Calibration Principles:
Calibration is the activity of checking, by comparison with a standard, the accuracy of a measuring instrument of any type.  It may also include adjustment of the instrument to bring it into alignment with the standard.  Even the most precise measurement instrument is of no use if you cannot be sure that it is reading accurately. 


  • Calibration Range – the region between the within which a quantity is measured, received, or transmitted which is expressed by stating the lower and upper range values.
  • Zero Value – The lower end of the calibration range.
  • Span – the difference between the upper and lower range.
  • Instrument Range – the capability of the instrument (may be different than the calibration range)

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.  (Do not confuse the range the instrument is capable of with the range for which the instrument has been calibrated).

An electronic pressure transmitter may have an instrument range of 0-750 psig and output of 4 to 20 milliamps (mA).  However, the engineer has determined the instrument will be calibrated for 0 to 300 psig = 4 to 20 mA.  Therefore, the calibration range would be specified as 0 to 300 psig = 4 to 20 mA. 

Why Calibrate:
Virtually all equipment degrades in some fashion over time.  As components age, they lose stability and drift from their published specifications.  Even normal handling can adversely affect calibration, and rough handling can throw a piece of equipment completely out of calibration even though it may appear to be okay physically.  Regular calibration assures that equipment continually meets the specification required. 

Who Should Calibrate:
When planning and implementing a calibration program it is important to use a provider that is qualified and adheres to a national standard. Choosing a company with accreditation to the ISO 17025 standard is the best choice, and in some industries, required. ISO/IEC 17025: 2005 refers specifically to the requirements of testing and calibration laboratories and lays down very rigorous standards for those that use it. Accredited calibration providers have some oversight protection through their accrediting body with regular audits and reviews, along with specific Quality Management System requirements.

When Should You Calibrate:
Calibration intervals can vary greatly within an industry (or plant).  Frequency depends on the equipment and the type of application.  As a rule, calibration should be performed at least once a year.  In more critical applications, the frequency will be much greater.


All Calibrations should be performed traceable to a nationally or internationally recognized standard.   Traceability is accomplished by ensuring the test standards we use are routinely calibrated by “higher level” reference standards.   Our Calibration technician’s role in maintaining traceability is to ensure the test standard is within its calibration interval and the unique identifier is recorded on the applicable calibration data sheet when the instrument calibration is performed.

 As a leader in Scientific Equipment Repair and Medical Equipment Calibrations, Scientific Instrument Center offers a variety of calibration services that keep your operations consistent and cost effective. 

SIC works with many corporations, universities, and hospital providing the highest level of laboratory services. Whether we are providing biosafety cabinet calibration or medical equipment calibration, we keep your equipment performing to industry codes and regulations.

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