Bilateral comparison in dew-point temperature

Project Description

Since 2003 the company E+E Elektronik Ges.m.b.H. is authorised by Bundesamt für Eich- und Vermessungswesen (BEV) to hold the Austrian national reference for gas humidity. With reference to this decision there exists great mutual interest to compare the national references for humidity. A dew point hygrometer is to be used as transfer standard for the comparison in the range from -20 °C to +65 °C dew point temperature.

Final Report 2005-03-18

Since 2004 E+E Elektronik Ges.m.b.H in Engerwitzdorf, Austria, is maintaining the Austrian national standard for humidity on behalf of BEV - Bundesamt für Eich- und Vermessungswesen, Vienna, Austria. In order to ensure measurement capability and accuracy this bilateral comparison with PTB has been set up. The measurements have been carried out using a chilled mirror hygrometer as transfer standard. The humidity generators at both partners were two-pressure national standard generators.

Five dew- / frostpoint temperatures have been measured by both partners. Each dew- / frostpoint temperature has been realized by three different sets of pressure / temperature values. Each set of pressure / temperature values have been measured at least two times. The results were obtained by recording the resistance of the second Pt-100 PRT of the transfer standard at a measuring current of 1 mA with a resistance bridge. The resistance values have been converted into temperature values using an equation similar to IEC 60751 with individual calibration coefficients for the Pt-100 PRT. The deviations from the reference value recorded in the following table are the mean values for each dew- / frostpoint. From the deviation and the associated expanded uncertainty of each partner the normalized error En was calculated and recorded in the table.

Td, Tf
UPTB (k=2)
UBEV/E+E (k=2)
-20 0,032 0,035 0,054 0,035 0,46
0 0,038 0,035 0,041 0,035 0,05
20 0,029 0,035 0,041 0,035 0,25
40 0,030 0,035 0,053 0,035 0,47
60 0,052 0,035 0,057 0,035 0,10

Thermometry (T)
Dr Norbert Böse, PTB (Germany)
Coordinating Institute
PTB (Germany)