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What Is Wavelength Standard? Advantages Of Wavelength Standards and Disadvantages of Material Standards

In the line and end standard , the working standard is derived by successive comparison of a physical standard. This may lead to an unaccept...

What Is Wavelength Standard? Advantages Of Wavelength Standards and Disadvantages of Material Standards

Wavelength


In the line and end standard, the working standard is derived by successive comparison of a physical standard. This may lead to an unacceptable error of the standard itself. The dependency of working standard on physical standard is eliminated by using wavelength of monochromatic radiation as a natural and invariable unit of length. By doing so, the definition of standard length relative to the meter is expressed in terms of the accurately known wavelength of light.

Difference Between Line Standard and End Standard in Metrology


Read: Line Standard and End Standard of Measurement - Characteristics, Pros and Cons

Comparison between line standard and end standard is given below.


Line Standard

End Standard

Distance between two engraved lines is used for measurement.

Distance between two flat parallel surfaces is used for measurement.

 

Scale graduations marking are not subjected to wear.

 

End surfaces subjected to wear.

Quick and easy measurement.

Only one measurement at time. So, it is time consuming.

 

Limited accuracy of 0.2mm. It can’t use for close tolerance measurement.

High accuracy. Dimensional tolerance as close as 0.0005mm.

 

It does not has built in datum, so alignment with measurement axis difficult.

It has built in datum, so it is easy to align with measurement axis.

 

Parallax error can be occurred in measurement.

Not subjected to parallax error.

 

Its manufacture is simple and cost low.

Complex manufacturing process required. Cost is high.

 

Example: Meter scale, Yard, etc.

Example: Slip gauges, End bars, Gap gauges etc.

 

 

🔗Difference between material standard and wavelength standard


Line Standard and End Standard of Measurement - Characteristics, Advantages and Disadvantages

linear measurement


What is line standard and end standard?

For accurate measurement, it is crucial to choose a suitable measuring device that suits the particular situation. There are mainly two methods for the measurement of distance. When the distance between two engraved lines is used for the measurement of length then it is called line standard or line measurement. They are used for direct length comparison, and they have no auxiliary devices. The most common line standard is the division marked meter rule.

Comparison Between Systematic Error and Random Error



🔗Systematic Error and Random Error in Metrology


The following table shows the difference between systematic error and random error


Systematic Error

Random Error

A replicable error that are consistently in same magnitude and direction.

Random in nature, magnitude and direction is unpredictable. It can be positive and negative.

Not easy to detect.

Easy to detect.

It can be assessed easily; statistical analysis not required.

Statistical analysis is required.

It cannot be eliminated by repeated measurement.

Can be eliminated by repeated measurement.

Characterization is not necessary.

Characterized by mean, standard deviation, and variance.

Routinely calibration of measuring instrument help to minimize the systematic error.

Calibration of measuring instruments does not affect random error.

Minimization of systematic error increase accuracy of measurement.

Minimization of random error increase repeatability.



Systematic Error and Random Error in Metrology and What Are the Reason for It

Systematic Error and Random Error

No matter how careful you are, there will always be an error in physical quantity measurement. This “error” is a part of measuring process. They are mainly classified into Systematic error and random error.


What is the systematic error in metrology?

The systematic error is defined as the type of error that deviates by a fixed amount from the true measurement. Systematic error is reproducible inaccuracy and that are consistently in the same direction. So, it cannot be eliminated by taking a large number of readings and then averaging them. But This type of error is controllable in both magnitude and direction, can be assessed and minimized by good analysis.

Laws Of Radiation Heat Transfer – Wien’s Law, Kirchhoff’s Law And Stefan-Boltzmann Law

radiation

 

Wien’s displacement law and equation

Wien’s law states that in a black body radiation the wavelength of radiation corresponding to the maximum energy is inversely proportional to the temperature of the body.