1 / 27

INTERNATIONAL ACTIVITIES AT THE NMISA HUMIDITY LABORATORY DURING 2009/2010 Deona Jonker

INTERNATIONAL ACTIVITIES AT THE NMISA HUMIDITY LABORATORY DURING 2009/2010 Deona Jonker. Introduction. Need for traceable measurements in the temperature range 5 °C to 55 °C (humidity range 10 % rh to 95 % rh ) Saturated and unsaturated salts provide traceable

yitta
Download Presentation

INTERNATIONAL ACTIVITIES AT THE NMISA HUMIDITY LABORATORY DURING 2009/2010 Deona Jonker

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. INTERNATIONAL ACTIVITIES AT THE NMISA HUMIDITY LABORATORY DURING 2009/2010 Deona Jonker

  2. Introduction • Need for traceable measurements in the temperature range • 5 °C to 55 °C (humidity range 10 %rh to 95 %rh) • Saturated and unsaturated salts provide traceable • measurements only over temperature range of 15 °C to • 30 °C • Bilateral comparison between NMISA and Mikes (Finland) – • compare relative humidity calibration capabilities over • temperature range 5 °C to 55 °C and humidity range 10 %rh • to 95 %rh

  3. Introduction (continued) • NMISA two-pressure generator used in follow-up • measurements to investigate results of bilateral comparison • Two posters presented by NMISA at Tempmeko–ISHM 2010 • symposium

  4. NMISA – MIKES Bilateral Comparison • Comparison arrangements and measurements • Five thermohygrometers used in comparison • Comparison range: • Humidity – 10 %rh to 95 %rh • Temperature – 5 °C to 55 °C; 10 °C intervals (six • temperature points) • Calibrations at MIKES: • By comparison with chilled mirror hygrometers in climatic • chamber

  5. NMISA – MIKES Bilateral Comparison (continued) • Constant temperature; rising humidity; air flow over • sensors • Calibration at NMISA: • In small 100 ml chambers placed in large temperature- • and humidity-variable chamber • Against reference unsaturated salt solutions • Metal filters not removed from sensors • No air flow over sensors • Constant humidity and rising temperature

  6. NMISA – MIKES Bilateral Comparison (continued) • MIKES measured transfer standard set before and after • initial measurements at NMISA • MIKES compiled comparison report • Comparison results: • Results obtained with fifth hygrometer (MI70) agreed • fairly well at most of measurement points • Transfer standard set showed non-linearity in high • humidity range and few other points

  7. NMISA – MIKES Bilateral Comparison (continued) • Possible reasons: • Metal filters over sensors should been removed when • measuring in static conditions (no air flow) • Using the same salt solution at different temperature • points

  8. NMISA – MIKES Bilateral Comparison (continued) • Follow-up measurements: to investigate the influence of metal filters on sensors • Use same 100 ml chambers placed in temperature- and • humidity-variable chamber • Measuring points: • 10 %rh at 5 °C and 15 °C • 50 %rh at 25 °C and 35 °C • 90 %rh at 45 °C and 55 °C • Unsaturated salt solutions as reference standards

  9. NMISA – MIKES Bilateral Comparison (continued) • No air flow over sensors • Metal filters removed from sensors • Results - influence of metal filters much more significant for • transfer standard set than for fifth hygrometer (MI70) • Good laboratory practice to remove filters from sensors • during calibration

  10. NMISA Two-Pressure Generator • Design and improvements made • Generator originally consisted of: • Saturator – 0.9 m long, made of one inch diameter, • stainless steel tubing • 70 L stirred bath • Air bath – to control temperature of test chamber • Compressed air supplied to mass flow controller • to saturator through heat exchanger coil (app. 1.6 m) • to T-piece

  11. NMISA Two-Pressure Generator (continued) • to chilled mirror dew point meter and test chamber for • relative humidity measurements • Pressure and temperature were constantly monitored • Initial design of generator lacked sufficient and proper • temperature equilibrium and air saturation • Modifications: • Add second liquid bath with independent temperature • control

  12. NMISA Two-Pressure Generator (continued) • Bath contains heat exchanger coil (6 m long, made of • 6.35 mm diameter stainless steel tubing) and pre- • saturator coil (1.45 m long, made of 25.4 mm diameter • stainless steel tubing) • Bath placed between mass flow controller and saturator • bath • Heat exchanger coil removed – caused leak in system • Dry air to mass flow controller – to pre-saturator – to main • saturator (no heat exchanger) • Air bath replaced with temperature-variable chamber

  13. NMISA Two-Pressure Generator (continued) • Follow-up measurements: to investigate air flow over sensors • Generator used to investigate influence of air flow over • sensors during calibration • Generator outlet connected to small stainless steel • chambers, connected in series • Small chambers placed in large temperature- and humidity • variable chamber • Flow rate over sensors app. 0.5 l/min

  14. NMISA Two-Pressure Generator (continued) • Measurements performed at 5 °C; 25 °C and 55 °C • At each temperature point – humidity measurements at 10 • %rh to 95 %rh and back to 10 %rh • Measurements with two-pressure generator agreed much • better with MIKES’ results for transfer standard set than did • NMISA’s initial measurements

  15. NMISA Two-pressure generator (continued) Figure 1. Results of the laboratories obtained with the transfer standard set at +5 °C. Error bars show the estimated expanded uncertainty.

  16. NMISA Two-pressure generator (continued) Figure 2. Results of the laboratories obtained with the transfer standard set at +25 °C. Error bars show the estimated expanded uncertainty. (Note: the NMISA result at 95 %rh is off scale (12.9 ± 1.2 %rh)

  17. NMISA Two-pressure generator (continued) Figure 3. Results of the laboratories obtained with the transfer standard set at +45 °C. Error bars show the estimated expanded uncertainty.

  18. NMISA Two-pressure generator (continued) Figure 4. Results of the laboratories obtained with the transfer standard set at +55 °C. Error bars show the estimated expanded uncertainty.

  19. NMISA Two-pressure generator (continued) Figure 5. Results of the laboratories obtained with the fifth hygrometer at +5 °C. Error bars show the estimated expanded uncertainty. The long-term instability is not included.

  20. NMISA Two-pressure generator (continued) Figure 6. Results of the laboratories obtained with the fifth hygrometer at +25 °C. Error bars show the estimated expanded uncertainty. The long-term instability is not included.

  21. NMISA Two-pressure generator (continued) Figure 7. Results of the laboratories obtained with the fifth hygrometer at +35 °C. Error bars show the estimated expanded uncertainty. The long-term instability is not included.

  22. NMISA Two-pressure generator (continued) Figure 8. Results of the laboratories obtained with the fifth hygrometer at +55 °C. Error bars show the estimated expanded uncertainty. The long-term instability is not included.

  23. Tempmeko-ISHM 2010 Symposium • Joint International Symposium on Temperature, Humidity, • Moisture and Thermal Measurements in Industry and • Science – Tempmeko-ISHM 2010, 31 May to 4 June 2010, • Portoroz, Slovenia • Two posters presented: • Improvements made to the NMISA two-pressure • generator • Bilateral comparison of relative humidity standards • between NMISA and MIKES

  24. Tempmeko-ISHM 2010 Symposium (continued) • Typical topics discussed: • Development / improvement of primary humidity • standards (humidity generators) • Hygrometer and moisture sensor developments • Humidity uncertainty estimations • Interlaboratory comparisons • Calibration procedures • Calibration facilities • Industrial applications of humidity measurements

  25. Tempmeko-ISHM 2010 Symposium (continued) • Presentations on interlaboratory comparisons: • Dew-point temperature realizations in the range -50 °C to • +20 °C; 24 NMIs (22 EURAMET, South Africa, Russia) • participated • Bilateral comparison between Egypt (NIS) and Turkey • (TUBITAK UME); dew and frost point temperatures over • the range -40 °C to + 50 °C • Comparison of frost-point temperature scales between • -80 °C and -10 °C; MIKES (Finland), INRIM (Italy), • LNE-CETIAT (France) participated

  26. Tempmeko-ISHM 2010 Symposium (continued) • Presentations on humidity standards: • NIST presented paper on their newly developed • second-generation gravimetric hygrometer and steam • generator • National Metrology Institute of Japan (NMIJ) established • primary humidity standard in trace moisture region using • diffusion tube method • New primary low- and high-range dew-point generators • developed by Croatian NMI in cooperation with MIKES

  27. Tempmeko-ISHM 2010 Symposium (continued) • Paper on psychrometer comparison between NMIs • Denmark, Slovenia, Finland • Paper on homogeneity and stability of humidity test • chambers • Measurement of moisture content in materials: • New facility at NPL (UK) • INRIM (Italy) investigating traceability of moisture content • in wood

More Related