CN201821336U - High-precision analog-digital collection circuit based on negative feedback - Google Patents
High-precision analog-digital collection circuit based on negative feedback Download PDFInfo
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- CN201821336U CN201821336U CN2010205501776U CN201020550177U CN201821336U CN 201821336 U CN201821336 U CN 201821336U CN 2010205501776 U CN2010205501776 U CN 2010205501776U CN 201020550177 U CN201020550177 U CN 201020550177U CN 201821336 U CN201821336 U CN 201821336U
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Abstract
The utility model belongs to the field of data collection, and particularly relates to a high-precision analog-digital collection circuit based on negative feedback. The high-precision analog-digital collection circuit comprises a voltage following circuit, an amplifying circuit, a filtering circuit, an A/D (analog to digital) conversion circuit, a CPU (computer processing unit) and a D/A (digital to analog) feedback circuit, wherein after an analogue signal Vi inputted from the outside passes the voltage following circuit, the analogue signal Vi and an output Vf of the D/A feedback circuit subtract each other; the operation result is inputted in the A/D conversion circuit through the inverted amplifying circuit and the filtering circuit to conduct sampling-and-holding and analog-to-digital conversion; after being processed by the CPU, the analog-to-digital conversion result of the A/D conversion circuit is transmitted to the D/A feedback circuit to conduct digital-to-analog conversion; and an 18-bit D/A chip AD760AQ is adopted to serve as a D/A conversion chip. By adopting a floating point type DSP (digital signal processor), a middle-precision ADC (analog-to-digital converter), and a high-precision DAC (digital-to-analog converter), the analog-digital collection circuit capable of collecting 18-bit high-precision analog quantity is schemed out, and the collection voltage ranges from minus 10 V to plus 10 V.
Description
Technical field
The utility model belongs to data collecting field, is specifically related to a kind of based on degenerative high precision analogue Acquisition Circuit.
Background technology
Traditional modulus conversion technique is because the restriction of structural manufacturing process, for-10V～+ the analog acquisition conversion of 10V input range is difficult to realize the high-resolution more than 16.In recent years along with the develop rapidly of large scale integrated circuit, computer technology, digital system, digital system demonstrates high-performance, good reliability, flexibility day by day, reaches little, low in energy consumption, the low cost and other advantages of volume, utilize the modulus switching device of present existing high speed, medium accuracy, carry out corresponding data processing, calculating, calibration in conjunction with DSP, realized 18 high precision analogue Acquisition Circuit.
In practical engineering application, the high-speed, high precision A/D conversion system has high using value.Adopt the high-precision A/D chip of resolution 〉=18 (to have only the A/D converter of ∑-Δ type can reach this precision simply, its input range can only less than-5V～+ 5V, and adopt this transducer to be not suitable for the analog signal sampling of high-precision requirement system owing to characteristics on its principle, generally be used for the collection of voice), and because noise, situations such as transmission line coupled interference, do not having actually under the situation of filtering can only to guarantee 11 left and right sides precision, and after the additional filtering, to introduce the hysteresis of phase place and the distortion of actual signal, and precision also can only about 14.
Summary of the invention
Technical problem to be solved by this invention is that a kind of Acquisition Circuit that can realize 18 bit resolution sampling precision requirements is provided.
The technical solution adopted in the present invention is:
A kind of based on degenerative high precision analogue Acquisition Circuit, comprise voltage follower circuit, amplifying circuit, filter circuit, A/D change-over circuit, CPU processor and D/A feedback circuit; Wherein, the analog signal V of extraneous input
iBy behind the voltage follower circuit with the output V of D/A feedback circuit
fDo subtraction, operation result is sent into the A/D change-over circuit by reverse amplification circuit, filter circuit and is sampled and keep and analog-to-digital conversion; Deliver to the D/A feedback circuit after the analog-to-digital conversion result of A/D change-over circuit handles and carry out digital-to-analogue conversion in CPU, the D/A analog-digital chip adopts 18 D/A chip AD760AQ.
Aforesaid a kind of based on degenerative high precision analogue Acquisition Circuit, wherein: the multiplication factor of amplifier is 2 n power in the described reverse amplification circuit.
Aforesaid a kind of based on degenerative high precision analogue Acquisition Circuit, wherein: the multiplication factor of described amplifier is 256 times or 128 times.
Aforesaid a kind of based on degenerative high precision analogue Acquisition Circuit, wherein: the A/D chip in the described A/D change-over circuit adopts 12 accuracy A D7874RN of 4 passages.
Aforesaid a kind of based on degenerative high precision analogue Acquisition Circuit, wherein: the sampling period of described Acquisition Circuit is 0.625mS.
The invention has the beneficial effects as follows:
1. system configuration is simple and satisfied the sampling precision requirement of system's 18 bit resolutions.
2. adopt floating type DSP, middle Precision A C and high accuracy DAC to design the modulus acquisition method that to gather 18 (guaranteeing 17 no frame hoppings) high-precision analog amounts.
3. adopted and in system, introduced degenerative method, can effectively reduce the common mode disturbances that noise causes, provided corresponding algorithm according to system's characteristics simultaneously, thereby can obtain the AD acquisition system of 18 bit resolutions.
4. gather voltage range can reach-10V～+ 10V.
Description of drawings
Fig. 1 be the utility model provide a kind of based on degenerative high precision analogue Acquisition Circuit operation principle block diagram;
Fig. 2 is that high-precision A/D gathers negative feedback partial circuit figure;
Among Fig. 2: D1, D2 are operational amplifiers, and D3 is the A/D conversion chip, and D4 is the D/A conversion chip.
Embodiment
Below in conjunction with drawings and Examples to a kind ofly being introduced of the utility model proposes based on degenerative high precision analogue Acquisition Circuit:
As shown in Figure 1, a kind ofly comprise voltage follower circuit, amplifying circuit, filter circuit, A/D change-over circuit, CPU processor and D/A feedback circuit based on degenerative high precision analogue Acquisition Circuit.
Wherein, the A/D chip adopts 12 accuracy A D7874RN of 4 passages (can select the A/D conversion chip of more high accuracy and faster sample rate).Analog signal V
iBy exporting V with D/A behind the voltage follower circuit
fDo subtraction, operation result is sent into the A/D chip and is sampled and keep and analog-to-digital conversion by oppositely amplifying (multiplication factor is 256), filter circuit, and described reverse amplification and filter circuit are those skilled in the art of the present technique's common practise; Deliver to the D/A chip after transformation result is handled and carry out digital-to-analogue conversion in CPU (using DSP in the present embodiment), the D/A analog-digital chip adopts 18 D/A chip AD760AQ to realize.By a such closed loop tracing process, can when carrying out signal filtering, follow the tracks of input signal, satisfy the dynamic characteristic requirement of gatherer process.
Its rudimentary algorithm is as follows:
V
o(n)＝V
i(n)+K
1e(n)′+K
2[e(n)-e(n-1)]′
e(n)＝[V
i-V
f]*256 n＝1，2，3ΛΛ
e(n)′＝e(n)/4
σ＝[e(n)-e(n-1)]′＝[e(n)-e(n-1)]/256
Wherein, V
i(n) for the final output end value of last time of keeping (according to the actual requirements, the sampling computing cycle that designs in native system is 0.625mS, because the restriction of AD760AQ chip, be 13uS the settling time at twice conversion output maximum voltage difference 20V, so system is 13uS in the minimum sampling period, if pressure reduction is less than 10V between twice conversion generally speaking certainly, then its sampling period can narrow down to 8uS); V
o(n) being the voltage measuring value of current calculating gained, also is the Voltage Feedback value, is exported by the AD760AQ chip; E (n) feeds back output valve after amplifying 256 times, the current sampled value of A/D for outside input with D/A; Because the existence of system noise, the AD7874RN sampling can only guarantee 10 not frame hoppings, thus with e (n) divided by 4 (promptly 2
2Thereby) obtain e (n) ', so the anti-big multiple of amplifier is 256 times, promptly 2
8The σ item is the prediction that is used for signal, because the effect of capacitor filtering, sampling maintenance will make input signal postpone, σ can reduce to postpone compensation of phase.K
1, K
2Selection be to come by experiment to determine according to the characteristics of sorts of systems, in native system, select 0.83,0.94 respectively.
What specify is, if the AD7874RN sampled result can guarantee 11 not frame hoppings, then constant 4 just changes 2 into, and constant 256 changes 128 into, can realize the requirement of system equally.
As shown in Figure 2, external analog signal becomes voltage signal V after by sampling with high precision resistance R 1, R2
i, and carry out filtering by capacitor C 2.AD760AQ (being D4) output feedback signal V
f, V
iAnd V
fCarry out subtraction circuit at operational amplifier D2 place and handle, operation result is input A/D conversion chip AD7874RN (being D3) through amplification and after carrying out capacitor C 1 filtering.The data wire of AD7874RN directly is connected with float-point DSP processor (optional TMS320C31) data wire, control signal cs_7874#, rd_7874#, INT_7874#, convst# can directly connect external equipments such as CPLD, can be controlled by float-point DSP processor TMS320C31.AD760AQ adopts the work in series pattern, and its data are connected with outside CPLD (finishing conversion of string and data flow and logic control) with control signal, also finish control by TMS320C31.TMS320C31 control AD7874RN and AD760AQ sample and feed back output, and by respective algorithms, system has satisfied the sampling precision requirement of 18 bit resolutions.
In system, introduce degenerative method by having adopted, can effectively reduce plate and play the common mode disturbances that noise causes interiorly, provided corresponding algorithm according to system's characteristics simultaneously, utilized low precision device can obtain the AD acquisition system of 18 bit resolutions.
Claims (5)
1. one kind based on degenerative high precision analogue Acquisition Circuit, comprises voltage follower circuit, amplifying circuit, filter circuit, A/D change-over circuit, CPU processor and D/A feedback circuit; It is characterized in that: the analog signal V of extraneous input
iBy behind the voltage follower circuit with the output V of D/A feedback circuit
fDo subtraction, operation result is sent into the A/D change-over circuit by reverse amplification circuit, filter circuit and is sampled and keep and analog-to-digital conversion; Deliver to the D/A feedback circuit after the analog-to-digital conversion result of A/D change-over circuit handles and carry out digital-to-analogue conversion in CPU, the D/A analog-digital chip adopts 18 D/A chip AD760AQ.
2. according to claim 1 a kind of based on degenerative high precision analogue Acquisition Circuit, it is characterized in that: the multiplication factor of amplifier is 2 n power in the described reverse amplification circuit.
3. according to claim 2 a kind of based on degenerative high precision analogue Acquisition Circuit, it is characterized in that: the multiplication factor of described amplifier is 256 times or 128 times.
4. according to claim 1 a kind of based on degenerative high precision analogue Acquisition Circuit, it is characterized in that: the A/D chip in the described A/D change-over circuit adopts 12 accuracy A D7874RN of 4 passages.
5. according to claim 1 a kind of based on degenerative high precision analogue Acquisition Circuit, it is characterized in that: the sampling period of described Acquisition Circuit is 0.625mS.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2010205501776U CN201821336U (en) | 2010-09-30 | 2010-09-30 | High-precision analog-digital collection circuit based on negative feedback |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010205501776U CN201821336U (en) | 2010-09-30 | 2010-09-30 | High-precision analog-digital collection circuit based on negative feedback |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103064456A (en) * | 2011-10-24 | 2013-04-24 | 北京强度环境研究所 | Reaction type extra-high precision voltage source |
| CN104300982A (en) * | 2014-10-11 | 2015-01-21 | 福建星云电子股份有限公司 | High-speed resolution-settable and high-precision AD sampling circuit and control algorithm thereof |
| CN106771460A (en) * | 2017-01-16 | 2017-05-31 | 佛山科学技术学院 | A kind of high resolution measurement change-over circuit |
| CN108055018A (en) * | 2017-11-28 | 2018-05-18 | 东华理工大学 | The filter circuit of digital signal |
-
2010
- 2010-09-30 CN CN2010205501776U patent/CN201821336U/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103064456A (en) * | 2011-10-24 | 2013-04-24 | 北京强度环境研究所 | Reaction type extra-high precision voltage source |
| CN103064456B (en) * | 2011-10-24 | 2014-11-05 | 北京强度环境研究所 | Reaction type extra-high precision voltage source |
| CN104300982A (en) * | 2014-10-11 | 2015-01-21 | 福建星云电子股份有限公司 | High-speed resolution-settable and high-precision AD sampling circuit and control algorithm thereof |
| CN106771460A (en) * | 2017-01-16 | 2017-05-31 | 佛山科学技术学院 | A kind of high resolution measurement change-over circuit |
| CN106771460B (en) * | 2017-01-16 | 2023-03-31 | 佛山科学技术学院 | High-resolution measurement conversion circuit |
| CN108055018A (en) * | 2017-11-28 | 2018-05-18 | 东华理工大学 | The filter circuit of digital signal |
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Granted publication date: 20110504 |
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