Calibration is the comparison of measured values taken from a device under test, with those of a standard of known accuracy, for the purpose of detecting and reporting, or eliminating by adjustment, errors in the instrument tested.
The calibration standard is normally traceable to a national standard held by an accredited National Metrological Institute such as NIST in USA or the National Measurement Institute Australia (NMIA).
The comparison results in either:
The term calibration means the act of comparison. A compliant calibration does not necessarily include adjustments to bring the instrument up to specified performance. It may only require evidence of performance to within manufacturer’s specification. Note that the results of a calibration have to be written up in a calibration record that lists the calibration points and the correction values at each point with a given uncertainty, determined by the calibration process.
Note that only an accredited metrology laboratory is allowed to produce an official calibration report and only for the scope (parameter and accuracy level of a physical quantity) the laboratory is accredited for.Vacuum calibration and gauge calibration in Sydney.
Within Australia any standard used for calibration purposes needs itself be traceable to the most accurate (primary or working) standard usually held by national metrology laboratories such as NMIA. Depending on the application, the highest level of accuracy may not necessarily be required in calibration of instrumentation / gauges. Calibration at a primary metrology institute can often be a timely and expensive exercise.
The primary standards for pressure and gas (mass) flow are held at the NMIA in Port Melbourne and in Lindfield (Sydney), respectively. These are the most accurate standards available to calibrate against. Vacuum calibration and gauge calibration will become available in Sydney shortly.
In Australia the accreditation body for calibration laboratories is the National Accreditation and Testing Authority (NATA), based in Sydney. This organization performs audits of calibration laboratories to verify / update the scope of accreditation and if ISO NATA 17025 standard is upheld.
Only NATA accredited calibration laboratories are allowed to use the NATA logo on calibration reports they issue, which provides an additional level of confidence to the industry.
Some industries in Australia may require their hardware to be calibrated on a periodic (typically yearly) basis, such as metering devices and a range of transmitters. e.g. for pressure, temperature, electrical power, mass flow rate, force, etc.