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Resistance Measurement. Most Often Used Methods Ampermeter and Voltmeter Method Whetstone Bridge Method. A-m and V-m Method. Easy to perform, Easy to calculate the resistance, Easy to calculate the measurement error, Accuracy depend on the accuracy of instrumentation,
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Resistance Measurement • Most Often Used Methods • Ampermeter and Voltmeter Method • Whetstone Bridge Method
A-m and V-m Method • Easy to perform, • Easy to calculate the resistance, • Easy to calculate the measurement error, • Accuracy depend on the accuracy of instrumentation, • Resistance of contacts influences the results,
Two A-m V-m Methods • V-m Connected in Front of A-m, • A-m Connected in Front of V-m • Which method to use when??? A A Vs Vs V Rx V Rx
Ia I Iv V-m Connected in Front of A-m A Ra Vs Vv V Rx Vx Rv
Calculation • Approximate Value of Unknown Resistance
Calculation Exact Value of Unknown Resistance Where Vx is:
Percentage Error This methods is used for larger resistance!
Example 1 Calculation: Approximate Value of Unknown Resistance: Exact Value of Unknown Resistance:
Example 1 Error Calculation Absolute Error: Percentage Error:
Example 2 If we use the same circuit to measure unknown approximate resistance of: Percentage error would be:
Ix Ia Iv A-m Connected in Front of V-m A Ra Vv Vs V Rx Vx Rv
Calculation • Approximate Value of Unknown Resistance
Calculation Exact Value of Unknown Resistance Where Ix is:
Percentage Error This methods is used for smaller resistance!
Example 3 Calculation: Approximate and Exact Value of Unknown Resistance:
Example 3 Error Calculation Absolute Error: Percentage Error:
Example 4 If we use the same circuit to measure unknown approximate resistance of: Percentage error would be:
CONCLUSION • V-m in front of A-m - for LARGER “R” • A-m in front of V-m - for SMALLER “R”