CN102769436A - Inexpensive micro-power-consumption miniaturized signal conditioning module applicable to portable apparatuses - Google Patents
Inexpensive micro-power-consumption miniaturized signal conditioning module applicable to portable apparatuses Download PDFInfo
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- CN102769436A CN102769436A CN2012102433709A CN201210243370A CN102769436A CN 102769436 A CN102769436 A CN 102769436A CN 2012102433709 A CN2012102433709 A CN 2012102433709A CN 201210243370 A CN201210243370 A CN 201210243370A CN 102769436 A CN102769436 A CN 102769436A
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Abstract
The invention discloses an inexpensive micro-power-consumption miniaturized signal conditioning module applicable to portable apparatuses. The signal conditioning module comprises a signal amplification circuit, a filtering circuit and a voltage reference circuit, wherein the signal amplification circuit is connected with the filtering circuit and is an instrument grade amplifier INA122 of a non-inverting input differential structure, the filtering circuit is a two-order active Butterworth low-pass filter circuit, and the voltage reference circuit adopts a micro-power-consumption voltage reference chip LM385-1.2 of a TI company. The signal conditioning module is simple in structure, small in size, low in power consumption and less in required component quantity and provides an inexpensive micro-power-consumption miniaturized signal conditioning solution.
Description
Technical field
The present invention relates to a kind of microminiaturized signal condition module of low-cost little power consumption that is applicable to portable instrument equipment.
Background technology
In the electronic engineering field, generally come physical quantitys such as gaging pressure, temperature, light intensity with transducer, transducer converts these measurands into the small signal of telecommunication (being generally voltage signal).These signals of telecommunication generally all are analog quantitys, and signal amplitude is generally all very small, include unwanted frequency composition (as coming from interference source) toward contact, generally can not directly use.Need to be transformed to suitable signal form to these analog signals, make it be applicable to the input of A/D converter (ADC) through the signal condition module.Subsequently, be digital signal by ADC with these analog signal conversion, and deliver to microcontroller (MCU) or other digital devices to digital signal, for use in further data processing.
Signal condition is exactly the process that measured signal is converted into the signal that can be fit to sample through operations such as buffering, amplification, filtering, shapings; Have signal waveform and the signal amplitude that is fit to sampling through the signal after the conditioning, and should comprise required useful information.
Specifically, the effect of signal condition module is that ultra-weak electronic signal (being generally voltage signal) with transducer output amplifies without distortion or adjusts to the enough signals of telecommunication of amplitude that can directly be sampled by A/D converter.The signal condition module generally comprises signal amplification circuit, filter circuit and voltage reference circuit etc., mainly realizes the functions such as buffering, amplification, shaping and filtering of signal.
For portable instrument equipment, realize the signal condition of tested tiny signal, the signal condition Module Design has specific (special) requirements.
(1) little power consumption can be worked under single supply.This is the basic demand of portable instrument equipment.
(2) have higher common-mode rejection ratio and differential amplifying power.Both comprise the common mode part in the analog signal of general transducer output, comprised the differential mode part again.The common mode part of its output can reach the volt level, and the differential mode part generally is merely several～tens millivolt.Therefore require the actual common-mode rejection ratio (CMRR) of signal condition module higher.
(3) has bigger input impedance.Equivalent resistance to reduce transducer changes the error of bringing.
(4) has less offset voltage and temperature drift.This will effectively reduce the error of signal condition, elevator system reliability.
Lack a kind of solution that is applicable to the signal condition module of the low cost of portable instrument equipment, little power consumption, microminiaturization at present.
Summary of the invention
Technical problem to be solved by this invention is that the deficiency that is directed against prior art provides a kind of microminiaturized signal condition module of low-cost little power consumption that is applicable to portable instrument equipment.
A kind of microminiaturized signal condition module of low-cost little power consumption that is applicable to portable instrument equipment comprises signal amplification circuit, filter circuit and voltage reference circuit, and said signal amplification circuit connects said filter circuit; Said signal amplification circuit is the instrument grade amplifier INA122 with homophase input difference structure; Said filter circuit is the active Butterworth low-pass filter circuit of second order; Adopted the OPA4336 operational amplifier chip of high accuracy, little power consumption in the said filter circuit; Said voltage reference circuit adopts the little power consumption voltage reference of the LM385-1.2 chip of TI company; The reference voltage of LM385-1.2 chip output is exported through a follower circuit, and said follower circuit use and said filter circuit are with the amplifier in a slice OPA4336 chip.
Signal condition module among the present invention can make faint tested physical signalling by amplification without distortion, shaping and filtering, and its output signal can directly be used for follow-up A/D conversion.This signal condition modular structure is simple, and volume is little, and is low in energy consumption, and required component number is few, and the solution of the signal condition of a kind of low cost, little power consumption, microminiaturization is provided for portable instrument equipment.
Description of drawings
Fig. 1 is the structured flowchart of portable system;
Fig. 2 is the circuit diagram of signal condition module;
Fig. 3 is the circuit diagram of signal amplification circuit;
Fig. 4 is the circuit diagram of second order active low-pass filter circuit;
Fig. 5 is the circuit diagram of 1.25V voltage reference circuit.
Embodiment
Below in conjunction with specific embodiment, the present invention is elaborated.
In general; Portable system can adopt structure as shown in Figure 1, and wherein the effect of signal condition module is that ultra-weak electronic signal (being generally voltage signal) with transducer output amplifies without distortion or adjusts to the enough signals of telecommunication of amplitude that can directly be sampled by A/D converter.And the signal condition module is as much as possible little with the influence of the A/D converter of back level to the transducer of its prime.
As shown in Figure 2, the signal condition module comprises signal amplification circuit, filter circuit and voltage reference circuit, mainly realizes the functions such as buffering, amplification, shaping and filtering of signal.
Useful differential signal for effective amplification sensor output; Signal amplification circuit in the signal condition module should have stronger common mode inhibition and differential amplifying power; Actual common-mode rejection ratio (CMRR) height, input impedance is bigger, and imbalance and temperature are floated less; These can both effectively reduce the influence of signal amplification circuit to sensor input signal, reduce temperature error.Filter circuit in the synchronous signal conditioning module should adopt with the accurate amplifier of phase structure and RC network forms active filter circuit, and certain gain and buffering effect can be provided like this, can reduce again the back level especially influence of A/D conversion.The signal condition module has characteristics such as low cost, little power consumption, microminiaturization simultaneously, can under single supply, work, and needed signal amplitude was consistent when its signal amplification range will be changed with A/D.
Signal amplification circuit
For the designing requirement of signal amplification circuit in the signal condition module, mainly should consider from following three aspects:
(1) signal of transducer output differential wave normally, wherein the common mode part can reach the volt level, and the general appearance of differential mode part is several～tens millivolt.
(2) for piezoresistive transducer, the equivalent resistance of transducer can change along with the variation of measurand.Promptly for thereafter signal amplification circuit, the internal resistance of signal source changes, if the input impedance of amplifying circuit is big inadequately, the variation of signal source internal resistance will great errors.Owing to the bridge resistor in the transducer can change along with temperature, low excessively simultaneously like the input impedance of amplifying circuit, also will introduce an additional temperature error.
(3) because sensor output signal is the millivolt level, so the input offset voltage V of amplifying circuit
1OMore little good more.Its input bias current I
1BAlso should be less, like I
1BBigger, then during the sensor bridge resistance variations, the influence of pair amplifier quiescent point is big.While I
1BGreatly, its input offset current I
1OAlso big easily, I
1BCan influence also that temperature is floated and operational precision.So input bias current I of amplifying circuit
1BIt is better to elect the nA level as.The bandwidth of amplifying circuit should be largely greater than the frequency bandwidth of tested physical signalling.
In sum, the amplifying circuit in the signal condition module must satisfy following designing requirement: have stronger common mode inhibition and differential amplifying power, actual common-mode rejection ratio is high; Input impedance is bigger; Imbalance and temperature are floated less, little power consumption, and peripheral component is few; Volume is little, can under single supply, work.
In general, the three amplifier differential amplifier circuits of importing based on homophase have the input impedance height, gain-adjusted is convenient, drifting about compensates and export the advantage that does not comprise common-mode signal each other.But be based on the three amplifier differential amplifier circuits that accurate amplifier is built; Mutual compensation difficulty between the amplifier is bigger; And compensation precision is wayward; Resistance is difficult for accurately coupling, increased that circuit is installed and the workload and the difficulty of debugging, simultaneously also to reduce system cost, the elevator system integrated level is unfavorable.
Selected for use instrument grade amplifier INA122 as signal amplification circuit in this module with homophase input difference structure.The maximum input common mode voltage of INA122 can reach 3.4V, has high cmrr (96db), high input impedance (1010 Ω), low maladjustment voltage (100 μ V), low input bias current (10nA) and low temperature drift (1 μ A/ ℃).INA122 be aim at portable, use and design based on battery powered little power consumption, have the power range (2.2V～36V) of very low quiescent current (＜60 μ A) and broad.Its gain can set out 5～10000 times amplifying power through a high accuracy outer meeting resistance.If use digital regulation resistance to replace adjustable resistance, can also realize that programme-controlled gain amplifies.
As shown in Figure 3, the R of INA122
EfPin is a reference voltage input terminal.All adopt the single power supply of 2.5V like the simulation in the system and digital circuit part, i.e. lower voltage limit during A/D conversion is 0V, and upper voltage limit is 2.5V.So need at R in the signal amplification circuit
EfPin inserts the voltage reference signal of 1 1.25V, and making the actual effective range after signal amplifies is 0～1.25V (negative signal) and 1.25～2.5V (positive signal).
As shown in Figure 3, connected a 1K Ω resistance (Rg1) and a 5K Ω adjustable resistance (Rg2) between 1 pin of INA122 chip and 8 pin, make that the signal amplification factor G of INA122 is adjustable within the specific limits.
As a part of signal condition module, the passband gain of the filter circuit of the sensitivity of the multiplication factor G of signal amplification circuit and the transducer of its prime, back level is closely related.The small voltage signal of transducer output can reach the requirement of follow-up mould/number conversion after signal amplification circuit and the amplification of filter circuit two-stage.Therefore in the process of modelled signal conditioning module, can confirm the span of G by formula (2-1).
After the span of the signal amplification factor G of INA122 is confirmed, can confirm the numerical value of Rg1 and Rg2 according to formula (2-2).
As shown in Figure 3, because Rg1 is the fixed value resistance of a 1K Ω, Rg2 is a 5K Ω adjustable resistance, so G is adjustable continuously between 38～205 times scope.
The output voltage V of this signal amplification circuit
OUTCan calculate by formula (2-3):
Filter circuit
Signal of sensor generally is low-frequency weak signal, and frequency band is narrower, is easy to receive external interference and The noise.Unwanted frequency composition in the filtering amplifying circuit output signal need add a low-pass filter circuit at the back at signal amplification circuit usually, and its cut-off frequency is by the frequency range decision of tested physical signalling.
This low-pass filter circuit can be higher than the part of nyquist frequency in the filtered signal in advance to eliminate aliasing, to guarantee can not owe sampling to tested physical signalling before sampling.Especially the high-frequency harmonic of before sampling, being introduced by power circuit or electromagnetic radiation in the filtered signal in advance can also play the effect of eliminating noise.
Be simplified structure, reduce cost, adopt accurate amplifier and RC network to form active low-pass filter circuit in this module.Compare with passive filter circuit, active filter circuit has been avoided shortcomings such as inductance unintentional nonlinearity characteristic, magnetic field shielding, loss, volume and weight without inductance element, the extra power consumption of also effectively having avoided inductance element to cause simultaneously.And because the gain and the input impedance of amplifier are higher, and output impedance is lower, active filter circuit can also provide certain gain and buffering effect.For portable system, active filter circuit is because its output impedance is less, and the A/D transformed error that due to leakage current is introduced can reduce greatly.
In this signal condition module, selected the second-order low-pass filter circuit of Butterworth type for use, it can provide in stopband-decay of 40db/ ten octaves.The flat region of Butterworth type filter circuit is bigger, does not have ripple in its passband, and phase-frequency characteristic can be thought linear within the specific limits.
Concrete low-pass filter circuit is as shown in Figure 4.The 1.25V reference voltage that provides of GND1.25 representative voltage reference circuit wherein.
Concrete RC Determination of Parameters can adopt the normalizing method for designing of tabling look-up.During the normalization design; Normalization coefficient is Hz for the unit of f in
formula, and the unit of C is μ F.In the design, look into corresponding form, find required component parameters normalized value, again it multiply by coefficient k, promptly get required device parameter values according to selected Butterworth filter circuit.The cut-off frequency f of tested physical signalling for example
0=20Hz gets C=0.1 μ F, then
=50.When tabling look-up, go back the resistors match problem of considered amplifier peripheral circuit, i.e. R
1+ R
2=R
3//R
4
The selecting frequency characteristic of whole filter circuit depends on RC network,
The passband gain of this filter circuit
According to K
PActual size get the resistance that closes on nominal value after tabling look-up.
As shown in Figure 4, the amplifier of filter circuit should adopt same phase structure, and it presents very high input impedance to RC network, but during the amplifier push-push operation, input has higher common-mode voltage, so must select the higher operational amplifier of input voltage for use.The selection of amplifier also has certain influence to the precision of filter circuit.The open-loop gain and the gain band width product of selected amplifier are bigger, the too small closed loop gain K that directly causes filter circuit of open-loop gain and input impedance
PReduce, damping coefficient δ increases, thereby reduces the precision of filter circuit.And the too small closed loop frequency band that not only makes of gain bandwidth product narrows down, and has also strengthened amplitude and phase error.
Adopted the OPA4336 operational amplifier chip of high accuracy, little power consumption in this filter circuit.Cheng Yousi amplifier of OPA4336 chip integration, the quiescent dissipation of each amplifier is merely 20 μ A, single supply work (voltage range 2.3V～5.5V); Low maladjustment voltage (60 μ V); Low input bias current (1pA), low input offset current (1pA), the big (0.2V～V of common-mode voltage range
DD-1V), common-mode rejection ratio is up to 86db, and unity gain bandwidth is long-pending to be 100kHz, its SSOP that adopts encapsulation, the spacing between the pin is merely 0.635mm, has saved the space of circuit board largely.
Voltage reference circuit
The signal condition module adopts the power supply of single 2.5V power supply, lower limit and upper voltage limit when adopting 0V and 2.5V voltage to change respectively as A/D, i.e. and the full scale amplitude of signal amplification is 0V～2.5V.Actual effective range after signal amplifies is 0～1.25V (negative signal) and 1.25V～2.5V (positive signal).Therefore the reference voltage that needs a 1.25V in the whole signal condition module.
Here adopt the little power consumption voltage reference of the LM385-1.2 chip of TI company to constitute concrete voltage reference circuit, its reference voltage that provides is 1.235V (representative value).This circuit can provide the operating current of 15 μ A～20mA, has little power consumption, low motional impedance and good characteristics such as temperature stability, job stability and low noise.
As shown in Figure 5, isolate in order to make other part of this reference voltage circuit and analog circuit, the reference voltage of LM385-1.2 chip output is exported through a follower circuit.This follower circuit used with filter circuit with the amplifier in a slice OPA4336 chip, made full use of hardware resource, saved circuit board space.
Should be understood that, concerning those of ordinary skills, can improve or conversion, and all these improvement and conversion all should belong to the protection range of accompanying claims of the present invention according to above-mentioned explanation.
Claims (1)
1. the microminiaturized signal condition module of low-cost little power consumption that is applicable to portable instrument equipment is characterized in that comprise signal amplification circuit, filter circuit and voltage reference circuit, said signal amplification circuit connects said filter circuit; Said signal amplification circuit is the instrument grade amplifier INA122 with homophase input difference structure; Said filter circuit is the active Butterworth low-pass filter circuit of second order; Adopt the OPA4336 operational amplifier chip of high accuracy, little power consumption in the said filter circuit; Said voltage reference circuit adopts the little power consumption voltage reference of the LM385-1.2 chip of TI company; The reference voltage of LM385-1.2 chip output is exported through a follower circuit, and said follower circuit use and said filter circuit are with the amplifier in a slice OPA4336 chip.
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Cited By (6)
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| CN104639078A (en) * | 2015-01-12 | 2015-05-20 | 南京亚派科技股份有限公司 | Simplified sampling conditioning circuit |
| CN106501136A (en) * | 2016-11-23 | 2017-03-15 | 西南大学 | A kind of Acquisition Circuit system of compound ion electrode electromotive force and acquisition method |
| CN108364455A (en) * | 2018-02-11 | 2018-08-03 | 许少辉 | The signal compensation circuit of medical remote monitoring system |
| CN110750126A (en) * | 2019-12-11 | 2020-02-04 | 合肥本源量子计算科技有限责任公司 | Multi-channel voltage source suitable for low-temperature environment |
| CN112179528A (en) * | 2020-08-21 | 2021-01-05 | 武汉中航传感技术有限责任公司 | CMOS integrated circuit and pressure sensor |
| CN114167252A (en) * | 2021-12-01 | 2022-03-11 | 中南大学 | Conduction voltage drop measuring circuit of semiconductor device |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104639078A (en) * | 2015-01-12 | 2015-05-20 | 南京亚派科技股份有限公司 | Simplified sampling conditioning circuit |
| CN104639078B (en) * | 2015-01-12 | 2018-08-17 | 南京亚派科技股份有限公司 | A kind of over-sampling modulate circuit of simplification |
| CN106501136A (en) * | 2016-11-23 | 2017-03-15 | 西南大学 | A kind of Acquisition Circuit system of compound ion electrode electromotive force and acquisition method |
| CN106501136B (en) * | 2016-11-23 | 2023-10-03 | 西南大学 | Acquisition circuit system and acquisition method for composite ion electrode electromotive force |
| CN108364455A (en) * | 2018-02-11 | 2018-08-03 | 许少辉 | The signal compensation circuit of medical remote monitoring system |
| CN108364455B (en) * | 2018-02-11 | 2020-07-03 | 上海柯渡医学科技股份有限公司 | Signal compensation circuit of medical remote monitoring system |
| CN110750126A (en) * | 2019-12-11 | 2020-02-04 | 合肥本源量子计算科技有限责任公司 | Multi-channel voltage source suitable for low-temperature environment |
| CN110750126B (en) * | 2019-12-11 | 2023-02-03 | 合肥本源量子计算科技有限责任公司 | Multi-channel voltage source suitable for low-temperature environment |
| CN112179528A (en) * | 2020-08-21 | 2021-01-05 | 武汉中航传感技术有限责任公司 | CMOS integrated circuit and pressure sensor |
| CN114167252A (en) * | 2021-12-01 | 2022-03-11 | 中南大学 | Conduction voltage drop measuring circuit of semiconductor device |
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Application publication date: 20121107 |