Reduction in Calibration Uncertainty has Top Laboratory Priority

The UKAS laboratory at Rotronic (UK) has long made a name for itself in high quality calibrations and, thanks to constant improvements in measurement procedures, is growing into one of the most advanced commercial facilities in this specialised field.

The ISO 17025 accredited calibration of humidity and temperature sensors and dew point instruments confirms performance and is increasingly a requirement of industry regulations and company quality management systems. The UKAS laboratory at Rotronic UK has spent the last two years increasing confidence in the calibrations performed and as a consequence lowering the Calibration and Measurement Capability (CMC) of the laboratory. Significant improvements have been made in the measurement procedures for dewpoint and temperature in air, enabling the following projected CMC’s in future: Dew/Frost point measurement (°Cdp/fp): -60 to -40 °Cfp; uncertainty ±0.15 °Cfp (currently ±0.30 to ±0.22 °Cfp); -40 °Cfp to +60 °Cdp; uncertainty±0.11 °Cdp (currently ±0.22 to ±0.30 °Cdp) and +60 °Cdp to 70 °Cdp; uncertainty±0.13 °Cdp (currently ±0.30 °Cdp).

Temperature in air/ °C; 0 °C to +70 °C; uncertainty ±0.05 °C (currently ±0.17 to ±0.26 °C).

In the laboratory RH is derived from vapour pressure formulations. Improvements in dew point and temperature in air CMC ‘s therefore affect the RH CMC’s profoundly. The projected improvement lies in the range 0 to 70 °C; in the worst case RH CMCwill be ±1 %rh. In all parts of the HC2-S specified range covered by the accreditation the CMC is projected to be better than the specification of the probe. This is the first time this has been achieved.

Within the next 12 months the temperaturein air range will be extended from -60 °C to+150 °C, with a projected CMC at <±0.1 °C.The dew/frost point measurement rangewill go down to -90 °Cdp and up to +90 °Cdp in combination with RH calibrationin an extended range up to 90 °C and95 %rh.

For example, at the new upper limit of 90 °C/95 %rh the projected CMC is anticipated to be <±2 %rh and with these levels of calibration measurement uncertainty and range of accredited calibration services, the purpose-built calibration laboratory at Rotronic UK will be one of the most advanced commercial facilities in the world.