CN203672507U - High-precision thermocouple input module - Google Patents
High-precision thermocouple input module Download PDFInfo
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- CN203672507U CN203672507U CN201320623835.3U CN201320623835U CN203672507U CN 203672507 U CN203672507 U CN 203672507U CN 201320623835 U CN201320623835 U CN 201320623835U CN 203672507 U CN203672507 U CN 203672507U
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- 238000006243 chemical reaction Methods 0.000 claims abstract description 37
- 230000009286 beneficial effect Effects 0.000 abstract 1
- 238000000034 method Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- 229910018487 Ni—Cr Inorganic materials 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- VNNRSPGTAMTISX-UHFFFAOYSA-N chromium nickel Chemical compound [Cr].[Ni] VNNRSPGTAMTISX-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910000570 Cupronickel Inorganic materials 0.000 description 1
- 230000005678 Seebeck effect Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000005039 memory span Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000005619 thermoelectricity Effects 0.000 description 1
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Abstract
The utility model relates to a high-precision thermocouple input module. The input module comprises an isolator, an amplifier, an analog-digital conversion unit, a controller, a digital-analog conversion unit and an electronic switch, wherein the isolator is connected with a thermocouple; an output terminal of the amplifier is connected with the analog-digital conversion unit; and an output terminal of the analog-digital conversion unit is connected with the controller. The input module is characterized in that a grounding terminal of the isolator is grounded, and a grounding interface is led out from the grounding terminal; two interfaces are led out from a voltage output terminal of the isolator; the controller outputs a feedback signal to the digital-analog conversion unit according to a signal obtained by the analog-digital conversion unit; and an output interface is led out from the output terminal of the digital-analog unit. The beneficial effects of the utility model are that the overall absolute precision of thermocouple signals is ensured to be within 0.1-0.2 DEG C, and the relative precision reaches 0.005-0.01%, meeting the true needs of industrial control.
Description
Technical field
The utility model relates to a kind of high-precision thermopair load module, for improving the occasionally measuring accuracy of the small-signal such as millivolt of thermoelectricity, belongs to instrument for automatic control technical field.
Background technology
Thermopair is to connect to form closed-loop path by the metal wire of two kinds of different components in its end, directly be called working end (also referred to as measuring junction) as one end of measuring media temperature, the other end is called cold junction (also referred to as compensation end), in the time there is temperature difference between working end and cold junction, in loop, just having electric current passes through, now between two ends, just there is thermopower (Seebeck effect), according to circumstances select different metal materials just can draw approximately Voltage-output proportional to temperature difference.But this voltage is all very very little, for example more modal nickel chromium triangle-nisiloy K type thermocouple-270 ℃～1372 ℃ of corresponding thermoelectrical potentials are-6.458mV～54.886mV, and nickel chromium triangle-cupronickel E type thermocouple-270 ℃～1000 ℃ of corresponding thermoelectrical potentials are-9.835mV～76.373mV.
The signal processing method of the thermopair load module of scattered control system (DCS) or programmable control system (PLC) dispatch control system is to obtain the thermopower (millivolt voltage signal) being produced by thermopair, set it as analog electrical signal and be amplified to volt voltage signal through amplifier, be input in the numerical data of control chip via analog to digital converter (ADC) again, by control chip or transfer to host computer to table look-up according to calibration number or adopt the processing of temperature estimation model formation to convert actual temperature to.
Because semiconductor technology is relatively backward, in order to overcome the problem that control chip processing speed is slow and memory span is little, adopt various temperature estimation model formations to process in early days.Along with the technical indicator of control chip processing speed and memory capacity significantly promotes, adopt the most original tabling look-up to overcome the small error of temperature estimation model formation and actual temperature.
From surface, thermocouple signal measuring accuracy can focus on analog to digital converter (ADC), general analog to digital converter adopts 12, although analog to digital converter theoretical resolution is 1/4096 (2/10000ths), but due to the temperature of the components and parts such as reference voltage and resistance of the components and parts such as amplifier and the analog to digital converter reason of wafing etc., the measuring accuracy of in fact whole thermocouple signal is generally between 0.1～0.2%, even if analog to digital converter is brought up to 13 or 14, even 15 by some producer, but overall measurement accuracy can not improve how many.
In industrial process control, this relative accuracy is for the valve seat opening of topworks, pressure, flow, liquid level, electric current and voltage etc. process variable problem little, but for temperature signal, because it does not have concrete range ability, generally thermopair load module is the thermocouple signal of compatible various calibration number, the thermoelectrical potential signal adopting has enough upper limit nargin, be converted to the temperature range upper limit and can reach 2000 ℃, at this moment relative accuracy is converted to absolute value and can arrives 2 ℃～4 ℃.And in fact, low temperature generally can occur in device start process, in the time that industrial process normally moves, main temperature course parameter can be carried out variation by a small margin at a higher temperature.For example 600MW ultra supercritical thermal power generation unit boiler superheater outlet temperature is in the temperature operation between 560 ± 10 ℃ substantially when above of 50% declared working condition; range of temperature is at 20 ℃; if and used as boiler safety guard signal; jump stove value and be also only 597 ℃, temperature variation is that the absolute error of+37 ℃ at this moment 2 ℃～4 ℃ just seems very serious.
Summary of the invention
The technical problems to be solved in the utility model is the precision that guarantees thermocouple signal.
In order to solve the problems of the technologies described above, the technical solution of the utility model has been to provide a kind of high-precision thermopair load module, comprise isolator, amplifier, AD conversion unit, controller, D/A conversion unit and electronic switch, isolator is connected with thermopair, the output terminal AD conversion unit of amplifier, the output terminal of AD conversion unit connects controller, it is characterized in that: the earth terminal of isolator is outwards drawn ground interface in ground connection, the voltage output end of isolator is outwards drawn two interfaces simultaneously, be respectively the first Voltage-output interface and second voltage output interface, the signal that controller basis is obtained by AD conversion unit is to D/A conversion unit output feedback signal, the output terminal of D/A conversion unit is outwards drawn output interface, make the in-phase input end of amplifier be connected with the first Voltage-output interface by the action of electronic switch, the inverting input of amplifier is connected with ground interface simultaneously, or the in-phase input end of amplifier is connected with output interface, the inverting input of amplifier is connected with ground interface simultaneously, or the in-phase input end of amplifier is connected with output interface, the inverting input of amplifier is connected with second voltage output interface simultaneously.
Preferably, described amplifier is programmable operational amplifier.
Preferably, described electronic switch has two, is single-pole double-throw (SPDT) electronic switch.
Preferably, described AD conversion unit and described D/A conversion unit are selected the converter of 12 precision.
The utility model has the advantages that: guarantee that thermocouple signal entirety absolute precision is at 0.1～0.2 ℃, relative accuracy can reach 0.005～0.01%, can meet the real needs of industrial control process.
Accompanying drawing explanation
The high-precision thermopair load module of the one schematic diagram that Fig. 1 provides for the utility model.
Embodiment
For the utility model is become apparent, hereby with preferred embodiment, and coordinate accompanying drawing to be described in detail below.
As shown in Figure 1, the high-precision thermopair load module of one that the utility model provides, comprise isolator, amplifier, AD conversion unit ADC, controller, D/A conversion unit DAC and electronic switch, isolator is connected with thermopair, the output terminal AD conversion unit ADC of amplifier, the output terminal of AD conversion unit ADC connects controller, it is characterized in that: the earth terminal of isolator is outwards drawn ground interface 4 in ground connection, the voltage output end of isolator is outwards drawn two interfaces simultaneously, be respectively the first Voltage-output interface 1 and second voltage output interface 3, the signal that controller basis is obtained by AD conversion unit ADC is to D/A conversion unit DAC output feedback signal, the output terminal of D/A conversion unit DAC is outwards drawn output interface 2, make the in-phase input end SA of amplifier be connected with the first Voltage-output interface 1 by the action of electronic switch, the inverting input SB of amplifier is connected with ground interface 4 simultaneously, or the in-phase input end SA of amplifier is connected with output interface 2, the inverting input SB of amplifier is connected with ground interface 4 simultaneously, or the in-phase input end SA of amplifier is connected with output interface 2, the inverting input SB of amplifier is connected with second voltage output interface 3 simultaneously.
Amplifier is programmable operational amplifier.
Electronic switch has two, is single-pole double-throw (SPDT) electronic switch.
AD conversion unit ADC and described D/A conversion unit DAC select the converter of 12 precision, and those skilled in the art also can select the converter of other precision as required.
The thermopair input measurement method of utilizing above-mentioned module, the steps include:
The first step, operation electronic switch, the in-phase input end SA of amplifier is connected with the first Voltage-output interface 1, the inverting input SB of amplifier is connected with ground interface 4 simultaneously, the enlargement factor of amplifier is set to A, controller obtains the initial value by the output voltage V p of AD conversion unit ADC, according to the initial value of output voltage V p and corresponding temperature Tp thereof, the upper limit range value of thermopair load module is defined as to Tp+A ℃, lower limit range value is defined as Tp-A ℃, tables look-up and finds the thermopower V0 corresponding with Tp+A ℃ according to calibration number;
Second step, operation electronic switch, the in-phase input end SA of amplifier is connected with output interface 2, the inverting input SB of amplifier is connected with ground interface 4 simultaneously, adjust the feedback voltage V f of controller, make the reference voltage Vref=V0+ Δ 1 on output interface 2, Δ 1 is the input composition error of amplifier and AD conversion unit ADC;
The derivation of above-mentioned second step is:
If adjusting the feedback voltage V f of controller is thermopower V0, Vref reference voltage=V0-Δ 2, Δ 2 is feedback integration error, output voltage V p=Vref-Δ 1=V0-Δ 2-Δ 1.If make output voltage V p=V0,, by backwards calculation, the output feedback voltage V f of controller need to be adjusted into V0+ Δ 2+ Δ 1, now, Vref=Vf-Δ 2=V0+ Δ 2+ Δ 1-Δ 2=V0+ Δ 1.
The 3rd step, operation electronic switch, the in-phase input end SA of amplifier is connected with output interface 2, the inverting input SB of amplifier is connected with second voltage output interface 3 simultaneously, the enlargement factor of amplifier is set to B, B is much larger than A, now, reference voltage Vref=V0+ Δ 1 on the in-phase input end SA of amplifier, the output voltage V i that voltage on the inverting input SB of amplifier is isolator, end difference is V0+ Δ 1-Vi, deduct after the input composition error Δ 1 of amplifier and AD conversion unit ADC, the output voltage V p=V0+ Δ 1-Vi-Δ 1=V0-Vi of final AD conversion unit ADC, the temperature T i that this thermopower is corresponding, final temperature value is Tp+A-Ti.
Further illustrate the utility model below in conjunction with data.
Utilize the first passage output 27.025mV (this thermopower K calibration correspondence 650 ℃) of high-precision signal generator to thermopair load module, the course of work following (for ease of understanding, when computation and measurement value, enlargement factor is left in the basket) of thermopair load module:
The first step, operation electronic switch, the in-phase input end SA of amplifier is connected with the first Voltage-output interface 1, the inverting input SB of amplifier is connected with ground interface 4 simultaneously, the enlargement factor that amplifier is set is 50, obtain the initial value 26.856mV of Vp, according to the initial value 26.878mV of Vp and corresponding temperature Tp (646.53 ℃), its upper limit range value is defined as to 28.984mV (696.53 ℃), and lower limit range value is defined as 24.758mV (596.53 ℃).
Second step, operation electronic switch, the in-phase input end SA of amplifier is connected with output interface 2, the inverting input SB of amplifier is connected with ground interface 4 simultaneously, the feedback voltage V f of controller is 28.984mV, the Vp obtaining by input end is 28.704mV, by backwards calculation, be 28.984mV if will make Vp, the feedback voltage V f of controller is set as to 29.264mV.
The 3rd step, operation electronic switch, the in-phase input end SA of amplifier is connected with output interface 2, and the inverting input SB of amplifier is connected with second voltage output interface 3 simultaneously, and the enlargement factor that amplifier is set is 500, now, Vref is 29.131mV, the actual input 27.025mV that Vi is signal generator, and end difference is 2.106, finally obtaining Vp is 1.959mV, the thermopower of converting final measured signal is 27.025, and corresponding temperature is 650 ℃, and measuring error is 0%.
Claims (4)
1. a high-precision thermopair load module, comprise isolator, amplifier, AD conversion unit (ADC), controller, D/A conversion unit (DAC) and electronic switch, isolator is connected with thermopair, the output terminal AD conversion unit (ADC) of amplifier, the output terminal of AD conversion unit (ADC) connects controller, it is characterized in that: the earth terminal of isolator is outwards drawn ground interface (4) in ground connection, the voltage output end of isolator is outwards drawn two interfaces simultaneously, be respectively the first Voltage-output interface (1) and second voltage output interface (3), the signal that controller basis is obtained by AD conversion unit (ADC) is to D/A conversion unit (DAC) output feedback signal, the output terminal of D/A conversion unit (DAC) is outwards drawn output interface (2), make the in-phase input end (SA) of amplifier be connected with the first Voltage-output interface (1) by the action of electronic switch, the inverting input (SB) of amplifier is connected with ground interface (4) simultaneously, or the in-phase input end (SA) of amplifier is connected with output interface (2), the inverting input (SB) of amplifier is connected with ground interface (4) simultaneously, or the in-phase input end (SA) of amplifier is connected with output interface (2), the inverting input (SB) of amplifier is connected with second voltage output interface (3) simultaneously.
2. the high-precision thermopair load module of one as claimed in claim 1, is characterized in that: described amplifier is programmable operational amplifier.
3. the high-precision thermopair load module of one as claimed in claim 1, is characterized in that: described electronic switch has two, is single-pole double-throw (SPDT) electronic switch.
4. the high-precision thermopair load module of one as claimed in claim 1, is characterized in that: described AD conversion unit (ADC) and described D/A conversion unit (DAC) are selected the converter of 12 precision.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320623835.3U CN203672507U (en) | 2013-10-10 | 2013-10-10 | High-precision thermocouple input module |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201320623835.3U CN203672507U (en) | 2013-10-10 | 2013-10-10 | High-precision thermocouple input module |
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| CN203672507U true CN203672507U (en) | 2014-06-25 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103542954A (en) * | 2013-10-10 | 2014-01-29 | 上海发电设备成套设计研究院 | High-precision thermocouple input module and measurement method |
| CN110849494A (en) * | 2015-05-01 | 2020-02-28 | 沃特洛电气制造公司 | Active grounding thermocouple and operation method |
-
2013
- 2013-10-10 CN CN201320623835.3U patent/CN203672507U/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103542954A (en) * | 2013-10-10 | 2014-01-29 | 上海发电设备成套设计研究院 | High-precision thermocouple input module and measurement method |
| CN103542954B (en) * | 2013-10-10 | 2015-12-09 | 上海发电设备成套设计研究院 | A kind of high-precision thermocouple input module and measuring method |
| CN110849494A (en) * | 2015-05-01 | 2020-02-28 | 沃特洛电气制造公司 | Active grounding thermocouple and operation method |
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Granted publication date: 20140625 |
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