It is the degree to which the measuredvalue of the quality characteristicagree with the true value.

The difference between the true valueand the measured value is known aserror of measurement.

Calibration is the process of establishing the relationship between a measuring device and the units of measure.

This is done by comparing a device or the output of an instrument to a standard having known measurement characteristics.

Calibration is the process of configuring an instrument to provide aresult for a sample within an acceptable range.

Eliminating or minimizing factors that cause inaccuratemeasurements is a fundamental aspect of instrumentation design.

The results are used to establish a relationship between themeasurement technique used by the instrument and the knownvalues.

The instrument can then provide more accurate results whensamples of unknown values are tested in the normal usage of theproduct.

A YARD is a unit of length in several differentsystems, including English units, Imperial units, andUnited States customary units.

It is equal to 3 feet or 36 inches, although its length inSI units varied slightly from system to system.

The most commonly used yard today is theinternational yard, which is equal to precisely 0.9144meter.

The meter is the length of the path travelled by light in vacuum during a timeinterval of 1/299 792 458 of a second.

International Prototype meter is defined as the straight line distance, at 0’cbetween the engraved lines of a platinum iridium alloy of 1020 mm of totallength and having a cross-section as shown in the figure.

The graduations are on the upper surface of the web, which coincides with theneutral axis of the section.

The sectional shape gives better rigidity for the amount of metal involved and istherefore economic in use for an expensive metal.

The metre or meter is the basic unit of length in the InternationalSystem of Units (SI).

The metre was defined by the French Academy of Sciences as thelength between two marks on a platinum-iridium bar, which wasdesigned to represent one ten-millionth of the distance from theEquator to the North Pole through Paris.

In 1983, the metre was redefined as the distance travelled by light infree space in 1⁄299,792,458 of a second.

Scale can be accurately embalmed, but the engraved lines posses thicknessand it is not possible to accurately measure.

Scale is used over a wide range.

Scale markings are subjected to wear. However the ends are subjected towear and this leads to undersize measurements.

Scale does not posses built in datum. Therefore it is not possible to align thescale with the axis of measurement.

Scales are subjected to parallax errors.

Assistance of magnifying glass or microscope is required.

Highly accurate and used for measurement of closed tolerances in precisionengineering as well as standard laboratories, tool rooms, inspectiondepartments.

They require more time for measurement and measure only one dimension.

They wear at their measuring faces

They are not subjected to parallax error.

Not a material standard and hence it is not influenced by effects of variationof environmental conditions like temperature, pressure

It need not be preserved or stored under security and thus there is not fear ofbeing destroyed.

It is subjected to destruction by wear and tear.

It gives the unit of length which can be produced consistently at all times.

The standard facility can be easily available in all standard laboratories andindustries

Can be used for making comparative measurements of very high accuracy.