The project will investigate the frost point temperature scales as realized by CETIAT, CNR-IMGC, MIKES and VNIIM by a comparison of humidity standards in the frost point temperature range from -80°C to -10°C. A chilled-mirror dew point hygrometer will be used as a travelling standard.The travelling standard hygrometer will be calibrated first at the CNR-IMGC humidity laboratory against its IMGC-02 frost-point generator. Then, it will be delivered to CETIAT humidity laboratory where it will be calibrated by comparison to CETIAT new frost-point generator.
Subsequently, it will be delivered to MIKES where it will be calibrated again by comparison to MIKES frost point generator. The travelling standard hygrometer will come back to CNR-IMGC in order to check for its stability and will, subsequently, be delivered to VNIIM for a calibration against the VNIIM frost point generator. A final calibration to selected frost points will be carried out at CNR-IMGC to check again for its stability.A measurement protocol will be agreed among the participants.
CNR-IMGC will supply the circulating chilled-mirror hygrometer.
Progress Report 2005-03-22
The project investigate the frost point temperature scales as realized by CETIAT, IMGC-CNR, MIKES and VNIIM by a comparison of humidity standards in the frost point temperature range -80°C to -10°C.
A chilled-mirror dew point hygrometer is used as a traveling standard. A measurement protocol was agreed among the participants. The measurement points are -80 °C, -70 °C, -50 °C, -30 °C and -10 °C fp.
The traveling standard hygrometer was characterized and, then, calibrated at the IMGC humidity laboratory against the IMGC-02 frost-point primary generator in April-May 2003.
It was delivered to CETIAT humidity laboratory where it was calibrated by comparison to CETIAT new frost-point generator in June 2003. It was delivered to MIKES where it was calibrated again by comparison to MIKES frost point generator in October 2003. During the calibration, MIKES reported an unusual drift of the instrument readings. It was decided to stop the calibration and send the hygrometer back to IMGC, where a 0,3-0,5 °C drift from initial calibration was measured. The drift was attributed to a failure of the PRTs embedded into the mirror.
The instrument was sent to manufacturer for repair which confirmed the PRTs failure (moisture leakage) and returned it to IMGC at the end of 2004. Currently, it is under test in order to check for its stability. Afterwards it will be calibrated at IMGC and, then, delivered to CETIAT to re-start the comparison exercise according to the agreed project plan.