CN106768449A - A kind of digital AC electric bridge platinum resistance thermometer - Google Patents
A kind of digital AC electric bridge platinum resistance thermometer Download PDFInfo
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- CN106768449A CN106768449A CN201710145577.5A CN201710145577A CN106768449A CN 106768449 A CN106768449 A CN 106768449A CN 201710145577 A CN201710145577 A CN 201710145577A CN 106768449 A CN106768449 A CN 106768449A
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- electric bridge
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims abstract description 40
- 229910052697 platinum Inorganic materials 0.000 title claims abstract description 20
- 230000005540 biological transmission Effects 0.000 claims abstract description 15
- 238000000605 extraction Methods 0.000 claims abstract description 15
- 230000010354 integration Effects 0.000 claims abstract description 8
- 238000011896 sensitive detection Methods 0.000 claims description 9
- 230000003321 amplification Effects 0.000 claims description 8
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 8
- 238000012546 transfer Methods 0.000 claims description 5
- 230000005284 excitation Effects 0.000 claims description 3
- 239000000284 extract Substances 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000000034 method Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 230000008054 signal transmission Effects 0.000 description 2
- 230000011664 signaling Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
- G01K7/20—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit
Abstract
The invention provides a kind of digital AC electric bridge platinum resistance thermometer, including：Ac-excited source, resistance bridge, amplifying unit, phase-sensitive detector, low pass filter, A/D change-over circuits, data transmission unit and MCU control unit, wherein, the ac-excited source connects and composes helipot bridge with the resistance bridge, described phase-sensitive detector, low pass filter constitutes lowpass band signal extraction system, the helipot bridge is connected by the amplifying unit with the lowpass band signal extraction system, the lowpass band signal extraction system is connected with the A/D change-over circuits, the data signal of the A/D change-over circuits output is transmitted by the data transmission unit, the MCU control unit respectively with the amplifying unit, the A/D change-over circuits and the data transmission unit connect to realize digital integration and bus marco.
Description
Technical field
The present invention relates to a kind of temperature measurement system, more particularly to a kind of digital AC electric bridge platinum resistance thermometer.
Background technology
Platinum resistance temperature sensor is using its resistance and temperature into certain functional relation and the temperature sensor that is made.By
In platinum resistance temperature sensor accuracy of measurement is high, temperature-measuring range big, it is repeatability and good stability, cheap, extensively should
For the temperature survey of mesophilic range.Current direct current RTD electric bridge is more general temperature measuring circuit.Direct current RTD
The characteristics of electric bridge is simple structure, and hardware costs are smaller, but antijamming capability is weaker, and thermometric resolution ratio is relatively low.
The content of the invention
Present invention aim above mentioned problem of the prior art is solved, a kind of digital AC electric bridge RTD temperature is proposed
Degree meter, its high-resolution thermometric ability can be obtained by AC bridge and phase sensitive detection technology and by MCU control unit and
RS485 signal transmissions can realize digital integration and bus marco.
A kind of digital AC electric bridge platinum resistance thermometer of the invention, including：Ac-excited source, resistance bridge, amplification
Unit, phase-sensitive detector, low pass filter, A/D change-over circuits, data transmission unit and MCU control unit, wherein, the friendship
Stream driving source and the resistance bridge connect and compose helipot bridge, and described phase-sensitive detector, low pass filter constitute low
Passband signals extraction system, the helipot bridge is by the amplifying unit and the lowpass band signal extraction system
Connection, the lowpass band signal extraction system is connected with the A/D change-over circuits, the numeral of the A/D change-over circuits output
Signal is transmitted by the data transmission unit, and the MCU control unit is electric with the amplifying unit, A/D conversions respectively
Road and the data transmission unit connect to realize digital integration and bus marco.
Preferably, the ac-excited source is sinusoidal excitation source.
Preferably, the resistance bridge include the first fixed resistance R1, the second fixed resistance R2, the 3rd fixed resistance R3,
Adjustable resistance and RTD, the first fixed resistance R1, the second fixed resistance R2 and adjustable resistance of series connection, the 3rd fixation of series connection
It is in parallel between resistance R3 and RTD and the ac-excited source, the first fixed resistance R1 and the second fixed resistance R2 it
Between B points ground connection, the A points between the 3rd fixed resistance R3 and the RTD are connected with the amplifying unit.
Preferably, the lowpass band signal extraction system extracts the direct current width of AC signal by phase sensitive detection technology
Degree signal.
Preferably, the data transmission unit is RS485 buses.
Preferably, the amplifying unit includes preamplifier and demodulator amplifier.
Preferably, the reverse scaling circuit of the demodulator amplifier, wherein using digital regulation resistance as amplification resistance.
Preferably, the MCU control unit is single-chip microcomputer.
Preferably, the thermometer carries out temperature survey in the range of-200-650 degrees Celsius.
The beneficial effects of the invention are as follows：Due to having used AC bridge and phase sensitive detection signalling technique extractive technique, improve
The resolution ratio and antijamming capability of system, the precision of temperature survey can be greatly improved.Also, it is program control due to introducing
Unit (MCU control unit) and bus transfer (signal transmission, RS485), can make sensor realize digital integration, total line traffic control
System.
Brief description of the drawings
Fig. 1 is the structural representation of digital AC electric bridge platinum resistance thermometer of the invention.
Fig. 2 is phase sensitive detection electrical schematic diagram.
Fig. 3 is that the part-structure of a specific embodiment of digital AC electric bridge platinum resistance thermometer of the invention shows
It is intended to.
Specific embodiment
Below by embodiment, the invention will be further described, and its purpose is only that and more fully understands research of the invention
The protection domain that content is not intended to limit the present invention.
Digital AC electric bridge platinum resistance thermometer of the invention, can be used for the high-resolution hydrocode of mesophilic range, example
Temperature survey can be such as carried out in the range of-200-650 degrees Celsius.
As shown in figure 1, including：Ac-excited source 1, resistance bridge 2, amplifying unit 3, phase-sensitive detector 4, low pass filter
5th, A/D change-over circuits 6, data transmission unit 7 and MCU control unit (Microcontroller Unit, microprocessing unit) 8.
Wherein, the ac-excited source 1 is connected in parallel composition helipot bridge with the resistance bridge 2.The phase-sensitive detector 4,
Low pass filter 5 constitutes lowpass band signal extraction system.The helipot bridge is low with described by the amplifying unit 3
Passband signals extraction system is connected, and the lowpass band signal extraction system is connected with the A/D change-over circuits 6, the A/D
The data signal of the output of change-over circuit 6 is transmitted by the data transmission unit 7, and the MCU control unit 8 is put with described respectively
Big unit 3, the A/D change-over circuits 6 and the data transmission unit 7 connect to realize digital integration and bus marco.
The ac-excited source 1 is sinusoidal excitation source.The resistance bridge 2 includes that the first fixed resistance R1, second are fixed
Resistance R2, the 3rd fixed resistance R3, adjustable resistance and RTD.Wherein, the first fixed resistance R1, the second fixed resistance R2 and can
Resistant series connection is adjusted, the 3rd fixed resistance R3 and RTD are connected in series, and in parallel with the ac-excited source 1, so that structure
Into helipot bridge.B points ground connection between the first fixed resistance R1 and the second fixed resistance R2, the described 3rd fixes electricity
A points between resistance R3 and the RTD are connected with the amplifying unit.Bridge can be made to reach balance by adjusting adjustable resistance,
That is A points current potential over the ground is zero.Now resistance variations of the RTD caused by minimum temperature change can cause bridge not
Balance, i.e. A points current potential over the ground changes.The potential change is extracted by amplifying unit by signal extraction system.
Bridge for measuring temperature (above-mentioned helipot bridge) is exchanged for resistance, should be tried one's best and be taken big valued resistor, make electricity in bridge
The amount of flowing to end it is small, with avoid electric current by resistance produce heat influence temperature survey accuracy；Resistance value again should not mistake simultaneously
Greatly, cause the output impedance of bridge too high, (modulation, the input impedance of amplifying circuit are in M for the modulation of influence signal voltage, amplification
Ω magnitudes).The standard mains voltage of digital circuit is 3.3V or 5V, therefore ac-excited voltage amplitude is in 6~10V (peak-to-peaks
Value), while RTD conventional on the market is generally PT100 (resistance is 100 Ω) and two kinds of PT1000 (resistance is 1K Ω), therefore
Resistance value should select 1K Ω to be advisable in bridge.So bridge current is in 3~5mA, and caused resistance heating amount is smaller；Bridge it is defeated
Go out resistance in 2K or so, compared with the input impedance of the M Ω magnitudes of modulation circuit differ more than 1000 times, meet signal modulation,
Amplify and require, while the market penetration rate of device is also higher, can preferably control cost.More preferable thermometric is obtained if desired
Effect, while excessive consideration hardware cost is not required to, the RTD of customizable PT10K Ω (resistance is 10K Ω), bridge resistance,
(i.e. R1, R2, R3) also selects the optimal thermometric effect resistance that 10K Ω resistance, i.e. 10K Ω resistance are this bridge.
The amplifying unit includes preamplifier 31 and demodulator amplifier 32.Preamplifier 31 is used for AC bridge
The unbalance voltage signal of electric bridge of A points output be amplified.Demodulator amplifier 32 is used for amplifying through preamplifier 31
Signal afterwards is demodulated amplification, will the unbalanced voltage signal of bridge DC component removal, and by AC signal according to
Certain multiple amplifies.
Because ac-excited source 1 forms AC bridge, therefore the electric bridge unbalanced signal of sensor output is sharp to exchange
Encourage the range value for carrier wave.For the signal system for having carrier wave, noise is directly proportional to bandwidth, therefore the signal to noise ratio of measuring system is available
The method of bandwidth is limited to improve.0.1Hz is even lower to be led to keep stably amplifier using phase sensitive detection technology
Frequency band.Modulated wave can completely be recovered modulated signal by phase sensitive detection in amplitude and polarity, and it is according to modulating wave and carrier wave
Phase difference differentiate modulated signal polarity.Its operation principle is as shown in Figure 2.
In Fig. 2, if reference signal Ur directly draws from signal source, expression formula is：
Uγ=UmSinω0t (1)
In above-mentioned formula (1), Ur represents reference signal, and Um represents signal source.ω0Represent signal(-) carrier frequency.
Amplify input in addition to the unbalanced voltage signal of electric bridge, also there is the interference of various frequencies, it is to simplify the analysis, false
Surely frequency is only existed for ω1Interference signal, then have：
C=EsSi(nω0t+φ1)+EnSi(nω1t+φ2) (2)
In above-mentioned formula (2), C represents interference signal, and Es represents the intensity of signal, and En represents the intensity of interference, φ1Represent
The phase of signal, φ2Represent the phase of interference.
Multiplier is output as：
In above-mentioned formula (3), e represents detection multiplier, and K represents amplification coefficient.
It is by exporting Uout after LPF：
The unbalance degree of electric bridge, U are reflected in above formula (1)γSteady state value is taken, regulation phase shifter can make Uout maximums so as to obtain
Detection sensitivity higher is obtained, only when Es → 0, above formula (1) is just zero.Above formula (2) represents interference signal, because LPF
The output of device is raised and decayed with frequency, by taking RC low pass filters as an example, filter centre frequency f=1/2 π RC, and it is determined
Bandwidth deltaf ω=2 (the ω of phase-sensitive detector1- ω0)=2/RC.If selecting time constant RC=10s, f=0.016Hz, then only have
When the frequency of interference signal is between 781.234Hz~781.266Hz, its difference frequency with f could by wave filter, equivalent to
One quality factor is more than 104Narrow band filter, it is thus possible to preferably suppress noise and interference.And frequency is 781Hz's
Electric bridge unbalanced signal but can be with gain (Ku very high>3×104) detected.
Therefore, using phase sensitive detection technology, the unbalance voltage of bridge is passed through after preamplifier 31, modulated amplifier 32
Crossing phase-sensitive detector 4, low pass filter 5 can extract the DC amplitude signal of AC signal with gain very high.
Said extracted d. c. voltage signal out, should again by obtaining corresponding data signal after digital A/D converter 6
Data signal passes through RS485 bus transfers.Demodulator amplifier 32, A/D converter 6, data transmission unit 7 (RS485 buses) are
By MCU control unit (Microcontroller Unit, microprocessing unit) 8 it is program control with control, be achieved in sensor
Digital integration and bus marco.
Fig. 3 is that the part-structure of a specific embodiment of digital AC electric bridge platinum resistance thermometer of the invention shows
It is intended to.
To reduce hardware costs, the present invention is using market penetration rate 51 series monolithics higher as MCU control unit
8.Demodulator amplifier 32 uses reverse scaling circuit, and amplification resistance, single-chip microcomputer 8 and digital current potential are done using digital regulation resistance
Device is connected, and the resistance of digital regulation resistance is adjusted by I/O mouthfuls of control, reaches the purpose of program control control demodulation amplifying unit 32.Together
When, single-chip microcomputer 8 is passed through again by I/O mouthfuls of control A/D chip (A/D converter 6), collection voltages signal, the voltage signal for collecting
RS485 bus transfers are to user or host computer.The external DS18B20 chips of single-chip microcomputer 8 as temperature survey bigness scale sensor, while
The E that DS18B20 chips are carried2PROM can store parameters.
In the present invention, due to having used AC bridge and phase sensitive detection signalling technique extractive technique, dividing for system is improve
Resolution and antijamming capability, the precision of temperature survey can be greatly improved.Also, (MCU is controlled due to introducing program-controlled unit
Unit processed) and bus transfer (digital data transmission, RS485), sensor can be made to realize digital integration, bus marco.
Obviously, those of ordinary skill in the art is it should be appreciated that the embodiment of the above is intended merely to explanation originally
Invention, and be not used as being limitation of the invention, as long as in spirit of the invention, to embodiment described above
Change, modification will all fall in the range of claims of the present invention.
Claims (9)
1. a kind of digital AC electric bridge platinum resistance thermometer, it is characterised in that including：Ac-excited source, resistance bridge, amplification
Unit, phase-sensitive detector, low pass filter, A/D change-over circuits, data transmission unit and MCU control unit, wherein, the friendship
Stream driving source and the resistance bridge connect and compose helipot bridge, and described phase-sensitive detector, low pass filter constitute low
Passband signals extraction system, the helipot bridge is by the amplifying unit and the lowpass band signal extraction system
Connection, the lowpass band signal extraction system is connected with the A/D change-over circuits, the numeral of the A/D change-over circuits output
Signal is transmitted by the data transmission unit, and the MCU control unit is electric with the amplifying unit, A/D conversions respectively
Road and the data transmission unit connect to realize digital integration and bus marco.
2. the digital AC electric bridge platinum resistance thermometer according to right will go 1, it is characterised in that the ac-excited source
It is sinusoidal excitation source.
3. the digital AC electric bridge platinum resistance thermometer according to right will go 1, it is characterised in that the resistance bridge bag
The first fixed resistance R1, the second fixed resistance R2, the 3rd fixed resistance R3, adjustable resistance and RTD are included, the first of series connection consolidates
Determine the 3rd fixed resistance R3 and RTD and described ac-excited of resistance R1, the second fixed resistance R2 and adjustable resistance, series connection
It is in parallel between source, the B points ground connection between the first fixed resistance R1 and the second fixed resistance R2, the 3rd fixed resistance R3
It is connected with the amplifying unit with the A points between the RTD.
4. digital AC electric bridge platinum resistance thermometer according to claim 1, it is characterised in that the lowpass band letter
Number extraction system extracts the DC amplitude signal of AC signal by phase sensitive detection technology.
5. digital AC electric bridge platinum resistance thermometer according to claim 1, it is characterised in that the data transfer list
Unit is RS485 buses.
6. digital AC electric bridge platinum resistance thermometer according to claim 1, it is characterised in that the amplifying unit bag
Include preamplifier and demodulator amplifier.
7. digital AC electric bridge platinum resistance thermometer according to claim 6, it is characterised in that the demodulator amplifier
It is reverse scaling circuit, wherein using digital regulation resistance as amplification resistance.
8. digital AC electric bridge platinum resistance thermometer according to claim 1, it is characterised in that the MCU controls are single
Unit is single-chip microcomputer.
9. digital AC electric bridge platinum resistance thermometer according to claim 1, it is characterised in that the thermometer-
Temperature survey is carried out in the range of 200-650 degrees Celsius.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710145577.5A CN106768449A (en) | 2017-03-13 | 2017-03-13 | A kind of digital AC electric bridge platinum resistance thermometer |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710145577.5A CN106768449A (en) | 2017-03-13 | 2017-03-13 | A kind of digital AC electric bridge platinum resistance thermometer |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109375291A (en) * | 2018-10-09 | 2019-02-22 | 成都信息工程大学 | A kind of temperature and air pressure suitable for sonde and humidity measuring instrument and method |
| CN115183897A (en) * | 2022-09-09 | 2022-10-14 | 之江实验室 | Temperature measuring system and method based on high-frequency alternating current signals |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN87214459U (en) * | 1987-10-21 | 1988-06-22 | 河北省标准计量学校 | Thermal resistance type thermometer with precision digital display |
| CN102520257A (en) * | 2011-12-07 | 2012-06-27 | 华中科技大学 | Alternating current (AC) impedance spectroscopy automatic testing device of positive temperature coefficient (PTC) thermistor |
| CN102843102A (en) * | 2012-09-28 | 2012-12-26 | 江苏物联网研究发展中心 | Phase-locked amplifying circuit of monolithic integrated MEMS (Micro Electro Mechanical Systems) capacitive sensor |
| CN103098133A (en) * | 2010-11-17 | 2013-05-08 | 希捷科技有限公司 | Head transducer with multiple resistance temperature sensors for head-medium spacing and contact detection |
| CN203606434U (en) * | 2013-10-17 | 2014-05-21 | 西北师范大学 | Impedance measurement circuit |
| CN206523244U (en) * | 2017-03-13 | 2017-09-26 | 中国地震局地壳应力研究所 | A kind of digital AC electric bridge platinum resistance thermometer |
-
2017
- 2017-03-13 CN CN201710145577.5A patent/CN106768449A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN87214459U (en) * | 1987-10-21 | 1988-06-22 | 河北省标准计量学校 | Thermal resistance type thermometer with precision digital display |
| CN103098133A (en) * | 2010-11-17 | 2013-05-08 | 希捷科技有限公司 | Head transducer with multiple resistance temperature sensors for head-medium spacing and contact detection |
| CN102520257A (en) * | 2011-12-07 | 2012-06-27 | 华中科技大学 | Alternating current (AC) impedance spectroscopy automatic testing device of positive temperature coefficient (PTC) thermistor |
| CN102843102A (en) * | 2012-09-28 | 2012-12-26 | 江苏物联网研究发展中心 | Phase-locked amplifying circuit of monolithic integrated MEMS (Micro Electro Mechanical Systems) capacitive sensor |
| CN203606434U (en) * | 2013-10-17 | 2014-05-21 | 西北师范大学 | Impedance measurement circuit |
| CN206523244U (en) * | 2017-03-13 | 2017-09-26 | 中国地震局地壳应力研究所 | A kind of digital AC electric bridge platinum resistance thermometer |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109375291A (en) * | 2018-10-09 | 2019-02-22 | 成都信息工程大学 | A kind of temperature and air pressure suitable for sonde and humidity measuring instrument and method |
| CN115183897A (en) * | 2022-09-09 | 2022-10-14 | 之江实验室 | Temperature measuring system and method based on high-frequency alternating current signals |
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Address after: 100085, Anning Road, Haidian District, Beijing, 1, Xisanqi Applicant after: National natural disaster prevention and Control Research Institute Ministry of emergency management Address before: 100085, Anning Road, Haidian District, Beijing, 1, Xisanqi Applicant before: THE INSTITUTE OF CRUSTAL DYNAMICS, CHINA EARTHQUAKE ADMINISTRATION |
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