CN113820030A - Resistance value error correction method - Google Patents
Resistance value error correction method Download PDFInfo
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- CN113820030A CN113820030A CN202111098649.8A CN202111098649A CN113820030A CN 113820030 A CN113820030 A CN 113820030A CN 202111098649 A CN202111098649 A CN 202111098649A CN 113820030 A CN113820030 A CN 113820030A
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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
- G01K7/24—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 in a specially-adapted circuit, e.g. bridge circuit
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- 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
- G01K15/005—Calibration
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Abstract
The invention provides a resistance value error correction method, which is used for setting the resistance value of a thermistor in a temperature monitoring system, collecting the voltage code value of the thermistor, correcting errors according to the collected voltage code value and further correcting the resistance value of the thermistor. According to the resistance value error correction method of the thermistor, after the thermistor is corrected, the temperature accuracy of the thermistor is less than or equal to +/-0.1 ℃ within a range of-30-25 ℃, and the temperature accuracy of the thermistor is less than or equal to +/-0.3 ℃ within a range of 25-50 ℃, so that the temperature measurement accuracy of the thermistor is effectively improved.
Description
Technical Field
The invention belongs to the technical field of temperature detection, and particularly relates to a resistance value error correction method.
Background
The key components in the temperature monitoring system are temperature sensors which are mainly divided into thermocouples, thermal resistors, thermistors, platinum resistors and the like. The thermistor is a kind of sensitive element, shows different resistance values at different temperatures, has the characteristics of high sensitivity, wide working temperature range, small volume, good stability and the like, and is widely applied to a temperature monitoring system. The NTC thermistor in the existing temperature measurement scheme is used more, the temperature value is generally obtained by a table look-up method, which involves the corresponding relation between the temperature and the resistance value, and a temperature resistance value comparison table can be requested from a manufacturer. In addition, a standard thermometer can be used, the resistance value of the thermistor can be measured once the ambient temperature rises, and the corresponding relation between the resistance value and the temperature obtained by the method is relatively complex.
When the NTC thermistor is used for temperature monitoring, a plurality of resistors are used in a temperature acquisition circuit, because the resistors selected by hardware circuit design are all ideal values, and each resistor has poor precision in practice, the precision of the selected kiloohm resistor is 0.1%, and the precision of the selected megaohm resistor is 1%, and potential accumulated errors are formed in the circuit by the aid of the precisions, so that the obtained resistance value and the actually input resistance value result are greatly deviated through calculation of a theoretical formula, the actually obtained temperature and the actual temperature have large deviation, the actual temperature cannot be accurately represented, inaccurate temperature display is caused, and the temperature control effect is influenced.
Disclosure of Invention
The invention overcomes the defects of the prior art and provides a resistance error correction method.
A resistance error correction method is used for correcting the resistance of a thermistor in a temperature monitoring system, and the temperature monitoring system comprises the following steps: the device comprises a thermistor to be corrected, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an operational amplifier, a reference voltage chip, an AD conversion chip and a data processing chip.
The thermistor to be corrected, the first resistor, the second resistor and the third resistor form a bridge circuit; the thermistor to be corrected and the third resistor form a second branch of the bridge circuit; the reference voltage provided by the reference voltage chip is subjected to voltage division processing in the first branch and the second branch, and the second branch is grounded; one end of the fourth resistor is connected with the inverting input end of the operational amplifier, and the other end of the fourth resistor is connected between the first resistor and the second resistor; one end of the fifth resistor is connected with the non-inverting input end of the operational amplifier, and the other end of the fifth resistor is connected between the thermistor to be corrected and the third resistor; one end of the sixth resistor is connected with the non-inverting input end of the operational amplifier, and the other end of the sixth resistor is grounded; one end of the seventh resistor is connected with the inverting input end of the operational amplifier, and the other end of the seventh resistor is connected with the output end of the operational amplifier; the output end of the operational amplifier is connected with the AD conversion chip, and the AD conversion chip is connected with the data processing chip.
The error correction method of the thermistor resistance value comprises the following steps:
s1, setting the resistance value of the first resistor to be equal to the resistance value of the third resistor; the resistance value of the second resistor is equal to the resistance value of the thermistor to be corrected; the resistance value of the fourth resistor is equal to that of the fifth resistor; the resistance value of the sixth resistor is equal to that of the seventh resistor; the resistance values of the fourth resistor, the fifth resistor, the sixth resistor and the seventh resistor are all larger than the resistance values of the first resistor and the second resistor after being connected in parallel, and are all larger than the resistance values of the third resistor and the seventh resistor after being connected in parallel.
S2, short-circuiting the thermistor to be corrected, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chipCODEMeasuring the voltage value V at the output of the operational amplifierF(ii) a Passing voltage value VFDetermining the voltage V at the inverting input of an operational amplifier-(ii) a Passing voltage value VFAnd AD Voltage code value MCODEReference voltage V provided to reference voltage chipSTDAnd (6) correcting.
S3, replacing the thermistor to be corrected with a first preset resistor, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chipMAX(ii) a Voltage code value M by ADMAXTo obtain the voltage value V of the output terminal of the operational amplifierF-MAX(ii) a Passing voltage value VF-MAXTo find the voltage V of the operational amplifierO-MAX(ii) a Voltage V through operational amplifierO-MAXTo find the voltage V of the non-inverting input terminal of the operational amplifier+MAX(ii) a Passing voltage V+MAXResistance value R 'to third resistor'3And (6) correcting.
S4, replacing the thermistor to be corrected with a second preset resistor, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chipMIN(ii) a Through the resistance R 'of the third resistor'3Calculating the voltage value V of the non-inverting input terminal of the operational amplifier+MIN(ii) a Passing voltage value V+MINCalculating the voltage value V of the output end of the operational amplifierO-MIN(ii) a By said voltage value VO-MINThe AD voltage code value MMINObtaining a correction value M of the AD voltage code value of the AD conversion chipC。
S5, connecting the thermistor to be corrected in a temperature monitoring system, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chiptAD Voltage code value M 'of AD conversion chip after correction'CODEIs AD Voltage code value MtAnd a correction value MCThe sum of (1).
S6, converting the AD voltage code value M 'of the AD conversion chip after correction'CODEThe resistance value of the thermistor to be corrected is converted.
Further, before step S1, the method further includes the following steps:
and S0, calibrating the temperature resistance parameter of the thermistor to be corrected.
Further, the AD conversion chip is subjected to zero position and range correction.
Further, step S2 specifically includes the following steps:
s201, short-circuiting the thermistor to be corrected;
s202, measuring the voltage value V through a data processing chipFSubstituting into formula (1) to obtain the voltage V at the inverting input terminal of the operational amplifier-；
Wherein G is the amplification factor of the operational amplifier;
s203, converting the voltage value VFAD voltage code value MCODESubstituting into formula (2) for the reference voltage V provided by the reference voltage chipSTDCorrecting;
further, step S3 specifically includes the following steps:
s301, replacing the thermistor to be corrected with a first preset resistor;
s302, obtaining the AD voltage code value M of the AD conversion chip through the data processing chipMAX(ii) a The AD voltage code value MMAXSubstituting into formula (3) to obtain the voltage value V at the output end of the operational amplifierF-MAX；
S303, calculating the voltage value VF-MAXSubstituting into formula (4) to obtain the voltage V of the operational amplifierO-MAX；
S304, calculating the voltage VO-MAXSubstituting into formula (5) to obtain the voltage V of the non-inverting input terminal of the operational amplifier+MAX；
V+MAX-V-MAX＝VO-MAX (5)
Wherein, V-MAXIs the voltage at the inverting input of the operational amplifier;
s305, obtaining the voltage V+MAXSubstituting into formula (6), and obtaining resistance R 'of third resistor'3Correcting;
wherein R isMAXIs the resistance value of the first preset resistor.
Further, step S4 specifically includes the following steps:
s401, replacing the thermistor to be corrected with a second preset resistor;
s402, obtaining the AD voltage code value M of the AD conversion chip through the data processing chipMIN；
S403, calculating the obtained voltage R'3Substituting into formula (7) to obtain the voltage V of the non-inverting input terminal of the operational amplifier+MIN；
Wherein R isMINThe resistance value of the second preset resistor is obtained;
s404, obtaining the voltage value V+MINSubstituting into formula (8) to obtain the voltage V at the output end of the operational amplifierO-MIN；
VO-MIN＝(V+MIN-V-)×G (8)
S405, converting the AD voltage code value MMINSaid voltage VO-MINThe reference voltage VSTDSubstituting into formula (9) to obtain correction value M of AD voltage code value of the AD conversion chipC；
Further, after step S6, the method further includes the following steps:
and S7, converting the resistance value of the thermistor into temperature in a table look-up mode.
Compared with the prior art, the invention has the beneficial effects that:
1. the resistance error correction method of the resistor can quickly obtain the corrected resistance of the thermistor;
2. the resistance value error correction method provided by the invention can effectively reduce the deviation between the actually obtained temperature and the actual temperature;
3. according to the resistance value error correction method of the thermistor, after the thermistor is corrected, the temperature accuracy of the thermistor is less than or equal to +/-0.1 ℃ within a range of-30-25 ℃, and the temperature accuracy of the thermistor is less than or equal to +/-0.3 ℃ within a range of 25-50 ℃, so that the temperature measurement accuracy of the thermistor is effectively improved.
Drawings
FIG. 1 is a schematic block diagram of a temperature monitoring system according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for correcting an error in resistance of a resistor according to an embodiment of the present invention;
3(a) -3 (d) are schematic diagrams comparing the temperature change of the thermistor in the thermostatic bath and the temperature change of the thermostatic bath after being corrected by the resistance error correction method in the embodiment of the invention;
fig. 4(a) -4 (d) are schematic diagrams of temperatures collected in a thermostatic bath by a thermistor after being corrected by a resistance error correction method in an embodiment of the invention.
Wherein the reference numerals are as follows:
thermistor R to be correctedtA first resistor R1A second resistor R2A third resistor R3A fourth resistor R4A fifth resistor R5A sixth resistor R6A seventh resistor Rf。
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 shows a schematic structural framework diagram of a temperature monitoring system according to an embodiment of the present invention. The embodiment of the invention uses a temperature monitoring system to be matched with a resistor resistance error correction method.
As shown in fig. 1, a temperature monitoring system according to an embodiment of the present invention includes: thermistor R to be correctedtA first resistor R1A second resistor R2A third resistor R3A fourth resistor R4A fifth resistor R5A sixth resistor R6A seventh resistor RfThe device comprises an operational amplifier, a reference voltage chip, an AD conversion chip and a data processing chip. Thermistor R to be correctedtAnd a first resistor R1A second resistor R2A third resistor R3Forming a bridge circuit; wherein the first resistor R1A second resistor R2The thermistor R to be corrected constituting the first branch of the bridge circuittA third resistor R3A second branch constituting a bridge circuit; the reference voltage chip is connected to the first branch, the reference voltage provided by the reference voltage chip is subjected to voltage division processing on the first branch and the second branch, and the second branch is grounded; a fourth resistor R4One end of the resistor is connected with the inverting input end of the operational amplifier, and the other end of the resistor is connected with the first resistor R1And a second resistor R2To (c) to (d); fifth resistor R5One end of the resistor is connected with the non-inverting input end of the operational amplifier, and the other end is connected with the thermistor R to be correctedtAnd a third resistor R3To (c) to (d); a sixth resistor R6One end of the operational amplifier is connected with the non-inverting input end of the operational amplifier, and the other end of the operational amplifier is grounded; a seventh resistor RfOne end of the output end of the operational amplifier is connected with the inverting input end of the operational amplifier, and the other end of the output end of the operational amplifier is connected with the inverting input end of the operational amplifier.
In the embodiment of the invention, the reference voltage of the temperature monitoring system is provided by a reference chip with the model number of AD 581; the model of the operational amplifier is OP 474; the model of the AD conversion chip is AD574A, and in order to ensure the correction precision, the AD chip is at least capable of performing 12-bit A/D conversion during model selection; the model of the data processing chip is AT89S52, and in order to ensure the correction precision, the data processing chip is selected to be capable of AT least floating point operation and calculating data with length more than 16 bits.
Fig. 2 is a flowchart illustrating a resistance error correction method according to an embodiment of the present invention. The method for correcting the resistance error of the resistor provided by the embodiment of the invention is described in detail below by combining a temperature monitoring system.
As shown in fig. 2, the embodiment of the present invention utilizes the temperature monitoring system to perform the following steps to correct the resistance error of the resistor:
s1, setting the first resistance R1And the third resistor R3Are equal; a second resistor R2Resistance value of and thermistor R to be correctedtAre equal; a fourth resistor R4And the resistance of the fifth resistor R5Are equal; a sixth resistor R6And the seventh resistor RfAre equal; a fourth resistor R4A fifth resistor R5A sixth resistor R6A seventh resistor RfAre all larger than the resistance values of the first resistor R1 and the second resistor R2 which are connected in parallel, and are all larger than the third resistor R3And a seventh resistor RfResistance after parallel connection.
The resistance value setting parameters in the embodiment of the invention are as follows: a first resistor R1Third resistance R3150K Ω; a second resistor R239K Ω; a fourth resistor R4Fifth resistance R51M Ω; a sixth resistor R6Seventh resistor Rf4.7M Ω. After the resistance values of the resistors in the temperature monitoring system are determined, the amplification factor G of the operational amplifier can be calculated to be 4.7. The parameter setting in the embodiment of the invention can correct the resistance value of the thermistor with the resistance value of 2K-100K omega in the temperature measurement range of-30-50 ℃.
S2, thermistor R to be correctedtShort circuit, and obtaining AD voltage code value M of AD conversion chip through data processing chipCODEMeasuring the voltage value V at the output of the operational amplifierF(ii) a Passing voltage value VFDetermining the voltage V at the inverting input of an operational amplifier-(ii) a Passing voltage value VFAnd AD Voltage code value MCODEReference voltage supplied to reference voltage chipVSTDAnd (6) correcting.
S3, replacing the thermistor to be corrected with a first preset resistor, where the first preset resistor is a resistor with a resistance of 100K Ω in the embodiment provided by the present invention, that is, the maximum resistance of the thermistor that can be corrected in the embodiment provided by the present invention. Obtaining AD voltage code value M of AD conversion chip through data processing chipMAX(ii) a Voltage code value M by ADMAXTo obtain the voltage value V of the output terminal of the operational amplifierF-MAX(ii) a Passing voltage value VF-MAXTo find the voltage V of the operational amplifierO-MAX(ii) a Voltage V through operational amplifierO-MAXTo find the voltage V of the non-inverting input terminal of the operational amplifier+MAX(ii) a Passing voltage V+MAXResistance value R 'to third resistor'3And (6) correcting.
And S4, replacing the thermistor to be corrected with a second preset resistor, wherein the second preset resistor is a resistor with the resistance value of 2K omega in the embodiment provided by the invention, namely the minimum resistance value of the thermistor which can be corrected in the embodiment provided by the invention. Obtaining AD voltage code value M of AD conversion chip through data processing chipMIN(ii) a Through resistance R 'of third resistor'3To obtain the voltage value V of the non-inverting input terminal of the operational amplifier+MIN(ii) a Passing voltage value V+MINTo obtain the voltage value V of the output terminal of the operational amplifierO-MIN(ii) a Passing voltage value VO-MINReference voltage VSTDAD voltage code value MCODEObtaining a correction value M of the AD voltage code value of the AD conversion chipC。
S5, connecting the thermistor to be corrected in a temperature monitoring system, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chiptAnd then the AD voltage code value M 'of the AD conversion chip after correction'CODEIs AD Voltage code value MtAnd a correction value MCThe sum of (1).
S6, converting the AD voltage code value M 'of the AD conversion chip after correction'CODEThe resistance value of the thermistor to be corrected is converted. The conversion mode may be any mode in the prior art, which is not limited in the embodiment of the present invention and may be selected according to the actual application situation.
The embodiment of the present invention provides a preferable implementation manner, and before step S1, the method further includes the following steps:
s0 thermistor R to be correctedtThe temperature resistance value parameter is calibrated. The calibration mode in the embodiment of the invention is as follows: used thermistor R to be correctedtCalibrating once every 1 ℃ within the temperature range of-30-50 ℃, and calibrating 81 temperature points in total. Thermistor R to be correctedtThe calibration of the temperature resistance parameter can improve the correction precision of resistance error.
The embodiment of the invention provides a preferable implementation mode, and zero position and range correction is carried out on the AD conversion chip.
The thermistor to be corrected can be replaced by a resistor with any resistance value in the middle position between 2K and 200K omega to perform zero position and range correction on the AD conversion chip. The implementation of the invention selects the resistor with the resistance value of 39K omega to carry out zero position and measuring range correction. And replacing the thermistor to be corrected with a resistor with the resistance value of 39K omega, and adjusting the reference input voltage of the AD conversion chip to enable the code value acquired by the AD conversion chip AD574A to reach 0x800 so as to calibrate the reference voltage of the AD conversion chip. The zero position and the measuring range of the AD conversion chip are corrected, so that errors caused by the AD conversion chip can be avoided, and the correction precision of the resistance value error correction method is improved.
The embodiment of the present invention provides a preferable implementation manner, and step S2 specifically includes the following steps:
s201, short-circuiting the thermistor to be corrected;
s202, measuring the obtained voltage value V through a data processing chipFSubstituting into formula (1) to obtain the voltage V at the inverting input terminal of the operational amplifier-；
Wherein G is the amplification factor of the operational amplifier;
s203, converting the voltage value VFAD voltage code value MCODESubstituting into formula (2) for the reference voltage V provided by the reference voltage chipSTDCorrecting;
reference voltage V provided to reference voltage chipSTDAnd the correction is carried out, so that errors caused by the reference voltage provided by the reference voltage chip can be avoided, and the correction precision of the resistance value error correction method is improved.
The embodiment of the present invention provides a preferable implementation manner, and the step S3 specifically includes the following steps:
s301, replacing the thermistor to be corrected with a first preset resistor with the resistance value of 100K omega;
s302, obtaining the AD voltage code value M of the AD conversion chip through the data processing chipMAX(ii) a The AD voltage code value MMAXSubstituting into formula (3) to obtain the voltage value V at the output end of the operational amplifierF-MAX；
S303, calculating the voltage value VF-MAXSubstituting into formula (4) to obtain the voltage V of the operational amplifierO-MAX；
S304, calculating the voltage VO-MAXSubstituting into formula (5) to obtain the voltage V of the non-inverting input terminal of the operational amplifier+MAX；
V+MAX-V-MAX＝VO-MAX (5)
Wherein, V-MAXIs the voltage at the inverting input of the operational amplifier;
s305, obtaining the voltage V+MAXSubstituting into formula (6), and obtaining resistance R 'of third resistor'3Make a correction；
Wherein R isMAXIs the resistance value of the first preset resistor.
The embodiment of the present invention provides a preferable implementation manner, and the step S4 specifically includes the following steps:
s401, replacing the thermistor to be corrected with a second preset resistor with the resistance value of 2K omega;
s402, obtaining the AD voltage code value M of the AD conversion chip through the data processing chipMIN；
S403, calculating the obtained voltage R'3Substituting into formula (7) to obtain the voltage V of the non-inverting input terminal of the operational amplifier+MIN；
Wherein R isMINThe resistance value of the second preset resistor is obtained;
s404, obtaining the voltage value V+MINSubstituting into formula (8) to obtain the voltage V at the output end of the operational amplifierO-MIN；
VO-MIN＝(V+MIN-V-)×G (8)
S405, converting the AD voltage code value MMINSaid voltage VO-MINThe reference voltage VSTDSubstituting into formula (9) to obtain correction value M of AD voltage code value of the AD conversion chipC；
The embodiment of the present invention provides a preferable implementation manner, and after step S6, the method further includes the following steps:
and S7, converting the resistance value of the thermistor into temperature in a table look-up mode.
According to the resistance value error correction method of the thermistor provided by the embodiment of the invention, the temperature of the thermistor is accurately measured at-30-50 ℃ after correction, and the temperature measurement precision of the thermistor is improved.
The present invention also provides a preferable embodiment, before step S1, further comprising the steps of:
s0 thermistor R to be correctedtThe temperature resistance value parameter is calibrated. The calibration mode in the embodiment of the invention is as follows: used thermistor R to be correctedtCalibrating once every 1 ℃ within the temperature range of-30-50 ℃, and calibrating 81 temperature points in total.
According to the resistance value error correction method provided by the embodiment of the invention, the temperature accuracy of the corrected thermistor is less than or equal to +/-0.1 ℃ within the range of-30-25 ℃, and the temperature accuracy of the corrected thermistor is less than or equal to +/-0.3 ℃ within the range of 25-50 ℃, so that the temperature measurement accuracy of the thermistor is effectively improved. The parameter setting in the embodiment of the invention can correct the resistance value of the thermistor with the resistance value of 2K-100K omega in the temperature measurement range of-30-50 ℃, and the embodiment of the invention can also correct the resistance values of the thermistors with other resistance values, wherein the resistance value of the first preset resistor can be the maximum value of the thermistor which can be corrected, and the resistance value of the second preset resistor can be the minimum value of the thermistor which can be corrected.
The thermistor is placed in an ultrahigh-precision thermostatic bath for testing experiments, the controllable temperature range of the thermostatic bath is-50-100 ℃, the temperature fluctuation degree is +/-0.005- +/-0.01 ℃, the temperature uniformity is +/-0.005- +/-0.01 ℃ in the horizontal and vertical directions, the display resolution is 0.001 ℃, and the medium is alcohol. The temperature range of the thermostatic bath is controlled to be-30-50 ℃, the thermostatic bath is kept at constant temperature every 0.5 ℃ for half an hour, and compared with the temperature obtained through correction and conversion of the resistance error of the thermistor, the experimental results are shown in fig. 3(a) -3 (d). When the temperature is changed in the range of-30 to 25 ℃, the deviation between the temperature obtained by correcting the resistance error of the resistor and the actual temperature is within +/-0.1 ℃, and when the temperature is changed in the range of 25 to 50 ℃, the deviation between the temperature and the actual temperature is within +/-0.3 ℃, because the resistance of the thermistor is not obviously changed along with the temperature when the temperature exceeds 25 ℃, the AD chip selected in the embodiment of the invention can carry out 12-bit A/D conversion, and the resolution ratio cannot meet the resistance change.
Four characteristic temperature points are selected from the constant temperature tank, namely-20 ℃, 0 ℃, 20 ℃ and 30 ℃. The constant temperature is maintained at each characteristic temperature point for 8 hours, the temperature value corrected by the resistance value error correction method is recorded every 1 minute, and the experimental results are shown in fig. 4(a) -4 (d). It can be seen from the figure that the temperature deviation obtained by the correction of the resistance error correction method is within + -0.1 ℃ when the temperature is kept constant at-20, 0 and 20 ℃, and within + -0.25 ℃ when the temperature is kept constant at 30 ℃.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be taken as limiting the invention. Variations, modifications, substitutions and alterations of the above-described embodiments may be made by those of ordinary skill in the art without departing from the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (7)
1. A resistance error correction method for correcting a resistance of a thermistor in a temperature monitoring system, the temperature monitoring system comprising: the correction circuit comprises a thermistor to be corrected, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an operational amplifier, a reference voltage chip, an AD conversion chip and a data processing chip; wherein the content of the first and second substances,
the thermistor to be corrected, the first resistor, the second resistor and the third resistor form a bridge circuit; the first resistor and the second resistor form a first branch of the bridge circuit, and the thermistor to be corrected and the third resistor form a second branch of the bridge circuit; the reference voltage provided by the reference voltage chip is subjected to voltage division processing in the first branch and the second branch, and the second branch is grounded; one end of the fourth resistor is connected with the inverting input end of the operational amplifier, and the other end of the fourth resistor is connected between the first resistor and the second resistor; one end of the fifth resistor is connected with the non-inverting input end of the operational amplifier, and the other end of the fifth resistor is connected between the thermistor to be corrected and the third resistor; one end of the sixth resistor is connected with the non-inverting input end of the operational amplifier, and the other end of the sixth resistor is grounded; one end of the seventh resistor is connected with the inverting input end of the operational amplifier, and the other end of the seventh resistor is connected with the output end of the operational amplifier; the output end of the operational amplifier is connected with the AD conversion chip, and the AD conversion chip is connected with the data processing chip;
the error correction method of the thermistor resistance value comprises the following steps:
s1, setting the resistance value of the first resistor to be equal to that of the third resistor; the resistance value of the second resistor is equal to the resistance value of the thermistor to be corrected; the resistance value of the fourth resistor is equal to that of the fifth resistor; the resistance value of the sixth resistor is equal to that of the seventh resistor; the resistance values of the fourth resistor, the fifth resistor, the sixth resistor and the seventh resistor are all larger than the resistance values of the first resistor and the second resistor after being connected in parallel, and are all larger than the resistance values of the third resistor and the seventh resistor after being connected in parallel;
s2, short-circuiting the thermistor to be corrected, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chipCODEMeasuring the voltage value V at the output end of the operational amplifierF(ii) a By said voltage value VFCalculating a voltage V at an inverting input of the operational amplifier-(ii) a By said voltage value VFAnd the AD voltage code value MCODEA reference voltage V provided to the reference voltage chipSTDCorrecting;
s3, replacing the thermistor to be corrected with a first preset resistor, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chipMAX(ii) a By the AD voltage code value MMAXCalculating the voltage value V of the output end of the operational amplifierF-MAX(ii) a By said voltage value VF-MAXCalculating the voltage V of the operational amplifierO-MAX(ii) a Voltage V through the operational amplifierO-MAXCalculating the voltage V of the non-inverting input terminal of the operational amplifier+MAX(ii) a Passing voltage V+MAXResistance value R 'to the third resistor'3Correcting;
s4, replacing the thermistor to be corrected with a second preset resistor, and acquiring the AD voltage code value M of the AD conversion chip through the data processing chipMIN(ii) a Through the resistance R 'of the third resistor'3Calculating the voltage value V of the non-inverting input terminal of the operational amplifier+MIN(ii) a Passing voltage value V+MINCalculating the voltage value V of the output end of the operational amplifierO-MIN(ii) a By said voltage value VO-MINThe AD voltage code value MMINThe reference voltage VSTDObtaining a correction value M of the AD voltage code value of the AD conversion chipC；
S5, connecting the thermistor to be corrected to the temperature monitoring system, and acquiring the AD conversion chip through the data processing chipAD Voltage code value MtAnd the corrected AD voltage code value M 'of the AD conversion chip'CODEIs the AD voltage code value MtAnd the correction value MCThe sum of (1);
s6, correcting the AD voltage code value M 'of the AD conversion chip'CODEAnd converting the resistance value into the resistance value of the thermistor to be corrected.
2. The resistance error correction method according to claim 1, further comprising, before step S1, the steps of:
and S0, calibrating the temperature resistance parameter of the thermistor to be corrected.
3. The resistance error correction method according to claim 2, wherein the AD conversion chip is subjected to zero and span corrections.
4. The method for correcting the resistance error according to claim 1, wherein the step S2 specifically includes the following steps:
s201, short-circuiting the thermistor to be corrected;
s202, measuring the voltage value V through the data processing chipFSubstituting the voltage into formula (1) to obtain the voltage V of the inverting input end of the operational amplifier-；
Wherein G is the amplification factor of the operational amplifier;
s203, converting the voltage value VFThe AD voltage code value MCODESubstituting into formula (2) for the reference voltage V provided by the reference voltage chipSTDCorrecting;
5. the method for correcting the resistance error according to claim 1, wherein the step S3 specifically includes the following steps:
s301, replacing the thermistor to be corrected with a first preset resistor;
s302, obtaining the AD voltage code value M of the AD conversion chip through the data processing chipMAX(ii) a The AD voltage code value MMAXSubstituting the voltage value into the formula (3) to obtain the voltage value V of the output end of the operational amplifierF-MAX；
S303, calculating the voltage value VF-MAXSubstituting into formula (4) to obtain the voltage V of the operational amplifierO-MAX；
S304, the obtained voltage VO-MAXSubstituting into formula (5) to obtain the voltage V of the non-inverting input terminal of the operational amplifier+MAX；
V+MAX-V-MAX＝VO-MAX (5)
Wherein, V-MAXIs the voltage at the inverting input of the operational amplifier;
s305, obtaining the voltage V+MAXSubstituting into formula (6), and obtaining resistance R 'of the third resistor'3Correcting;
wherein R isMAXThe resistance value of the first preset resistor is obtained.
6. The method for correcting the resistance error according to claim 1, wherein the step S4 specifically includes the following steps:
s401, replacing the thermistor to be corrected with a second preset resistor;
s402, obtaining the AD voltage code value M of the AD conversion chip through the data processing chipMIN；
S403, calculating the obtained voltage R'3Substituting into formula (7) to obtain the voltage V of the non-inverting input terminal of the operational amplifier+MIN；
Wherein R isMINThe resistance value of the second preset resistor is obtained;
s404, obtaining the voltage value V+MINSubstituting into formula (8) to obtain the voltage V at the output end of the operational amplifierO-MIN；
VO-MIN＝(V+MIN-V-)×G (8)
S405, converting the AD voltage code value MMINSaid voltage VO-MINThe reference voltage VSTDSubstituting into formula (9) to obtain correction value M of AD voltage code value of the AD conversion chipC；
7. The resistance error correction method according to claim 1, further comprising, after step S6, the steps of:
and S7, converting the resistance value of the thermistor into temperature in a table look-up mode.
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