CN109405992B - Circuit for measuring tiny temperature change and temperature measuring method thereof - Google Patents
Circuit for measuring tiny temperature change and temperature measuring method thereof Download PDFInfo
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- CN109405992B CN109405992B CN201811343399.8A CN201811343399A CN109405992B CN 109405992 B CN109405992 B CN 109405992B CN 201811343399 A CN201811343399 A CN 201811343399A CN 109405992 B CN109405992 B CN 109405992B
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- 238000000034 method Methods 0.000 title claims abstract description 11
- 230000001105 regulatory effect Effects 0.000 claims abstract description 14
- 238000006243 chemical reaction Methods 0.000 claims description 23
- 238000013459 approach Methods 0.000 claims description 11
- 238000009529 body temperature measurement Methods 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 3
- 238000004448 titration Methods 0.000 description 8
- 238000004364 calculation method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 238000003918 potentiometric titration Methods 0.000 description 2
- XOFYZVNMUHMLCC-ZPOLXVRWSA-N prednisone Chemical compound O=C1C=C[C@]2(C)[C@H]3C(=O)C[C@](C)([C@@](CC4)(O)C(=O)CO)[C@@H]4[C@@H]3CCC2=C1 XOFYZVNMUHMLCC-ZPOLXVRWSA-N 0.000 description 2
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- 239000007795 chemical reaction product Substances 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
- 238000004313 potentiometry Methods 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 239000012488 sample solution Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000004861 thermometry Methods 0.000 description 1
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- 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
- G01K7/22—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 non-linear resistance, e.g. thermistor
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Abstract
The invention discloses a circuit for measuring micro temperature change and a temperature measuring method thereof, comprising a temperature acquisition module, a temperature reference module, a temperature output module and a temperature controller, wherein the temperature signal output end of the temperature acquisition module is connected with the first signal input end of the temperature output module, the first signal output end of the temperature controller is connected with the signal input end of the temperature reference module, the signal output end of the temperature reference module is connected with the second signal input end of the temperature output module, the output regulating end of the temperature controller is connected with the input regulating end of the temperature output module, and the temperature signal output end of the temperature output module is connected with the temperature signal input end of the temperature controller. The invention can obtain the current temperature rapidly, dynamically and with high precision.
Description
Technical Field
The invention relates to the technical field of temperature measurement, in particular to a circuit for measuring tiny temperature change and a temperature measurement method thereof.
Background
Titration is the most classical, ancient and widely used analytical method, most of which uses potentiometric methods, namely potentiometric titration, but some reactions have no corresponding indicator electrode or the sample has interference to the electrode and even cannot be used, and potentiometric titration is not used at this time, while thermometry has great effort.
It is known that the potential change in electrochemistry is only a partial manifestation of chemical reaction, and the change of reaction enthalpy can reflect chemical reaction, and all chemical reactions have enthalpy change (delta H) with the following characteristics:
ΔH＝ΔG+T*ΔS，
where Δg is the free energy variation, T is the temperature, and Δs is the variation of the entropy.
As soon as there is a chemical reaction, the sample solution undergoes a change in temperature (either an increase or decrease), i.e. an exothermic reaction or an endothermic reaction. The amount of temperature rise or drop is directly related to the amount of reaction product for a simple chemical reaction. When the titrant is added into the titrated object at a constant speed, the titrant and the titrated object generate chemical reaction, the temperature changes, and when the titrated object does not completely react, the temperature change rate is constant; when the titrant is reacted completely, the temperature change rate will change, and the inflection point appearing on the curve corresponding to the temperature change rate can be regarded as the titration end point.
The most critical point of the temperature titration is how to obtain the current temperature change rapidly, dynamically and accurately, in order to improve the measurement accuracy, the constant-speed addition is usually required, the addition speed is relatively low, and the minimum possible addition amount is 0.02mL (0.005 mL each time), so that the temperature change generated by the chemical reaction is very little due to the small actual addition amount, basically the temperature change is in the order of 0.001 ℃, and a brand-new temperature measurement method is required for timely acquiring the temperature change in the order.
Disclosure of Invention
The invention aims at least solving the technical problems existing in the prior art, and particularly creatively provides a circuit for measuring small temperature change and a temperature measuring method thereof.
In order to achieve the above object, the present invention discloses a circuit for measuring minute temperature change, comprising a temperature acquisition module, a temperature reference module, a temperature output module and a temperature controller,
The temperature signal output end of the temperature acquisition module is connected with the first signal input end of the temperature output module, the first signal output end of the temperature controller is connected with the signal input end of the temperature reference module, the signal output end of the temperature reference module is connected with the second signal input end of the temperature output module, the output regulating end of the temperature controller is connected with the input regulating end of the temperature output module,
The temperature signal output end of the temperature output module is connected with the temperature signal input end of the temperature controller.
The invention firstly initializes the temperature collected by the temperature collection module to be consistent with the temperature output by the temperature reference module, and finally rapidly and accurately measures the real-time tiny temperature change.
In a preferred embodiment of the present invention, the temperature acquisition module includes a thermistor Rt, a first end of the thermistor Rt is connected to a power ground, a second end of the thermistor Rt is connected to a first end of a resistor R1 and an input end of a follower U4, an output end of the follower U4 is connected to a first signal input end of the temperature output module, and a second end of the resistor R1 is connected to a first reference voltage. The resistance of the thermistor Rt changes under the influence of temperature, and the corresponding output voltage value also changes. The follower is beneficial to enhancing input impedance, reducing output impedance and reducing error.
In a preferred embodiment of the present invention, the temperature reference module includes an adder U5, a voltage unit U2 and M voltage units U3, where M is a positive integer, the reference voltage of the (i+1) th voltage unit U3 is lower than the reference voltage of the (i) th voltage unit U3, and the reference voltage of the voltage unit U2 is greater than the reference voltage of the (j) th voltage unit U3, where i is a positive integer less than M, and j is a positive integer not greater than M;
Or/and the voltage resolution of the (i+1) th voltage unit U3 is higher than the voltage resolution of the (i) th voltage unit U3, and the voltage resolution of the (U2) th voltage unit is lower than the voltage resolution of the (j) th voltage unit U3;
The signal input end of the voltage unit U2 is connected with the first signal output end of the temperature controller, and the voltage output end of the voltage unit U2 is connected with the first signal input end of the adder U5;
the signal input end of the jth voltage unit U3 is connected with the jth+1 signal output end of the temperature controller, and the signal output end of the jth voltage unit U3 is connected with the jth+1 signal input end of the adder;
The voltage output end of the adder is connected with the second signal input end of the temperature output module.
The voltage unit U2 serves as a coarse adjustment voltage; the j-th voltage unit U3 is used for fine adjustment of the voltage, and the output result is more approaching zero.
In a preferred embodiment of the present invention, when m=1,
The reference voltage of the voltage unit U2 is greater than the reference voltage of the 1 st voltage unit U3,
Or/and the voltage resolution of the voltage unit U2 is lower than the voltage resolution of the 1 st voltage unit U3;
The signal input end of the voltage unit U2 is connected with the first signal output end of the temperature controller, and the voltage output end of the voltage unit U2 is connected with the first signal input end of the adder U5;
the signal input end of the 1 st voltage unit U3 is connected with the 2 nd signal output end of the temperature controller, and the signal output end of the 1 st voltage unit U3 is connected with the 2 nd signal input end of the adder;
The voltage output end of the adder is connected with the second signal input end of the temperature output module.
The voltage unit U2 takes 2.5V as a voltage reference and is used for coarse adjustment of voltage; the 1 st voltage unit U3 uses 50mV as a reference voltage and is used as a fine tuning voltage, and the output result is more approximate to zero.
In a preferred embodiment of the invention, the temperature output module comprises a differential amplifier U6 and an electronic switch U7, wherein the non-inverting input end of the differential amplifier U6 is respectively connected with the temperature signal output end of the temperature acquisition module and the first input end X0 of the electronic switch U7,
The inverting input end of the differential amplifier U6 is respectively connected with the signal output end of the temperature reference module and the second input end X2 of the electronic switch U7, the output end of the differential amplifier U6 is connected with the third input end X1 of the electronic switch U7, the output end X of the electronic switch U7 is connected with the temperature signal input end of the temperature controller, and the input regulating end of the electronic switch U7 is connected with the output regulating end of the temperature controller; the initial value is enabled to be close to zero through the differential amplifier, so that errors are reduced, and accuracy is improved.
Or/and the temperature controller comprises a controller U1 and an A/D conversion module U8, wherein the temperature signal input end of the A/D conversion module U8 is connected with the temperature signal output end of the temperature output module, and the temperature signal output end of the A/D conversion module U8 is connected with the temperature signal input end of the controller U1. The acquired analog signals are converted into digital signals and input into a controller.
The invention also discloses a calculation method for measuring the micro temperature change circuit, which comprises the following steps:
s1, an adjusting temperature acquisition module acquires an initialization value close to zero;
s2, the temperature acquisition module acquires a real-time temperature value.
In a preferred embodiment of the present invention, step S1 comprises the steps of:
S11, a controller U1 sends a control signal to an input adjusting end of an electronic switch U7 to control the electronic switch U7 to be switched to a first input end X0 of the electronic switch U7;
S12, the controller U1 collects the voltage value output by the temperature collection module and marks the voltage value as E; only the temperature value output by the temperature acquisition module is acquired at the moment.
S13, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a second input end X2 of the electronic switch U7;
S14, the controller U1 controls the 1 st to M voltage units U3 to output zero values; the controller U1 controls the voltage unit U2 to output an adjusting voltage value, so that the voltage value of the temperature reference module acquired by the controller U1 is close to E; at this time, only the temperature value output by the temperature reference module is acquired.
S15, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7;
S16, the controller U1 controls the 1 st to M voltage units U3 according to the sequence, and the output value is repeatedly adjusted, so that the voltage value of the temperature output module acquired by the controller U1 approaches zero. The electronic switch U7 is switched to the third input end X1, and then the output voltage values of the 1 st to M th voltage units U3 are sequentially adjusted, so that the step is simplified, the voltage value detected by the controller approaches zero, and if the output voltage values of the 1 st to M th voltage units U3 are sequentially adjusted to approach E, the output voltage value of the 1 st to M th voltage units U3 is required to be readjusted when the electronic switch U7 is controlled to be switched to the third input end X1 of the electronic switch U7, the voltage value detected by the controller approaches zero, the load of the controller is increased, and the efficiency is reduced.
In a preferred embodiment of the present invention, S15 and S16 are that the controller U1 controls the 1 st to M-th voltage units U3 according to the sequence, and repeatedly adjusts the output value, so that the voltage value of the temperature output module collected by the controller U1 approaches zero;
the controller U1 sends a control signal to the input adjustment terminal of the electronic switch U7, controlling the electronic switch U7 to switch to the third input terminal X1 of the electronic switch U7.
In a preferred embodiment of the present invention, when m=1,
S11, a controller U1 sends a control signal to an input adjusting end of an electronic switch U7 to control the electronic switch U7 to be switched to a first input end X0 of the electronic switch U7;
s12, the controller U1 collects the voltage value output by the temperature collection module and marks the voltage value as E;
s13, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a second input end X2 of the electronic switch U7;
S14, the controller U1 controls the 1 st voltage unit U3 to output zero value; the controller U1 controls the voltage unit U2 to output an adjusting voltage value, so that the voltage value of the temperature reference module acquired by the controller U1 is close to E;
s15, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7;
S16, the controller U1 controls the 1 st voltage unit U3, and the output value is repeatedly adjusted, so that the voltage value of the temperature output module acquired by the controller U1 approaches zero.
In a preferred embodiment of the present invention, step S2 comprises the steps of:
s21, the controller U1 collects a voltage value, and the voltage value is recorded as delta E;
s22, converting the voltage value into a resistance value;
the calculation formula of the resistance value:
wherein R1 is the resistance value of the resistor R1, and the unit is kΩ;
u is a first reference voltage, in mV;
rt is the resistance value of the corresponding thermistor Rt at the current temperature, and is a unit kΩ;
e is the potential collected before adjustment, and the unit is mV;
Δe is the potential collected after adjustment, in mV;
k is the amplification factor of the differential amplifier;
S23, obtaining a temperature value from an R-T curve of the thermistor.
In summary, due to the adoption of the technical scheme, the beneficial effects of the invention are as follows: the invention can obtain the current temperature rapidly, dynamically and with high precision.
Drawings
Fig. 1 is a schematic diagram of a circuit connection of the present invention.
Fig. 2 is a block diagram of the main stream Cheng Shiyi of the present invention.
FIG. 3 is a schematic block diagram of the potential adjustment process of the present invention.
FIG. 4 is a schematic block diagram of the potential measurement flow of the present invention.
FIG. 5 is a graph showing titration volume versus temperature for the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
The invention discloses a circuit for measuring tiny temperature change, which comprises a temperature acquisition module, a temperature reference module, a temperature output module and a temperature controller,
The temperature signal output end of the temperature acquisition module is connected with the first signal input end of the temperature output module, the first signal output end of the temperature controller is connected with the signal input end of the temperature reference module, the signal output end of the temperature reference module is connected with the second signal input end of the temperature output module, the output regulating end of the temperature controller is connected with the input regulating end of the temperature output module,
The temperature signal output end of the temperature output module is connected with the temperature signal input end of the temperature controller.
In a preferred embodiment of the present invention, the temperature acquisition module includes a thermistor Rt, a first end of the thermistor Rt is connected to a power ground, a second end of the thermistor Rt is connected to a first end of a resistor R1 and an input end of a follower U4, an output end of the follower U4 is connected to a first signal input end of the temperature output module, and a second end of the resistor R1 is connected to a first reference voltage.
In a preferred embodiment of the present invention, the temperature reference module includes an adder U5, a voltage unit U2 and M voltage units U3, where M is a positive integer, the reference voltage of the (i+1) th voltage unit U3 is lower than the reference voltage of the (i) th voltage unit U3, and the reference voltage of the voltage unit U2 is greater than the reference voltage of the (j) th voltage unit U3, where i is a positive integer less than M, and j is a positive integer not greater than M;
or/and the voltage resolution of the (i+1) th voltage unit U3 is higher than the voltage resolution of the (i) th voltage unit U3, and the voltage resolution of the (U2) th voltage unit is lower than the voltage resolution of the (j) th voltage unit U3; for example, the voltage resolution of the voltage unit U2 employs a 24-bit D/a converter, and the voltage resolution of the 1 st voltage unit U3 employs a 32-bit D/a converter.
The signal input end of the voltage unit U2 is connected with the first signal output end of the temperature controller, and the voltage output end of the voltage unit U2 is connected with the first signal input end of the adder U5;
the signal input end of the jth voltage unit U3 is connected with the jth+1 signal output end of the temperature controller, and the signal output end of the jth voltage unit U3 is connected with the jth+1 signal input end of the adder;
The voltage output end of the adder is connected with the second signal input end of the temperature output module.
In a preferred embodiment of the present invention, when m=1,
The reference voltage of the voltage unit U2 is greater than the reference voltage of the 1 st voltage unit U3,
Or/and the voltage resolution of the voltage unit U2 is lower than the voltage resolution of the 1 st voltage unit U3;
The signal input end of the voltage unit U2 is connected with the first signal output end of the temperature controller, and the voltage output end of the voltage unit U2 is connected with the first signal input end of the adder U5;
the signal input end of the 1 st voltage unit U3 is connected with the 2 nd signal output end of the temperature controller, and the signal output end of the 1 st voltage unit U3 is connected with the 2 nd signal input end of the adder;
The voltage output end of the adder is connected with the second signal input end of the temperature output module.
In a preferred embodiment of the invention, the temperature output module comprises a differential amplifier U6 and an electronic switch U7, wherein the non-inverting input end of the differential amplifier U6 is respectively connected with the temperature signal output end of the temperature acquisition module and the first input end X0 of the electronic switch U7,
The inverting input end of the differential amplifier U6 is respectively connected with the signal output end of the temperature reference module and the second input end X2 of the electronic switch U7, the output end of the differential amplifier U6 is connected with the third input end X1 of the electronic switch U7, the output end X of the electronic switch U7 is connected with the temperature signal input end of the temperature controller, and the input regulating end of the electronic switch U7 is connected with the output regulating end of the temperature controller;
Or/and the temperature controller comprises a controller U1 and an A/D conversion module U8, wherein the temperature signal input end of the A/D conversion module U8 is connected with the temperature signal output end of the temperature output module, and the temperature signal output end of the A/D conversion module U8 is connected with the temperature signal input end of the controller U1. The model of the A/D conversion module U8 is a 24-bit AD7710 sampling chip.
In the present embodiment, the initial resistance of the thermistor Rt is 100K, the resistance of the resistor R1 is 100K, the first reference voltage is 2.5V, and the differential amplifier amplifies 100 times; the reference voltage of the voltage unit U2 is 2.5V, and the reference voltage of the 1 st voltage unit U3 is 50mV.
As shown in fig. 1, the specific circuit connection of the present invention is: the first end of the thermistor Rt is connected with power ground, the second end of the thermistor Rt is connected with the first end of a resistor R1 and the input end of a follower U4 respectively, the second end of the resistor R1 is connected with a first reference voltage, the output end of the follower U4 is connected with the normal phase input end of a differential amplifier U6 and the first input end X0 of an electronic switch U7, the reverse phase input end of the differential amplifier U6 is connected with the voltage output end of an adder and the second input end X1 of the electronic switch U7 respectively, the output end of the differential amplifier U6 is connected with the third input end X2 of the electronic switch U7, the output end X of the electronic switch U7 is connected with the temperature signal input end of an A/D conversion module U8, and the temperature signal output end of the A/D conversion module U8 is connected with the temperature signal input end of a controller U1; the signal input part of the 1 st voltage unit U3 is connected with the 2 nd signal output part of the controller U1, the signal output part of the 1 st voltage unit U3 is connected with the 2 nd signal input part of the adder, the signal input part of the voltage unit U2 is connected with the first signal output part of the controller U1, the signal output part of the voltage unit U2 is connected with the first signal input part of the adder, the voltage output part of the adder is connected with the second signal input part of the temperature output module, and the output regulating part of the controller U1 is connected with the input regulating part of the electronic switch U7.
The invention also discloses a calculation method for measuring the micro temperature change circuit, as shown in figure 1, comprising the following steps:
S1, an adjusting temperature acquisition module acquires an initialization value close to zero; this step is to adjust the potential portion.
S2, a temperature acquisition module acquires a real-time temperature value, and the step is to measure a potential part.
Because the A/D sampling chip always has a certain measuring range, and the signal is amplified by 100 times, when the potential exceeds the range of A/D due to temperature change, the phase can be returned to the adjusting phase, and the measurement can be carried out after the adjustment is carried out again.
In a preferred embodiment of the present invention, step S1 comprises the steps of: the temperature acquisition module is placed in the solution to be measured, the solution is not titrated into the solution to be measured at the moment,
S11, a controller U1 sends a control signal to an input adjusting end of an electronic switch U7 to control the electronic switch U7 to be switched to a first input end X0 of the electronic switch U7; at this time, the first input terminal X0 of the electronic switch U7 is in a conductive state with the output terminal X of the electronic switch U7, and the third input terminal X1 of the electronic switch U7 and the second input terminal X2 of the electronic switch U7 are in a disconnected state with the output terminal X of the electronic switch U7;
s12, the controller U1 collects the voltage value output by the temperature collection module and marks the voltage value as E;
S13, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a second input end X2 of the electronic switch U7; at this time, the second input terminal X2 of the electronic switch U7 is in a conductive state with the output terminal X of the electronic switch U7, and the first input terminal X0 of the electronic switch U7 and the third input terminal X1 of the electronic switch U7 are in a disconnected state with the output terminal X of the electronic switch U7;
S14, the controller U1 controls the 1 st to M voltage units U3 to output zero values; the controller U1 controls the voltage unit U2 to output an adjusting voltage value, so that the voltage value of the temperature reference module collected by the controller U1 is close to E (E ' is close to E ', that is, E-E ' is smaller than or equal to a preset first threshold value, and the preset first threshold value can be 5mV or other smaller values);
S15, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7; at this time, the third input terminal X1 of the electronic switch U7 is in an on state with the output terminal X of the electronic switch U7, the first input terminal X0 of the electronic switch U7 and the second input terminal X2 of the electronic switch U7 are in an off state with the output terminal X of the electronic switch U7,
S16, the controller U1 controls the 1 st to M voltage units U3 according to the sequence, and repeatedly adjusts the output values, so that the voltage value of the temperature output module collected by the controller U1 approaches zero (in actual use, the adjustment time relationship is considered, and the adjustment time relationship is only required to be lower than a certain small potential value, for example, a value of 2mV or less).
In a preferred embodiment of the present invention, S15 and S16 are that the controller U1 controls the 1 st to M-th voltage units U3 according to the sequence, and repeatedly adjusts the output value, so that the voltage value of the temperature output module collected by the controller U1 approaches zero;
the controller U1 sends a control signal to the input adjustment terminal of the electronic switch U7, controlling the electronic switch U7 to switch to the third input terminal X1 of the electronic switch U7.
In a preferred embodiment of the present invention, when m=1, as shown in fig. 3,
S11, a controller U1 sends a control signal to an input adjusting end of an electronic switch U7 to control the electronic switch U7 to be switched to a first input end X0 of the electronic switch U7; at this time, the first input terminal X0 of the electronic switch U7 is in a conductive state with the output terminal X of the electronic switch U7, and the third input terminal X1 of the electronic switch U7 and the second input terminal X2 of the electronic switch U7 are in a disconnected state with the output terminal X of the electronic switch U7;
s12, the controller U1 collects the voltage value output by the temperature collection module and marks the voltage value as E;
S13, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a second input end X2 of the electronic switch U7; at this time, the second input terminal X2 of the electronic switch U7 is in a conductive state with the output terminal X of the electronic switch U7, and the first input terminal X0 of the electronic switch U7 and the third input terminal X1 of the electronic switch U7 are in a disconnected state with the output terminal X of the electronic switch U7;
S14, the controller U1 controls the 1 st voltage unit U3 to output zero value; the controller U1 controls the voltage unit U2 to output an adjusting voltage value, so that the voltage value of the temperature reference module acquired by the controller U1 is close to E;
S15, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7; at this time, the third input terminal X1 of the electronic switch U7 is in an on state with the output terminal X of the electronic switch U7, the first input terminal X0 of the electronic switch U7 and the second input terminal X2 of the electronic switch U7 are in an off state with the output terminal X of the electronic switch U7,
S16, the controller U1 controls the 1 st voltage unit U3, and the output value is repeatedly adjusted, so that the voltage value of the temperature output module acquired by the controller U1 approaches zero.
In a preferred embodiment of the present invention, as shown in fig. 4, step S2 includes the steps of:
The controller sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7; at this time, the third input terminal X1 of the electronic switch U7 and the output terminal X of the electronic switch U7 are in a conductive state, the first input terminal X0 of the electronic switch U7 and the second input terminal X2 of the electronic switch U7 and the output terminal X of the electronic switch U7 are in a non-conductive state, titrate the solution into the solution to be measured,
S21, the controller U1 collects a voltage value, and the voltage value is recorded as delta E;
s22, converting the voltage value into a resistance value;
the calculation formula of the resistance value:
wherein R1 is the resistance value of the resistor R1, and the unit is kΩ;
u is a first reference voltage, in mV;
rt is the resistance value of the corresponding thermistor Rt at the current temperature, and is a unit kΩ;
e is the potential collected before adjustment, and the unit is mV;
Δe is the potential collected after adjustment, in mV;
k is the amplification factor of the differential amplifier;
S23, obtaining a temperature value from an R-T curve of the thermistor.
As shown in FIG. 5, which is a graph of a certain type of temperature titration, in which the abscissa represents the titration volume and the ordinate represents the temperature value, initial data of titration volume and temperature are shown in Table 1, it can be seen from the table that when 0.019844mL of titrant is added, the temperature of the solution changes from 00029.341060 to 00029.332280, only 0.00878 ℃and some temperature changes are much smaller.
Table 1 shows initial data of titration volume and temperature
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
Claims (3)
1. The circuit comprises a temperature acquisition module, a temperature reference module, a temperature output module and a temperature controller, wherein the temperature signal output end of the temperature acquisition module is connected with the first signal input end of the temperature output module, the first signal output end of the temperature controller is connected with the signal input end of the temperature reference module, and the signal output end of the temperature reference module is connected with the second signal input end of the temperature output module; the output adjusting end of the temperature controller is connected with the input adjusting end of the temperature output module, and the temperature signal output end of the temperature output module is connected with the temperature signal input end of the temperature controller;
The temperature acquisition module comprises a thermistor Rt, a first end of the thermistor Rt is connected with power supply ground, a second end of the thermistor Rt is respectively connected with a first end of a resistor R1 and an input end of a follower U4, an output end of the follower U4 is connected with a first signal input end of the temperature output module, and a second end of the resistor R1 is connected with a first reference voltage;
The temperature reference module comprises an adder U5, a voltage unit U2 and M voltage units U3, wherein M is a positive integer, the reference voltage of the (i+1) th voltage unit U3 is lower than the reference voltage of the (i) th voltage unit U3, the reference voltage of the voltage unit U2 is greater than the reference voltage of the (j) th voltage unit U3, i is a positive integer smaller than M, and j is a positive integer not greater than M; or/and the voltage resolution of the (i+1) th voltage unit U3 is higher than the voltage resolution of the (i) th voltage unit U3, and the voltage resolution of the (U2) th voltage unit is lower than the voltage resolution of the (j) th voltage unit U3; the signal input end of the voltage unit U2 is connected with the first signal output end of the temperature controller, and the voltage output end of the voltage unit U2 is connected with the first signal input end of the adder U5; the signal input end of the jth voltage unit U3 is connected with the jth+1 signal output end of the temperature controller, and the signal output end of the jth voltage unit U3 is connected with the jth+1 signal input end of the adder; the voltage output end of the adder is connected with the second signal input end of the temperature output module;
When m=1, the reference voltage of the voltage unit U2 is greater than the reference voltage of the 1 st voltage unit U3, or/and the voltage resolution of the voltage unit U2 is lower than the voltage resolution of the 1 st voltage unit U3; the signal input end of the voltage unit U2 is connected with the first signal output end of the temperature controller, and the voltage output end of the voltage unit U2 is connected with the first signal input end of the adder U5; the signal input end of the 1 st voltage unit U3 is connected with the 2 nd signal output end of the temperature controller, and the signal output end of the 1 st voltage unit U3 is connected with the 2 nd signal input end of the adder; the voltage output end of the adder is connected with the second signal input end of the temperature output module;
The temperature output module comprises a differential amplifier U6 and an electronic switch U7, wherein the normal phase input end of the differential amplifier U6 is respectively connected with the temperature signal output end of the temperature acquisition module and the first input end X0 of the electronic switch U7, the reverse phase input end of the differential amplifier U6 is respectively connected with the signal output end of the temperature reference module and the second input end X2 of the electronic switch U7, the output end of the differential amplifier U6 is connected with the third input end X1 of the electronic switch U7, the output end X of the electronic switch U7 is connected with the temperature signal input end of the temperature controller, and the input regulating end of the electronic switch U7 is connected with the output regulating end of the temperature controller; or/and the temperature controller comprises a controller U1 and an A/D conversion module U8, wherein the temperature signal input end of the A/D conversion module U8 is connected with the temperature signal output end of the temperature output module, and the temperature signal output end of the A/D conversion module U8 is connected with the temperature signal input end of the controller U1;
the method is characterized in that the method for measuring the temperature by adopting the circuit for measuring the tiny temperature change specifically comprises the following steps:
S1, an adjusting temperature acquisition module acquires an initialization value close to zero; s2, the temperature acquisition module acquires a real-time temperature value.
2. The minute temperature measurement method according to claim 1, wherein step S1 comprises the steps of: s11, a controller U1 sends a control signal to an input adjusting end of an electronic switch U7 to control the electronic switch U7 to be switched to a first input end X0 of the electronic switch U7; s12, the controller U1 collects the voltage value output by the temperature collection module and marks the voltage value as E; s13, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a second input end X2 of the electronic switch U7; s14, the controller U1 controls the 1 st to M voltage units U3 to output zero values; the controller U1 controls the voltage unit U2 to output an adjusting voltage value, so that the voltage value of the temperature reference module acquired by the controller U1 is close to E, wherein the approaching E is E ', that is, E-E' is smaller than or equal to a preset first threshold value, and the preset first threshold value is 5mV; s15, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7; s16, the controller U1 controls the 1 st to M voltage units U3 according to the sequence, and repeatedly adjusts the output value, so that the voltage value of the temperature output module collected by the controller U1 approaches zero, and when the temperature output module is actually used, the adjustment time relationship is considered, and the temperature output module is only required to be lower than 2 mV.
3. The micro temperature measurement method according to claim 2, wherein when m=1, S11, the controller U1 sends a control signal to the input adjustment terminal of the electronic switch U7, controlling the electronic switch U7 to switch to the first input terminal X0 of the electronic switch U7; s12, the controller U1 collects the voltage value output by the temperature collection module and marks the voltage value as E; s13, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a second input end X2 of the electronic switch U7; s14, the controller U1 controls the 1 st voltage unit U3 to output zero value; the controller U1 controls the voltage unit U2 to output an adjusting voltage value, so that the voltage value of the temperature reference module acquired by the controller U1 is close to E; s15, the controller U1 sends a control signal to an input adjusting end of the electronic switch U7 to control the electronic switch U7 to be switched to a third input end X1 of the electronic switch U7; s16, the controller U1 controls the 1 st voltage unit U3, and the output value is repeatedly adjusted, so that the voltage value of the temperature output module acquired by the controller U1 approaches zero.
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