Summary of the invention
In view of this, fundamental purpose of the present invention is to propose a kind of strain acquirement Circuits System, reduces the power consumption of strain acquirement Circuits System, the acquisition precision of raising strain acquirement Circuits System.
Another object of the present invention is to propose a kind of strain acquirement method, reduce the power consumption of strain acquirement Circuits System, the acquisition precision of raising strain acquirement Circuits System.
For achieving the above object, the invention provides a kind of strain acquirement Circuits System, this strain acquirement Circuits System comprises: constant-current source circuit, bridge circuit configuration circuit, hardware leveling circuit, amplifying and conditioning circuit and A/D acquisition chip, wherein,
Constant-current source circuit is used to the bridge circuit configuration circuit constant current source electric current is provided;
The bridge circuit configuration circuit is used for the connection bridge circuit type according to the required external strain transducer of monitoring, and through switching the multi-way switch chip, the resistance with external strain transducer replacement resistance bridge constitutes the test bridge circuit;
Hardware leveling circuit is used for after the test bridge circuit of bridge circuit configuration circuit makes up, and when the strain transducer of test bridge circuit is not in running order, the compliance voltage signal of A/D acquisition chip collection is carried out spirit correction partially;
Amplifying and conditioning circuit is used for that the compliance voltage signal that produces because of the bridge circuit small strain to bridge circuit configuration circuit output amplifies, conditioning and Filtering Processing;
The A/D acquisition chip be used for the compliance voltage signal of amplifying and conditioning circuit output is carried out the A/D conversion, and output is to carry out signal analysis.
Said constant-current source circuit comprises: first resistance, second resistance, operational amplifier, the 3rd resistance and the 4th resistance, wherein,
First utmost point of operational amplifier inserts reference voltage through first resistance; Second utmost point is through second resistance eutral grounding; And through the utmost point of the 4th resistance as constant current input bridge circuit configuration circuit; The 3rd utmost point ground connection of operational amplifier, the 4th utmost point connects aanalogvoltage, and the 5th utmost point is through the 3rd resistance another utmost point as constant current input bridge circuit configuration circuit.
Said bridge circuit configuration circuit comprises multi-way switch chip and resistance bridge, wherein,
Resistance bridge is used for the resistance with external strain transducer replacement resistance bridge, constitutes the test bridge circuit;
The multi-way switch chip is used for the connection bridge circuit type according to the required external strain transducer of monitoring, the formation of control test bridge circuit.
Said multi-way switch chip comprises first switch, second switch, the 3rd switch and the 4th switch;
Resistance bridge comprises the 5th arm resistance, the 6th arm resistance, the 7th arm resistance and the 8th arm resistance;
The 5th arm resistance extremely links to each other with one of constant current input bridge circuit configuration circuit respectively with an end of the 6th arm resistance, and the other end of the 5th arm resistance extremely links to each other with the 3rd of second switch, and the other end of the 6th arm resistance extremely links to each other with second of the 3rd switch;
Second utmost point of second switch extremely links to each other with the 3rd of first switch; Second utmost point of first switch links to each other with an end of the 8th arm resistance; Another of the other end of the 8th arm resistance and constant current input bridge circuit configuration circuit extremely links to each other; And link to each other with an end of the 7th arm resistance, the other end of the 7th arm resistance extremely links to each other with the 3rd of the 4th switch, and second utmost point of the 4th switch extremely links to each other with the 3rd of the 3rd switch; The first extremely parallel connection of first switch, second switch, the 3rd switch and the 4th switch inserts aanalogvoltage;
The connecting place of second utmost point of the 4th switch and the 3rd utmost point of the 3rd switch is as a utmost point of input amplifying and conditioning circuit, and the connecting place of second utmost point of second switch and the 3rd utmost point of first switch is as another utmost point of input amplifying and conditioning circuit.
Said connection bridge circuit type comprises: full-bridge, half-bridge, 1/4 bridge.
Said hardware leveling circuit comprises: bridge circuit leveling the 9th auxiliary resistance, adjustable potential meter and bridge circuit leveling the tenth auxiliary resistance, wherein,
One termination of bridge circuit leveling the 9th auxiliary resistance is gone into a utmost point of constant current input hardware leveling circuit; The other end extremely links to each other with second of adjustable potential meter; The connecting place of second utmost point of first utmost point access second switch of adjustable potential meter and the 3rd utmost point of first switch, the 3rd utmost point links to each other with an end of bridge circuit leveling the tenth auxiliary resistance, and the other end of bridge circuit leveling the tenth auxiliary resistance inserts another utmost point of constant current input hardware leveling circuit; The 4th utmost point of adjustable potential meter inserts aanalogvoltage, the 5th utmost point ground connection.
Said amplifying and conditioning circuit comprises: the 11 resistance, the 12 resistance, the 13 resistance, the 14 resistance, the 15 resistance, first electric capacity, second electric capacity, the 3rd electric capacity, the 4th electric capacity and instrument amplifier, wherein,
One termination of the 11 resistance is gone into the connecting place of the 3rd utmost point of second utmost point and the 3rd switch of the 4th switch, and the other end extremely links to each other with first of instrument amplifier, and an end of first electric capacity extremely links to each other with first of instrument amplifier; Other end ground connection, a termination of the 12 resistance are gone into the connecting place of the 3rd utmost point of second utmost point and first switch of second switch, and the other end extremely links to each other with second of instrument amplifier; One end of second electric capacity extremely links to each other with second of instrument amplifier; Other end ground connection, the 13 resistance extremely link to each other with the 4th with the 3rd utmost point of instrument amplifier respectively, the 5th utmost point ground connection of instrument amplifier; Sextupole extremely links to each other with the 7th and inserts aanalogvoltage; Reference voltage is inserted in the ends of the earth, and the 9th utmost point links to each other with an end of the 14 resistance and the 3rd electric capacity respectively, and the other end of the 14 resistance and the 3rd electric capacity extremely links to each other with the tenth of instrument amplifier; Simultaneously; The tenth utmost point links to each other with an end of the 15 resistance, and the other end of the 15 resistance links to each other with an end of the 4th electric capacity and as the utmost point of input A/D acquisition chip, and the other end of the 4th electric capacity links to each other with the ends of the earth and as another utmost point of importing the A/D acquisition chip.
A kind of strain acquirement method, this method comprises:
For the bridge circuit configuration circuit constant current source electric current is set in advance;
According to strain transducer to be tested, switch the multi-way switch chip in the bridge circuit configuration circuit, form the test bridge circuit;
According to strain transducer performance parameter configuration amplifying and conditioning circuit parameter to be tested;
Regulate hardware leveling circuit, make the test bridge balancing that is in quiescent operation;
Start the test bridge circuit and monitor, and pass through the strain information of A/D acquisition chip collection monitoring.
Visible by above-mentioned technical scheme, a kind of strain acquirement Circuits System provided by the invention and strain acquirement method, this system comprises: be used to the constant-current source circuit that the bridge circuit configuration circuit provides the constant current source electric current; Be used for connection bridge circuit type,,, constitute the bridge circuit configuration circuit of test bridge circuit the resistance of external strain transducer replacement resistance bridge through switching the multi-way switch chip according to the required external strain transducer of monitoring; Be used for after the test bridge circuit of bridge circuit configuration circuit makes up, when the strain transducer of test bridge circuit is not in running order, the hardware leveling circuit that the compliance voltage signal of A/D acquisition chip collection is carried out the inclined to one side correction of spirit; Be used for that the compliance voltage signal that produces because of the bridge circuit small strain to bridge circuit configuration circuit output amplifies, the amplifying and conditioning circuit of conditioning and Filtering Processing; And, be used for the compliance voltage signal of amplifying and conditioning circuit output is carried out the A/D conversion, and output is to carry out the A/D acquisition chip of signal analysis.Like this, the constant current source electric current is provided, makes that the size of bridge current and arm resistance is irrelevant, thereby reduced power consumption through constant-current source circuit; Further; Through hardware leveling circuit; The bridge circuit configuration circuit is carried out spirit to be proofreaied and correct partially; Can avoid environmental change, the strain transducer index of dispatching from the factory to differ of the influence of the inevitable factors such as inconsistency of big, foil gauge resistance, improve the acquisition precision of strain acquirement Circuits System and gathered stability monitoring result.
Embodiment
For making the object of the invention, technical scheme and advantage clearer, will combine accompanying drawing and specific embodiment that the present invention is done to describe in detail further below.
Fig. 1 is an embodiment of the invention strain acquirement circuit system structure synoptic diagram.Referring to Fig. 1, this strain acquirement Circuits System comprises: constant-current source circuit 101, bridge circuit configuration circuit 102, hardware leveling circuit 103, amplifying and conditioning circuit 104 and A/D acquisition chip 105, wherein,
Constant-current source circuit 101 is used to bridge circuit configuration circuit 102 the constant current source electric current is provided;
In the embodiment of the invention; The proportioning that constant-current source circuit 101 is to use operational amplifier to pass through second resistance R 2 and reference voltage V_REF is calculated and is produced steady current; Being used to bridge circuit configuration circuit 102 provides work needed constant current source excitation; Thereby make the bridge current of bridge circuit configuration circuit 102 no longer contact directly with the size generation of arm resistance; And then reduced the power consumption of bridge circuit configuration circuit 102 overall operation, be particularly suitable for making the long term monitoring of battery-powered wireless sensor network to use.
Constant-current source circuit 101 comprises first resistance R 1, second resistance R 2, operational amplifier, the 3rd resistance R 3 and the 4th resistance R 4; First utmost point of operational amplifier inserts reference voltage through first resistance; Second utmost point passes through second resistance eutral grounding (AGND), and through the utmost point of the 4th resistance as constant current input bridge circuit configuration circuit 102, the 3rd utmost point ground connection of operational amplifier; The 4th utmost point meets aanalogvoltage AVCC; The 5th utmost point is through the 3rd resistance another utmost point as constant current input bridge circuit configuration circuit 102, and first resistance, the 3rd resistance and the 4th resistance are decided according to empirical value, and its resistance is close with second resistance.
In the practical application, can be according to the supply voltage situation of aanalogvoltage, confirm the size of reference voltage according to experience, so with second resistance R, 2 couplings, accomplish the bridge current size and be provided with, make bridge current I=V_REF/R2.
Bridge circuit configuration circuit 102 is used for the connection bridge circuit type according to the required external strain transducer of monitoring, and through switching the multi-way switch chip, the resistance with external strain transducer replacement resistance bridge constitutes the test bridge circuit;
In the embodiment of the invention, connect the bridge circuit type and comprise: full-bridge, half-bridge, 1/4 bridge.
Bridge circuit configuration circuit 102 comprises multi-way switch chip and resistance bridge, wherein,
Resistance bridge is used for the resistance with external strain transducer replacement resistance bridge, constitutes the test bridge circuit;
The multi-way switch chip is used for the connection bridge circuit type according to the required external strain transducer of monitoring, the formation of control test bridge circuit.
The multi-way switch chip comprises first switch S 1, second switch S2, the 3rd switch S 3 and the 4th switch S 4;
Resistance bridge comprises the 5th arm resistance R5, the 6th arm resistance R6, the 7th arm resistance R7 and the 8th arm resistance R8;
The 5th arm resistance extremely links to each other with one of constant current input bridge circuit configuration circuit 102 respectively with an end of the 6th arm resistance, and the other end of the 5th arm resistance extremely links to each other with the 3rd of second switch, and the other end of the 6th arm resistance extremely links to each other with second of the 3rd switch;
Second utmost point of second switch extremely links to each other with the 3rd of first switch; Second utmost point of first switch links to each other with an end of the 8th arm resistance; Another of the other end of the 8th arm resistance and constant current input bridge circuit configuration circuit 102 extremely links to each other; And link to each other with an end of the 7th arm resistance, the other end of the 7th arm resistance extremely links to each other with the 3rd of the 4th switch, and second utmost point of the 4th switch extremely links to each other with the 3rd of the 3rd switch; The first extremely parallel connection of first switch, second switch, the 3rd switch and the 4th switch inserts aanalogvoltage;
The connecting place of second utmost point of the 4th switch and the 3rd utmost point of the 3rd switch is as a utmost point of input amplifying and conditioning circuit 104, and the connecting place of second utmost point of second switch and the 3rd utmost point of first switch is as another utmost point of input amplifying and conditioning circuit 104;
One utmost point of constant current input bridge circuit configuration circuit 102 is as a utmost point of input hardware leveling circuit 103, and another utmost point of constant current input bridge circuit configuration circuit 102 is as another utmost point of input hardware leveling circuit 103.Be that bridge circuit configuration circuit and hardware leveling circuit are imported the utmost point altogether.
In the embodiment of the invention; Break-make through control multi-way switch chip is come the inner arm resistance of convert resistance bridge circuit, thereby inserts outside strain transducer, can adapt to the bridge circuit connection request of differently strained sensor connection type neatly; For example; Full-bridge, half-bridge, 1/4 bridge etc. have increased the dirigibility that the strain acquirement circuit sets up greatly, and the long term monitoring that is particularly suitable for the wireless sensor network of characteristics such as setting up in batches, external strain transducer specification is more is used.
Hardware leveling circuit 103 is used for after the test bridge circuit of bridge circuit configuration circuit 102 makes up, and when the strain transducer of test bridge circuit was not in running order, the compliance voltage signal that A/D acquisition chip 105 is gathered carried out spirit correction partially;
In the embodiment of the invention, carrying out inclined to one side correction of spirit is the resistance size completion through the adjustable potential meter in the control hardware leveling circuit 103.
Hardware leveling circuit 103 comprises: bridge circuit leveling the 9th auxiliary resistance R9, adjustable potential meter and bridge circuit leveling the tenth auxiliary resistance R10, wherein,
One termination of bridge circuit leveling the 9th auxiliary resistance is gone into a utmost point of constant current input hardware leveling circuit; The other end extremely links to each other with second of adjustable potential meter; The connecting place of second utmost point of first utmost point access second switch of adjustable potential meter and the 3rd utmost point of first switch, the 3rd utmost point links to each other with an end of bridge circuit leveling the tenth auxiliary resistance, and the other end of bridge circuit leveling the tenth auxiliary resistance inserts another utmost point of constant current input hardware leveling circuit 103; The 4th utmost point of adjustable potential meter inserts aanalogvoltage, the 5th utmost point ground connection.
In the embodiment of the invention; Through the resistance size of control or adjustment adjustable potential meter, can accomplish the spirit of hardware leveling circuit 103 and proofread and correct partially, make the bridge circuit spirit that brings because of inevitable factor such as environmental change, foil gauge resistance inconsistency be able to partially proofread and correct; Proofread and correct under the completed situation partially in spirit; Strain transducer is under the normality that deformation does not take place, can carries out the data acquisition of A/D, make monitoring result more accurate; Improve the acquisition precision of strain acquirement circuit, expanded test specification.
Amplifying and conditioning circuit 104 is used for that the compliance voltage signal that produces because of the bridge circuit small strain to bridge circuit configuration circuit 102 output amplifies, conditioning and Filtering Processing;
In the embodiment of the invention, the constant current of constant-current source circuit 101 is exported respectively as the input of bridge circuit configuration circuit 102 and hardware leveling circuit 103, and the output of bridge circuit configuration circuit 102 is as the input of amplifying and conditioning circuit 104.
Through amplifying and conditioning circuit 104 rational enlargement factor and frequency filterings are set; The compliance voltage signal that the distortion of the strain transducer that can farthest reduce monitoring solid material produces; Thereby the situation of change of real time reaction test bridge circuit, and make the compliance voltage signal become a comparatively stable voltage signal at entering A/D acquisition chip pre-conditioning.
After the test bridge circuit is confirmed,, carry out analysis-by-synthesis based on experience to calculate the enlargement factor of configuration instrument amplifier and the cutoff frequency of filtering according to the sensitivity of strain transducer, the factors such as actual range, test bridge circuit resolution and SF of test.
Amplifying and conditioning circuit 104 comprises: the 11 resistance, the 12 resistance, the 13 resistance, the 14 resistance, the 15 resistance, first electric capacity, second electric capacity, the 3rd electric capacity, the 4th electric capacity and instrument amplifier; One termination of the 11 resistance is gone into the connecting place of the 3rd utmost point of second utmost point and the 3rd switch of the 4th switch; The other end extremely links to each other with first of instrument amplifier, and an end of first electric capacity extremely links to each other other end ground connection with first of instrument amplifier; One termination of the 12 resistance is gone into the connecting place of the 3rd utmost point of second utmost point and first switch of second switch; The other end extremely links to each other with second of instrument amplifier, and an end of second electric capacity extremely links to each other other end ground connection with second of instrument amplifier; The 13 resistance extremely links to each other with the 4th with the 3rd utmost point of instrument amplifier respectively; The 5th utmost point ground connection of instrument amplifier, sextupole extremely link to each other with the 7th and insert aanalogvoltage, and reference voltage is inserted in the ends of the earth; The 9th utmost point links to each other with an end of the 14 resistance and the 3rd electric capacity respectively; The other end of the 14 resistance and the 3rd electric capacity extremely links to each other with the tenth of instrument amplifier, and simultaneously, the tenth utmost point links to each other with an end of the 15 resistance; The other end of the 15 resistance links to each other with an end of the 4th electric capacity and as the utmost point of input A/D acquisition chip 105, and the other end of the 4th electric capacity links to each other with the ends of the earth and as another utmost point of importing A/D acquisition chip 105.
Through adjusting the 11 resistance~the 15 resistance and first electric capacity~the 4th electric capacity, can adjust the enlargement factor of instrument amplifier and the cutoff frequency of filtering, the flow process of concrete adjustment can repeat no more at this referring to the correlation technique document.
A/D acquisition chip 105 be used for the compliance voltage signal of amplifying and conditioning circuit 104 outputs is carried out the A/D conversion, and output is to carry out signal analysis.
In the embodiment of the invention, after the adjustment completion is proofreaied and correct in spirit partially, the compliance voltage signal that strain transducer produced; Amplification, Filtering Processing through amplifying and conditioning circuit 104 can convert digital signal to through A/D acquisition chip 105, and through other digital interfaces; For example; Interfaces such as Serial Peripheral Interface (SPI, Serial Peripheral Interface), serial ports are transferred to main control chip, carry out work such as subsequent treatment, analysis.
Fig. 2 is the strain acquirement method flow synoptic diagram of the embodiment of the invention.Referring to Fig. 2, this flow process comprises:
Step 201 is provided with the constant current source electric current for the bridge circuit configuration circuit in advance;
In this step,, bridge current is not had with the size of testing the arm resistance in the bridge circuit contact directly for the test bridge circuit in the bridge circuit configuration circuit is provided with the constant current source electric current, thus the power consumption of reduction bridge circuit configuration circuit overall operation.
Step 202 according to strain transducer to be tested, is switched the multi-way switch chip in the bridge circuit configuration circuit, forms the test bridge circuit;
In this step,,, thereby form the test bridge circuit then with the arbitrary resistance in this strain transducer replacement resistance bridge if the bridge circuit connection request of strain transducer to be tested is 1/4 bridge; If the bridge circuit connection request of strain transducer to be tested is a half-bridge, then, form the test bridge circuit with any two resistance in this strain transducer replacement resistance bridge; If the bridge circuit connection request of strain transducer to be tested is a full-bridge, then, form the test bridge circuit with all resistance in this strain transducer replacement resistance bridge.
Step 203 is according to strain transducer performance parameter configuration amplifying and conditioning circuit parameter to be tested;
In this step; According to the sensitivity of strain transducer to be tested, the strain transducer performance parameters such as actual range, test bridge circuit resolution and SF of test; Carrying out analysis-by-synthesis based on experience calculates; Configuration amplifying and conditioning circuit parameter, for example, the enlargement factor of instrument amplifier and the cutoff frequency of filtering.
Step 204 is regulated hardware leveling circuit, makes the test bridge balancing that is in quiescent operation;
In this step; Quiescent operation is meant and is not starting under the situation that strain transducer carries out data acquisition, makes constant-current source circuit, bridge circuit configuration circuit, hardware leveling circuit, amplifying and conditioning circuit and A/D acquisition chip get into duty, according to the output of A/D acquisition chip; Regulate hardware leveling circuit; Make adjusted A/D acquisition chip be output as zero, like this, can confirm to be in the test bridge balancing of quiescent operation.
Step 205 starts the test bridge circuit and monitors, and passes through the strain information of A/D acquisition chip collection monitoring.
In this step; After confirming to be in the test bridge balancing of quiescent operation, strain transducer is placed duty, begin monitoring and gather strain information; Through the amplification and the Filtering Processing of amplifying and conditioning circuit, gather treated strain information by the A/D acquisition chip at last.
By above-mentioned visible; The strain acquirement Circuits System of the embodiment of the invention and strain acquirement method; Constant-current source circuit is that bridge circuit configuration circuit and hardware leveling circuit provide the constant current source electric current, thereby makes the bridge current of test bridge circuit and the size of arm resistance have nothing to do, and hardware leveling circuit working electric current and adjustable resistance size are irrelevant; Thereby reduced the power consumption of bridge circuit configuration circuit and hardware leveling circuit overall operation, can satisfy the long term monitoring needs of wireless sensor network system; Simultaneously, wireless strain collecting device volume is less, has reduced the difficulty that radio node sets up, and adaptability is strong; Further; Through hardware leveling circuit; The bridge circuit configuration circuit is carried out spirit to be proofreaied and correct partially; Can avoid environmental change, the strain transducer index of dispatching from the factory to differ of the influence of the inevitable factors such as inconsistency of big, foil gauge resistance, improve the acquisition precision of strain acquirement Circuits System and gathered stability monitoring result; And; Switching controls through the multi-way switch chip; Can satisfy different strain transducer test requests; Can be adapted to the needs of different sensors neatly, increase the dirigibility that the strain acquirement circuit sets up, the long term monitoring that is particularly suitable for the wireless sensor network of characteristics such as setting up in batches, external strain transducer specification is more is used.
Below based on Fig. 1 and Fig. 2, lift two specific embodiments, the present invention is done to describe in detail further.
Embodiment one
Fig. 3 is the strain acquirement Circuits System logical organization synoptic diagram of the embodiment of the invention one.Referring to Fig. 3; Structure and Fig. 1 are similar, comprising: constant-current source circuit, bridge circuit configuration circuit, hardware leveling circuit, amplifying and conditioning circuit and A/D acquisition chip, wherein; The strain resistor of external strain transducer is 120 Ω; Aanalogvoltage is 3V, adopts the half-bridge mode to insert the bridge circuit configuration circuit, second switch in the multi-way switch chip of closed bridge circuit configuration circuit and the 3rd switch; Constant-current source circuit provides the exciting current of 1.25mA to testing bridge circuit, and the enlargement factor that amplifying and conditioning circuit is set is 400 times.
Fig. 4 is the strain acquirement Circuits System physical arrangement synoptic diagram of the embodiment of the invention one.Referring to Fig. 4, be the equivalent schematic of Fig. 3 based on Fig. 1, through adopting strain transducer to replace respectively the 7th arm resistance in Fig. 1 bridge circuit configuration circuit and the 8th arm resistance, thereby obtain the physical arrangement of Fig. 4.
At first because this strain acquirement circuit supply partly is 3V, so constant-current source circuit partly to select the voltage of reference voltage V REF for use be 1.25V, the resistance of second resistance R 2 is chosen as 1k Ω, thereby the constant current source exciting current of setting is 1.25mA.
Secondly; Because external strain transducer is a half-bridge; Need second switch and the 3rd switch in the closed multi-way switch chip, thereby make the strain resistor of inner arm resistance (the 5th arm resistance and the 6th arm resistance) and external strain sensor form complete test bridge circuit.
Then, through analysis-by-synthesis is carried out in bridge circuit exciting current, electrostrictive strain resistance and sensitivity etc., the enlargement factor of instrument amplifier is set to 400 times.
At last, strain transducer is placed under the normality that does not have deformation, carry out the A/D signals collecting, dynamically adjust the resistance of adjustable potential meter, proofread and correct partially thereby make the test bridge circuit accomplish spirit.After the completion to be calibrated, the A/D that just can carry out actual strain gathers, and converts dependent variable to digital quantity and transmits, handles, analyzes.
Embodiment two
Fig. 5 is the strain acquirement Circuits System logical organization synoptic diagram of the embodiment of the invention two.Referring to Fig. 5, structure and Fig. 3 are similar, and different is that external strain transducer adopts 1/4 bridge mode to insert the bridge circuit configuration circuit.
Fig. 6 is the strain acquirement Circuits System physical arrangement synoptic diagram of the embodiment of the invention two.Referring to Fig. 6, be the equivalent schematic of Fig. 5 based on Fig. 1, through adopting strain transducer to replace the 8th arm resistance in Fig. 1 bridge circuit configuration circuit, thereby obtain the physical arrangement of Fig. 6.
Because external strain transducer is 1/4 bridge; Need second switch, the 3rd switch and the 4th switch in the closed multi-way switch chip, thereby make the strain resistor of inner arm resistance (the 5th arm resistance, the 6th arm resistance and the 7th arm resistance) and external strain sensor form complete test bridge circuit.
Be provided with instrument amplifier enlargement factor, carry out that spirit is partially proofreaied and correct and the A/D of actual strain gathers, identical with Fig. 4, repeat no more at this.
The above is merely preferred embodiment of the present invention, is not to be used to limit protection scope of the present invention.All within spirit of the present invention and principle, any modification of being done, be equal to replacement and improvement etc., all should be included within protection scope of the present invention.