CN203630655U - Wheatstone bridge device - Google Patents

Wheatstone bridge device Download PDF

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Publication number
CN203630655U
CN203630655U CN201320825481.0U CN201320825481U CN203630655U CN 203630655 U CN203630655 U CN 203630655U CN 201320825481 U CN201320825481 U CN 201320825481U CN 203630655 U CN203630655 U CN 203630655U
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wheatstone bridge
current source
output end
voltage
output terminal
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葛康康
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Hangzhou Silan Microelectronics Co Ltd
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Hangzhou Silan Microelectronics Co Ltd
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Abstract

The utility model provides a Wheatstone bridge device. The Wheatstone bridge device comprises a Wheatstone bridge and a current source set connected with the power end and the output end of the Wheatstone bridge. The current source set comprises a plurality of current sources, and each current source is connected with the positive output end through a switch element and connected with the negative output end through a switch element. according to the Wheatstone bridge device, the current output by the current source set is adjusted to enable the voltage output by the positive output end of the Wheatstone bridge to be equal to or basically equal to the voltage output by the negative output end of the Wheatstone bridge, and therefore errors (namely offset voltages) caused by mismatching resistance in the Wheatstone bridge can be conveniently eliminated or basically eliminated.

Description

Wheatstone bridge configuration
Technical field
The utility model relates to electronic circuit technology field, particularly a kind of wheatstone bridge configuration.
Background technology
Wheatstone bridge is widely used in the sensor such as Magnetic Sensor and pressure transducer, and its differential configuration can be used for improving resolution and the sensitivity of device, reduces temperature coefficient impact.But its four resistance are due to the deviation of manufacture craft, the coupling completely that can not do, this does not mate caused error and can cause sensor detectability to decline.
With the Wheatstone bridge of anisotropic magnetoresistive (AMR) in Magnetic Sensor, be applied as example: suppose in without external magnetic field situation, the offset voltage of Wheatstone bridge (causing owing to the reason such as manufacturing and do not mate) is 12mV; Under magnetic field of the earth (0.5 Gauss), the Wheatstone bridge output voltage being caused by magnetic field of the earth is 1mV; When the output voltage of Wheatstone bridge is 30mV, ADC(analog to digital converter) output saturation.So under normal circumstances, saturation magnetic field can measure and approach 15 Gausses; And in the situation that having offset voltage to exist, saturation magnetic field can only measure and approach 9 Gausses, now the total output voltage of Wheatstone bridge is 30mV, comprises the offset voltage 12mV of Wheatstone bridge and the output voltage 18mV that outside 9 gauss magnetic fields cause, offset voltage has accounted for 40% of total output voltage.The thermal drift meeting that the offset voltage of Wheatstone bridge causes further reduces the detectability of Magnetic Sensor.
Concrete, please refer to Fig. 1, its circuit diagram that is Wheatstone bridge.As shown in Figure 1, resistance R 1～R4 is anisotropic magnetoresistive, and wherein, resistance R 1 and R2 have formed II arm, and resistance R 3 and R4 have formed I arm.By controlling direction of magnetization and direction of current, can make two resistance on Wheatstone bridge single armed magnetoresistance variation tendency under magnetic fields contrary (as R1 reduces, R2 increases), and also contrary (as R1 reduces, R3 increases) of two resistance variations trend on both arms same position.
Wherein, in the situation that having external magnetic field: suppose R1=R2=R3=R4=R, Vb is bridge voltage, and Δ R is the resistance change being caused by external magnetic field.While existence without offset voltage,
I arm: V 0+=V b[(R+ Δ R)/2R]
II arm: V 0-=V b[(R-Δ R)/2R]
V out=V 0+-V 0-=V b{[(R+ΔR)/2R]-[(R-ΔR)/2R]}＝V b(ΔR/R)
There is offset voltage V oSwhile existence,
Vout=V b(△R/R)+V OS
The offset voltage of this Wheatstone bridge in use all remains unchanged, and therefore after manufacture completes, only needs compensation once.The method of traditional this offset voltage of elimination mainly comprises: blow resistive method and switching capacity method etc.
Please refer to Fig. 2, it is for eliminating the circuit theory diagrams of offset voltage by blowing resistive method.Concrete, in without external magnetic field situation, by the one or more resistance that blows of parallel connection between the output terminal and power supply of Wheatstone bridge, again to make Wheatstone bridge balance.In order to reduce to blow the quantity of resistance, first to find resistance maximum in four resistance of Wheatstone bridge.Find large output terminal by an automatic testing equipment (ATE), then in parallel upper one calculate blow resistance.The weak point of this method is all to place and to blow resistance four positions, but also will have a large variable quantity.
Please refer to Fig. 3, it is for eliminating the circuit theory diagrams of offset voltage by switching capacity method.Concrete, by eliminate the offset voltage of Wheatstone bridge at negative voltage of amp.in generation.If Wheatstone bridge has the offset voltage of a 10mV, produce an inverse current by adjusting (trimming) resistance, be equivalent to produce a V at the output terminal of Wheatstone bridge bthe voltage of/2-10mV, is used for eliminating offset voltage.The shortcoming of this kind of method is that resistors match degree is low, causes degree of regulation limited.
In traditional elimination Wheatstone bridge, not mate the method that causes error all comparatively complicated for resistance, therefore proposes a kind of new, easier method and eliminate in Wheatstone bridge resistance and do not mate and cause that the method for error has become those skilled in the art's problem demanding prompt solution.
Utility model content
The purpose of this utility model is to provide a kind of wheatstone bridge configuration, does not mate to solve resistance in existing elimination Wheatstone bridge comparatively complexity or the limited problem of precision of method that causes error.
For solving the problems of the technologies described above, the utility model provides a kind of wheatstone bridge configuration, and described wheatstone bridge configuration comprises: Wheatstone bridge; And the current source group being connected with output terminal with the power end of described Wheatstone bridge; Described current source group comprises multiple current sources, and each current source is respectively connected with positive output end and is respectively connected with negative output terminal by an on-off element by an on-off element.
Optionally, in described wheatstone bridge configuration, described multiple current sources are the current source that the electric current of output increases with scale-of-two ratio.
Optionally, in described wheatstone bridge configuration, each on-off element is all controlled by register or digital to analog converter.
In the wheatstone bridge configuration providing at the utility model, by regulating the electric current of current source group output, the positive output end of Wheatstone bridge and voltage that negative output terminal is exported are equated or substantially equal, thus, can eliminate very easily/substantially eliminate resistance in Wheatstone bridge and not mate the error (being offset voltage) causing.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of Wheatstone bridge;
Fig. 2 is the circuit theory diagrams of eliminating offset voltage by blowing resistive method;
Fig. 3 is the circuit theory diagrams of eliminating offset voltage by switching capacity method;
Fig. 4 is the circuit diagram of the wheatstone bridge configuration of the utility model embodiment.
Embodiment
Below in conjunction with the drawings and specific embodiments, the wheatstone bridge configuration the utility model proposes is described in further detail.According to the following describes and claims, advantage of the present utility model and feature will be clearer.It should be noted that, accompanying drawing all adopts very the form of simplifying and all uses non-ratio accurately, only in order to convenient, the object of aid illustration the utility model embodiment lucidly.
Please refer to Fig. 4, it is the circuit diagram of the wheatstone bridge configuration of the utility model embodiment.As shown in Figure 4, described wheatstone bridge configuration comprises: Wheatstone bridge 10; And with power end VCC and the output terminal V of described Wheatstone bridge 10 0+/ V 0-the current source group 11 being connected; Described current source group 11 comprises multiple current sources, and each current source is respectively by an on-off element and positive output end V 0+connect and respectively by on-off element and negative output terminal V 0-connect.
In the present embodiment, described current source group comprises n+1 current source (wherein n+1 is natural number), is respectively current source I 0current source I n, wherein, current source I 0pass through K switch i0with negative output terminal V 0-connect and pass through K switch iI0with positive output end V 0+connect ... current source I npass through K switch inwith negative output terminal V 0-connect and pass through K switch iInwith positive output end V 0+connect.
In the present embodiment, each on-off element is controlled by register or digital to analog converter.Be controlled by register as example take each on-off element, suppose that current source group 11 comprises 7 current sources, can whether positive output end V be exported and be exported to electric current by these 7 current sources of eight bit register control 0+or negative output terminal V 0-.Concrete, first can determine to export to positive output end V by register most significant digit 0+or negative output terminal V 0-, for example register most significant digit is 0, electric current exports negative output terminal V to 0-, now, K switch iIx(wherein 0≤x≤n) all disconnect K switch ix(wherein 0≤x≤n) still open to determine closure according to the size of current of output; Register most significant digit is 1, and electric current exports positive output end V to 0+, now, K switch ix(wherein 0≤x≤n) all disconnect K switch iIx(wherein 0≤x≤n) still open to determine closure according to the size of current of output.
Preferably, the electric current of multiple current source outputs increases with scale-of-two ratio, if I 0=IREF, I n=2 n*iREF, wherein, IREF is a constant current source, and it can be produced by device internal circuit, does not change with mains voltage variations, and its temperature coefficient is very little.
In above-mentioned wheatstone bridge configuration, by regulating the electric current of current source group output, just can make the positive output end of Wheatstone bridge and voltage that negative output terminal is exported equate or substantially equal, thus, can eliminate very easily/substantially eliminate resistance in Wheatstone bridge and not mate the error (being offset voltage) causing.
Further, the present embodiment also provides a kind of adjustment method of wheatstone bridge configuration, specifically comprises:
One wheatstone bridge configuration is provided, and described wheatstone bridge configuration comprises: Wheatstone bridge; And the current source group being connected with output terminal with the power end of described Wheatstone bridge; Described current source group comprises multiple current sources, and each current source is respectively connected with positive output end and is respectively connected with negative output terminal by an on-off element by an on-off element;
Regulate the electric current of current source group output, the positive output end of Wheatstone bridge and voltage that negative output terminal is exported are equated or substantially equal.
Further, before regulating the electric current of current source group output, also comprise: obtain the offset voltage between positive output end and the negative output terminal of Wheatstone bridge.Concrete, can under without external magnetic field condition, record the offset voltage (V at Wheatstone bridge two ends by high-precision multimeter o+-V o-); Also can calculate offset voltage by the output that (SET) and the analog to digital converter (ADC) of replacement when (RESET) are set, etc. kinds of schemes of the prior art be achieved.
In the present embodiment, in the time that the voltage of positive output end is greater than the voltage of negative output terminal, the current load of current source group output is in negative output terminal; In the time that the voltage of negative output terminal is greater than the voltage of positive output end, the current load of current source group output is in positive output end.Thus, just can make the positive output end of Wheatstone bridge and voltage that negative output terminal is exported equate or substantially equal.Further, in the time that the voltage of positive output end is greater than the voltage of negative output terminal, be connected in the some or all of conducting of on-off element of current source and negative output terminal; In the time that the voltage of negative output terminal is greater than the voltage of positive output end, be connected in the some or all of conducting of on-off element of current source and positive output end.
Concrete, if R1=1000 Ω, R2=1002 Ω, R3=1003 Ω, R4=1001 Ω, Vb=3V:
V 0 + = R 2 R 1 + R 2 * V b = 1002 1000 + 1002 * 3 = 1002 2002 * 3 V
V 0 - = R 4 R 3 + R 4 * V b = 1001 1003 + 1001 * 3 = 1001 2004 * 3 V
V 0 + - V 0 - = ( 1002 2002 - 1001 2004 ) * 3 V ≈ 9.985 × 10 - 4 V
Hence one can see that, V o+>V o-, now can register most significant digit be set to 0, i.e. K switch iIx(wherein 0≤x≤n) all disconnect, electric current exports negative output terminal V to 0-, concrete size is as follows:
Figure BDA0000436576130000061
Suppose IREF=200nA, need 5 IREF, can be set to 00000101 by register, i.e. current source I 0with current source I 2output current negative output terminal V 0-.By Closing Switch K i0and K switch i2, just can make the positive output end of Wheatstone bridge and voltage that negative output terminal is exported equate or substantially equal, do not mate thereby eliminate/substantially eliminate resistance in Wheatstone bridge the error (being offset voltage) causing.Wherein, used in this application term " voltage equates or is substantially equal ", its purpose is to make voltage suitable as far as possible, certainly, in some cases, equates very difficult or substantially impossible completely, substantially equates or approach to equate.
Suppose again R1=1003 Ω, R2=1001 Ω, R3=1000 Ω, R4=1002 Ω, Vb=3V:
V 0 + = R 2 R 1 + R 2 * V b = 1001 1003 + 1001 * 3 = 1001 2004 * 3 V
V 0 - = R 4 R 3 + R 4 * V b = 1002 1000 + 1002 * 3 = 1002 2002 * 3 V
V 0 + - V 0 - = ( 1001 2004 - 1002 2002 ) * 3 V ≈ 9.985 × 10 - 4 V
Hence one can see that, V o+<V o-, now can register most significant digit be set to 1, i.e. K switch ix(wherein 0≤x≤n) all disconnect, electric current exports positive output end V to 0+, concrete size is as follows:
Figure BDA0000436576130000065
Suppose IREF=200nA, need 5 IREF, can be set to 10000101 by register, i.e. current source I 0with current source I 2output current positive output end V 0+.By Closing Switch K iI0and K switch iI2, just can make the positive output end of Wheatstone bridge and voltage that negative output terminal is exported equate or substantially equal, do not mate thereby eliminate/substantially eliminate resistance in Wheatstone bridge the error (being offset voltage) causing.
As fully visible, in the wheatstone bridge configuration providing at the utility model embodiment, by regulating the electric current of current source group output, the positive output end of Wheatstone bridge and voltage that negative output terminal is exported are equated or substantially equal, thus, can eliminate very easily/substantially eliminate resistance in Wheatstone bridge and not mate the error (being offset voltage) causing.
Foregoing description is only the description to the utility model preferred embodiment; the not any restriction to the utility model scope; any change, modification that the those of ordinary skill in the utility model field does according to above-mentioned disclosure, all belong to the protection domain of claims.

Claims (3)

1. a wheatstone bridge configuration, is characterized in that, comprising: Wheatstone bridge; And the current source group being connected with output terminal with the power end of described Wheatstone bridge; Described current source group comprises multiple current sources, and each current source is respectively connected with positive output end and is respectively connected with negative output terminal by an on-off element by an on-off element.
2. wheatstone bridge configuration as claimed in claim 1, is characterized in that, described multiple current sources are the current source that the electric current of output increases with scale-of-two ratio.
3. wheatstone bridge configuration as claimed in claim 1, is characterized in that, each on-off element is all controlled by register or digital to analog converter.
CN201320825481.0U 2013-12-12 2013-12-12 Wheatstone bridge device Expired - Fee Related CN203630655U (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103631295A (en) * 2013-12-12 2014-03-12 杭州士兰微电子股份有限公司 Wheatstone bridge device and debugging method thereof
WO2016074058A1 (en) * 2014-11-14 2016-05-19 Bistrata Systems Inc. System and method for measuring grain cart weight
CN113238602A (en) * 2021-05-11 2021-08-10 西南科技大学 Unbalanced Wheatstone bridge device and determination method thereof
CN116805859A (en) * 2023-08-28 2023-09-26 江苏润石科技有限公司 Operational amplifier offset voltage regulation circuit and method

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103631295A (en) * 2013-12-12 2014-03-12 杭州士兰微电子股份有限公司 Wheatstone bridge device and debugging method thereof
CN103631295B (en) * 2013-12-12 2016-08-17 杭州士兰微电子股份有限公司 Wheatstone bridge configuration and adjustment method thereof
WO2016074058A1 (en) * 2014-11-14 2016-05-19 Bistrata Systems Inc. System and method for measuring grain cart weight
US10760946B2 (en) 2014-11-14 2020-09-01 Bitstrata Systems Inc. System and method for measuring grain cart weight
US11274958B2 (en) 2014-11-14 2022-03-15 Bitstrata Systems Inc. System and method for measuring grain cart weight
US11835377B2 (en) 2014-11-14 2023-12-05 Bitstrata Systems Inc. System and method for measuring grain cart weight
CN113238602A (en) * 2021-05-11 2021-08-10 西南科技大学 Unbalanced Wheatstone bridge device and determination method thereof
CN116805859A (en) * 2023-08-28 2023-09-26 江苏润石科技有限公司 Operational amplifier offset voltage regulation circuit and method
CN116805859B (en) * 2023-08-28 2023-11-07 江苏润石科技有限公司 Operational amplifier offset voltage regulation circuit and method

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Granted publication date: 20140604

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