The set of operation which establish, under specified conditions, the relationship between
values indicated by measuring instrument or measuring system, or values represented by a
material measure, and the corresponding known value of a measurand.
A quantity subjected to measurement.
An error is something which pertains to a measurement and not to an instrument. An error
is the difference between the value obtained on the basis of a set of measurements and the
conventional true value of the quantity measure.
The uncertainty of a measurement is the range about the measured value within which the
true value or the conventional true value of the measured quantity is likely to lie at the
stated level of confidence.
It is the ability of the measuring instrument to give identical indications or responses
for repeated applications of the same value of the measured quantity, under stated
conditions of use.
Accuracy of Instrument :
The accuracy of an instrument is its ability to give correct results. The accuracy and
repeatability are two different properties of an instrument. Accuracy is a measure of an
instrument's ability to tell the truth, while repeatability is a measure of its ability to
indicate the same value of the measured quantity. Consequently, good repeatability is not
a guarantee of good accuracy. Although poor repeatability is sure sign of poor accuracy.
The maximum permissible distance separating two imaginary parallel planes with in which
the surface under consideration can just be enclosed.
GENERAL ENQUIRES OF
INDUSTRIES REGARDING CALIBRATION :
Q 1. :Is it mandatory to level the surface plate precisely during use ?
Ans. :It is recommended to level the surface plate but in most of the actual uses it is
not Mandatory for small plates upto 1000 x 2000 mm.
Q 2. :If we shift our surface plate from one place to another does it need
Ans. :No, If the surface plate is placed at the same supports where is was originally
levelled /placed there will be no change in flatness upto the size of 1000x2000mm.
Q 3. : Can we calibrate a surface plate with single precision level/Electronic
Ans. :No, Precisely we can not calibrate because sagging of the floor and other Outside
vibrations will introduce errors in precision calibration. The sagging of Floor upto 10
Micron per meter have been observed in industries.
Q 4. :How does Bagson Calibration Lab Controls this sagging effect ?
Ans. :We at Bagson Calibration Lab. use precision electronic level in pair, which gives
the readings in differential mode hence eliminating all these kind of errors.
Q 5. :Can we use 0.1 Micron single probe for the calibration for Slip Gauge ?
Ans. : No, Slip Gauges of 0, 1 and 2 grades can not be calibrated with single probe, As
because the air film and bend in slip gauge introduces error. How ever with 0.1 micron
double probe method and rigid stand the grade 2 Slips gauge can be Calibrated.
Q 6. :Which master equipment is required for the calibration of slip gauges ?
Ans. : Rigid Slip gauge calibrator with double probes of least count of 0.01micron And
reference slip gauge set of grade 00 or grade K are required for the calibration of slip
Q 7. :The instruments are calibrated at 20 Degree Celsius, however in practical
use sometimes they are used at above 35 Degree Celsius , what compensation factor is to be
Ans. :The standard temp. of calibration is 20 degree Celsius but if the master equipment
and jobs under test are of the same material and are stabilized at the same temp. then the
difference in measurement is almost negligible .