Krichoff’s Law - Finding Unknown Resistance using Wheatstone Bridge (cont.)

• How to Find Unknown Resistance in a Wheatstone Bridge Circuit
• Step-by-Step Procedure for Solving Wheatstone Bridge Problems
• Example Problem 1: Finding Unknown Resistance
• Example Problem 2: Finding Unknown Resistance with Known Values
• Importance of Wheatstone Bridge in Electrical Measurement

Practical Application of Wheatstone Bridge

• Measurement of Resistance using Wheatstone Bridge
• Resistance Measurement Circuit Diagram
• Calculation of Resistance with Wheatstone Bridge
• Example problem on Resistance Measurement
• Variations of Wheatstone Bridge Circuit for Resistance Measurement

Practical Application of Wheatstone Bridge (cont.)

• Measurement of Low Resistance
• Measurement of High Resistance
• Measurement of Temperature using Resistance Thermometers
• Advantages of Wheatstone Bridge in Resistance Measurement
• Limitations of Wheatstone Bridge in Resistance Measurement

Wheatstone Bridge in Strain Measurement

• Introduction to Strain Measurement
• Basic Principles of Strain Measurement using Wheatstone Bridge
• Strain Gauge and its Construction
• Wheatstone Bridge Circuit with Strain Gauge
• Sensitivity and Practical Applications

Wheatstone Bridge in Strain Measurement (cont.)

• Calculation of Strain using Wheatstone Bridge
• Example Problem on Strain Measurement
• Benefits and Limitations of Wheatstone Bridge in Strain Measurement
• Comparison with Other Methods of Strain Measurement
• Importance of Strain Measurement in Engineering Applications

Wheatstone Bridge in Temperature Measurement

• Introduction to Temperature Measurement
• Temperature Measurement Techniques and Challenges
• The Role of Wheatstone Bridge in Temperature Measurement
• Thermistor as Temperature Sensor in Wheatstone Bridge
• Wheatstone Bridge Circuit with Thermistor for Temperature Measurement

Wheatstone Bridge in Temperature Measurement (cont.)

• Calculation of Temperature using Wheatstone Bridge
• Example Problem on Temperature Measurement
• Advantages and Limitations of Wheatstone Bridge for Temperature Measurement
• Comparison with Other Temperature Sensing Methods
• Applications and Significance in Various Industries

Summary

• Recap of Krichoff’s Laws and Wheatstone Bridge
• Importance of Wheatstone Bridge in Electrical and Engineering Measurements
• Practical Application of Wheatstone Bridge in Resistance, Strain, and Temperature Measurement
• Examples and Problem Solving Techniques
• Disclaimer: Understanding the Concepts and Formulas is Essential for Solving Problems

11. Measurement of Low Resistance using Wheatstone Bridge:

• Wheatstone Bridge can be used to measure low resistance values accurately.
• Low resistance values can be measured by balancing the bridge using a known resistance and an unknown resistance.
• A galvanometer is used to detect any deflection in the bridge.
• By adjusting the known resistance, the bridge can be balanced and the unknown resistance can be calculated.
• Example: Measuring the resistance of a wire or a small resistor.

12. Measurement of High Resistance using Wheatstone Bridge:

• Wheatstone Bridge can also be used to measure high resistance values.
• Here, the known resistance is kept fixed and the unknown resistance is adjusted until the bridge is balanced.
• A galvanometer is used to detect any deflection in the bridge.
• By adjusting the unknown resistance, the bridge can be balanced and the high resistance can be calculated.
• Example: Measuring the insulation resistance of a cable or an electronic component.

13. Measurement of Temperature using Resistance Thermometers:

• Resistance thermometers or RTDs (Resistance Temperature Detectors) are used to measure temperature based on the change in resistance with temperature.
• Wheatstone Bridge is employed to accurately measure the resistance of the RTD.
• The bridge is balanced by adjusting the known resistance while keeping the RTD in a temperature-controlled environment.
• The temperature can be determined by the change in resistance of the RTD at the balanced condition.
• Example: Measuring temperature in industrial processes or scientific experiments.

14. Calculation of Resistance with Wheatstone Bridge:

• The bridge equation can be used to calculate the unknown resistance in a Wheatstone Bridge circuit.
• The equation is given by R1/R2 = Rx/Runknown, where R1 and R2 are the known resistances and Rx is the resistance connected in series with the unknown resistance.
• By rearranging the equation, the value of the unknown resistance can be determined.
• Example equation: 100Ω/500Ω = 200Ω/Runknown.

15. Example Problem on Resistance Measurement:

• Given R1 = 100Ω, R2 = 200Ω, Rx = 300Ω, find Runknown.
• Using the bridge equation, R1/R2 = Rx/Runknown.
• Substituting the given values, 100Ω/200Ω = 300Ω/Runknown.
• Simplifying the equation, 0.5 = 300Ω/Runknown.
• Cross-multiplying, Runknown = 600Ω.

16. Sensitivity and Practical Applications:

• The sensitivity of a Wheatstone Bridge is determined by the ratio of the resistances used.
• Higher sensitivity is achieved with smaller resistance ratios.
• Wheatstone Bridge finds applications in precise resistance measurement, strain gauges, temperature measurement, and null detection circuits.
• It is widely used in scientific research, engineering, and industrial processes.
• Example application: Measuring small changes in resistance for strain or pressure sensors.

17. Calculation of Strain using Wheatstone Bridge:

• Strain can be defined as the change in length divided by the original length. It is usually given in units of microstrain (με).
• Strain gauges, which are resistive sensors, are used to measure strain in various applications.
• By using Wheatstone Bridge configuration, the change in resistance can be measured due to strain.
• The strain can be calculated using the formula: strain = (∆R/Rgauge)/GF, where ∆R is the change in resistance, Rgauge is the nominal resistance of the strain gauge, and GF is the gauge factor.
• Example equation: strain = (100Ω/120Ω)/2.

18. Example Problem on Strain Measurement:

• Given ∆R = 2Ω, Rgauge = 100Ω, GF = 4, calculate the strain.
• Substituting the values into the strain equation, strain = (2Ω/100Ω)/4.
• Simplifying the equation, strain = 0.005 or 5000με (microstrain).

19. Advantages of Wheatstone Bridge in Resistance Measurement:

• Wheatstone Bridge provides accurate and precise measurements of resistance.
• It eliminates the effects of contact resistance and lead resistance.
• It is versatile and can be used to measure a wide range of resistance values.
• It is a robust and reliable method of resistance measurement.
• It allows for easy calibration and adjustment for more accurate results.

20. Limitations of Wheatstone Bridge in Resistance Measurement:

• Wheatstone Bridge is sensitive to changes in temperature, so temperature compensation is required for accurate measurements.
• It requires a stable power supply and low noise environment.
• It is not suitable for measuring extremely low or high resistance values.
• Additional calibration and adjustments may be needed for accurate measurements.
• It does not work with non-linear resistances.

21. Wheatstone Bridge in Temperature Measurement (cont.)

• Example Problem on Temperature Measurement: Given R1 = 100Ω, R2 = 200Ω, R3 = 300Ω, R4 = 400Ω, determine the temperature using a Wheatstone Bridge circuit with a thermistor.
• Using the bridge equation, (R1/R2) = (R3/R4).
• Substituting the given values, (100Ω/200Ω) = (R3/400Ω).
• Simplifying the equation, 0.5 = (R3/400Ω).
• Cross-multiplying, R3 = 200Ω.
• By knowing the resistance of the thermistor at different temperatures, the corresponding temperature can be determined.

22. Advantages of Wheatstone Bridge for Temperature Measurement:

• Accurate measurement of temperature using resistance variation.
• Good linearity and high sensitivity for precise temperature measurements.
• Wide temperature range coverage with appropriate selection of thermistor.
• Simple and reliable circuit design for temperature sensing.
• Suitable for both laboratory and industrial temperature measurement applications.

23. Limitations of Wheatstone Bridge for Temperature Measurement:

• Sensitivity to changes in resistance due to factors like lead resistance and self-heating of the thermistor.
• Non-linearity at extreme temperature ranges might affect the accuracy.
• Requires careful calibration and temperature compensation for reliable results.
• Limited to resistive temperature sensor applications, cannot be used with non-resistive sensors like thermocouples.

24. Comparison with Other Temperature Sensing Methods:

• Thermocouples: Measure temperature based on the voltage generated by the junction of two dissimilar metals. Suitable for high-temperature applications, but less accurate and sensitive compared to Wheatstone Bridge with thermistors.
• RTDs: Similar to Wheatstone Bridge, they measure resistance variations with temperature. RTDs offer better accuracy but have a narrower temperature range compared to thermistors.
• Infrared Sensors: Measure temperature by detecting the infrared radiation emitted by objects. Useful for non-contact temperature measurement but have limitations in accuracy and distance range.

25. Importance of Temperature Measurement in Various Industries:

• Industrial Processes: Temperature measurement is essential for ensuring optimal efficiency and quality control in manufacturing processes, chemical reactions, and heat treatment.
• HVAC Systems: Temperature sensing provides feedback for controlling heating, ventilation, and air conditioning systems to maintain desired comfort levels in buildings.
• Medical Applications: Accurate temperature measurement is crucial in monitoring patients’ health, diagnosing diseases, and regulating medical equipment. Examples include thermometer readings and body temperature sensors.
• Environmental Monitoring: Temperature sensing is used in weather stations, climate studies, and ecological research to understand the impact of temperature variations on ecosystems and climate change.

26. Summary:

• Wheatstone Bridge plays a significant role in solving unknown resistance problems.
• It offers accurate and reliable resistance measurement for a wide range of applications.
• Practical applications include resistance measurement, strain measurement, and temperature measurement.
• Wheatstone Bridge ensures high precision and eliminates the effect of contact and lead resistance.
• Understanding the principles and equations involved is fundamental for solving problems effectively.

27. Recap of Krichoff’s Laws and Wheatstone Bridge:

• Krichoff’s Laws: Governing principles in circuit analysis based on the conservation of charge and energy.
• Wheatstone Bridge: A balanced bridge circuit used for resistance, strain, and temperature measurement.
• Balanced and Unbalanced Bridge Conditions: The bridge is balanced when there is no current flow through the galvanometer.
• Wheatstone Bridge Configuration: Four resistors, arranged as a diamond-shaped circuit with a galvanometer at one vertex and a known resistance at another.

28. Importance of Wheatstone Bridge in Electrical and Engineering Measurements:

• Provides precise resistance measurements with low error margins, essential for accurate circuit analysis and design.
• Enables strain measurement for structural analysis, stress testing, and material characterization.
• Facilitates temperature measurement for industrial processes, scientific research, and healthcare applications.
• Offers a versatile and reliable method for resistance measurements in various industries and engineering fields.

29. Practical Application of Wheatstone Bridge in Resistance, Strain, and Temperature Measurement:

• Measurement of strain in structural engineering, geotechnical monitoring, and materials testing.
• Resistance measurement in electronic circuits, quality control, and electrical equipment evaluation.
• Temperature measurement in industry, research, and medical fields for process control and monitoring.
• Innovative variations of Wheatstone Bridge circuits present new possibilities for diverse applications in various domains.

30. Examples and Problem Solving Techniques:

• Solving circuit problems using Wheatstone Bridge requires understanding Krichoff’s Laws and the bridge equation.
• Carefully analyze the given values and conditions to determine the unknown resistance, strain, or temperature.
• Practice solving a range of example problems to become proficient in applying Wheatstone Bridge techniques.
• Develop a systematic approach to problem-solving, considering all relevant factors and using appropriate formulas and equations.
• Always verify the results and consider potential limitations or sources of error in real-world applications.