Class 11 Automotive Service Technician Chapter 4 Measuring Equipment

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Class 11 Automotive Service Technician Chapter 4 Measuring Equipment

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Measuring Equipment

Chapter: 4

SESSION 1: HANDLING AND USAGE OF DIRECT AND INDIRECT MEASURING INSTRUMENTS

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A. Fill in the blanks: 

1. A ______________ is assigning a value to length, mass and time. 

Ans: Measurement.

2. The measuring instruments, which do not require the help of other ___________ for measuring are called ________________ measuring instruments. 

Ans: Instrument, direct.

3. Steel scale or rule is the ___________ measuring tool. 

Ans: Simplest.

4. The vernier caliper is a ___________ tool used to measure ___________ and external distances accurately. 

Ans: Measurement, internal.

5. In the vernier calliper the sliding jaw containing the ____________ scale, moves over the main scale. 

Ans: Vernier.

6. For measuring the depth of ___________, recesses and ___________ from a plane surface to a projection, the vernier depth gauge is employed. 

Ans: Holes, distance.

7. The micrometer is a precision measuring instrument, used by engineers and technicians for ___________ and measuring the distance between two ___________. 

Ans: Inspection, faces.

8. The digital micrometer the _____________ reading.

Ans: Final.

B. Multiple choice questions: 

1. Direct measuring instruments have a line, which is divided in equal parts, called _________________. 

(a) Graduated scale. 

(b) Firm joint calipers. 

(c) Spring joint meter. 

(d) All of the above. 

Ans: (a) Graduated scale.

2. Which measuring instrument is used to measure internal and external distances precisely? 

(a) Vernier caliper. 

(b) Spring joint meter.

(c) Micrometer. 

(d) None of the above. 

Ans: (a) Vernier caliper. 

3. The least count or the smallest reading which we get with the vernier caliper is calculated as ____________. 

(a) 0.01 cm. 

(b) 0.001 m. 

(c) 0.0001 cm. 

(d) None of the above.

Ans: (a) 0.01 cm.

4. Digital calipers are made of _____________. 

(a) Stainless steel.

(b) Iron. 

(c) Copper. 

(d) Aluminium. 

Ans: (a) Stainless steel.

5. Which devices are used for comparing measurements against known dimensions? 

(a) Firm joint calipers. 

(b) Spring joint callipers. 

(c) Micrometer. 

(d) None of the above.

Ans: (a) Firm joint calipers.

C. Answer the following questions: 

1. Give the importance of measuring instruments.

Ans: Measuring instruments are used to assign values to length, mass, time, or derived units like speed, acceleration, and pressure. In the automotive industry, these instruments are essential for determining the dimensions of various objects. Precision measuring equipment, such as gauges, is vital for the repair and maintenance of automobiles. Knowing the correct measuring tool for specific automotive parts is crucial to ensure accurate measurements and adjustments.

Measuring instruments are very important in many industries and science. They help take accurate measurements and collect exact data. They ensure products are made correctly, help with research, and support decisions. By giving reliable measurements, these tools help find mistakes, avoid problems, and improve how things work. This helps in creating new ideas, keeping things safe, and making processes more efficient.

2. What is the difference between direct and indirect measuring instruments? 

Ans: The difference between direct and indirect measuring instruments are as follows:

Direct	Indirect
Instruments that measure directly without needing any additional tools.	Instruments used when direct measurement is not possible; require comparisons or transfers.
Directly reads the value from the graduated scale or markings.	Measurements are inferred by transferring or comparing dimensions.
Measure quantity directly.	Measure related quantity or effect.
Simple to use, provide immediate results.	Can measure quantities that are difficult or impossible to measure directly, may offer greater accuracy or precision.
Rulers, micrometers, thermometers.	Measuring fluid flow via pressure drop, temperature via resistance changes.

3. Explain the procedure for determining the least count of vernier caliper.

Ans: The procedure for determining the least count of a vernier caliper is as follows:

(i) The sliding jaw is moved along the beam until it comes in contact with the object (e.g., cylinder) placed against the fixed jaw. In this way, the object is held between the fixed and sliding jaws.

(ii) The sliding jaw assembly is then clamped to the main beam with the help of a fine adjustment screw.

(iii) The knife edges of the two jaws are now in contact with the object.

(iv) The main slide assembly is then locked to the beam using the retainer to prevent any movement during the measurement.

(v) Remove the object held in the jaws for reading the measurement, or read the caliper while the object is still held between the jaws.

(vi) Read the main scale reading to the left of the zero of the vernier scale.

(vii) Read the vernier scale division that coincides with a division on the main scale.

(viii) Multiply the reading of the vernier scale with the least count and add it to the main scale reading to arrive at the final reading.

4. How do you determine the least count of micrometer?

Ans: Calculation of least count of a micrometer:

Calculation of least count of a micrometer

Least Count (L. C) = Pitch/No. of divisions on micrometer barrel (thimble) where Pitch = distance travelled by thimble on a linear scale in one rotation, which is usually 0.5 mm, unless mentioned.

For example, the number of divisions on the barrel are 50. Therefore, the least count of the micrometer will be 0.5/50 = 0.01

(i) Read the scale on the sleeve. The example shows 12 mm divisions. 

(ii) Still reading the scale on the sleeve, a further ½ mm (0.5) measurement can be seen on the bottom half of the scale. The measurement now reads 12.5mm. 

(iii) Finally, the thimble scale shows 16 full divisions (16 × 0.01 = 0.16 mm). 

The final measurement is 12.5mm + 0.16mm = 12.66 mm.

5. How do we measure using indirect measuring instruments?

Ans: The simple calipers can be used in these situations. For measuring, the object is held between the ends, the object is then removed, and the ends are placed on a steel scale to determine the distance. These calipers can be used to calculate the length, outside and inside diameters. Some of the calipers are as follows:

(i) Firm Joint Calipers: This device is used to compare measurements against known dimensions. It has two legs which are joined together by a rivet. The legs are set properly so that the working ends meet evenly and closely. The nominal sizes of joint calipers are 100 mm, 150 mm, 200 mm, and 300 mm.

(ii) Spring Joint Calipers: The functions of these calipers are similar to firm joint calipers. The legs of this caliper can be opened and closed by screwing the nut in and out of the bolt.

6. Differentiate between vernier and digital caliper.

Ans: The differences between vernier and digital caliper are as follows:

Vernier caliper	Digital caliper
It is an instrument used to measure internal and external distances precisely.	It is an electronic digital caliper that displays the final reading directly.
Analog display with vernier scale.	Digital display with LCD screen.
Vernier calipers can be more challenging to use for those without experience, as reading the vernier scale accurately can take practice.	Digital calipers are generally considered easier to use, as the measurement is displayed clearly and instantly.
The vernier caliper is a manual caliper commonly used in manufacturing for quality control.	Digital calipers have a “reading hold” feature, which makes it easier to read measurements in difficult or awkward locations.
Manual recording required.	Can often output data to external devices (e.g., PC).

7. Which parameters can be measured with vernier depth gauge?

Ans: The parameters that can be measured with a Vernier depth gauge are the distances from a plane surface to a projection and the depth of holes. The graduated scale in this gauge slides through the base while the vernier scale remains fixed .

8. What are the various alert signs found in a dashboard of a vehicle? 

Ans: The various alert signs found on a vehicle’s dashboard include:

(i) Seat Belt Warning Light – Reminds the driver and passengers to fasten their seat belts.

(ii) Oil Can: Low oil level or oil pressure issue.

(iii) Check Engine Light: This light can indicate a wide range of issues with the engine or emissions system. 

(iv) Tire Pressure Warning Light: Indicates that one or more tires are underinflated. 

(v) Airbag Fault Indicator – Alerts the driver of a fault in the airbag (SRS) system.

(vi) Low Fuel Indicator – Warns that the fuel level is low.

(vii) Brake: Brake system issue (e.g., low brake fluid).

9. Take any object round or square. Measure and write the reading with the help of vernier caliper in the table given below.

S. No	Main Scale Reading(A)	Vernier Scale Reading(B)	Least Count (C)	Least Count x Vernier Scale (BxC=D)	x Vernier Scale (BxC=D) Actual Reading (A+D

Ans: Students do it yourself.

SESSION 2: ANGULAR MEASURING INSTRUMENTS

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SESSION 3: DIAL INDICATOR OR GAUGE AND OTHER GAUGES

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SESSION 4: INSTRUMENTS ON THE DASHBOARD OF A VEHICLE

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