What are the Measuring Instruments?

Some Common Measuring Instruments

 

  1. The measuring tape is used to measure lengths of several meters. Measurements are accurate up to 0.01 m. It is suitable for measuring the distance jumped by a long jumper, the distance of the throw of a javelin and the height of a jump by a high jumper.
    What are the Measuring Instruments 1
  2. The meter rule is used to measure lengths of a few centimeters to a meter. Measurements are accurate up to 0.1 cm. It can be used to measure the length of a pencil, the width of a book and the height of a school bag.
    What are the Measuring Instruments 1a
  3. The vernier callipers is used to measure lengths of less than 10 cm. Measurements are accurate up to 0.01 cm. It can be used to measure the external and internal diameters of round objects like pipes and cylindrical containers. It can also measure the thickness of a book, a piece of glass pane and even the width of a crack.
    What are the Measuring Instruments 2
  4. The micrometer screw gauge is used for very small readings. Measurements are accurate up to 0.01 mm. It can be used to measure the thickness of a cardboard, a coin or a key and the diameter of a piece of wire.
    What are the Measuring Instruments 3

Reading the Vernier Callipers

Example 1. Figure shows a pair of vernier callipers being used to measure the diameter of a metal pipe.
What are the Measuring Instruments 4Solution:
Reading on main scale = 2.1 cm
Reading on the vernier scale = 0.07 cm
Therefore, the diameter of the metal pipe = 2.1 + 0.07
= 2.17 cm

Example 2. A boy uses a pair of vernier callipers to measure the width of a handphone as shown in Figure.
What are the Measuring Instruments 5What is the reading of the vernier callipers?
Solution:
Reading on main scale = 4.0 cm
Reading on the vernier scale = 0.04 cm
Therefore, the width of the handphone = 4.0 + 0.04 = 4.04 cm

Zero Errors in Vernier Callipers

What are the Measuring Instruments 6Above Figure shows three possible situations when using a pair of vernier callipers, that is,
(a) no zero error,
(b) positive zero error,
(c) negative zero error.
Hence,
Correct reading = Reading obtained – Zero error
What are the Measuring Instruments 7

Example 3. Figure shows a pair of vernier callipers with zero error being used to measure the thickness of a book.
What are the Measuring Instruments 8What is the thickness of the book?
Solution:
Zero error = +0.03 cm
Reading with zero error = 1.99 cm
Therefore, the thickness of the book
= 1.99 – 0.03
= 1.96 cm

Example 4. Figure shows a pair of vernier callipers with zero error being used to measure the width of a remote control.
What are the Measuring Instruments 9
What are the Measuring Instruments 10What is the width of the remote control?
Solution:
Negative zero error is involved. Hence, the reading cannot be made directly.
Zero error = -(0.63 – 0.6)
= -0.03 cm
What are the Measuring Instruments 11
Reading with zero error = 5.26 cm
Therefore, the width of the remote control = 5.26 – (-0.03)
= 5.29 cm

Example 5. The diagram shows the position of a vernier scale at the main scale of a vernier calipers. What is the value of s?
What are the Measuring Instruments 12Solution:
The reading of the measurement is 5.16 cm.
Hence s = 0.16 cm.

Reading the Micrometer Screw Gauge

Example 6. Figure shows a micrometer screw gauge being used to measure the thickness of a coin.
What are the Measuring Instruments 13What is the thickness of the coin?
Solution:
Reading on the main scale = 2.50 mm
Reading on the thimble scale = 0.27 mm
Thickness of the coin = (2.50 + 0.27) mm
= 2.77 mm

Example 7. Figure shows the scale of a micrometer screw gauge.
What are the Measuring Instruments 14What is the reading of the micrometer?
Solution:
Reading on the main scale = 5.50 mm
Reading on the thimble scale = 0.33 mm
Therefore, the reading of the micrometer = 5.50 + 0.33
= 5.83 mm

Zero Errors in Micrometer Screw Gauge

There are two possible types of zero errors in using the micrometer screw gauge, that is the positive zero error and the negative zero error.
What are the Measuring Instruments 15

Example 8. Figure (a) shows the zero error of a micrometer screw gauge and Figure (b) shows its subsequent reading of a measurement.
What are the Measuring Instruments 16What is the actual value of the measurement?
Solution:
Zero error = +0.01 mm Reading = 4.29 mm
Actual value of measurement = 4.29 – 0.01
= 4.28 mm

Example 9. Figure (a) shows the zero error of a micrometer screw gauge and Figure (b) shows its subsequent reading of a measurement.
What are the Measuring Instruments 17What is the actual value of the measurement?
Solution:
Zero error = -0.01 mm
Reading = 6.30 mm
Actual value of measurement = 6.30 – (-0.01)
= 6.31 mm