CN104833438A - Temperature transmitter - Google Patents
Temperature transmitter Download PDFInfo
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- CN104833438A CN104833438A CN201510191356.2A CN201510191356A CN104833438A CN 104833438 A CN104833438 A CN 104833438A CN 201510191356 A CN201510191356 A CN 201510191356A CN 104833438 A CN104833438 A CN 104833438A
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- operational amplifier
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- temperature transmitter
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Abstract
The invention discloses a temperature transmitter, comprising a constant current source circuit; a PT100 platinum resistor sensor connected to the output end of the constant current source circuit; a difference circuit connected to the output end of the PT100 platinum resistor sensor; a signal processing and filter circuit, connected to the output end of the difference circuit. The constant current source circuit comprises constant voltage source; a first operational amplifier with the constant voltage source being connected to the in-phase input end of the first operational amplifier; a negative feedback circuit, which is connected to the anti-phase input end of the first operational amplifier with the voltage of the anti-phase input end of negative feedback circuit, accessed to the first operational amplifier changes along with the resistance of the PT100 platinum resistor sensor; a switch element, which is connected between the output end of the first operational amplifier and the output end of the constant current source circuit, and is controlled by the negative feedback circuit. The temperature transmitter is advantageous in that the problems of the prior art that the temperature transmitter is affected by external interference and circuit stability is bad can be resolved.
Description
Technical field
The present invention relates to temperature detection technical field, in particular to a kind of temperature transmitter.
Background technology
PT100 temperature transmitter in the market mainly contains two kinds of implementations: one is adopt electric resistance partial pressure principle to build circuit, this temperature transmitter is larger by external influences, antijamming capability is poor, there will be collecting temperature unusual fluctuations problem in use procedure; Two is provide reference voltage by voltage stabilizing chip, then draws V/I signal through signal madulation, although its antijamming capability is pretty good, cost is higher, easily causes the wasting of resources.
Summary of the invention
A kind of temperature transmitter is provided in the embodiment of the present invention, comparatively large by external influences to solve temperature transmitter in prior art, the problem of circuit stability difference.
For solving the problems of the technologies described above, the embodiment of the present invention provides a kind of temperature transmitter, comprising: constant-current source circuit; PT100 platinum sensor, is connected to the output terminal of constant-current source circuit; Difference channel, is connected to the output terminal of PT100 platinum sensor; Signal transacting and filtering circuit, be connected to the output terminal of difference channel; Constant-current source circuit comprises: constant pressure source; First operational amplifier, constant pressure source is connected to the in-phase input end of the first operational amplifier; Negative-feedback circuit, is connected to the inverting input of the first operational amplifier, and negative-feedback circuit accesses the change in resistance of the voltage follow PT100 platinum sensor of the inverting input of the first operational amplifier and changes; On-off element, between the output terminal being connected to the first operational amplifier and the output terminal of constant-current source circuit, and controls break-make by negative-feedback circuit.
As preferably, negative-feedback circuit comprises the first resistance, second connection terminal of PT100 platinum sensor and the first resistance are connected to the inverting input of the first operational amplifier jointly, and the first connection terminal of PT100 platinum sensor is connected to the output terminal of on-off element.
As preferably, on-off element is triode, and the base stage of triode is connected to the output terminal of the first operational amplifier, and the collector of triode is connected to driving power, and the emitter of triode is connected to the first connection terminal of PT100 platinum sensor.
As preferably, the inverting input of the first operational amplifier is connected with the first voltage follower, and the output terminal of on-off element is connected with the second voltage follower.
As preferably, the input end of the first voltage follower is connected with the first filtering circuit, and the input end of the second voltage follower is connected with the second filtering circuit.
As preferably, the output terminal of constant pressure source is connected with the 3rd filtering circuit.
As preferably, difference channel comprises: the second operational amplifier, and the in-phase input end of the second operational amplifier is connected to the output terminal of the first voltage follower; 3rd operational amplifier, the in-phase input end of the 3rd operational amplifier is connected to the output terminal of the second voltage follower; Four-operational amplifier, the output terminal of the second operational amplifier is connected to the in-phase input end of four-operational amplifier, and the output terminal of the 3rd operational amplifier is connected to the inverting input of four-operational amplifier.
As preferably, the inverting input of the second operational amplifier is connected to the inverting input of the 3rd operational amplifier, is in series with the second resistance between the inverting input of the second operational amplifier and the inverting input of the 3rd operational amplifier.
As preferably, difference channel also comprises tertiary voltage follower, is connected to the output terminal of four-operational amplifier.
As preferably, the input end of tertiary voltage follower is provided with the 4th wave filter.
As preferably, constant pressure source is TL431.
Apply technical scheme of the present invention, temperature transmitter comprises: constant-current source circuit; PT100 platinum sensor, is connected to the output terminal of constant-current source circuit; Difference channel, is connected to the output terminal of PT100 platinum sensor; Signal transacting and filtering circuit, be connected to the output terminal of difference channel; Constant-current source circuit comprises: constant pressure source; First operational amplifier, constant pressure source is connected to the in-phase input end of the first operational amplifier; Negative-feedback circuit, is connected to the inverting input of the first operational amplifier, and negative-feedback circuit accesses the change in resistance of the voltage follow PT100 platinum sensor of the inverting input of the first operational amplifier and changes; On-off element, between the output terminal being connected to the first operational amplifier and the output terminal of constant-current source circuit, and controls break-make by negative-feedback circuit.The voltage of the negative-feedback circuit of this temperature transmitter changes with the change in resistance of PT100 platinum sensor, the voltage of the reverse input end of the first operational amplifier can be made to change with the change in resistance of PT100 platinum sensor, and then the cut-offfing of by-pass cock element, the circuit ensureing to flow through PT100 platinum sensor with this keeps constant, thus providing stable constant current source for PT100 platinum sensor, circuit stability is better.
Accompanying drawing explanation
Fig. 1 is the circuit theory diagrams of the temperature transmitter of the embodiment of the present invention;
Fig. 2 is the structural representation of the constant-current source circuit of the temperature transmitter of the embodiment of the present invention;
Fig. 3 is the structural representation of the difference channel of the temperature transmitter of the embodiment of the present invention.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail, but not as a limitation of the invention.
See shown in Fig. 1 to Fig. 3, according to embodiments of the invention, temperature transmitter comprises: constant-current source circuit; PT100 platinum sensor, is connected to the output terminal of constant-current source circuit; Difference channel, is connected to the output terminal of PT100 platinum sensor; Signal transacting and filtering circuit, be connected to the output terminal of difference channel.
Wherein constant-current source circuit comprises: constant pressure source; First operational amplifier U8-A, constant pressure source is connected to the in-phase input end 3 of the first operational amplifier U8-A; Negative-feedback circuit, be connected to the inverting input of the first operational amplifier U8-A, negative-feedback circuit accesses the change in resistance of the voltage follow PT100 platinum sensor (below referred to as PT100) of the inverting input of the first operational amplifier U8-A and changes; On-off element, between the output terminal being connected to the first operational amplifier U8-A and the output terminal of constant-current source circuit, and controls break-make by negative-feedback circuit.
PT100 is in certain temperature range, and temperature and the linear change of resistance, therefore can regard as PT100 in a variable resistance cut-in temperature transmitter.The electric current of constant current source in order to provide circuit constant, steady current flows through PT100, exports the voltage with PT100 change in resistance, this voltage obtained is through difference channel, signal transacting and filtering circuit, finally obtain required signal, this signal be with the temperature of PT100 one to one.
When this temperature transmitter works, constant voltage to the first operational amplifier U8-A can be exported by constant pressure source, the principle disconnected according to the short void of the void of operational amplifier, generally in-phase input end 3 voltage of the first operational amplifier U8-A is identical with the voltage of inverting input.After access PT100, prevention due to PT100 can be followed temperature variation and change, when the resistance of PT100 changes, the voltage that negative-feedback circuit accesses the inverting input of the first operational amplifier U8-A can be had influence on, now the anti-phase input terminal voltage of the first operational amplifier U8-A can change, gauge tap element cut-offs to control the voltage that negative-feedback circuit accesses the inverting input of the first operational amplifier U8-A, until the anti-phase input terminal voltage of the first operational amplifier U8-A and in-phase input end 3 voltage are consistent again.In this way, the continuous dynamic conditioning of current value flowing through PT100 can be made, and remain at a constant current value, make the current value flowing through PT100 realize mobile equilibrium, the stability of circuit when keeping whole temperature transmitter to work.In the present embodiment, constant pressure source selects TL431.
Negative-feedback circuit comprises the first resistance R19, the second connection terminal PT100_2 of PT100 and the first resistance R19 is connected to the inverting input of the first operational amplifier U8-A jointly, the first connection terminal PT100_1 of PT100 is connected to the output terminal of on-off element, the first resistance R19 ground connection.When the anti-phase input terminal voltage of the first operational amplifier U8-A is less than the voltage of the in-phase input end 3 of the first operational amplifier U8-A, it is just that first operational amplifier U8-A exports, on-off element is communicated with, electric current through the first resistance R19 increases, the anti-phase input terminal voltage of the first operational amplifier U8-A is increased, until consistent with the voltage of the in-phase input end 3 of the first operational amplifier U8-A.When the anti-phase input terminal voltage of the first operational amplifier U8-A is greater than the voltage of the in-phase input end 3 of the first operational amplifier U8-A, it is negative that first operational amplifier U8-A exports, on-off element disconnects, electric current through the first resistance R19 diminishes, the anti-phase input terminal voltage of the first operational amplifier U8-A is reduced, until consistent with the voltage of the in-phase input end 3 of the first operational amplifier U8-A.Preferably, be parallel with electric capacity C31 and electric capacity C32 at the two ends of the first resistance R19, electric capacity C31 and electric capacity C32 is arranged in parallel.Electric capacity C31 and electric capacity C32 can play the effect of filtering and voltage stabilizing to the voltage on the first resistance R19.
Two connection terminals of PT100 are parallel with electric capacity C30 and electric capacity C33, and the voltage that can export PT100 carries out filtering and voltage stabilizing, improves stability and the anti-interference of PT100 institute output voltage.
Preferably, on-off element is triode Q2, and the base stage of triode Q2 is connected to the output terminal of the first operational amplifier U8-A, and the collector of triode Q2 is connected to driving power, and the emitter of triode Q2 is connected to the first connection terminal PT100_1 of PT100.Between the output terminal and the base stage of triode Q2 of the first operational amplifier U8-A, be provided with resistance R10, the circuit between the collector and driving power of triode Q2 is in series with resistance R31.
In the present embodiment, TL431 provides constant 2.4V voltage, and this voltage accesses the in-phase input end of the first operational amplifier U8-A.To break principle according to the empty short void of amplifier, generally the voltage of the inverting input of the first operational amplifier U8-A is also 2.4V.In order to obtain constant electric current as much as possible, negative-feedback circuit control triode Q2 can be utilized to open/break and to reach electric current mobile equilibrium.Take steady current as 1mA be example, as the collector current > 1mA of triode Q2, the electric current flowing through the first resistance R19 increases, the voltage of the first resistance R19 also increases thereupon, the i.e. anti-phase input terminal voltage > 2.4V of the first operational amplifier U8-A, it is negative that the first operational amplifier U8-A exports, and triode Q2 turns off, output current is reduced, finally reaches 2.4V.Otherwise as the collector current < 1mA of triode Q2, the output of the first operational amplifier U8-A is just, triode Q2 conducting, the collector current of triode Q2 is increased, finally reaches 2.4V.Like this, the electric current flowing through PT100 just dynamically can remain on 1mA.
Preferably, the inverting input of the first operational amplifier U8-A is connected with the first voltage follower U1-A, the output terminal of on-off element is connected with the second voltage follower U2-A, can ensure that the change in resistance of the magnitude of voltage moment that constant current source exports after PT100 and PT100 is consistent, ensure the sensitivity of temperature transmitter.
The input end of the first voltage follower U1-A is connected with the first filtering circuit, and the input end of the second voltage follower U2-A is connected with the second filtering circuit.First filtering circuit comprises the electric capacity C6 being connected to resistance R4 on the second connection terminal PT100_2 of PT100 and ground connection, filtering can be carried out to the voltage of the input end entering the first voltage follower U1-A by resistance R4 and electric capacity C6, thus improve the stability and the antijamming capability that enter the voltage of the input end of the first voltage follower U1-A.Second filtering circuit comprises the electric capacity C5 being connected to resistance R3 on the first connection terminal PT100_1 of PT100 and ground connection, filtering can be carried out to the voltage of the input end entering the second voltage follower U2-A by resistance R3 and electric capacity C5, thus improve the stability and the antijamming capability that enter the voltage of the input end of the second voltage follower U2-A.The electric current of 1mA flows through PT100 and R19, R19 terminal voltage obtains an output voltage U1 through this firstorder filter of the first filtering circuit and the first voltage follower U1-A, PT100 terminal voltage obtains an output voltage U2 through this firstorder filter of the first filtering circuit and the first voltage follower U1-A, and wherein the amplitude of U2 is with PT100 change in resistance.
The output terminal of constant pressure source is connected with the 3rd filtering circuit, and the 3rd filtering circuit exports the first operational amplifier U8-A to voltage for spending constant pressure source carries out filtering, improves stability and the anti-interference of constant pressure source output voltage.
Difference channel comprises: the second operational amplifier U1-B, and the in-phase input end of the second operational amplifier U1-B is connected to the output terminal of the first voltage follower U1-A; 3rd operational amplifier U2-B, the in-phase input end of the 3rd operational amplifier U2-B is connected to the output terminal of the second voltage follower U2-A; The output terminal of four-operational amplifier U4-A, the second operational amplifier U1-B is connected to the in-phase input end of four-operational amplifier U4-A, and the output terminal of the 3rd operational amplifier U2-B is connected to the inverting input of four-operational amplifier U4-A.
Preferably, the inverting input of the second operational amplifier U1-B is connected to the inverting input of the 3rd operational amplifier U2-B, is in series with the second resistance R9 between the inverting input of the second operational amplifier U1-B and the inverting input of the 3rd operational amplifier U2-B.In the process of temperature transmitter work, the gain of circuit can be changed by the resistance changing separately the second resistance R9 and make common-mode rejection ratio large as far as possible, thus ensureing that bridge balance is not destroyed.
Circuit between the inverting input and output terminal of the second operational amplifier U1-B is in series with resistance R8, circuit between the inverting input and output terminal of the 3rd operational amplifier U2-B is in series with resistance R5, resistance R21 is in series with between the output terminal and the inverting input of four-operational amplifier U4-A of the second operational amplifier U1-B, resistance R22 is in series with between the output terminal and the in-phase input end of four-operational amplifier U4-A of the 3rd operational amplifier U2-B, circuit between the inverting input and output terminal of four-operational amplifier U4-A is in series with resistance R23.A stake resistance R26 is also connected with at the in-phase input end of four-operational amplifier U4-A.
The resistance of resistance R5, resistance R8 and the second resistance R9 is chosen according to demand, can draw two-way respectively with voltage U 1 and the proportional voltage of voltage U 2, then can draw according to this two-way voltage the voltage U 3 that final difference channel exports, wherein U3=x*U2-y*U1, x and y is constant, and the resistance according to resistance R5, resistance R8 and the second resistance R9 calculates.
In conjunction with shown in Figure 3, in figure, the resistance of R5 and R8 is equal, R21 and R22 resistance is equal, R21//R23=R22//R26;
To break principle according to the short void of void, the voltage of the backward end of U2-B is also the voltage of the backward end of U2, U1-B is also U1.Be not difficult to obtain following equation:
(Ua-Ub)/(2R5+R9)＝(U2-U1)/R9
Then: Ua-Ub=(1+2R5/R9) * (U2-U1) 1.
The output of U4-B circuit is calculated again according to basic subtraction circuit:
U3＝(R23/R21)*(Ua-Ub) ②
1. will substitute into 2. and obtain:
U3＝(1+2R5/R9)*(R23/R21)*(U2-U1)
Be not difficult to find out from above-mentioned formula, as U2=U1, then the electric current through R9 is 0, Ua=Ub, output voltage U3=0, so circuit can suppress common-mode signal.
Preferably, difference channel also comprises tertiary voltage follower U4-B, be connected to the output terminal of four-operational amplifier U4-A, the input end of tertiary voltage follower U4-B is provided with the 4th wave filter, 4th wave filter comprises resistance R27 and electric capacity C9, thus the voltage U 3 that finally can export difference channel plays better filtering and isolation effect, improve stability when voltage U 3 exports and antijamming capability.
The voltage U 3 that difference channel exports by signal processing circuit converts required semaphore to, and this circuit will be current signal or voltage signal according to demand and determine, and this signal obtains final output signal amount through first-level filtering wave circuit again.
The present invention adopts the method for constant current source to carry out temperature acquisition, makes the voltage linear at PT100 two ends substantially, improves the stability of temperature transmitter circuit.Add multi-stage filter circuit in circuit, voltage follower and difference channel, the antijamming capability of temperature transmitter is strengthened greatly.
Certainly, be more than the preferred embodiment of the present invention.It should be pointed out that for those skilled in the art, under the prerequisite not departing from its general principles, can also make some improvements and modifications, these improvements and modifications are also considered as protection scope of the present invention.
Claims (11)
1. a temperature transmitter, is characterized in that, comprising:
Constant-current source circuit;
PT100 platinum sensor, is connected to the output terminal of described constant-current source circuit;
Difference channel, is connected to the output terminal of described PT100 platinum sensor;
Signal transacting and filtering circuit, be connected to the output terminal of described difference channel;
Described constant-current source circuit comprises:
Constant pressure source;
First operational amplifier, described constant pressure source is connected to the in-phase input end of described first operational amplifier;
Negative-feedback circuit, is connected to the inverting input of described first operational amplifier, and described negative-feedback circuit accesses the change in resistance of the voltage follow PT100 platinum sensor of the inverting input of described first operational amplifier and changes;
On-off element, between the output terminal being connected to described first operational amplifier and the output terminal of described constant-current source circuit, and controls break-make by described negative-feedback circuit.
2. temperature transmitter according to claim 1, it is characterized in that, described negative-feedback circuit comprises the first resistance, second connection terminal of described PT100 platinum sensor and described first resistance are connected to the inverting input of described first operational amplifier jointly, and the first connection terminal of described PT100 platinum sensor is connected to the output terminal of described on-off element.
3. temperature transmitter according to claim 2, it is characterized in that, described on-off element is triode, the base stage of described triode is connected to the output terminal of described first operational amplifier, the collector of described triode is connected to driving power, and the emitter of described triode is connected to the first connection terminal of described PT100 platinum sensor.
4. temperature transmitter according to claim 1, is characterized in that, the inverting input of described first operational amplifier is connected with the first voltage follower, and the output terminal of described on-off element is connected with the second voltage follower.
5. temperature transmitter according to claim 4, is characterized in that, the input end of described first voltage follower is connected with the first filtering circuit, and the input end of described second voltage follower is connected with the second filtering circuit.
6. temperature transmitter according to claim 1, is characterized in that, the output terminal of described constant pressure source is connected with the 3rd filtering circuit.
7. temperature transmitter according to any one of claim 1 to 6, is characterized in that, described difference channel comprises:
Second operational amplifier, the in-phase input end of described second operational amplifier is connected to the output terminal of described first voltage follower;
3rd operational amplifier, the in-phase input end of described 3rd operational amplifier is connected to the output terminal of described second voltage follower;
Four-operational amplifier, the output terminal of described second operational amplifier is connected to the in-phase input end of described four-operational amplifier, and the output terminal of described 3rd operational amplifier is connected to the inverting input of described four-operational amplifier.
8. temperature transmitter according to claim 7, it is characterized in that, the inverting input of described second operational amplifier is connected to the inverting input of described 3rd operational amplifier, is in series with the second resistance between the inverting input of described second operational amplifier and the inverting input of described 3rd operational amplifier.
9. temperature transmitter according to claim 7, is characterized in that, described difference channel also comprises tertiary voltage follower, is connected to the output terminal of described four-operational amplifier.
10. temperature transmitter according to claim 9, is characterized in that, the input end of described tertiary voltage follower is provided with the 4th wave filter.
11. temperature transmitters according to any one of claim 1 to 6, is characterized in that, described constant pressure source is TL431.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201510191356.2A CN104833438A (en) | 2015-04-21 | 2015-04-21 | Temperature transmitter |
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| CN201510191356.2A CN104833438A (en) | 2015-04-21 | 2015-04-21 | Temperature transmitter |
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| CN104833438A true CN104833438A (en) | 2015-08-12 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107764295A (en) * | 2017-11-24 | 2018-03-06 | 广州充圆精密光电仪器有限公司 | Temperature-compensation circuit for portable three-coordinate measuring machine angular encoder |
| CN109459600A (en) * | 2018-12-25 | 2019-03-12 | 北京华峰测控技术股份有限公司 | A kind of floating wide-range voltage measuring circuit |
| CN110932690A (en) * | 2018-09-19 | 2020-03-27 | 森萨塔电子技术有限公司 | Amplifier with common mode detection |
| CN114235207A (en) * | 2021-12-20 | 2022-03-25 | 珠海格力电器股份有限公司 | Temperature sampling circuit, method, device, equipment, storage medium and electric automobile |
| CN116582106A (en) * | 2023-05-22 | 2023-08-11 | 青岛智腾微电子有限公司 | Low-pass filter circuit capable of adjusting stop band depth |
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| CN114235207A (en) * | 2021-12-20 | 2022-03-25 | 珠海格力电器股份有限公司 | Temperature sampling circuit, method, device, equipment, storage medium and electric automobile |
| CN116582106A (en) * | 2023-05-22 | 2023-08-11 | 青岛智腾微电子有限公司 | Low-pass filter circuit capable of adjusting stop band depth |
| CN116582106B (en) * | 2023-05-22 | 2023-10-27 | 青岛智腾微电子有限公司 | Low-pass filter circuit capable of adjusting stop band depth |
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Application publication date: 20150812 |