Verification and calibration of Vacuum Pressure Gauges

The similarities between pressure gauges verification and calibration

• They are both evaluation methods of measuring instruments and are the two most important ways to ensure the correct indication of instruments.

• They both belong to the field of metrology, which is the activity of achieving unit unity and accurate and reliable measurement values.
  

• In most cases, both are carried out according to the same measurement procedures.
  

The differences between pressure gauges verification and calibration

• The legal constraints of pressure gauges verification and calibration are different. Calibration has no legal requirements and is an act of voluntary service by users. The scope of service and service fees are determined through agreements between both parties. Calibration is not mandatory. However, calibration is a law-enforced act that belongs to the enforcement of metrology management. The target is within the range of legal metrological instruments. Personnel engaged in this activity must obtain a certificate as a legal metrology inspector issued by the relevant metrology administrative department. The charge is in accordance with national regulations, and both mandatory and non-mandatory inspections are considered legal inspections. Mandatory inspections are compulsory.

• Pressure gauges verification and calibration are based on different criteria. Calibration must be based on calibration specifications, calibration methods, or other technical documents recognized by both parties. This can be technical rules, specifications or customer requirements, or it can be established by the calibration agency itself. The calibration agency generally does not need to make a compliance declaration. The user of the measuring instrument evaluates the calibrated equipment according to the calibration results and can determine whether its performance meets the expected requirements.
  

• From the perspective of ensuring accurate and consistent measurement values, pressure gauges verification and calibration are different. Calibration traces values from the bottom up to the national standard, and can be upgraded. Users can choose the laboratory that provides the traceability service, traceability time and method according to their needs. Inspection transfers the value at each level from the national measurement standard to ordinary measuring instruments in a top-down manner.
  

• There are more inspection items than calibration. Inspection includes qualitative tests and quantitative tests, and is a comprehensive assessment of the measurement characteristics and technical requirements compliance of measuring instruments. Calibration generally only involves quantitative tests and only evaluates the indication error.
  

• The format of the result report is different. Inspection issues an inspection certificate or an inspection result notice, while calibration usually issues a calibration certificate. According to ISO/IEC17025:1999, technical bases such as procedures can exempt measurement result uncertainty, so the calibration certificate usually only provides the maximum allowable error or error limits, without providing the measurement uncertainty of the measured results.
  

In order to provide a quantitative statement on the correctness of the measurement results obtained by measuring instruments, calibration needs to establish measurement traceability and provide measurement uncertainty to enable users to establish their confidence in the measurement results obtained from calibration.