Measuring the diameter of a wire using a micrometer
Step 1: Read the zero error (as explained in Steps 4A–C). Step 2: Place the wire between the micrometer’s jaws (between the anvil and spindle).
Step 3: Tighten the jaws by spinning the ratchet until it clicks. Step 4: Read the distance using the Vernier scale.
Step 4A: Note the line on the main scale that is directly in front of the Vernier scale. This gives the distance accurate to half a millimetre.
Step 4B: Note the line on the Vernier scale that lines up precisely with the centre line on the main scale.This improves the accuracy to two decimal places.
Step 4C: Combine the two readings taken to give the distance in millimetres, accurate to one decimal place.
Step 4D: Subtract the ‘zero error’ to give the correct reading. SAMPLE PROBLEM 18E
What is the distance on the micrometer shown in Fig 18.14, assuming a zero error of 0.03 mm?
1 mm 5 05 10 The Vernier scale on a micrometer
Fig 18.14
SAMPLE ANSWER 18E
Step A: The Vernier scale is a little bit past 5.5. Step B: The line on the Vernier scale that lines up with the centre line on the main scale is 7. Step C: The distance, ignoring zero error, is 5.57 mm. Step D: Subtract the zero error; 5.57 0.03 5.54. The distance on the micrometer is 5.54 mm.
EXERCISE 18.3VERNIER SCALE ON A MICROMETER
Q1 What is the reading on the Vernier scale shown in Fig 18.15, assuming no zero error? Q2 What is the reading on the Vernier scale shown in Fig 18.16, assuming a zero error of 0.02 mm?
