Difference between Calibration and Re-ranging

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Calibration:

To calibrate an instrument means to check and adjust (if necessary) its response so the output
accurately corresponds to its input throughout a specified range. In order to do this, one must
expose the instrument to an actual input stimulus of precisely known quantity. For a pressure
gauge, indicator, or transmitter, this would mean subjecting the pressure instrument to known fluid
pressures and comparing the instrument response against those known pressure quantities. One
cannot perform a true calibration without comparing an instrument’s response to known, physical stimuli.

Re-ranging:

To range an instrument means to set the lower and upper range values so it responds with the
desired sensitivity to changes in input. For example, a pressure transmitter set to a range of 0 to
200 PSI (0 PSI = 4 mA output ; 200 PSI = 20 mA output) could be re-ranged to respond on a scale of 0 to 150 PSI (0 PSI = 4 mA ; 150 PSI = 20 mA).

In analog instruments, re-ranging could (usually) only be accomplished by re-calibration, since
the same adjustments were used to achieve both purposes. In digital instruments, calibration and
ranging are typically separate adjustments (i.e. it is possible to re-range a digital transmitter without having to perform a complete recalibration), so it is important to understand the difference.

check about Calibration procedure of DPT transmitter