Podcast
Questions and Answers
Force measurement can only be achieved through the direct method.
Force measurement can only be achieved through the direct method.
False (B)
A proving ring is designed to measure tensile forces only.
A proving ring is designed to measure tensile forces only.
False (B)
The formula Ft = Fg * (b / a) relates the test force to the distances a and b in an unequal arm balance.
The formula Ft = Fg * (b / a) relates the test force to the distances a and b in an unequal arm balance.
True (A)
An analytical balance is an example of an indirect method of measuring force.
An analytical balance is an example of an indirect method of measuring force.
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The National Bureau of Standards established the design specifications for proving rings in 1946.
The National Bureau of Standards established the design specifications for proving rings in 1946.
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Tensile forces are also known as push forces.
Tensile forces are also known as push forces.
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A physical balance is an example of a direct method for measuring force.
A physical balance is an example of a direct method for measuring force.
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Unequal arm balances can only be used for compressive force measurements.
Unequal arm balances can only be used for compressive force measurements.
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A Wheatstone bridge is primarily used to measure changes in voltage.
A Wheatstone bridge is primarily used to measure changes in voltage.
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The output voltage from a Wheatstone bridge typically requires amplification due to its low signal level.
The output voltage from a Wheatstone bridge typically requires amplification due to its low signal level.
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Strain gauges are used in load cells to measure very large changes in resistance.
Strain gauges are used in load cells to measure very large changes in resistance.
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All load cell types can be used for moisture regain testing in textiles.
All load cell types can be used for moisture regain testing in textiles.
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The balance of a Wheatstone bridge is disrupted by very small changes in the resistance of the unknown resistor.
The balance of a Wheatstone bridge is disrupted by very small changes in the resistance of the unknown resistor.
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Strain is defined as the fractional change in width.
Strain is defined as the fractional change in width.
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A load cell can measure a force range from 25 grams to 3,000,000 pounds.
A load cell can measure a force range from 25 grams to 3,000,000 pounds.
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Strain gauges measure changes in temperature rather than changes in dimensions.
Strain gauges measure changes in temperature rather than changes in dimensions.
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The bonded metallic strain gauge is the most commonly used type of strain gauge.
The bonded metallic strain gauge is the most commonly used type of strain gauge.
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Electrical resistance strain gauges can be used for dynamic strain measurements.
Electrical resistance strain gauges can be used for dynamic strain measurements.
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Load cells only use electrical types of measurement.
Load cells only use electrical types of measurement.
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A strain gauge gage changes its resistance in relation to the amount of tension experienced.
A strain gauge gage changes its resistance in relation to the amount of tension experienced.
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Mechanical type load cells cannot convert force into an electrical signal.
Mechanical type load cells cannot convert force into an electrical signal.
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Pneumatic load cells use air pressure changes to measure force.
Pneumatic load cells use air pressure changes to measure force.
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Resistance based load cells are classified as mechanical devices.
Resistance based load cells are classified as mechanical devices.
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Hydraulic load cells are ideal for use in hazardous areas due to the presence of electrical components.
Hydraulic load cells are ideal for use in hazardous areas due to the presence of electrical components.
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Pneumatic load cells provide higher accuracy than hydraulic load cells.
Pneumatic load cells provide higher accuracy than hydraulic load cells.
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A strain gauge converts the weight of an object into electrical signals through changes in temperature.
A strain gauge converts the weight of an object into electrical signals through changes in temperature.
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The gauge factor of a strain gauge is defined as the ratio of change in resistance to change in length.
The gauge factor of a strain gauge is defined as the ratio of change in resistance to change in length.
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In a strain gauge under tension, the resistance decreases.
In a strain gauge under tension, the resistance decreases.
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An electrical load cell operates on the same principles as hydraulic and pneumatic load cells.
An electrical load cell operates on the same principles as hydraulic and pneumatic load cells.
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The resistivity of a conductor is typically in the range of $10^{-8}$ to $10^{-6}$.
The resistivity of a conductor is typically in the range of $10^{-8}$ to $10^{-6}$.
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The length of the gauge influences the resistance measured by a strain gauge, where resistance is directly proportional to length.
The length of the gauge influences the resistance measured by a strain gauge, where resistance is directly proportional to length.
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Constantan strain gauges have a gauge factor range from 1.5 to 2.0.
Constantan strain gauges have a gauge factor range from 1.5 to 2.0.
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Strain gauges are attached to objects using a suitable adhesive.
Strain gauges are attached to objects using a suitable adhesive.
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A proving ring can calibrate material testing machines with a capacity of 1000 N to 1000 kN.
A proving ring can calibrate material testing machines with a capacity of 1000 N to 1000 kN.
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The deflection of a proving ring is measured using a traditional tape measure.
The deflection of a proving ring is measured using a traditional tape measure.
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An LVDT is utilized in a proving ring to sense displacement caused by force.
An LVDT is utilized in a proving ring to sense displacement caused by force.
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The formula for measuring force using a proving ring includes Young's modulus and moment of inertia.
The formula for measuring force using a proving ring includes Young's modulus and moment of inertia.
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Strain is defined as the total mass of a body disregarding any applied force.
Strain is defined as the total mass of a body disregarding any applied force.
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Proving rings can only be used with micrometers and do not support any other measuring devices.
Proving rings can only be used with micrometers and do not support any other measuring devices.
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When forces are applied through the bosses on a proving ring, it causes a change in the diameter of the ring.
When forces are applied through the bosses on a proving ring, it causes a change in the diameter of the ring.
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The resulting voltage signal from an LVDT in a proving ring is directly proportional to the force applied.
The resulting voltage signal from an LVDT in a proving ring is directly proportional to the force applied.
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Integral external bosses A and B are responsible for sensing the displacement in the proving ring.
Integral external bosses A and B are responsible for sensing the displacement in the proving ring.
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Ring deflection in a proving ring is irrelevant for accurate force measurement.
Ring deflection in a proving ring is irrelevant for accurate force measurement.
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Study Notes
Course Information
- Course Title: Design of Applied Measuring Systems
- Course Code: ENM 4239
- Academic Year: 2024-2025
- Instructor: Prof. Mohamed Essa, Assoc. Prof. of Automatic Control Systems
- Course Dates: No specific dates given
Force Measurement
- Force is the reaction between two bodies or components
- Force can be tensile (pull) or compressive (push)
- Two methods for measuring force:
- Direct Method: Direct comparison with a known gravitational force on a standard mass (e.g., physical balance).
- Indirect Method: Measuring the effect of force on a body, calculating it from acceleration due to gravity and the mass of the component.
Direct Method: Analytical Balance (Equal Arm Balance)
- Diagram depicting the balance arm and components (W1, L, dG, G, W2, WB, θ).
- Balance arm is used for direct comparison
Unequal arm balance
- Different types of unequal arm balances illustrated.
- Different diagram showing the load arm, power arm, knife edge, lever, pointer, scale, mass and force.
Proving Ring
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A device for measuring force using an elastic ring of known diameter with a measuring device at its center.
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Made of steel alloy.
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Design specifications established in 1946 by the National Bureau of Standards (NBS).
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Can be designed for compression or tension forces.
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Proving ring used for calibrating material testing machine.
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Deflection is measured using a precision micrometer.
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Mathematical relation to determine moment is given.
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A ring used to calibrate tensile testing machines.
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Uses LVDT, which senses displacement and outputs a proportional voltage.
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Integral internal bosses used to apply force on the device, which changes the ring’s diameter.
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Resulting deflection is measured using LVDT.
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Formula for calculating the force, involving the ring's outer diameter, Young's modulus, moment of inertia, and deflection.
Components of a Measuring System
- Components for measuring system:
- Sensor: Measures physical parameters.
- Conditioning/transmission system: Processes the signal.
- Recorder/indicator: Displays or records the results.
- List of physical parameters measured by sensors.
Measuring Strain (Strain Gages)
- Strain: Amount of deformation due to an applied force; it is the fractional change in length.
- Strain is measured using strain gauges, which measure small changes in dimensions.
What devices can be used to measure strain?
- Electrical Resistance Strain Gage.
- Ideal strain sensor characteristics include: good spatial resolution, insensitivity to ambient conditions, and high frequency response.
What is a Strain Gage?
- A strain gauge is a device whose electrical resistance changes in proportion to strain.
- Most common is the bonded metallic strain gauge.
Bending and Strain
- Diagram of a deflected beam subjected to force, showing strain and stress.
- Formula for calculation of strain is provided.
Foil strain gage
- Diagram of a foil strain gage.
- Components of a foil strain gauge are labeled.
Load Cell
- An electro-mechanical device converting force/weight into an electrical signal.
- Can measure force, torque, and pressure across a wide range of values.
- Different types: hydraulic, pneumatic, and electrical (with different characteristics and applications)
Load Cell Comparison
- A table comparing load cell types based on weight range, accuracy, applications, strength, and weaknesses
Types of Load Cells
- Mechanical: hydraulic & pneumatic (using fluid pressure)
- Electrical: strain gauge (measuring resistance changes), capacitance, & inductance
Continued... Mechanical and Other Load Cells
- A chart for load cell types including hydraulic, pneumatic, helical, fiber optic and piezo-resistive, listing the weight range, accuracy, application, strength and weaknesses for each
LVDT Based Load Cell
- Diagram of an LVDT-based load cell showing primary and secondary coils, core, motion, constant AC voltage and difference voltage.
Bending Beam Load Cell
- Diagram of a bending beam load cell with labeled strain gauges and force direction.
Shear Beam Load Cell
- Diagram of a shear beam load cell with labeled strain gauges and force directions.
Load Cell Application in Textiles
- Applications in different textile testing processes
- Textile testing (Instron).
- Measuring weight (moisture regain testing).
- Online tension measurement during various process steps (e.g., printing)
Instron Tensile Tester
- Used to measure tensile strength and load-elongation curves for fabrics and yarns.
- Effectively detects strain using strain gauges placed where strain is largest.
Measurement of Weight (Moisture Regain Tester)
- Measures the weight of a textile sample after drying.
- A cantilever design with strain gauges is used to record continuously the rate of moisture regain for the material.
Cost of Load Cell
- Table listing different load cell types, their load capacities, and prices.
Report
- Students are instructed to prepare a hardware implementation for force or mass digital device.
- Given guidelines for the format, including required information on the first page, as well as a deadline of 6 weeks.
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Description
Explore the different methods of measuring force, including direct and indirect techniques, through this engaging quiz. Test your knowledge on proving rings, analytical balances, and Wheatstone bridges used in various applications. Understand the principles and calculations that govern force measurement.
