# Difference between Calibration and Re-ranging

**URL:** <https://forumautomation.com/t/difference-between-calibration-and-re-ranging/2760>\
**Category:** Calibration\
**Tags:** interviewquestions\
**Created:** [December 3, 2017, 9:54pm UTC](https://forumautomation.com/t/difference-between-calibration-and-re-ranging/2760 "2017-12-03T21:54:40Z")\
**Posts on this page:** 1\
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**Author:** ![sivaranjith](https://forumautomation.com/letter_avatar_proxy/v4/letter/s/ba9def/32.png) [@sivaranjith](https://forumautomation.com/u/sivaranjith)\
**Post date:** [December 3, 2017, 9:54pm UTC](https://forumautomation.com/t/difference-between-calibration-and-re-ranging/2760/1 "2017-12-03T21:54:41Z")

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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](https://automationforum.co/2018/02/calibration-procedure-dpt-transmitter.html)