CN204043810U - A kind of thermocouple signal cold junction compensation device - Google Patents
A kind of thermocouple signal cold junction compensation device Download PDFInfo
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- CN204043810U CN204043810U CN201420509015.6U CN201420509015U CN204043810U CN 204043810 U CN204043810 U CN 204043810U CN 201420509015 U CN201420509015 U CN 201420509015U CN 204043810 U CN204043810 U CN 204043810U
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Abstract
The utility model relates to a kind of thermocouple signal cold junction compensation device, comprises cold junction compensation computing circuit, and cold junction compensation computing circuit is connected to cold junction temperature input circuit and zeroing bias voltage circuit; Cold junction compensation computing circuit comprises operational amplifier, the negative input end of operational amplifier is connected with its output terminal by resistance R6, one end of positive input terminal difference contact resistance R5 and R7 of operational amplifier, the other end ground connection of resistance R7, the other end of resistance R5 is connected with thermocouple signal, one end of the positive input terminal of operational amplifier also contact resistance R4, the other end of resistance R4 is connected with described cold junction temperature input circuit, one end of the negative input end contact resistance R3 of operational amplifier, the other end of described resistance R3 is connected with described zeroing bias voltage circuit.The design has linearly excellent, stable performance, highly sensitive, thermal capacity is little, antijamming capability is strong, can remote temperature measurement and easy to use.
Description
Technical field
The utility model relates to a kind of thermocouple signal cold junction compensation device, belongs to sensor signal processing technology field.
Background technology
Thermopair is very general as a kind of contact type temperature sensor application.It has that measuring accuracy is high, the response time is fast, measurement range is large, dependable performance, physical strength are good, long service life, the advantage such as easy for installation.The most frequently used capitalization of specifying of thermopair forms to indicate it, and such as K type nickel chromium triangle and nickel aluminium are made.
Traditional Method of Cold Terminal Compensation is thermal resistance electric bridge penalty method.Be made up of discrete component, its volume is large, use convenient not and when changing thermocouple type, need the component value readjusting circuit.Electric bridge compensation way is the electromotive force utilizing unbalanced bridge to produce, and carrys out the change of combined potential that Compensative thermoelectric couple causes because cold junction temperature change, it be a kind of can along with temperature variation the method for auto-compensation.As thermocouple cold junction is placed in equivalent environment temperature, the output terminal of electric bridge is serially connected in For Thermocouple Circuit, and wherein 3 arm resistances and current-limiting resistance all use manganese-copper filament coiling, and its resistance varies with temperature hardly.Another bridge arm resistance R is by the compensating resistance of the larger nickel wire coiling of temperature-coefficient of electrical resistance, and its resistance raises along with temperature and increases, and electric bridge is powered by D.C. regulated power supply.
It is not quite identical that hot thermocouple electromotive force and compensator bridge output voltage vary with temperature characteristic, therefore less than full remuneration in junction compensator compensation temperature range, error is larger.Thus the nonlinear characteristic of thermal resistance, the precision that result in compensation is lower.
Utility model content
The technical problems to be solved in the utility model is: for overcoming the problems referred to above, provides a kind of thermocouple signal cold junction compensation device of auto-compensation.
The utility model solves the technical scheme that its technical matters adopts:
A kind of thermocouple signal cold junction compensation device, comprises cold junction compensation computing circuit, and described cold junction compensation computing circuit is connected to cold junction temperature input circuit and zeroing bias voltage circuit;
Described zeroing bias voltage circuit comprises reference voltage source, described reference voltage source one end is connected with external 5V power supply, its other end is connected with one end of potentiometer RP1, and the other end of described potentiometer RP1 is connected with one end of resistance R2, the other end ground connection of described resistance R2;
Described cold junction temperature input circuit comprises temperature sensor, and described temperature sensor one end is connected with external 5V power supply, and its other end is connected with one end of resistance R1, the other end ground connection of described resistance R1;
Described cold junction compensation computing circuit comprises operational amplifier, the negative input end of described operational amplifier is connected with its output terminal by resistance R6, one end of positive input terminal difference contact resistance R5 and R7 of described operational amplifier, the other end ground connection of described resistance R7, one end of the positive input terminal of described operational amplifier also contact resistance R4, the other end of described resistance R4 is connected between described temperature sensor and described resistance R1, one end of the negative input end contact resistance R3 of described operational amplifier, the other end of described resistance R3 is connected between described potentiometer RP1 and resistance R2.
Preferably, described temperature sensor is AD590 temperature sensor.
Preferably, described base voltage source is AD584 reference voltage source.
Preferably, described operational amplifier is OP07 operational amplifier.
The beneficial effects of the utility model are: the utility model structure is simple, and compared with compensating with electric bridge, the design has linearly excellent, stable performance, highly sensitive, thermal capacity is little, antijamming capability is strong, can remote temperature measurement and the advantage such as easy to use.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the utility model is further illustrated.
Fig. 1 is the structural representation of the utility model embodiment;
Fig. 2 is the circuit diagram of cold junction temperature input circuit described in the utility model;
Fig. 3 is the circuit diagram of zeroing bias voltage circuit described in the utility model;
Fig. 4 is the circuit diagram of cold junction compensation computing circuit described in the utility model.
Embodiment
By reference to the accompanying drawings the utility model is described in further detail now.These accompanying drawings are the schematic diagram of simplification, only basic structure of the present utility model are described in a schematic way, and therefore it only shows the formation relevant with the utility model.
Described in the utility model a kind of thermocouple signal cold junction compensation device as shown in Figure 1, comprises cold junction compensation computing circuit, and described cold junction compensation computing circuit is connected to cold junction temperature input circuit and zeroing bias voltage circuit;
Described cold junction compensation computing circuit comprises operational amplifier, as shown in Figure 4, the negative input end of described operational amplifier is connected with its output terminal by resistance R6, one end of positive input terminal difference contact resistance R5 and R7 of described operational amplifier, the other end ground connection of described resistance R7, the other end of described resistance R5 is connected with thermocouple signal, one end of the positive input terminal of described operational amplifier also contact resistance R4, the other end of described resistance R4 is connected with described cold junction temperature input circuit, one end of the negative input end contact resistance R3 of described operational amplifier, the other end of described resistance R3 is connected with described zeroing bias voltage circuit,
In the present embodiment, for K type chromel-alumel thermocouple, basis is novel analyzes integrated temperature sensor Method of Cold Terminal Compensation, and then improves temperature survey accuracy, and provides specific implementation.When using other types thermopair, need the resistance adjusting related resistors.
Described zeroing bias voltage circuit comprises reference voltage source, as shown in Figure 3, described reference voltage source one end is connected with external 5V power supply, its other end is connected with one end of potentiometer RP1, the other end of described potentiometer RP1 is connected with one end of resistance R2, the other end ground connection of described resistance R2, the other end of described resistance R3 is connected between potentiometer RP1 and resistance R2, described reference voltage source can produce accurate 2.5V voltage in the present embodiment, its regulator potentiometer RP1, the zeroing bias voltage U0 that resistance R2 produces is made to be 10.65mV, can as the zeroing bias voltage of cold junction temperature input circuit,
Described cold junction temperature input circuit comprises temperature sensor, as shown in Figure 2, described temperature sensor one end is connected with external 5V power supply, its other end is connected with one end of resistance R1, the other end ground connection of described resistance R1, the other end of described resistance R4 is connected between described temperature sensor and described resistance R1, and in the present embodiment, resistance R1 is the precision resistor of 39 Ω low-temperature coefficients.When the temperature of measurement point changes, the output current I of described temperature sensor changes thereupon, and its rate of change is directly proportional to KShi temperature, i.e. 1 μ A/K.
The electric current that described temperature sensor provides produces voltage difference delta U on resistance R1, and its voltage change ratio is directly proportional to Celsius temperature, i.e. 0.039mV/ DEG C.Its voltage change ratio is consistent with the cold junction voltage change ratio of thermopair, therefore can linear compensation cold junction temperature.
ΔU＝(1μA/K)*R1＝(1μA/℃)*R1＝(1μA/℃)*39＝0.039mv/℃(1)。
When measurement point is 0 DEG C (KShi temperature is 273K), the electric current that described temperature sensor provides produces voltage U L on resistance R1, i.e. 10.65mV.
UL＝(1μA/K)*273*R1＝(1μA/K)*273*39＝10.65mV(2)。
Cold junction temperature input voltage, temperature sensor zeroing bias voltage, thermocouple cold junction voltage are carried out plus and minus calculation, realizes the compensation of thermocouple cold junction.Its operational formula is:
E＝ET+UL-U0＝ET0+ΔE+ΔU(3)；
In formula: ET is the thermocouple voltages with cold junction temperature change, its voltage is made up of ET0+ Δ E, the thermocouple voltages that ET0 is cold junction temperature T0 when being 0 DEG C, Δ E is that cold junction temperature T-phase is poor for the relative voltage of T0, and the value Δ U of UL-U0 is the cold junction compensation voltage changed with temperature.
Thermocouple cold junction compensation process, exactly add a compensating potential by same environment temperature control, opposite polarity at cold junction, thus makes total thermoelectrical potential of cold junction no longer change with environment temperature, realizes cold junction temperature and automatically entirely compensate.
When the cold junction temperature measurement point of thermopair is 0 DEG C (KShi temperature is 273K), the electric current that temperature sensor provides produces voltage U L on resistance R1, i.e. 10.65mV, temperature sensor zeroing bias voltage U0 is 10.65mV, substitutes into operational formula (3) and can show that cold junction compensation voltage is 0V.
Search K phasing meter, when known cold junction temperature is 0 DEG C, E=ET0.
When the cold junction temperature measurement point of thermopair is 25 DEG C (KShi temperature is 298K), the electric current that temperature sensor provides produces voltage U L on R1, i.e. 11.62mV, temperature sensor zeroing bias voltage U0 is 10.65mV, substitutes into operational formula (3) and can show that cold junction compensation voltage is 0.97mV.
Search K phasing meter, when known cold junction temperature is 25 DEG C, ET is temperature variant voltage, and Δ E is-0.968mV, from formula:
E＝ET0+ΔE+ΔU＝ET0-0.968mV+0.97mV＝ET0-0.002mV。
Cold junction compensation voltage error is 0.002mV, and correspond to 0.05 DEG C, error is minimum, and the linearity is high, and compensation effect is good.
In preferred embodiments, described temperature sensor is AD590 temperature sensor, integrated temperature sensor AD590 is utilized to carry out cold junction compensation to thermopair, there is the advantages such as precision is high, cost is low, volume is little, debugging is simple, use is flexible, cold junction compensation scope is large, in use, only the cold junction of thermopair and integrated temperature sensor AD590 need be placed in same environment, no matter how environment temperature changes, all can obtain at the output terminal of circuit the magnitude of voltage being proportional to thermopair working end temperature.
In preferred embodiments, described base voltage source is AD584 reference voltage source, AD584 reference voltage source is a eight pin accurate reference voltage, provides four of pin-programmable kinds of conventional output voltages to select: 10.000 V, 7.500 V, 5.000 V and 2.500 V.
In preferred embodiments, described operational amplifier is OP07 operational amplifier, the most outstanding feature of OP07 operational amplifier be offset voltage low be 10 μ V, offset voltage temperature coefficient is 0.2 μ V/ DEG C, without the need to external compensation and external device protection element.Be widely used in stable integration, accurate totalizer, comparer, threshold voltage detection circuit and circuit is accurately amplified etc. to feeble signal.
With above-mentioned according to desirable embodiment of the present utility model for enlightenment, by above-mentioned description, relevant staff in the scope not departing from this utility model technological thought, can carry out various change and amendment completely.The technical scope of this utility model is not limited to the content on instructions, must determine its technical scope according to right.
Claims (4)
1. a thermocouple signal cold junction compensation device, is characterized in that, comprises cold junction compensation computing circuit, and described cold junction compensation computing circuit is connected to cold junction temperature input circuit and zeroing bias voltage circuit;
Described zeroing bias voltage circuit comprises reference voltage source, described reference voltage source one end is connected with external 5V power supply, its other end is connected with one end of potentiometer RP1, and the other end of described potentiometer RP1 is connected with one end of resistance R2, the other end ground connection of described resistance R2;
Described cold junction temperature input circuit comprises temperature sensor, and described temperature sensor one end is connected with external 5V power supply, and its other end is connected with one end of resistance R1, the other end ground connection of described resistance R1;
Described cold junction compensation computing circuit comprises operational amplifier, the negative input end of described operational amplifier is connected with its output terminal by resistance R6, one end of positive input terminal difference contact resistance R5 and R7 of described operational amplifier, the other end ground connection of described resistance R7, one end of the positive input terminal of described operational amplifier also contact resistance R4, the other end of described resistance R4 is connected between described temperature sensor and described resistance R1, one end of the negative input end contact resistance R3 of described operational amplifier, the other end of described resistance R3 is connected between described potentiometer RP1 and resistance R2.
2. thermocouple signal cold junction compensation device as claimed in claim 1, it is characterized in that, described temperature sensor is AD590 temperature sensor.
3. thermocouple signal cold junction compensation device as claimed in claim 1, it is characterized in that, described reference voltage source is AD584 reference voltage source.
4. thermocouple signal cold junction compensation device as claimed in claim 1, it is characterized in that, described operational amplifier is OP07 operational amplifier.
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| CN201420509015.6U CN204043810U (en) | 2014-09-04 | 2014-09-04 | A kind of thermocouple signal cold junction compensation device |
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| CN201420509015.6U CN204043810U (en) | 2014-09-04 | 2014-09-04 | A kind of thermocouple signal cold junction compensation device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105651409A (en) * | 2016-04-06 | 2016-06-08 | 中国南方航空工业(集团)有限公司 | Thermocouple cold junction compensation and temperature measurement circuit and device |
| RU2623196C1 (en) * | 2016-05-31 | 2017-06-22 | федеральное государственное бюджетное образовательное учреждение высшего образования "Тамбовский государственный университет имени Г.Р. Державина" | Temperature measuring device |
| CN108007596A (en) * | 2017-11-27 | 2018-05-08 | 陕西电器研究所 | A kind of Thermocouple Temperature Signal modulate circuit |
-
2014
- 2014-09-04 CN CN201420509015.6U patent/CN204043810U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105651409A (en) * | 2016-04-06 | 2016-06-08 | 中国南方航空工业(集团)有限公司 | Thermocouple cold junction compensation and temperature measurement circuit and device |
| CN105651409B (en) * | 2016-04-06 | 2018-11-16 | 中国南方航空工业(集团)有限公司 | Cold junction compensation temperature measurement circuit and device |
| RU2623196C1 (en) * | 2016-05-31 | 2017-06-22 | федеральное государственное бюджетное образовательное учреждение высшего образования "Тамбовский государственный университет имени Г.Р. Державина" | Temperature measuring device |
| CN108007596A (en) * | 2017-11-27 | 2018-05-08 | 陕西电器研究所 | A kind of Thermocouple Temperature Signal modulate circuit |
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