Which of the following instruments is used to measure the surface roughness?
Profilometer
Understanding Surface Roughness Measurement
The question asks to identify the instrument used specifically for measuring surface roughness. Surface roughness is a component of surface texture, and it quantifies the fine irregularities on a surface.
Analyzing the Given Instruments
Let's examine each instrument listed in the options to determine its primary function:
- Profilometer: A profilometer is a measuring instrument used to measure a surface's profile, in order to quantify its roughness. It typically traces a stylus across the surface, recording the vertical displacement.
- Auto-collimator: An auto-collimator is an optical instrument used to measure small angular deviations. It is widely used for alignment and calibration in optical and mechanical systems, not for surface roughness.
- Clinometer: A clinometer is an instrument used for measuring the angle of slope (or tilt) and elevation or depression of an object with respect to gravity's direction. It is also known as an inclinometer. It does not measure surface roughness.
- Optical Square: An optical square is a surveying instrument used to lay out lines at right angles to a chain line or other reference line. It uses prisms or mirrors to achieve this. It is used in surveying, not for measuring surface roughness.
Identifying the Correct Instrument for Surface Roughness
Based on the functions of the instruments, the profilometer is the instrument designed specifically to measure the surface profile and quantify surface roughness.
Summary of Instruments and Uses
| Instrument | Primary Measurement | Relevant to Surface Roughness? |
|---|---|---|
| Profilometer | Surface Profile, Roughness | Yes |
| Auto-collimator | Small Angular Displacements | No |
| Clinometer | Angle of Slope/Tilt | No |
| Optical Square | Right Angles (Surveying) | No |
Therefore, the instrument used to measure surface roughness among the given options is the Profilometer.
Revision Table: Surface Metrology Instruments
| Instrument Type | Principle | Typical Applications |
|---|---|---|
| Profilometer (Stylus) | Mechanical stylus tracing surface profile | Measuring Ra, Rq, Rz, etc. parameters on various surfaces. |
| Optical Profilometer | Interference or focus variation of light | Non-contact measurement of surface topography, complex shapes. |
| Atomic Force Microscope (AFM) | Scanning cantilever tip interaction with surface forces | Nanoscale surface roughness and topography measurement. |
| Roughness Comparator | Visual/tactile comparison with standard samples | Quick, qualitative assessment of surface finish. |
Additional Information: Importance of Surface Roughness
Surface roughness is a critical characteristic in many engineering applications. It affects:
- Friction and Wear: Rougher surfaces generally exhibit higher friction and wear rates.
- Lubrication: Surface texture influences how well a lubricant film can be maintained between moving parts.
- Fatigue Life: Surface irregularities can act as stress concentration points, reducing the fatigue life of a component.
- Corrosion Resistance: Surface finish can influence the susceptibility of a material to corrosion.
- Appearance: The visual quality and feel of a surface are affected by its roughness.
- Part Assembly: Surface finish impacts how well components fit together.
Common parameters used to quantify surface roughness include $R_a$ (arithmetical mean roughness), $R_q$ (root mean square roughness), and $R_z$ (maximum height of the profile).
Important Questions from Surface Roughness
The Centre Line Average (CLA) method for surface finish measurement is also commonly referred to as the _______ value.
For which surfaces, is a spirit level used for testing straightness ?
Mecrin instrument assesses -
The Tomlinson recorder is associated with the measurement of-
The average height from a mean line of all ordinates of the surface, regardless of sign, is the _______.
