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Temperature measurements

Humidity in gases and mixtures

Range: 0.1 MPa to 3 MPa

Humidity calibrations in a variety of gas species and mixtures at pressures up to 3 MPa (30 bar) 

NPL operates a multi-gas, multi-pressure primary standard humidity generator which has been developed in-house.

Full range options

Humidity calibration can be performed in air, nitrogen, inert gases, methane, hydrogen, natural gas components including mixtures blended in the laboratory or pre-made cylinder gas mixtures, and at pressures from 0.1 MPa to 3 MPa (1 bar to 30 bar):

  • Dew-point temperature range: -60 °C to +15 °C, best uncertainty ± 0.12 °C
  • Water vapour fraction: from 1 μmol/mol to 100 μmol/mol (known informally as ppmv), best uncertainty ± 0.04 μmol/mol to ± 1.25 μmol/mol

In a sub-range

Humidity calibration in air or nitrogen, in pressure sub-range 0.1 MPa to 1 MPa (1 bar to 10 bar):

  • Dew-point range -60 °C to +10 °C, best uncertainty ± 0.07 °C.

Additional services

As well as calibration of hygrometers, traceable to the SI, NPL’s multi-gas multi-pressure humidity facility can also provide a versatile test capability for different aspects of hygrometer performance.

Wider services offered using this facility include research and independent testing for manufacturing, energy, oil and gas, in areas such as:

  • Natural gas mixtures
  • Hydrogen fuel for vehicles
  • Biogas
  • Nuclear blanketing gases

Industrial humidity measurements are made in a wide variety of conditions. But some hygrometer types can be influenced by background gas composition or pressure. These sensitivities are not revealed in typical calibrations carried out in air, near atmospheric pressure. NPL can provide specialised traceable calibration of humidity instruments in the gases and pressures relevant to use, eliminating errors associated with interference of the gas species and pressure dependence. The resulting confidence in the instrument response can improve process control, save money and energy, and improve product quality and safety.

Are you interested in moisture in materials?

Humidity calibrations in air, with smaller uncertainties

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

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