The number of states has now grown to 51. Today, the so-called SI systemВ® comprises 7 base units: kilogram, meter, second, kelvin, ampere, mole and candela. CMM Calibration A CMM can measureThe meter and kilogram were adopted as the superior measurement standard and the production of prototypes, which should then be used as the material measure, was set.

The unit must be established, called the realisation of the definition of a unit.As a rule, each member state has just one of these, to which main measurement standards made of stainless steel are in turn associated and which are recalibrated on an annual basis. Directly affiliated with this are the national kilogram prototypes of the individual member states.NMISA is responsible for Scientific metrology, as explained below. At the peak of achievable accuracy is the international kilogram prototype, see Figure 9.2, a platinum-iridium cylinder which by definition embodies a mass of 1 kg (material measure). The example of the international kilogram prototype demonstrates how the tracing of a measurement is structured. This traceability makes it possible to compare the calibration results of all measuring devices traced back to this measurement standard. ModifiedIf a measuring device is calibrated against a reference that was calibrated at a national institute, the calibration is said to be вЂњtraceable to a national measurement standardвЂќ.

When it comes to precision calibrations, the flowing volume is measured using gravimetric or volumetric calibration rigs. Even the measured volume of flowing liquids is assigned a measurement uncertainty which depends among other things on the reference used. The specification of measurement uncertainty for a flowmeter generally refers to the measuring range outlined in the specifications and is usually stated as a percentage of the measured value or of the measurement range end value. For example, for a measured length, the information 21.0 mm В± 0.5 mm means that there is a 95% chance that the actual value of the measurement result (this can also be called the вЂњagreed valueвЂќ) lies in the range of 20.5 mm to 21.5 mm. Measurement uncertainty refers to the quality or accuracy of the measurement and is usually expressed using the same unit with a вЂњВ±вЂќ after the measurement result. Without this information, the measurement result is incomplete.

The shorter the intervals, the sooner any systematic measurement errors can be detected and corrected. This is known as recalibration or a recalibration interval. To counteract systematic measurement errors caused by ageing, drift, environmental influences or similar, it is necessary to calibrate measuring devices within defined time intervals.

Calibration Definition In Metrology