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Calibration (Terms and Definitions)
19 July 2019 - 13:43, by , in Calibration, No comments

Basic Terms related to Calibration 

  • Calibration range is the region between the limits within which you measure, receive or transmit a quantity. You express it by stating the lower and upper range values. Typically, you check calibration of an instrument at several points throughout the calibration range of the instrument
  • Zero and span values define the limits.
  • The zero value is the lower end of the range.
  • Span is defined as the algebraic difference between the upper and lower range values.
  • The calibration range may differ from the instrument range, which refers to the capability of the instrument.

An electronic pressure transmitter may have a nameplate instrument range of 0-750 pounds per square inch, gauge (psig) and output of 4-to-20 milliamps (mA). However, the engineer has determined he should calibrate the instrument for 0-to-300 psig = 4-to-20 mA. In this example, the zero input value is 0 psig, and zero output value is 4 mA. The input span is 300 psig, and the output span is 16 mA.

Source: ISA

Note: To understand the difference between calibration and instrument range, let's consider an example. A Calibration Technician receive pressure gauge of 300 psi and instructed to calibrate that gauge from 0 to 100 psi according to process requirement. Technician will calibrate the pressure gauge within it’s decided calibration range (0~100psi) and not according to its instrument range (0~300psi). Calibration can be performed on 0, 25, 50, 75 and 100% of its calibration range.

Zero Input Value: 0 psi

Input span: 100 psi

About author:
Fahid completed his Electrical Engineering from Pakistan in 2011 and Msc Quality Management with Distinction from United Kingdom in 2018. Along with the couple of Certifications and Training, he holds Technical and Managerial expertise within the field of Automation, Instrument Calibration, Testing, Quality and Operations Management. He is enthusiast about content writing specifically related to Inspection and Testing Business.

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