CN204301886U - Temperature measurement circuit - Google Patents
Temperature measurement circuit Download PDFInfo
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- CN204301886U CN204301886U CN201420775654.7U CN201420775654U CN204301886U CN 204301886 U CN204301886 U CN 204301886U CN 201420775654 U CN201420775654 U CN 201420775654U CN 204301886 U CN204301886 U CN 204301886U
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Abstract
The utility model provides a kind of temperature measurement circuit, comprising: the first reference power supply and the second reference power supply: constant-current source, is connected with described first reference power supply; Analog switching circuit, is connected with described constant-current source; Subtraction circuit, is connected with described analog switching circuit respectively and described second reference power supply connects; RTD, one end ground connection of described RTD, one end is connected with described analog switching circuit and described subtraction circuit respectively in addition; Detect resistance, one end ground connection of described detection resistance, one end is connected with analog switching circuit and described subtraction circuit respectively in addition.According to temperature measurement circuit of the present utility model, the error effect that line resistance causes measuring method can be avoided as far as possible, thus make thermometric accurate.
Description
Technical field
The utility model relates to thermometry, particularly relates to a kind of temperature measurement circuit.
Background technology
Along with greatly developing of rail traffic vehicles, the trip of people becomes very convenient.Like this, the normal problem run into needing solution badly of rail traffic vehicles how is ensured.
In prior art, become to ensure the important step that rail traffic vehicles normally runs to the monitoring of the temperature of current transformer, the platinum resistor temperature measuring mode of general employing two-wire system gathers the temperature in the converter cabinet in rail traffic vehicles, to prevent the temperature in just fluid cabinet too high, affect the normal operation of rail traffic vehicles.
But the platinum resistor temperature measuring mode of two-wire system, due to the impact by line resistance, there is error in its measurement result.
Utility model content
The utility model provides a kind of temperature measurement circuit, to solve the inaccurate problem of platinum resistor temperature measuring mode of two-wire system in prior art.
The utility model provides a kind of temperature measurement circuit, comprising:
First reference power supply and the second reference power supply:
Constant-current source, is connected with described first reference power supply;
Analog switching circuit, is connected with described constant-current source;
Subtraction circuit, is connected with described analog switching circuit respectively and described second reference power supply connects;
RTD, one end ground connection of described RTD, one end is connected with described analog switching circuit and described subtraction circuit respectively in addition;
Detect resistance, one end ground connection of described detection resistance, one end is connected with analog switching circuit and described subtraction circuit respectively in addition.
As shown from the above technical solution, the temperature measurement circuit that the utility model provides, comprise the first voltage of the temperature measurement circuit of RTD by acquisition and adopt the second voltage detecting this temperature measurement circuit after resistance replaces RTD, and then obtain the current actual resistance of RTD, and then obtain current actual temperature value, the error effect that line resistance causes measuring method can be avoided as far as possible, thus make thermometric accurate.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the temp measuring method according to the utility model one embodiment;
Fig. 2 is the structural representation of the temperature measurement circuit according to another embodiment of the utility model;
Fig. 3 is the instantiation figure according to the utility model temperature measurement circuit of an embodiment again.
Detailed description of the invention
Embodiment one
The utility model provides a kind of temp measuring method, specifically may be used for carrying out thermometric to the converter cabinet in rail traffic vehicles, and the executive agent of the present embodiment can be temperature measuring equipment.As shown in Figure 1, be the schematic flow sheet of the temp measuring method according to the present embodiment.
Step 101, measure the first magnitude of voltage of temperature measurement circuit, this temperature measurement circuit comprises RTD.
The resistance of RTD can change along with the change of temperature.RTD specifically has PT100 and PT1000 etc. series of products, can adopt the RTD of PT100 model in the present embodiment.Namely after PT 100 represent that its resistance 0 DEG C time is 100 ohm, and 100 DEG C time, its resistance is about 138.5 ohm.The operation principle of PT100 RTD is: when PT100 at 0 degree Celsius time RTD resistance be 100 ohm, the resistance of RTD can rise along with temperature, and its resistance becomes and at the uniform velocity rises.
Temperature measurement circuit specifically can as shown in Figure 2, and this temperature measurement circuit comprises the first reference power supply 201, second reference power supply 202, constant-current source 203, analog switching circuit 204, subtraction circuit 205, RTD 206 and detects resistance 207.
Step 102, adopts and detects resistance replacement RTD, and measure the second magnitude of voltage of temperature measurement circuit.
Alternatively, resistance and the RTD resistance 0 DEG C time detecting resistance is equal, and when the RTD of selection PT100, the value of the detection resistance of the present embodiment can be 100 ohm.RTD is replaced with detection resistance, and measure the second magnitude of voltage that this detection resistance replaces the temperature measurement circuit after RTD.
It is noted that detect resistance have fixing resistance, the resistance namely detecting resistance can not with the environmental change of surrounding.
Step 103, according to the current actual resistance of the first magnitude of voltage and the second magnitude of voltage determination RTD, and according to current actual resistance determination current actual temperature.
The value of the first magnitude of voltage and the second magnitude of voltage and the voltage change at RTD two ends, can obtain the change in resistance value of RTD accordingly, and then obtain the current actual resistance of RTD.
Step 103 is specifically as follows:
According to the current actual resistance R of following known acquisition RTD:
R=(U1-U2)/0.03329+R1, wherein, U1 is the first magnitude of voltage, and U2 is the second magnitude of voltage, and R1 is the resistance detecting resistance;
Obtain current actual temperature value according to the phasing meter preset, phasing meter comprises the resistance of RTD and the corresponding relation of temperature.
It is owing to there is approximately linear corresponding relation between temperature and the resistance of RTD, concrete as shown in formula (1),
R=0.39T+100 formula (1)
Wherein, R is the current actual resistance of RTD, and T is current actual temperature.
Voltage U in temperature measurement circuit and the relation existed between all-in resistance Rn as formula (2):
U=0.03329Rn-2.5373 formula (2)
Like this, U1=0.03329 (R+Rs)-2.5373 formula (3)
Wherein Rs is temperature measurement circuit center line roadlock value, namely except the resistance of other resistance of RTD.
U2=0.03329 (R1+Rs)-2.5373 formula (4)
Formula (3) and formula (4) subtract each other can obtain formula (1).
In the present embodiment, when adopting the RTD of PT100, phasing meter is the phasing meter that PT100 RTD is corresponding.
According to the temp measuring method of the present embodiment, comprise the first voltage of Pt Resistance Temperature Measuring Circuit by acquisition and adopt the second voltage detecting this temperature measurement circuit after resistance replaces RTD, and then obtain the current actual resistance of RTD, and then obtain current actual temperature value, the error effect that line resistance causes measuring method can be avoided as far as possible, thus make thermometric accurate.
Embodiment two
The present embodiment provides a kind of temperature measurement circuit, for the temp measuring method of above-described embodiment.
As shown in Figure 2, the temperature measurement circuit of the present embodiment comprises: the first reference power supply 201, second reference power supply 202, constant-current source 203, analog switching circuit 204, subtraction circuit 205, RTD 206 and detection resistance 207.
Wherein, constant-current source 203 is connected with the first reference power supply 201, analog switching circuit 204 is connected with constant-current source 203, subtraction circuit 205 is connected with analog switching circuit 204 respectively and the second reference power supply 202 connects, one end ground connection of RTD 206, one end is connected with analog switching circuit 204 and subtraction circuit 205 respectively in addition, and detect one end ground connection of resistance 207, one end is connected with analog switching circuit 204 and subtraction circuit 205 respectively in addition.
The analog switching circuit 204 of the present embodiment can be specifically chip type analog switch, can play the effect of port switching, namely switches between RTD 206 and detection resistance 207.
Alternatively, the temperature measurement circuit of the present embodiment also comprises CPU (Central Processing Unit, central processing unit) 208, and this CPU208 is connected with subtraction circuit 205.
Particularly, first reference power supply 201 is powered for constant-current source 203, second reference power supply 202 is powered for subtraction circuit 205, constant-current source 203 and subtraction circuit 205 can be avoided like this to use same Power supply can drag down the problem of reference voltage, and then make measurement result more accurate.
First reference power supply 201 provides reference voltage on constant-current source 203, constant-current source 203 generates electric current, electric current flows through RTD 206, now analog switching circuit 204 gathers first voltage at temperature measurement circuit two ends, and by subtraction circuit 205, the reference voltage that this first voltage and the second reference power supply 202 provide is subtracted each other, generate the first result voltage.Similar, connected by analog switching circuit 204 and detect resistance 207, now, owing to detecting adding of the resistance of resistance 207, overall resistance changes, like this, and the second voltage of what analog switching circuit 204 collected again is temperature measurement circuit, and by subtraction circuit 205, the reference voltage that this second voltage and the second reference power supply 202 provide is subtracted each other, generate the second result voltage.First result voltage and the second result voltage are sent to CPU by subtraction circuit 205, and the first result voltage and the second result voltage are subtracted each other the change magnitude of voltage obtaining RTD 206 by CPU, and obtain the current actual resistance R of RTD by following formula:
R=(U1-U2)/0.03329+R1, wherein, U1 is the first magnitude of voltage, and U2 is the second magnitude of voltage, and R1 is the resistance detecting resistance.U1-U2 is change magnitude of voltage.
As shown in Figure 3, be an instantiation figure of the temperature measurement circuit of the present embodiment.The first reference power supply 201 in the on-off circuit of the present embodiment comprises the first chip 301, first electric capacity 302, second electric capacity 303 and the 3rd electric capacity 304.
Wherein, first chip 301 is connected with constant-current source 203, specifically can pass through OUT (output) pin to be connected with constant-current source 203, first chip 301 can pass through GND (ground connection) pin ground connection, and the first chip 301 can also access the first external power supply by IN (input) pin; First electric capacity 302 one end ground connection, one end is connected with the first chip 301 in addition; Second electric capacity 303 one end ground connection, one end is connected with the first chip 301 in addition; One end of 3rd electric capacity 304 is connected between the first chip 301 and constant-current source 203, one end ground connection in addition.
Alternatively, the constant-current source 203 in the present embodiment comprises the first amplifier 310, first resistance 311, second resistance 312, the 3rd resistance 313, second amplifier 314, the 4th electric capacity 315, the 4th resistance 316 and the 5th resistance 317.
Wherein, the positive input terminal of the first amplifier 310 is connected with the first reference power supply 201; One end of first resistance 311 is connected with the negative input end of the first amplifier 310, one end is connected with the output of the 3rd resistance 313 with the first amplifier 310 by the second resistance 312 in addition, one end of second resistance 312 is connected to the first resistance 311, one end is connected to one end of the 3rd resistance 313 in addition, and other one end of the 3rd resistance 313 is connected to the output of the first amplifier 310; The output of the second amplifier 314 is connected with the negative output terminal of the first amplifier 310 and the first resistance 311 respectively, and the negative input end of the second amplifier 314 is connected between the first resistance 311 and the second resistance 312; 4th electric capacity 315 is in parallel with the first resistance 311; One end ground connection of the 4th resistance 316, one end is connected to the positive input terminal of the second amplifier 314 in addition, one end of 5th resistance 317 is connected to the output of the first amplifier 310, and one end is connected between the positive input terminal of the second amplifier 314 and the 4th resistance 316 in addition.
Alternatively, the analog switching circuit of the present embodiment specifically comprises: the 6th resistance 319, second chip 320, the 7th resistance 321 and the 8th resistance 322.
Wherein, one end ground connection of the 6th resistance 319, one end is connected to and detects between resistance 207 and RTD 206 in addition; First pin 3201 of the second chip 320 is connected with constant-current source 203, this first pin can be COM (public) 1 pin, second pin 3202 of the second chip 320 is connected with detection resistance 207, this second pin can be NO1 pin, one end of RTD 206 is connected with detection resistance 207 and the 6th resistance 319 respectively, other one end of RTD 206 is connected with the three-prong 3203 of the second chip 320, this three-prong 3203 can be NC1 pin, and the second chip 320 also has a pin to be connected with the second external power supply; One end of 7th resistance 321 is connected between constant-current source 203 and the first pin 3201, and other one end of the 7th resistance 321 is connected between three-prong 3203 and RTD 206; One end of 8th resistance 322 is connected between the 4th pin 3204 of the second chip 320 and subtraction circuit 205, and the 4th pin can be COM2, between the three-prong 3203 that other one end of the 8th resistance 322 is connected to the second chip 320 and RTD 206.
The model of second chip 320 of the present embodiment is SGM3005.
Alternatively, the subtraction circuit 205 of the present embodiment comprises the 9th resistance 331, the tenth resistance 332, the 3rd amplifier the 333, the 11 resistance the 334, the 12 resistance the 335, the 13 resistance 336, the 5th electric capacity the 337 and the 14 resistance 338.
Wherein, one end of the 9th resistance 331 is connected with the 4th pin 3204, and other one end of the 9th resistance 331 is connected with one end of the tenth resistance 332 and the positive input terminal of the 3rd amplifier 333 respectively, other one end ground connection of the tenth resistance 332; The negative input end of the 3rd amplifier 333 connects the 11 resistance 334; 11 resistance 334 is connected with the second reference power supply 202; One end of 12 resistance 335 is connected between the negative input end of the 11 resistance 334 and the 3rd amplifier 333, between the output that other one end of the 12 resistance 335 is connected to the 3rd amplifier 333 and the 13 resistance 336; One end of 13 resistance 336 is connected to the output of the 3rd amplifier 333, and one end is connected to the 5th electric capacity 337 in addition; One end of 5th electric capacity 337 is connected to the 13 resistance 336, in addition one end ground connection; One end of 14 resistance 338 is connected between the 13 resistance 336 and the 5th electric capacity 337, in addition one end ground connection.
Alternatively, the second reference power supply 202 comprises the 6th electric capacity 341, the 7th electric capacity 343 of the 3rd chip 342 and parallel connection and the 8th electric capacity 344.
Wherein, one end of the 6th electric capacity 341 is connected to the first pin 3421 of the 3rd chip 342, and this first pin 3421 can be IN (input) pin, in addition one end ground connection; First pin IN of the 3rd chip 342 is connected between the 6th electric capacity 341 and power supply 350, the second pin 3422 ground connection of the 3rd chip 342, and this second pin 3422 can be COM pin; One end of 7th electric capacity 343 is connected to the three-prong 3423 of the 3rd chip 342, and this three-prong can be OUT (output) pin, and one end is connected to the second pin 3422 of the 3rd chip 342 in addition.
In the present embodiment, the model of the first chip 301 can be specifically MAX6250AESA, and constant-current source 203 produces the DC current of 20mA and is added to RTD 206 by analog switching circuit 204 or detects on resistance 207.The resistance detecting resistance 207 can be 100 ohm.The model of the second chip 320 can be specifically SGM3005 or other there is the chip of single-pole double-throw switch (SPDT) function, the present embodiment does not limit.The model of the 3rd chip 342 can be specifically LD1117S12CTR, and it can be 1.2V that the second reference power supply 202 generates reference voltage.
If the model of the second chip 320 is SGM3005, when IN/OUT pin is input as low level, RTD 206 accesses, and when IN/OUT pin is input as high level, detects resistance 207 and accesses.
The scope of the magnitude of voltage that can receive due to the modular converter of the analog signal/data signal in CPU is 0 volt to 3 volts, and be the RTD phasing meter of PT100 according to model, the resistance of RTD corresponding when-50 degrees Celsius is 80 ohm, and the resistance of RTD corresponding when 130 degrees Celsius is 155 ohm.Adopt temperature detecting resistance as shown in Figure 3, when the resistance of RTD 206 is 80 ohm, the first voltage recording RTD 206 two ends is about 0.3V, when the resistance of RTD 206 is 155 ohm, the first voltage recording RTD 206 two ends is about 3V, therefrom can find out, the temperature measured by the temperature measurement circuit of the present embodiment tallies with the actual situation, and thermometric is effective.
According to the temperature measurement circuit of the present embodiment, comprise the first voltage of the temperature measurement circuit of RTD by acquisition and adopt the second voltage detecting this temperature measurement circuit after resistance replaces RTD, and then obtain the current actual resistance of RTD, and then obtain current actual temperature value, the error effect that line resistance causes measuring method can be avoided as far as possible, thus make thermometric accurate.
Last it is noted that above embodiment is only in order to illustrate the technical solution of the utility model, be not intended to limit; Although be described in detail the utility model with reference to previous embodiment, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein portion of techniques feature; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the scope of each embodiment technical scheme of the utility model.
Claims (7)
1. a temperature measurement circuit, is characterized in that, comprising:
First reference power supply and the second reference power supply:
Constant-current source, is connected with described first reference power supply;
Analog switching circuit, is connected with described constant-current source;
Subtraction circuit, is connected with described analog switching circuit respectively and described second reference power supply connects;
RTD, one end ground connection of described RTD, one end is connected with described analog switching circuit and described subtraction circuit respectively in addition;
Detect resistance, one end ground connection of described detection resistance, one end is connected with analog switching circuit and described subtraction circuit respectively in addition.
2. temperature measurement circuit according to claim 1, is characterized in that, also comprises:
Central processor CPU, is connected with described subtraction circuit.
3. temperature measurement circuit according to claim 1 and 2, is characterized in that, described first reference power supply comprises:
First chip, described first chip is connected with described constant-current source;
First electric capacity, described first electric capacity one end ground connection, one end is connected with described first chip in addition;
Second electric capacity, described second electric capacity one end ground connection, one end is connected with described first chip in addition;
3rd electric capacity, one end of described 3rd electric capacity is connected between described first chip and described constant-current source, one end ground connection in addition.
4. temperature measurement circuit according to claim 3, is characterized in that, described constant-current source comprises:
First amplifier, the positive input terminal of described first amplifier is connected with described first reference power supply;
First resistance, the second resistance and the 3rd resistance, one end of described first resistance is connected with the negative input end of described first amplifier, one end is connected with the output of described first amplifier with described 3rd resistance by described second resistance in addition, one end of described second resistance is connected to described first resistance, one end is connected to one end of described 3rd resistance in addition, and other one end of described 3rd resistance is connected to the output of described first amplifier;
Second amplifier, the output of described second amplifier is connected with the negative output terminal of described first amplifier and described first resistance respectively, and the negative input end of described second amplifier is connected between described first resistance and described second resistance;
4th electric capacity, described 4th electric capacity and described first resistor coupled in parallel;
Described 4th resistance and the 5th resistance, one end ground connection of described 4th resistance, one end is connected to the positive input terminal of described second amplifier in addition, one end of described 5th resistance is connected to the output of described first amplifier, and one end is connected between the positive input terminal of described second amplifier and described 4th resistance in addition.
5. temperature measurement circuit according to claim 4, is characterized in that, described analog switching circuit comprises:
6th resistance, one end ground connection of described 6th resistance, one end is connected between described detection resistance and described RTD in addition;
Second chip, first pin of described second chip is connected with described constant-current source, second pin of described second chip is connected with described detection resistance, one end of described RTD is connected with described detection resistance and described 6th resistance respectively, and other one end of described RTD is connected with the three-prong of described second chip;
7th resistance, one end of described 7th resistance is connected between described constant-current source and described first pin, and other one end of described 7th resistance is connected between described three-prong and described RTD;
8th resistance, one end of described 8th resistance is connected to the 4th of described second chip the between pin and subtraction circuit, and other one end of described 8th resistance is connected between described three-prong and described RTD.
6. temperature measurement circuit according to claim 5, is characterized in that, described subtraction circuit comprises:
9th resistance and the tenth resistance, one end of described 9th resistance is connected with described 4th pin, and other one end of described 9th resistance is connected with one end of the tenth resistance and the positive input terminal of the 3rd amplifier respectively, other one end ground connection of described tenth resistance;
Described 3rd amplifier, the negative input end of described 3rd amplifier connects the 11 resistance;
Described 11 resistance, is connected with described second reference power supply;
12 resistance, one end of described 12 resistance is connected between the negative input end of described 11 resistance and described 3rd amplifier, between the output that other one end of described 12 resistance is connected to described 3rd amplifier and the 13 resistance;
Described 13 resistance, one end of described 13 resistance is connected to the output of described 3rd amplifier, and one end is connected to the 5th electric capacity in addition;
5th electric capacity, one end of described 5th electric capacity is connected to described 13 resistance, one end ground connection in addition;
14 resistance, one end of described 14 resistance is connected between described 13 resistance and described 5th electric capacity, one end ground connection in addition.
7. temperature measurement circuit according to claim 6, is characterized in that, described second reference power supply comprises:
6th electric capacity, one end of described 6th electric capacity is connected to the first pin of described 3rd chip, one end ground connection in addition;
3rd chip, the second pin ground connection of described 3rd chip;
7th electric capacity in parallel and the 8th electric capacity, one end of described 7th electric capacity is connected to the three-prong of described 3rd chip, and one end is connected to the second pin of described 3rd chip in addition.
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| CN201420775654.7U CN204301886U (en) | 2014-12-10 | 2014-12-10 | Temperature measurement circuit |
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| CN201420775654.7U CN204301886U (en) | 2014-12-10 | 2014-12-10 | Temperature measurement circuit |
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| CN204301886U true CN204301886U (en) | 2015-04-29 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105738004A (en) * | 2014-12-10 | 2016-07-06 | 中车大连电力牵引研发中心有限公司 | Temperature measurement method and circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105738004A (en) * | 2014-12-10 | 2016-07-06 | 中车大连电力牵引研发中心有限公司 | Temperature measurement method and circuit |
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Address after: 116045 Liaoning province Dalian City Lushun Economic Development Zone Dalian Hao Yang No. 1 North Street Patentee after: CRRC DALIAN ELECTRIC TRACTION R & D CENTER CO., LTD. Address before: 116045 Liaoning province Dalian City Lushun Economic Development Zone Dalian Hao Yang No. 1 North Street Patentee before: Co., Ltd of Bei Che Dalian Electric Traction R & D Center |