electronics- wheatstone bridge circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfwheatstone bridges...
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![Page 1: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/1.jpg)
Wheatstone bridges
ElectronicsWheatstone Bridge Circuits
Terry Sturtevant
Wilfrid Laurier University
October 18, 2016
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 2: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/2.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridges
A common type of circuit is a Wheatstone bridge.It is really a pair of voltage dividers using a common voltagesource.It’s usually operated with the output voltage at or close tozero.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 3: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/3.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridges
A common type of circuit is a Wheatstone bridge.
It is really a pair of voltage dividers using a common voltagesource.It’s usually operated with the output voltage at or close tozero.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 4: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/4.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridges
A common type of circuit is a Wheatstone bridge.It is really a pair of voltage dividers using a common voltagesource.
It’s usually operated with the output voltage at or close tozero.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 5: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/5.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridges
A common type of circuit is a Wheatstone bridge.It is really a pair of voltage dividers using a common voltagesource.It’s usually operated with the output voltage at or close tozero.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 6: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/6.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 7: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/7.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 8: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/8.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Vin
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 9: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/9.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Vin Vout
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 10: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/10.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Vin Vout
This is a Wheatstone bridge.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 11: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/11.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Vin Vout
Here it’s redrawn to show the two voltage dividers.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 12: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/12.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Vin Vout
Here’s one voltage divider.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 13: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/13.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 R3
R2 R4
Vin Vout
Here’s the other voltage divider.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 14: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/14.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Often a Wheatstone bridge is used with one resistor variable,such as a resistive sensor.
Knowing the other resistors allows the variable one to beeasily determined.The circuit is very sensitive to small changes in the variableresistor.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 15: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/15.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Often a Wheatstone bridge is used with one resistor variable,such as a resistive sensor.Knowing the other resistors allows the variable one to beeasily determined.
The circuit is very sensitive to small changes in the variableresistor.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 16: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/16.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Often a Wheatstone bridge is used with one resistor variable,such as a resistive sensor.Knowing the other resistors allows the variable one to beeasily determined.The circuit is very sensitive to small changes in the variableresistor.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 17: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/17.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R1 Rv
R2 R4
Vin VoutVA VB
The variable resistor could be in any of the four positions; this isone example.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 18: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/18.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.(This will happen when R1
R2= Rv
R4.)
For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.If Rv increases, VB will decrease, and vice versa.For optimum performance, all resistors should be of the sameorder of magnitude.If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 19: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/19.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.
(This will happen when R1R2
= RvR4
.)For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.If Rv increases, VB will decrease, and vice versa.For optimum performance, all resistors should be of the sameorder of magnitude.If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 20: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/20.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.(This will happen when R1
R2= Rv
R4.)
For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.If Rv increases, VB will decrease, and vice versa.For optimum performance, all resistors should be of the sameorder of magnitude.If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 21: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/21.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.(This will happen when R1
R2= Rv
R4.)
For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.
If Rv increases, VB will decrease, and vice versa.For optimum performance, all resistors should be of the sameorder of magnitude.If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 22: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/22.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.(This will happen when R1
R2= Rv
R4.)
For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.If Rv increases, VB will decrease, and vice versa.
For optimum performance, all resistors should be of the sameorder of magnitude.If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 23: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/23.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.(This will happen when R1
R2= Rv
R4.)
For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.If Rv increases, VB will decrease, and vice versa.For optimum performance, all resistors should be of the sameorder of magnitude.
If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 24: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/24.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Balancing a Wheatstone Bridge
When the bridge is “balanced”, Vo = 0 or VA = VB.(This will happen when R1
R2= Rv
R4.)
For our diagram R1 → R2 is the reference branch, andRv → R4 is the evaluation branch.If Rv increases, VB will decrease, and vice versa.For optimum performance, all resistors should be of the sameorder of magnitude.If using a resistive sensor, use a meter to measure resistanceof sensor to get a correct order of magnitude.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 25: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/25.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
R Rv = R + ∆R
R R
Vin VoutVA VB
If resistors are chosen to be equal, except for Rv , then the outputvoltage will vary with changes in Rv .
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 26: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/26.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,
VA = V R2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 27: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/27.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 28: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/28.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 29: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/29.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B then
VA − VB ≈ V ∆R4R
which can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 30: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/30.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4R
which can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 31: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/31.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give
∆R ≈ (VA−VB)V 4R
So we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 32: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/32.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give∆R ≈ (VA−VB)
V 4R
So we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 33: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/33.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.
(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 34: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/34.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Specifically,VA = V R
2R = V /2
VB = V R2R+∆R = V R+∆R/2−∆R/2
2R+∆R = V /2− V ∆R/22R+∆R ≈
V /2− V ∆R/22R
If no current flows between A and B thenVA − VB ≈ V ∆R
4Rwhich can be rearranged to give∆R ≈ (VA−VB)
V 4RSo we can determine ∆R.(This approximation is true as long as ∆R << R)
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 35: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/35.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge optionsLead wire compensation
Temperature compensationInstrumentation amplifiersdifferential op amp circuit with voltage followers on the inputs
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 36: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/36.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge optionsLead wire compensationTemperature compensation
Instrumentation amplifiersdifferential op amp circuit with voltage followers on the inputs
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 37: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/37.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge optionsLead wire compensationTemperature compensationInstrumentation amplifiers
differential op amp circuit with voltage followers on the inputs
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 38: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/38.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge optionsLead wire compensationTemperature compensationInstrumentation amplifiersdifferential op amp circuit with voltage followers on the inputs
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 39: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/39.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Lead wire compensation
long leads;unknownresistance
Uncompensated
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 40: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/40.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Lead wire compensation
No current flows in measurement lead; similar resistance in bothother leads
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 41: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/41.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Temperature compensation
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 42: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/42.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Temperature compensation
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 43: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/43.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Temperature compensation
active
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 44: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/44.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Temperature compensation
inactive
active
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 45: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/45.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Temperature compensation
inactive
active
Temperature response of non-active sensor similar to active sensor
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 46: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/46.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Doubling sensitivity
Sensors in diagonal positions produce opposite responses.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 47: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/47.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Doubling sensitivity
Sensors in diagonal positions produce opposite responses.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 48: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/48.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Doubling sensitivity
Sensors in diagonal positions produce opposite responses.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 49: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/49.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge current limitPut resistor in series with bridge
Choose Rs � Rt
thus current controlled by Rs (fixed) rather than Rt (variable).
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 50: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/50.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge current limitPut resistor in series with bridgeChoose Rs � Rt
thus current controlled by Rs (fixed) rather than Rt (variable).
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 51: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/51.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Wheatstone bridge current limitPut resistor in series with bridgeChoose Rs � Rt
thus current controlled by Rs (fixed) rather than Rt (variable).
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 52: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/52.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Reducing current
Rs
This is useful if the voltage supply is fixed.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 53: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/53.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Reducing current
Rs
This is useful if the voltage supply is fixed.
Terry Sturtevant Electronics Wheatstone Bridge Circuits
![Page 54: Electronics- Wheatstone Bridge Circuitsdenethor.wlu.ca/pc320/lectures/wbbeam.pdfWheatstone bridges Balancing a Wheatstone Bridge Wheatstone bridge options Wheatstone bridge current](https://reader036.vdocuments.net/reader036/viewer/2022081511/610c2822a2030925e41725e0/html5/thumbnails/54.jpg)
Wheatstone bridgesBalancing a Wheatstone BridgeWheatstone bridge optionsWheatstone bridge current limit
Reducing current
Rs
This is useful if the voltage supply is fixed.
Terry Sturtevant Electronics Wheatstone Bridge Circuits