Calibration of instruments is nothing but comparing the 
actual value of the instrument which u use with the 
standard value of that instrument model.

Calibration of instruments is nothing but comparing the 
actual value of the instrument which u use with the 
standard value of that instrument model......

If an instrument operates throughout it's full range
 with linearity and porportionality when compared to
 an NIST Standard, it is considered in calibration
 ( National Institute of Standards and Technology )

calibration is nothing but the "testing" . it compares the 
actual value to real value and realise that value takes the 
decisions

cALIBRATION IS NOTHING BUT THE COMPARISON BETWEEN THE 
STANDERED VALUE AND THE MEASURED VALUE.

Calibration procedure:
calibration equipment: calibrator with handpump
For ex: Range of Transmitter is 0-100psi

Step1: connect the calibrator to the transmitter 
Step2: connect the multimeter in series with transmitter to 
verify the transmitter o/p in mA
step2: Apply the pressure to the transmitter by hand pump 
in calibrator
Step3: compare whether both calibrator and the transmitter 
showing the same value.if you applied 50 psi throuhg the 
calibrator then the transmitter should have to show the 
same value.If you find any error.Do the zero/span 
Adjustment.by adjusting the zero/span screw 
increasing/decreasing
step4: compare the transmitter and calibrator as per follows
 
calibrator     Transmitter           Transmitter o/p
in psi            in psi                in mA
0                   0                     4
25                  25                    8 
50                  50                    12
75                  75                    16
100                 100                    20