National Physical Laboratory

Power standards, meters and sensors

RF PowerWaveguide microcalorimeterThe function of the Power Section is to research, develop and disseminate standards of microwave power. Much of the work is directed at supplying traceability to high level standards laboratories accredited through the calibration of transfer standards. We are also able to develop and supply primary power standards and transfer systems.

Present capabilities include:

Power Calorimeters:

NPL has a range of calorimeters in waveguide and in coaxial line. In coaxial line NPL have systems operating in 14 mm line, 7 mm line, 3.5 mm line and 2.4 mm line.

In waveguide, NPL has systems operating from 8.2 GHz to 110 GHz in various bands, and lower frequency waveguide systems can be built to customer specifications.

Coaxial Measuring Systems:

Operating from DC up to 50 GHz, in which sensors are calibrated against coaxial power standards.

These include:

  • Twin load coaxial calorimeters in 14 mm, 7 mm, 3.5 mm and 2.4 mm line.
  • Use of waveguide systems in conjunction with accurately characterised waveguide to coaxial adaptors.

NPL can provide calorimeters and other systems for sale if required.

Waveguide Calibration Systems:

Primary Systems

The primary systems, based on microcalorimetry are capable of measuring the efficiency (power indicated / power delivered) or calibration factor (power indicated / power incident) of thermistor or similar power sensors in a manner traceable to fundamental national standards.  Currently the following waveguide sizes are supported:

WG16, R100, WR90 
WG18, R140, WR62 
WG20, R220, WR42 
WG22, R320, WR28 
WG23, R400, WR22 
WG25, R620, WR15 
WG27, R900, WR10 

Waveguide Transfer Systems

These are based on waveguide multistate reflectometers whose purpose is to enable the estimation of efficiencies (or calibration factors) of power sensors, which need not be of the thermistor or barretter type. The measurement is performed by comparing the power indicated by the sensor to that indicated by a sensor calibrated by microcalorimetry. Multistate systems are available in the waveguide sizes listed above.

Other Measurements: Output match of 50 MHz reference oscillators, power sensor and meter linearity, measurement of splitter/coupler and power sensor composite systems.


Customer Service tel: +44 20 8943 6796

Last Updated: 19 May 2014
Created: 17 Apr 2009


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