Measuring Tools MCQ Quiz - Objective Question with Answer for Measuring Tools - Download Free PDF

Explanation:

Shadow Projector

• A shadow projector is an optical instrument primarily used to produce undistorted magnified reflected images of an object. By projecting shadows of the object onto a screen, it allows users to observe and measure the shape, dimensions, and features of the object with high accuracy. It is widely used in industries and laboratories for precision inspection and measurement tasks.
• A shadow projector works by shining light onto an object, casting its shadow onto a screen or viewing surface. The image formed is magnified, enabling detailed inspection of the object's profile or surface features. The optical system ensures that the image remains undistorted and true to the object's dimensions, which is critical for applications requiring precision.

Advantages:

• Provides high accuracy in imaging and measurement.
• Allows inspection of intricate details that may not be visible to the naked eye.
• Non-contact method—ideal for delicate or sensitive objects.
• Can be used to inspect and measure objects of varying sizes and shapes.

Disadvantages:

• Limited to inspecting surface profiles and dimensions; cannot detect internal flaws.
• Requires proper calibration and alignment for accurate results.
• May not be suitable for analyzing material composition.

Applications:

• Precision measurement in manufacturing industries.
• Inspection of mechanical parts and tools.
• Quality control processes in industrial applications.
• Educational purposes for studying optical projection principles.

Explanation:

Surface Texture Measurement

Definition: Surface texture measurement is a critical aspect in manufacturing and engineering that involves evaluating the surface characteristics of a material or part. The surface texture includes various attributes such as roughness, waviness, and lay, which can significantly affect the performance, aesthetics, and longevity of the part.

Working Principle: To measure surface texture, an instrument known as a profilometer is used. The profilometer traverses across the surface of the workpiece to record the topographical features. The part of the profilometer that makes contact with the workpiece surface is crucial for capturing accurate measurements.

Correct Option Analysis:

The correct option is:

Option 2: a finely pointed stylus

This option correctly identifies the part of the profilometer that makes contact with the workpiece surface. The finely pointed stylus is responsible for tracing the surface profile, detecting and recording the minute variations in texture. This contact method allows for precise measurement of surface roughness and other texture parameters.

Advantages:

• High precision in measuring surface irregularities, providing detailed and accurate surface texture data.
• Capability to measure very small surface features, which is essential for high-precision engineering applications.

Disadvantages:

• The contact nature of the measurement can sometimes cause wear on both the stylus and the workpiece surface.
• Not suitable for very soft or delicate surfaces where the stylus might cause damage.

Applications: Surface texture measurement with a finely pointed stylus is widely used in various industries, including automotive, aerospace, and precision engineering, where high surface quality is critical.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: an electrical pickup

An electrical pickup typically refers to a component used in various electronic instruments to convert physical quantities into electrical signals. While profilometers may use electrical pickups to process the signals generated by the stylus, the electrical pickup itself does not make direct contact with the workpiece surface.

Option 3: a motorised mechanism

A motorised mechanism in a profilometer is responsible for moving the stylus or the workpiece to ensure a consistent and controlled measurement process. However, the motorised mechanism does not make contact with the workpiece surface; it simply facilitates the movement of the stylus.

Option 4: a recording unit

The recording unit in a profilometer is used to capture, process, and display the surface texture data obtained from the stylus. While it is an essential part of the measurement system, it does not make direct contact with the workpiece surface.

Conclusion:

Understanding the components and their functions in a profilometer is crucial for accurate surface texture measurement. The finely pointed stylus is the part that directly interacts with the workpiece surface, making it integral to capturing detailed surface characteristics. This contact method allows for high precision in measurements, though it requires careful handling to avoid damage to both the stylus and the workpiece.

Explanation:

Gas lasers:

• Gas lasers are the most commonly used type of lasers in laser interferometers for metrology applications. The reason for their widespread use lies in their stability, coherence, and ability to produce high-quality beams. Here are some detailed points explaining why gas lasers are preferred:

1. High Stability: Gas lasers, such as the Helium-Neon (He-Ne) laser, are known for their high frequency and amplitude stability. This is crucial in metrology applications where precise and accurate measurements are required. The stability ensures that the laser's output remains consistent over time, reducing the chances of measurement errors.

2. Long Coherence Length: Coherence length is a measure of how monochromatic (single-wavelength) the laser light is. Gas lasers typically have a long coherence length, which is essential for interferometry. A longer coherence length means that the laser light can maintain its phase relationship over longer distances, which is necessary for producing clear and accurate interference patterns in interferometry.

3. High Beam Quality: Gas lasers produce high-quality beams with low divergence and minimal beam distortion. This high beam quality ensures that the laser light can be precisely directed and focused, which is important for accurate interferometric measurements.

4. Narrow Linewidth: Gas lasers have a very narrow linewidth, meaning they emit light at a very precise wavelength. This narrow linewidth is important for high-resolution measurements in metrology, as it reduces the uncertainty in the measurement of distances.

5. Reliability and Longevity: Gas lasers are known for their reliability and long operational life. This makes them suitable for continuous and long-term use in metrology applications, where consistent performance over time is essential.

Explanation:

Clinometer

• A clinometer, also known as an inclinometer, is a device used to measure angles of slope (inclination) or elevation of an object with respect to gravity. It is a special case of a spirit-level device, as it uses the principle of a spirit level to determine angular displacement. The clinometer is often used in applications such as surveying, construction, and navigation to measure the tilt of surfaces or the elevation angle of objects.
• A clinometer typically consists of a graduated arc or dial, a movable pointer or bubble, and a sighting device. The basic working principle relies on the movement of a spirit-level bubble or a pendulum within the device. The bubble or pendulum aligns itself with the direction of gravity, allowing the user to measure the angle of inclination or elevation relative to a horizontal baseline.

Advantages:

• Simple and easy-to-use tool for measuring angles of inclination or elevation.
• Highly portable and widely applicable in various fields such as construction, geology, and navigation.
• Provides accurate measurements for determining slopes, gradients, or heights of objects.

Disadvantages:

• Limited precision compared to advanced digital devices.
• Requires a steady hand and careful alignment for accurate readings.

Applications:

• Surveying and Construction: Clinometers are used to measure the slope of land or the inclination of structures.
• Navigation: Used to determine the angle of elevation of celestial objects for navigation purposes.
• Forestry: Helps in measuring the height of trees by determining the angle of elevation and using trigonometric calculations.

Additional InformationOption 1: Micrometer

• A micrometer is a precision measuring instrument used to measure small dimensions with high accuracy. It operates based on a screw and spindle mechanism and is commonly used in machining and mechanical engineering.

Option 3: Autocollimator

• An autocollimator is an optical instrument used for precise angle measurements. It works based on the reflection of light and is widely used in metrology and alignment tasks.

Option 4: Kelvinometer

• A kelvinometer is a device used to measure temperature, typically in scientific and industrial applications.

Explanation:

Spirit Level Measuring Instrument

• A spirit level, also known as a bubble level or simply a level, is a measuring instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). It is widely used in construction, carpentry, and engineering to ensure proper alignment and accuracy during measurements and installations.
• A spirit level consists of a sealed tube filled with a liquid (commonly alcohol or a similar substance) and a bubble of air trapped inside. The tube is slightly curved, and when the spirit level is placed on a surface, the bubble moves to the highest point of the tube. When the bubble is centered between the marked lines on the tube, it indicates that the surface is level or plumb.

Functions of a Spirit Level:

• Determining whether a surface is horizontal or vertical.
• Checking the flatness or straightness of a surface.
• Measuring angles in some advanced spirit levels equipped with angular measurement features.
• Ensuring alignment and proper installation of machine parts or construction materials.

Surface Roughness:

• Surface roughness refers to the texture or irregularities present on a surface, usually measured in terms of the height, depth, and spacing of these irregularities. This measurement requires specialized instruments such as a profilometer or surface roughness tester, which are capable of detecting minute variations in surface texture.

Concept:

Steel Rule

• It is a straightedge with equally spaced markings along its length.
• It is used to measure distances or to rule straight lines.
• It is available in different lengths, the common sizes being 150 mm, 300 mm, and 600 mm.
• Its reading accuracy (least count) is 0.5 mm.​

Important Points

A micrometer may have a least count of 0.01 mm while a Vernier scale on a caliper may have a least count of 0.02 mm.

Explanation:

• Vernier Caliper is a precision instrument that can be used to measure internal and external distances accurately.
• This instrument based on 2 scales.
• Main Scale (Fixed) 
• Vernier Scale (Movable).
• on main scale, 1 division = 1 mm ⇒ 49 main scale division = 50 vernier scale division
• 1 vernier scale division = (49/50) main scale division = 0.98 main scale division = 0.98 mm
• Least count (L.C) = 1 M.S.D - 1 V.S.D = 1 - 0.98 = 0.02 mm

Explanation:

The least count of any instrument is the smallest value that it can measure accurately.

Vernier Caliper

• A vernier caliper consists of two main parts:
  1. the main scale engraved on a solid L-shaped frame
  2. the vernier scale that can slide along the main scale
• A Vernier scale on caliper may have a least count of 0.02 mm. 
• It is commonly used to measure accurately:
  • outside diameters of shafts
  • thicknesses of various parts
  • diameters of holes or rings
  • internal dimensions of hollow jobs or articles

Important Points

• A micrometer may have a least count of 0.01 mm 

Explanation:

• The Vernier bevel protractor is a precision instrument meant for measuring angles to an accuracy of 5 minutes i.e. (1/12)° i.e. 12th part of 1°. 
• The value of each main-scale division of a Vernier bevel protractor is 1° 

Important Points

• 1 degree = 60 minutes.
• A micrometer may have a least count of 0.01 mm while a Vernier scale on caliper may have a least count of 0.02 mm.

Concept:

There are several methods of measuring angles and tapers.

Angular measurement involves the measurement of angles of tapers and similar surfaces. Examples:

• Bevel protector
• Sine Bar
• Spirit level
• Clinometer
• Autocollimators
• Protector's head

Clinometer:

• It is an instrument for measuring angles of slope, elevation, or depression of an object with respect to the ground.
• A clinometer is a special case of a spirit level.
• While the spirit level is restricted to relatively small angles, clinometers can be used for much larger angles.
• These have an accuracy of one minute.
• Clinometers are used to determine the straightness and flatness of surfaces.

Bevel protector:

• Bevel protector is used for measuring the angles between two faces of components.

• It has a base plate or stock whose surface has a high degree of flatness and surface finish. The stock is placed on the workpiece whose angle is to be measured. It is normally used as a reference base for measuring angles.
• An adjustable blade attached to a circular dial is made to coincide with the angular surface. It can be swiveled to the required angle and can be locked.

• An optical flat is used in conjunction with a monochromatic light to measure the difference between two surfaces.
• A vertical beam of light of known wavelength is arranged to fall on the flat.
• An optical flat is a disk of high-quality glass or quartz. The surface of the disk is ground and lapped to a high degree of flatness.
• This is basically to measure very small deviations in the object in terms of the wavelength of light.
• The top surface and the bottom surface are completely made flat. And this is predominantly used for generating fringe patterns.

Concept:

A comparator is an indirect type of instrument with the help of which an unknown dimension of a workpiece is compared with a working standard (usually slip gauges).

Comparators are classified as:

• Mechanical Comparators: In These mechanical means are used to get the magnification, for example, gear system, levers, etc. Types:
  • Dial indicators
  • Lever comparators
  • Reed type comparator
  • Sigma comparator
  • Johansson Mikrokator Comparator
• Electrical Comparator: In this, the movement of the measuring contact is converted into an electrical signal. This electrical signal is recorded by an instrument that can be calibrated in terms of plunger movement.
• Optical Comparators: This type of comparator uses fundamental optical law and instead of a pointer, the edge of a shadow is projected onto a curved graduated scale to indicate the comparison measurement.
• Pneumatic Comparator: In these comparators, either airflow or air pressure is measured to give measurement deviation from a standard. The response of the comparators working on airflow is quicker than those working on air pressure, but the latter is more versatile than the former.

• Hydraulic Comparator: The hydraulic comparator is similar to a hydraulic deadweight tester except that, instead of a piston and weight assembly, a master test gage is employed. One type of hydraulic comparator is specified for military use. This unit is designed for opera- tion on light and medium weight oils, water, gasoline, alcohol, kerosene, and glycerine gages,

Concept:

For all ranges of micrometers, the graduations marked on the barrel is only 0-25 mm. 

First, note the minimum range of the outside micrometer. While measuring with a 50 to 75 mm micrometer, note it as 50 mm.

Then read the barrel graduations. Read the value of the visible lines on the left of the thimble edge.
13.00 mm (Main divison reading on barrel) + 00.50 mm (Sub division reading on barrel) = 13.50 mm (Main division + sub - division value) 

Read the thimble graduations:

Read the thimble graduations in line with the barrel datum line, 13th div. 

Multiply this value with 0.01 mm (least count). 13 x 0.01 mm = 0.13 mm.

Calculation:

Given: 

Minimum range = 75.00 mm

Barrel reading = 15.50 mm

Thimble reading = 10 × 0.01 = 0.1 mm

Total = 75 + 15.50 + 0.1 = 90.6 mm

Explanation:

Zero error

When the fixed jaw and sliding jaw are closed, but the zero on the vernier scale coincides with zero on the main scale. Then the vernier caliper does not have zero error.

When the fixed jaw and sliding jaw are closed, but the zero on the vernier scale does not coincide with zero on the main scale. Then the vernier caliper said to have zero error.

There are two types of error

1. Positive error
2. Negative error

Positive zero error

• Positive zero error occurs if zero on the vernier scale lies on right side of zero on the main scale.
• If the error is positive, correction is negative.

Negative zero error

• A negative zero error occurs if zero on the vernier scale lies on the left side of zero on the main scale.
• If the error is negative, correction is positive.

Important Points

Zero error is always subtracted from the observed readings. 

Explanation:

• A surface plate is used to test the flatness of other surfaces or to provide a truly flat datum surface in marking off work for machining. 
• The flat surface provides stability.
• It is also used for the inspection of gauges, jigs, and fixtures.
• Surface plates are generally made of good quality cast iron which is stress-relieved to prevent distortion.
• In order to retain its flatness, a surface pate must be treated with extreme care:
  • Always clean a surface plate with a soft dry cloth before use and cover it after use.
  • Slide heavy objects onto a surface plate rather than lowering them
  • Never hammer anything on a surface plate.

Explanation:

Measuring tool: 

• Measurement is the process or the result of determining the magnitude of a quantity, such as a length or mass. 
• When we measure an object, we are actually comparing it with a known Standard of measurement.
• A measuring tool is a device for measuring length or angles.
• Example: Protractor, Measuring tape, steel rule, etc.

• Classification of measuring instruments based on methods of measurement

  • Direct measuring tool: Determine the actual dimension and size of the workpiece

    Example: Steel rule, Vernier caliper, micrometer, etc.

  •  Indirect measuring tool: Transfer the measurement from the workpiece to the direct measuring instrument, then the comparison is made.

    Example: Divider, calipers, surface gauge, etc.