06 Strain Gages Problem Set
STRAIN GAGES | PRACTICE PROBLEMS Complete the following to reinforce your understanding of the concept covered in this module.
PROBLEM 1: A metallic strain gage is fastened to a steel beam in a power plant that runs on wood chips. In the mist of a hurricane hitting the plant, the strain gage is subjected to a strain of 1 Γ 10β6 . If the nominal resistance value of the strain gage is 130 Ξ©, the change in resistance most close to: A. 0.0026 B. 0.026 C. 0.26 D. ππππ ππ π‘βπ ππππ£π
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SOLUTION 1:
As we are GIVEN the STRAIN, INITIAL RESISTNACE, and TYPE of STRAIN GAGE, we can simply PLUG these into the FORMULA for GAGE FACTOR, and SOLVE for the CHANGE in RESISTANCE.
The FORMULA for the GAGE FACTOR can be referenced under the SUBJECT of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing.
A GAGE FACTOR (GF) is the RATIO of FRACTIONAL CHANGE in ELECTRICAL RESISTANCE to the FRACTIONAL CHANGE in LENGTH represented as STRAIN. The GAGE FACTOR represents the RATIO of the CHANGE in GAGE RESISTANCE to the CHANGE in LENGTH or STRAIN of the GAGE.
GF =
ΞR/R ΞR/R = ΞL/L Ξ΅
Where: β’ R is the NOMINAL RESISTANCE of the STRAIN GAGE at NOMINAL LENGTH L β’ ΞR is the CHANGE in RESISTANCE due to the CHANGE in LENGTH ΞL β’ Ξ΅ is the NORMAL STRAIN sensed by the GAGE The VALUE for the GAGE FACTOR OF METALLIC STRAIN GAGES can be referenced under the SUBJECT of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on
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page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. As we are told the STRAIN GAGE is METALLIC, we know that the GAGE FACTOR a METALLIC STRAIN GAGE is typically around 2. PLUGGING the given VALUE into the FORMULA for GAGE FACTOR, we can REWRITE the formula as: GF =
ΞR/R Ξ΅
Where: β’ R is the NOMINAL RESISTANCE of the STRAIN GAGE at NOMINAL LENGTH L β’ ΞR is the CHANGE IN RESISTANCE due to the CHANGE in LENGTH ΞL β’ Ξ΅ is the NORMAL STRAIN sensed by the GAGE
PLUGGING the given VALUES into the expression for the GAGE FACTOR, we can ISOLATE the term representing the CHANGE in RESISTANCE:
2=
ΞR/(130 Ξ©) 1 Γ 10β6
We can now SOLVE for the CHANGE in RESISTANCE: ΞR = 0.00026
Therefore, the correct answer choice is D. ππ¨π§π π¨π ππ‘π πππ¨π―π
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PROBLEM 2: A Wheatstone bridge circuit made up of four resistors, each with a resistance of 120 Ξ©. If an input voltage of 5 V is applied to the circuit, what is the net change in output voltage when one resistorβs value changes by 1.2 Ξ© most close to: A. 8.7 B. 9.3 C. 12.5 D. 14.7
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SOLUTION 2: The formula for an ΒΌ QUARTER WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A ΒΌ quarter arm Wheatstone bridge circuit is used for individual strain gages where the resistance π 1 is the strain gage and the other three resistances are precision resistors equal to the nominal resistance of equivalent resistance. If the strain gage experiences a strain, the strain gage resistance changes, causing the bridge to become unbalanced. The resulting output voltage is given by:
π0 β
π₯π βπ 4π πΌπ
As we are given the strain, initial resistance, and type of strain gage, we can simply plug in the given values to calculate the output voltage as:
V0 =
(1.2 Ξ©) β (5 V) = 12.5 Γ 10β3 V = 12.5 mV 4(120 Ξ©)
Therefore, the correct answer choice is C. ππ. π
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PROBLEM 3: A strain gage is measured to have a final resistance of 199.79 Ξ© and an initial resistance of 200.00 Ξ© when subjected to a strain. Knowing that the nominal length of the strain gage is 1 ππ and that length changes by 0.9994 cm, what is the gage factor most close to: A. 1.75 B. 2.00 C. 2.25 D. 2.50
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SOLUTION 3:
As we are given the strain, initial resistance, and type of strain gage, we can simply plug these into the formula for gage factor, and solve for the change in resistance.
The formula for the GAGE FACTOR can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A GAGE FACTOR (GF) is the ratio of fractional change in electrical resistance to the fractional change in length (strain). The gage factor represents the ratio of the change in gage resistance to the change in length or strain of the gage.
GF =
ΞR/R ΞR/R = ΞL/L Ξ΅
Where: β’ R is the nominal resistance of the strain gage at nominal length L β’ ΞR is the change in resistance due to the change in length ΞL β’ Ξ΅ is the normal strain sensed by the gage Plugging in the given values into the formula for strain gage, we can re-write formula as: 199.79 Ξ© β 200 Ξ© ΞR/R β0.00105 200 Ξ© GF = = = = 1.75 0.9994 cm β 1 cm Ξ΅ β0.0006 1 cm
Therefore, the correct answer choice is A. π. ππ Made with
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PROBLEM 4: There are three high-precision resistors known to be 10 kΞ© in a quarter bridge circuit. R1 is a sensor with a small resistance difference from 10 kΞ©. What is the change in resistance closest too if VIN = 5 V and V0 = 0.03 V most close to: A. 0.12 B. 0.24 C. 0.36 D. 0.48
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SOLUTION 4: The formula for an ΒΌ QUARTER WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A ΒΌ quarter arm Wheatstone bridge circuit is used for individual strain gages where the resistance π 1 is the strain gage and the other three resistances are precision resistors equal to the nominal resistance of equivalent resistance. If the strain gage experiences a strain, the strain gage resistance changes, causing the bridge to become unbalanced. The resulting output voltage is given by:
π0 β
π₯π βπ 4π πΌπ
As we are given the strain, initial resistance, and type of strain gage, we can simply plug in the given values:
(0.03 V) =
ΞR β (5 V) 4(10 kΞ©)
Solving for the change in resistance: ΞR = 0.24 kΞ©
Therefore, the correct answer choice is B. π. ππ
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PROBLEM 5: A strain gage is placed on a steel beam for a length of 10 cm, and is noted to have a resistance of 23 πΊ. If the beam is stretched to a distance of 12 cm, the resistance increases proportionally to 28 πΊ. What is the gage factor of the strain gage most close to: A. 1.10 B. 1.20 C. 2.25 D. 2.50
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SOLUTION 5:
As we are given the change in length and change in resistance, we can simply plug these into the formula for gage factor, and solve for the value of the gage factor.
The formula for the GAGE FACTOR can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A GAGE FACTOR (GF) is the ratio of fractional change in electrical resistance to the fractional change in length (strain). The gage factor represents the ratio of the change in gage resistance to the change in length or strain of the gage.
GF =
ΞR/R ΞR/R = ΞL/L Ξ΅
Where: β’ R is the nominal resistance of the strain gage at nominal length L β’ ΞR is the change in resistance due to the change in length ΞL β’ Ξ΅ is the normal strain sensed by the gage Plugging in the given values into the formula for strain gage, we can re-write formula as:
GF =
ΞR/R Ξ΅
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Solving for the gage factor, we find: 28 Ξ© β 23 Ξ© 23 Ξ© GF = = 1.087 12 cm β 10 cm 10 cm
Therefore, the correct answer choice is A. π. ππ
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PROBLEM 6: In order to maximize the voltage output for the Wheatstone bridge shown below, which resistor(s) should be considered in tension in addition to resistor 4, π 4 ?
A. π 1 B. π 2 C. π 3 D. π΄ππ ππ π‘βπ ππππ£π
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SOLUTION 6: The formula for a BALANCED WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. In the case that the resistance in each resistor is not identical, the equivalent resistance on the left leg and right leg is equivalent, the bridge is said to still be balanced. This is due to the current division being equally divided for each leg as shown by the formula:
πΌπ
π 1 π 3 = π‘βππ π0 = 0 π π 2 π 4
As we are told that resistor 4, π 4 is tensed, the resistor equal and opposite to it in the diamond configuration should be tensed as well to maximize the voltage output.
Therefore, the correct answer choice is A. π π
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PROBLEM 7: Looking at the Wheatstone bridge configuration below, what value of π 2 will balance the Wheatstone bridge so the voltage output is π0 = 0. Assume the resistance values are the following: π 1 = 1400 πΊ, π 3 = 21 πΊ, πππ π 4 = 638 πΊ.
A. 12.38 B. 21.48 C. 42.53 D. ππππ ππ π‘βπ ππππ£π
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SOLUTION 7: The formula for a BALANCED WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. In the case that the resistance in each resistor is not identical, the equivalent resistance on the left leg and right leg is equivalent, the bridge is said to still be balanced. This is due to the current division being equally divided for each leg as shown by the formula:
πΌπ
π 1 π 3 = π‘βππ π0 = 0 π π 2 π 4
As we are given three of the four resistance values, we can simply use the ratio of resistors for a balanced bridge, and solve for the missing resistance value. Plugging in the given resistance values, we find:
1400 21 = R2 638 Solving for the resistance in resistor 2, we find the value needed to get an output voltage of zero is:
R 2 = 42,533.33 πΊ = 42.53 ππΊ
Therefore, the correct answer choice is C. 42.53 Made with
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PROBLEM 8: What can be used to construct a quarter-bridge measurement circuit? A. πππ π π‘ππππ ππππ, πππ π£πππππππ πππ ππ π‘ππ, πππ π‘π€π πππ₯ππ πππ ππ π‘πππ B. πππ π π‘ππππ ππππ, πππ π£πππππππ πππ ππ π‘ππ, πππ πππ πππππππππ πππ ππ π‘ππ C. ππ€π π π‘ππππ πππππ πππ πππ π£πππππππ πππ ππ π‘ππ D. ππ€π π π‘ππππ πππππ , πππ π£πππππππ πππ ππ π‘ππ, πππ πππ πππππππππ πππ ππ π‘ππ
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SOLUTION 8: The formula for an ΒΌ QUARTER WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A Wheatstone bridge measurement has a total of four resistive elements. In a fullbridge arrangement, all four elements are strain gages. In a half-bridge arrangement, only two strain gages are used. A fixed (reference) resistor and an adjustment (variable) resistor constitute the rest of the bridge. In a quarter bridge arrangement, only one strain gage is used. Two fixed resistors and an adjustment resistor constitute the rest of the bridge.
Therefore, the correct answer choice is A. πΆππ ππππππ ππππ, one variable
resistor, and two fixed resistors
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PROBLEM 9: Which of the following statements is most accurate when describing a wheat stone bridge configuration? A. π΄ ππππππππ π€βπππ‘ π π‘πππ ππππππ π€πππ βππ£π ππ βππ£π π£πππ‘πππ ππ’π‘ππ’π‘ B. πΌππππππ ππ ππ ππππππ ππ π π π‘ππππ ππππ ππ πππ‘ ππππππ‘ π‘βπ π£πππ‘πππ ππ’π‘ππ’π‘ C. π΄ π€βπππ‘ π π‘πππ ππππππ π€πππ βππ£π ππππ¦ πππ πππ ππ π‘ππ D. ππππ ππ π‘βπ ππππ£π
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SOLUTION 9: The topic of WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. When the current flowing through all four resistors is identical, the bridge is said to be BALANCED as the current is the same on the left and right legs of the bridge. As the current is balanced on both sides of the bridge, the output voltage is π0 = 0.
Therefore, the correct answer choice is A. A balanced wheat stone bridge will have no voltage output
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PROBLEM 1: A metallic strain gage is fastened to a steel beam in a power plant that runs on wood chips. In the mist of a hurricane hitting the plant, the strain gage is subjected to a strain of 1 Γ 10β6 . If the nominal resistance value of the strain gage is 130 Ξ©, the change in resistance most close to: A. 0.0026 B. 0.026 C. 0.26 D. ππππ ππ π‘βπ ππππ£π
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SOLUTION 1:
As we are GIVEN the STRAIN, INITIAL RESISTNACE, and TYPE of STRAIN GAGE, we can simply PLUG these into the FORMULA for GAGE FACTOR, and SOLVE for the CHANGE in RESISTANCE.
The FORMULA for the GAGE FACTOR can be referenced under the SUBJECT of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing.
A GAGE FACTOR (GF) is the RATIO of FRACTIONAL CHANGE in ELECTRICAL RESISTANCE to the FRACTIONAL CHANGE in LENGTH represented as STRAIN. The GAGE FACTOR represents the RATIO of the CHANGE in GAGE RESISTANCE to the CHANGE in LENGTH or STRAIN of the GAGE.
GF =
ΞR/R ΞR/R = ΞL/L Ξ΅
Where: β’ R is the NOMINAL RESISTANCE of the STRAIN GAGE at NOMINAL LENGTH L β’ ΞR is the CHANGE in RESISTANCE due to the CHANGE in LENGTH ΞL β’ Ξ΅ is the NORMAL STRAIN sensed by the GAGE The VALUE for the GAGE FACTOR OF METALLIC STRAIN GAGES can be referenced under the SUBJECT of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on
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page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. As we are told the STRAIN GAGE is METALLIC, we know that the GAGE FACTOR a METALLIC STRAIN GAGE is typically around 2. PLUGGING the given VALUE into the FORMULA for GAGE FACTOR, we can REWRITE the formula as: GF =
ΞR/R Ξ΅
Where: β’ R is the NOMINAL RESISTANCE of the STRAIN GAGE at NOMINAL LENGTH L β’ ΞR is the CHANGE IN RESISTANCE due to the CHANGE in LENGTH ΞL β’ Ξ΅ is the NORMAL STRAIN sensed by the GAGE
PLUGGING the given VALUES into the expression for the GAGE FACTOR, we can ISOLATE the term representing the CHANGE in RESISTANCE:
2=
ΞR/(130 Ξ©) 1 Γ 10β6
We can now SOLVE for the CHANGE in RESISTANCE: ΞR = 0.00026
Therefore, the correct answer choice is D. ππ¨π§π π¨π ππ‘π πππ¨π―π
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PROBLEM 2: A Wheatstone bridge circuit made up of four resistors, each with a resistance of 120 Ξ©. If an input voltage of 5 V is applied to the circuit, what is the net change in output voltage when one resistorβs value changes by 1.2 Ξ© most close to: A. 8.7 B. 9.3 C. 12.5 D. 14.7
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SOLUTION 2: The formula for an ΒΌ QUARTER WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A ΒΌ quarter arm Wheatstone bridge circuit is used for individual strain gages where the resistance π 1 is the strain gage and the other three resistances are precision resistors equal to the nominal resistance of equivalent resistance. If the strain gage experiences a strain, the strain gage resistance changes, causing the bridge to become unbalanced. The resulting output voltage is given by:
π0 β
π₯π βπ 4π πΌπ
As we are given the strain, initial resistance, and type of strain gage, we can simply plug in the given values to calculate the output voltage as:
V0 =
(1.2 Ξ©) β (5 V) = 12.5 Γ 10β3 V = 12.5 mV 4(120 Ξ©)
Therefore, the correct answer choice is C. ππ. π
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PROBLEM 3: A strain gage is measured to have a final resistance of 199.79 Ξ© and an initial resistance of 200.00 Ξ© when subjected to a strain. Knowing that the nominal length of the strain gage is 1 ππ and that length changes by 0.9994 cm, what is the gage factor most close to: A. 1.75 B. 2.00 C. 2.25 D. 2.50
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SOLUTION 3:
As we are given the strain, initial resistance, and type of strain gage, we can simply plug these into the formula for gage factor, and solve for the change in resistance.
The formula for the GAGE FACTOR can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A GAGE FACTOR (GF) is the ratio of fractional change in electrical resistance to the fractional change in length (strain). The gage factor represents the ratio of the change in gage resistance to the change in length or strain of the gage.
GF =
ΞR/R ΞR/R = ΞL/L Ξ΅
Where: β’ R is the nominal resistance of the strain gage at nominal length L β’ ΞR is the change in resistance due to the change in length ΞL β’ Ξ΅ is the normal strain sensed by the gage Plugging in the given values into the formula for strain gage, we can re-write formula as: 199.79 Ξ© β 200 Ξ© ΞR/R β0.00105 200 Ξ© GF = = = = 1.75 0.9994 cm β 1 cm Ξ΅ β0.0006 1 cm
Therefore, the correct answer choice is A. π. ππ Made with
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PROBLEM 4: There are three high-precision resistors known to be 10 kΞ© in a quarter bridge circuit. R1 is a sensor with a small resistance difference from 10 kΞ©. What is the change in resistance closest too if VIN = 5 V and V0 = 0.03 V most close to: A. 0.12 B. 0.24 C. 0.36 D. 0.48
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SOLUTION 4: The formula for an ΒΌ QUARTER WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A ΒΌ quarter arm Wheatstone bridge circuit is used for individual strain gages where the resistance π 1 is the strain gage and the other three resistances are precision resistors equal to the nominal resistance of equivalent resistance. If the strain gage experiences a strain, the strain gage resistance changes, causing the bridge to become unbalanced. The resulting output voltage is given by:
π0 β
π₯π βπ 4π πΌπ
As we are given the strain, initial resistance, and type of strain gage, we can simply plug in the given values:
(0.03 V) =
ΞR β (5 V) 4(10 kΞ©)
Solving for the change in resistance: ΞR = 0.24 kΞ©
Therefore, the correct answer choice is B. π. ππ
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PROBLEM 5: A strain gage is placed on a steel beam for a length of 10 cm, and is noted to have a resistance of 23 πΊ. If the beam is stretched to a distance of 12 cm, the resistance increases proportionally to 28 πΊ. What is the gage factor of the strain gage most close to: A. 1.10 B. 1.20 C. 2.25 D. 2.50
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SOLUTION 5:
As we are given the change in length and change in resistance, we can simply plug these into the formula for gage factor, and solve for the value of the gage factor.
The formula for the GAGE FACTOR can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 125 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A GAGE FACTOR (GF) is the ratio of fractional change in electrical resistance to the fractional change in length (strain). The gage factor represents the ratio of the change in gage resistance to the change in length or strain of the gage.
GF =
ΞR/R ΞR/R = ΞL/L Ξ΅
Where: β’ R is the nominal resistance of the strain gage at nominal length L β’ ΞR is the change in resistance due to the change in length ΞL β’ Ξ΅ is the normal strain sensed by the gage Plugging in the given values into the formula for strain gage, we can re-write formula as:
GF =
ΞR/R Ξ΅
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Solving for the gage factor, we find: 28 Ξ© β 23 Ξ© 23 Ξ© GF = = 1.087 12 cm β 10 cm 10 cm
Therefore, the correct answer choice is A. π. ππ
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PROBLEM 6: In order to maximize the voltage output for the Wheatstone bridge shown below, which resistor(s) should be considered in tension in addition to resistor 4, π 4 ?
A. π 1 B. π 2 C. π 3 D. π΄ππ ππ π‘βπ ππππ£π
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SOLUTION 6: The formula for a BALANCED WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. In the case that the resistance in each resistor is not identical, the equivalent resistance on the left leg and right leg is equivalent, the bridge is said to still be balanced. This is due to the current division being equally divided for each leg as shown by the formula:
πΌπ
π 1 π 3 = π‘βππ π0 = 0 π π 2 π 4
As we are told that resistor 4, π 4 is tensed, the resistor equal and opposite to it in the diamond configuration should be tensed as well to maximize the voltage output.
Therefore, the correct answer choice is A. π π
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PROBLEM 7: Looking at the Wheatstone bridge configuration below, what value of π 2 will balance the Wheatstone bridge so the voltage output is π0 = 0. Assume the resistance values are the following: π 1 = 1400 πΊ, π 3 = 21 πΊ, πππ π 4 = 638 πΊ.
A. 12.38 B. 21.48 C. 42.53 D. ππππ ππ π‘βπ ππππ£π
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SOLUTION 7: The formula for a BALANCED WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. In the case that the resistance in each resistor is not identical, the equivalent resistance on the left leg and right leg is equivalent, the bridge is said to still be balanced. This is due to the current division being equally divided for each leg as shown by the formula:
πΌπ
π 1 π 3 = π‘βππ π0 = 0 π π 2 π 4
As we are given three of the four resistance values, we can simply use the ratio of resistors for a balanced bridge, and solve for the missing resistance value. Plugging in the given resistance values, we find:
1400 21 = R2 638 Solving for the resistance in resistor 2, we find the value needed to get an output voltage of zero is:
R 2 = 42,533.33 πΊ = 42.53 ππΊ
Therefore, the correct answer choice is C. 42.53 Made with
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PROBLEM 8: What can be used to construct a quarter-bridge measurement circuit? A. πππ π π‘ππππ ππππ, πππ π£πππππππ πππ ππ π‘ππ, πππ π‘π€π πππ₯ππ πππ ππ π‘πππ B. πππ π π‘ππππ ππππ, πππ π£πππππππ πππ ππ π‘ππ, πππ πππ πππππππππ πππ ππ π‘ππ C. ππ€π π π‘ππππ πππππ πππ πππ π£πππππππ πππ ππ π‘ππ D. ππ€π π π‘ππππ πππππ , πππ π£πππππππ πππ ππ π‘ππ, πππ πππ πππππππππ πππ ππ π‘ππ
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SOLUTION 8: The formula for an ΒΌ QUARTER WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A Wheatstone bridge measurement has a total of four resistive elements. In a fullbridge arrangement, all four elements are strain gages. In a half-bridge arrangement, only two strain gages are used. A fixed (reference) resistor and an adjustment (variable) resistor constitute the rest of the bridge. In a quarter bridge arrangement, only one strain gage is used. Two fixed resistors and an adjustment resistor constitute the rest of the bridge.
Therefore, the correct answer choice is A. πΆππ ππππππ ππππ, one variable
resistor, and two fixed resistors
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PROBLEM 9: Which of the following statements is most accurate when describing a wheat stone bridge configuration? A. π΄ ππππππππ π€βπππ‘ π π‘πππ ππππππ π€πππ βππ£π ππ βππ£π π£πππ‘πππ ππ’π‘ππ’π‘ B. πΌππππππ ππ ππ ππππππ ππ π π π‘ππππ ππππ ππ πππ‘ ππππππ‘ π‘βπ π£πππ‘πππ ππ’π‘ππ’π‘ C. π΄ π€βπππ‘ π π‘πππ ππππππ π€πππ βππ£π ππππ¦ πππ πππ ππ π‘ππ D. ππππ ππ π‘βπ ππππ£π
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SOLUTION 9: The topic of WHEATSTONE BRIDGE can be referenced under the topic of INSTRUMENTATION, MEASUREMENT, AND CONTROLS on page 126 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. When the current flowing through all four resistors is identical, the bridge is said to be BALANCED as the current is the same on the left and right legs of the bridge. As the current is balanced on both sides of the bridge, the output voltage is π0 = 0.
Therefore, the correct answer choice is A. A balanced wheat stone bridge will have no voltage output
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