05-11-2012, 04:43 PM
(1-2) Standards of measurement
Standards of measurement.pptx (Size: 849.18 KB / Downloads: 37)
Measuring Distance (Length):
Length is the distance between two points.
SI base unit for length is m
We need to use different unites sometimes:
cm for things like a pencil
Km for long distances like between RAK and Dubai.
Remember:
1m = 100 cm
1Km = 1000 m
1cm = 10 mm
1dm = 10 cm
Measuring Volume
Volume: the amount of space occupied by an object.
You’ll learn how to measure the volume of:
Regular solids, like a cube.
Liquids.
Irregular solids, like a pencil or a crown.
TERMS USED IN METROLOGYSPECIFICATION
Every product and part have some certain characteristics .It gives certain thoughts of that particular product. Its called specification. It gives easy to understand production method.
STANDARD :
Standard is define as , it is a physical quantity which is established by higher authority or organization .This standard is reliable and acceptable to measure physical quantity. Ex. METER
Line Standard
Distance is measured between two lines
A scale is quick and easy to employ
Scale marking are not subject to wear. However significant wear on leading edge leads to under sizing
A scale does not possess a built in datum
Scales are subjected to parallax effect
Not convenient for close tolerance measurement
Less accurate compared to end standard.
End Standard
Distance is measured between two surfaces.
Highly accurate and well suited for close tolerance(0.005) measurement.
Time consuming and prove one dimension at a time.
Subjected to wear on their measuring faces
Have built in datum.
Free from parallax.
Wavelength Standard
Orange radiation of Kr86 in hot cathode discharge lamp maintained at 68C. According this standard meter is defined as 1650763.73 wavelength.
It is not a material standard and hence not influenced by the effects of variation of environmental temperature, pressure, humidity and ageing.
It need not stored under security and thus there is no fear of its being destroyed as in the case of meter and yard.
There are problems of transferring this standard to other standards as in the case of meter and yard.
Easily available to all standardizing houses, laboratories and industries.
Easily reproducible and thus identical standard are available with all.
Can be used for comparative measurements of a much higher accuracy
Calibration
Calibration is a comparison of instrument performance to standards of known accuracy. Calibrations directly link customers' measurement equipment to national and international standards.
The advantages of calibration are accuracy in performing manufacturing operations, reduced inspection, and ensured quality products by reducing errors in measurement.