signal operational amplifier, a compensation operational amplifier and a follower adopt TLC2264, an inverse operational amplifier adopts TLC2262, a reference source adopts MC1403, a V/I operational amplifier adopts NJM4556A and the like.
The main circuit parameters in the invention are matched as follows:
setting: epH: potential of the pH composite electrode (unit: V); e0: electrode zero potential (unit: V), R: gas constant, 8.314 (unit: J/(mol. K)), F: faraday constant, 96485 (unit: C/mol); k is a radical ofpH: electrode transformation coefficients (unit: V/pH); beta: electrode temperature factor (unit: 1/. degree. C.) I0: the circuit outputs a current (unit: A), I0∈[I0min,I0max]；Vref: circuit reference voltage (unit: V); u. up: zero potential compensation signal (unit: V); u. ofi0: outputting an offset signal (unit: V); rT0: the thermal resistance zero temperature value (unit: Ω); t, tmax: ambient temperature of use and its maximum value (deg.C); vcc, Vss: the positive and negative power supply voltages (unit: V) of the circuit, respectively, and | Vcc | ═ Vss |.
The pH electrode outputs signals: :
Figure BDA0003024356250000051
thin film platinum thermal resistance characteristics:
Figure BDA0003024356250000052
Figure BDA0003024356250000053
R4＝R5 (4)
R6＝R7 (5)
R8＝R9
Figure BDA0003024356250000054
Figure BDA0003024356250000055
Figure BDA0003024356250000056
Figure BDA0003024356250000057
R13＝0.06755RT0 (10)
R15＝R16 (11)
R17＝R18 (12)
Figure BDA0003024356250000058
Figure BDA0003024356250000059
Figure BDA0003024356250000061
equation (15) is the relationship between the output current signal and the pH value achieved by the circuit.
The working process of the invention is as follows:
as shown in fig. 1, the composite glass electrode was used as a pH detection element, and the thin film platinum thermistor was used as a temperature detection element. In fig. 1, the amplifier IC1, the signal operational amplifier IC2 and the inverting operational amplifier IC5 mainly zero and amplify the output signal of the glass electrode shown in the formula (1), so that the signal operational amplifier IC2 outputs a signal upH0Zero potential E without electrode0Due to the output signal u of the compensated operational amplifier IC3pH＝-upH0(R14+RP1)/(RT+ R13), wherein the thin film platinum thermal resistance RTThe temperature characteristic of (3) is shown in the formula (2), and the resistance value of R13 can be selected by the formula (10)And the full compensation of the temperature characteristic of the glass electrode is realized. U in FIG. 1i0In order to output bias signals, the output stage of the circuit of the invention consists of a V/I operational amplifier IC6 with larger output current capability and a follower IC7, and the output current signal I is realized under the condition of matching the circuit parameters0The relationship with the measured pH value is shown in formula (15), in addition. The reference source IC4 in FIG. 1 is a voltage reference source that outputs a precise regulated voltage value VrefAs a reference voltage for circuit zero setting and biasing.

Claims (2)

1. A pH value transmitting circuit for automatic temperature compensation based on a thin film platinum thermal resistor is characterized by comprising: a thin film thermal resistor TD1, a composite electrode GE1, an amplifier IC1, a signal operational amplifier IC2, a compensation operational amplifier IC3, a reference source IC4, an inverse operational amplifier IC5, a V/I operational amplifier IC6, a follower IC7, a compensation potentiometer RP1, a reference potentiometer RP2, an input resistor R1, a bias resistor R2, an amplification resistor R3, a reference resistor R4, an inverse resistor R5, an upper voltage-dividing resistor R6, a lower voltage-dividing resistor R7, a reference resistor R8, a detection resistor R9, a detection resistor R10, a left voltage-dividing resistor R11, a right voltage-dividing resistor R12, a compensation resistor R13, an operational resistor R14, a positive terminal resistor R15, a negative terminal resistor R16, a positive feedback resistor R17, a negative feedback resistor R18, a follower resistor R19, a sampling resistor R20, a load resistor RL, a filter capacitor C1 and a follower capacitor C2;
one end of a thin-film thermal resistor TD1 is connected with one end of an output resistor R10 and an output end OUT end of the signal operational amplifier IC2, the other end of the thin-film thermal resistor TD1 is connected with one end of a compensation resistor R13, a negative end Eph-end of the composite electrode GE1 is grounded, a positive end Eph + end of the composite electrode GE1 is connected with one end of an input resistor R1, the other end of the input resistor R1 is connected with one end of a filter capacitor C1 and a positive end IN + end of the amplifier IC1, the other end of the filter capacitor C1 is grounded, a positive power end + V end of the reference source IC4 is connected with a positive power end + VCC end of the circuit, a ground end GND end of the reference source IC 82 4 is grounded, an output end OUT end of the reference source IC4 is connected with one end of a bias resistor R2, one end of a reference resistor R4 and one end of an upper resistor R6, the other end of a reference resistor R4, the other end of the negative end of an inverting resistor R5 and a negative input end of an inverting voltage-dividing input end IN voltage-dividing resistor 5, and the inverting resistor R3872 are connected with one end of the lower resistor R7, The output end OUT end of the inverting operational amplifier IC5 and one end of the left voltage-dividing resistor R11 are connected, the positive input end IN + end of the inverting operational amplifier IC5 is grounded, the positive power end + V end of the inverting operational amplifier IC5 is connected with the positive power end + VCC end of the circuit, the negative power end-V end of the inverting operational amplifier IC5 is connected with the negative power end-VSS end of the circuit, the other end of the left voltage-dividing resistor R11 is connected with one end of the right voltage-dividing resistor R12 and one end of the negative voltage-dividing resistor R16, the other end of the right voltage-dividing resistor R12 is grounded, the other end of the lower voltage-dividing resistor R7 is connected with the right end of the reference potentiometer RP2, the left end of the reference potentiometer RP2 is connected with the other end of the upper voltage-dividing resistor R6, the center end of the reference potentiometer RP2 is connected with one end of the reference resistor R8, the other end of the bias resistor R2 is connected with one end of the amplifying resistor R3, the negative input end of the amplifier IC1, the other end of the amplifier IC3 is connected with the output end of the amplifier OUT 1, One end of a detection resistor R9 is connected, a positive power source end + V end of an amplifier IC1 is connected with a positive power source end + VCC end of a circuit, a negative power source end-V end of an amplifier IC1 is connected with a negative power source end-VSS end of the circuit, a negative input end IN-end of a signal operational amplifier IC2 is connected with the other end of a reference resistor R8, the other end of a detection resistor R9 and the other end of an output resistor R10, a positive input end IN + end of a signal operational amplifier IC2 is grounded, a positive power source end + V end of the signal operational amplifier IC2 is connected with a positive power source end + VCC end of the circuit, a negative power source end-V end of a signal operational amplifier IC2 is connected with a negative power source end-VSS end of the circuit, the other end of a compensation resistor R13 is connected with one end of an operational resistor R14 and a negative input end IN-end of a compensation operational amplifier IC3, the other end of an operational resistor R14 is connected with one end of a compensation potentiometer RP1, the other end and the center end of the compensation potentiometer 1 and the center end of the compensation operational amplifier IC3 are connected with an OUT end of an output terminal OUT end, One end of a positive terminal resistor R15 is connected, the positive input terminal IN + of a compensation operational amplifier IC3 is grounded, the positive power terminal + V terminal of the compensation operational amplifier IC3 is connected with the positive power terminal + VCC terminal of the circuit, the negative power terminal-V terminal of the compensation operational amplifier IC3 is connected with the negative power terminal-VSS terminal of the circuit, the other end of the positive terminal resistor R15 is connected with one end of a positive feedback resistor R17 and the positive input terminal IN + of the V/I operational amplifier IC6, the other end of the positive feedback resistor R17 is connected with one end of a sampling resistor R20 and one end of a load resistor RL, the other end of the load resistor RL is grounded, the negative input terminal IN-terminal of the V/I operational amplifier IC6 is connected with the other end of a negative terminal R16 and one end of a negative feedback resistor R18, the output terminal OUT terminal of the V/I operational amplifier IC6 is connected with the other end of the sampling resistor R20 and one end of a follower resistor R19, the positive power terminal of the V/I operational amplifier IC6 is connected with the positive power terminal VCC terminal, the negative power supply end-V end of the V/I operational amplifier IC6 is connected with the negative power supply end-VSS end of the circuit, the positive input end IN + end of the following operational amplifier follower IC7 is connected with the other end of the following resistor R19 and one end of the following capacitor C2, the other end of the following capacitor C2 is grounded, the negative input end IN-end and the output end OUT end of the follower IC7 are both connected with the other end of the negative feedback resistor R18, the positive power supply end + V end of the follower IC7 is connected with the positive power supply end + VCC end of the circuit, and the negative power supply end-V end of the follower IC7 is connected with the negative power supply end-VSS end of the circuit.
2. The pH value transmitting circuit based on the thin film platinum thermal resistor for automatic temperature compensation as claimed in claim 1, wherein the circuit parameters are matched as follows:
setting: epH: potential of pH composite electrode, unit: v; e0: electrode zero potential, unit: v, R: gas constant, 8.314 units:
Figure FDA0003687858890000021
f: faraday constant, 96485, unit: c/mol; k is a radical ofpH: electrode transformation coefficient, unit: V/pH; beta: electrode temperature factor, unit: 1/DEG C; i is0: circuit output current, unit: a, I0∈[I0min,I0max]；Vref: circuit reference voltage, unit: v; u. ofp: zero potential compensation signal, unit: v; u. ofi0: output bias signal, unit: v; r isT0: thermal resistance zero temperature value, unit: omega; t, tmax: ambient temperature and its maximum, unit: DEG C; vcc, Vss: respectively, positive and negative power supply voltages of the circuit, unit: v, and | Vcc | ═ Vss |;
the pH electrode outputs signals:
Figure FDA0003687858890000031
thin film platinum thermal resistance characteristics:
Figure FDA0003687858890000032
Figure FDA0003687858890000033
R4＝R5 (4)
R6＝R7 (5)
R8＝R9
Figure FDA0003687858890000034
Figure FDA0003687858890000035
Figure FDA0003687858890000036
Figure FDA0003687858890000037
R13＝0.06755RT0 (10)
R15＝R16 (11)
R17＝R18 (12)
Figure FDA0003687858890000038
Figure FDA0003687858890000039
Figure FDA0003687858890000041
equation (15) is the relationship between the output current signal and the pH value achieved by the circuit.
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