National Physical Laboratory

Pressure balance calibration

High pressure gauge and absolute
Pneumatically operated pressure balances
Hydraulically operated pressure balances

NPL provides a UKAS accredited calibration service for both pneumatically (gas) - and hydraulically (oil) - operated pressure balances and the facilities are geared up to carry out this kind of work.

NPL's UKAS accreditation covers the calibration of:

  • Gas-operated pressure balances in the range 3.5 – 7000 kPa
    (in both the gauge and absolute modes)

  • Oil-operated pressure balances in the range 0.5 – 500 MPa

The calibration of a pressure balance determines its effective area and, where appropriate, a pressure dependent term. Pressure balances submitted for calibration are calibrated directly against an NPL working standard that is part of a hierarchy of working, reference and primary standards. Traceability to SI comes from dimensional measurements of the primary standard piston-cylinders.

An NPL Certificate of Calibration for a pressure balance provides the following information:

  • The effective area*
  • A pressure dependent term* (where appropriate)
  • The mass values of the floating elements* (the piston etc)
  • The certified range

* Together with the associated uncertainty

Generally speaking, only high quality laboratory standard pressure balances are considered for calibration at NPL. It is suggested that (lower quality) industrial pressure balances are calibrated at a UKAS accredited laboratory.

Gas-operated pressure balances are calibrated using nitrogen and oil-operated pressure balances are usually calibrated using sebacate (Monoplex® DOS manufactured by the C P Hall Company).


Customer Service tel: +44 20 8943 7070

Last Updated: 5 Mar 2012
Created: 1 Feb 2011


Please note that the information will not be divulged to third parties, or used without your permission