Why Least Count in Measuring Instruments are Important? Know Factors by Which Precision and Quality of Products Improve!

Abstract;

In the field of metrology and precision measurement, the concept of least count plays a crucial role. The least count refers to the smallest measurable increment or division on a measuring instrument. Understanding the least count is essential for accurate and precise measurements.

Keywords:

Measuring Instruments, Least Count, Instrument Design, Sensitivity, Precision, Resolution

Learning Outcomes:

After undergoing this article you will be able to understand the following

1. What's exactly Least Count?

2. Why Least Count is important?

3. Name of frequently used measuring instruments and their Least Count.

4. What Factors Affect the Least Count?

5. Applications of Least Count of Measuring Instruments

6. How to calibrate measuring instruments?

7. Advantages of measuring instruments having lowest Least Count.

8. Precautions for measuring instruments

9. Top manufacturers of world best measuring instruments

10. Conclusions

11. FAQs

References

1. What's exactly Least Count?

Least count is a term used in measurement that refers to the smallest unit of measurement that can be made using a particular instrument. It is defined as the reciprocal of the number of divisions on the instrument's scale. 

The formula for Least cont is as follows 

2. Why Least Count is important?

Importance of Least Count of Measuring Instruments

The least count is related to the precision of an instrument; an instrument that can measure smaller changes in a value relative to another instrument, has a smaller "least count" value and so is more precise.

Accurate and precise measurements are crucial in various fields, including engineering, science, manufacturing, and research. The least count of a measuring instrument directly impacts the accuracy of the measurements obtained. 

Instruments with a smaller least count offer higher precision, allowing for more detailed and reliable measurements. Conversely, instruments with a larger least count may introduce more significant measurement uncertainties. 

Therefore, understanding the least count and its implications is essential for obtaining reliable data and ensuring the quality of measurements.

3. Name of frequently used measuring instruments and their Least Count.

Instruments	Least count
Vernier Caliper	0.02 mm
Digital Caliper	0.01 mm
Outsite Micrometre	0.01 mm
Vernier Micrometre	0.001 mm
Digital Micrometre	0.001 mm
Vernier Depth gauge	0.02 mm
Vernier Height Gauge	0.02 mm
Electronic Height Gauge	0.001 or 0.0001 mm
Glass scale	0.1 mm
Steel scale	1 mm
Bevel Protractor	5′ (5 second)
Depth Micrometer	0.01 mm
Digital Protractor	0.1 degree
Pressure gauge	1 bar
Digital Pressure gauge	0.01 bar
Pressure Calibrator	0.001 bar or 0.0001 bar
Laser Interferometer	0.1 nm (nanometre)
Dial gauge	0.01 mm
Measuring tape	1 mm

4. What Factors Affect the Least Count?

Factors Affecting the least count of measuring instruments :

Several factors influence the least count in measuring instruments. Some key factors to consider include:

Instrument Design: 

The design and construction of the measuring instrument play a significant role in determining its least count. Instruments with higher precision often incorporate finer divisions, advanced mechanisms, or digital displays to achieve smaller least counts.

Sensitivity: 

The sensitivity of an instrument refers to its ability to detect small changes or variations. Instruments with higher sensitivity can measure smaller increments, resulting in a smaller least count.

Resolution: 

The resolution of a measuring instrument is closely related to its least count. Higher resolution instruments can discern smaller increments, leading to a smaller least count.

Calibration: 

Regular calibration ensures the accuracy and reliability of measuring instruments. Calibration processes can help identify and correct any errors or deviations that may affect the least count and overall measurement accuracy.

5. Applications of Least Count of Measuring Instruments

Applications of Least Count of Measuring Instruments

The concept of least count is relevant across various types of measuring instruments. Here are a few examples:

Vernier Caliper: 

Vernier calipers are widely used for linear measurements. The least count of a vernier caliper depends on the number of divisions on the vernier scale and the main scale. By aligning the scales, users can read measurements with a high level of precision. therefore the least count of vernier caliper is 0.02mm

Micrometer Screw Gauge: 

Micrometer screw gauges are commonly used to measure small distances or thicknesses. The least count of a micrometer screw gauge is determined by the pitch of the screw and the number of divisions on the thimble scale.

Digital Multimeter: 

Digital multimeters provide electrical measurements such as voltage, current, and resistance. The least count of a digital multimeter is typically defined by the resolution of its display, which determines the smallest increment it can measure accurately.

6. How to calibrate measuring instruments?

A calibration process starts with the basic step of comparing a known with an unknown to determine the error or value of the unknown quantity. However, in practice, a calibration process may consist of "as found" verification, adjustment, and "as left" verification.

When considering how calibration is done, it is important to note that each type of instrument have their own calibration method and process. However, there are general basic steps which must be taken into consideration before commencement of calibration.

First step

Identify the type of instrument you’re calibrating, e.g., Is it a pressure or temperature related instrument?

Second step

Choose the right calibration instrument that can check within the range of the instrument to be calibrated.

Third step

Set up your calibrating environment.

Fourth step

Ensure that every instrument you’re calibrating is properly connected to the calibrator. This will help avert inaccuracies in your readings and prevent you from noting wrong observations.

Fifth step

Now, you perform the calibration. It is however, advised to perform the calibration 2 – 3 times. This is known as “iteration;” done to ensure your readings are accurate. Always do this even if you get the right result the first time.

Sixth step

Note down your readings and calculate if there are any deviations. If there are, check to see if it is within the acceptable deviation of that equipment. If it’s not within the acceptable deviation of that particular equipment, that equipment did not pass that calibration. From the result, recommendations can be given accordingly.

7. Advantages of measuring instruments having lowest Least Count.

The least count is related to the precision of an instrument; an instrument that can measure smaller changes in a value relative to another instrument, has a smaller "least count" value and so is more precise.

The advantages of these instruments are: Accurate results. Improved quality control. Increased productivity.

8. Precautions for measuring instruments

Regularly clean and maintain the condition of all measuring instruments. Lubricate the hinge point on all calipers. Adjust and sharpen as required. Inspect and clean the spindle and anvil of micrometers.

In addition, it should go without saying to never use a measuring instrument to pry or hammer another object. 

In addition, keep instruments from experiencing temperature extremes. If you are handling a measuring instrument, it is important to avoid permitting it to either heat up or cool down.

9. Top manufacturers of world best measuring instruments

Top Testing and Measuring Instruments Manufacturers in India, to name few of them

• MEXTECH.
• Rishabh Instruments.
• Meco Instruments.
• Fluke Corporation.
• Microtek Instrument.
• Rohde & Schwarz India Pvt Ltd.
• Metro Electronic.
• Tektronics.

Top 6 Leading Testing Instruments Manufacturers

1. Presto Stantest

2. Testronix Instruments

3. Instron

4. Mecmesin

5. Imada

6. Mitutoyo 

10. Conclusions

Understanding the concept of least count is essential for anyone working with measuring instruments. The least count determines the precision and accuracy of measurements and plays a crucial role in various fields, including engineering, and science

11. FAQs

Q. What is considered a precision instrument?

As the name suggests, Precision Measuring Instruments are tools or devices used for directly measuring physical quantities, or obtaining measurements indirectly by making calculations on real-world objects in such a manner that one can get precise values.

Q. What are examples of precision measurements?

The closeness of two or more measurements to each other is known as the precision of a substance. If you weigh a given substance five times and get 3.2 kg each time, then your measurement is very precise but not necessarily accurate. Precision is independent of accuracy.

References

• Berka, Karel, 1983. Measurement, Its Concepts, Theories and Problems. Reidel, London.
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• Cooper, M. A. R. 1974. Fundamentals of Survey Measurement and Analysis. Crosby Lockwood Staples, London.
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