Question

Which of the following is the best analogy for the trace of a stylus instrument? 
1. A topographical map 
2. A rolling ball 
3. A pinball machine 
4. A phonograph

Answer 1

Correct Answer - Option 4 : A phonograph

Explanation:

Phonograph pickup:

• The stylus system of measurement is the most popular method to measure surface finish.
• The operation of stylus instruments is quite similar to a phonograph pickup.
• A stylus drawn across the surface of the workpiece generates electrical signals that are proportional to the dimensions of the asperities.
• The output can be generated on a hard copy unit or stored on some magnetizable media. This enables the extraction of measurable parameters from the data, which can quantify the degree of surface roughness.

The following are the features of a stylus system:

1. A skid or shoe drew over the workpiece surface such that it follows the general contours of the surface as accurately as possible (the skid also provides the datum for the stylus).
2. A stylus that moves over the surface along with the skid such that its motion is vertical relative to the skid, a property that enables the stylus to capture the contours of surface roughness independent of surface waviness.
3. An amplifying device for magnifying the stylus movements.
4. A recording device to produce a trace or record of the surface profile.
5. A means for analyzing the profile thus obtained.