Embed Size (px)
Citation preview
© NMISA 2010
INTERNATIONAL ACTIVITIES AT THE NMISA HUMIDITY LABORATORY DURING 2009/2010
Deona Jonker
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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.
0
1
2
3
4
5
6
7
8
0 25 50 75 100
Co
rrec
tio
n (%
rh)
Relative humidity (%rh)
5°C: HMP233 set
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts) NMISA (2-P generator)
© NMISA 2010
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)
0
1
2
3
4
5
6
7
8
0 25 50 75 100
Co
rrecti
on
(%
rh)
Relative humidity (%rh)
25°C: HMP233 set
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts) NMISA (2-P generator)
© NMISA 2010
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.
0
1
2
3
4
5
6
7
8
0 25 50 75 100
Co
rrec
tio
n (%
rh)
Relative humidity (%rh)
45°C: HMP233 set
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts)
© NMISA 2010
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.
0
1
2
3
4
5
6
7
8
0 25 50 75 100
Co
rrec
tio
n (%
rh)
Relative humidity (%rh)
55°C: HMP233 set
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts)
NMISA (2-P generator) NMISA (generator: modified)
© NMISA 2010
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.
-3
-2
-1
0
1
2
3
0 25 50 75 100
Co
rrecti
on
(%
rh)
Relative humidity (%rh)
5°C: MI70
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts) NMISA (2-P generator)
© NMISA 2010
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.
-3
-2
-1
0
1
2
3
0 25 50 75 100
Co
rrec
tio
n (%
rh)
Relative humidity (%rh)
25°C: MI70
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts) NMISA (2-P generator)
© NMISA 2010
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.
-3
-2
-1
0
1
2
3
0 25 50 75 100
Co
rrec
tio
n (%
rh)
Relative humidity (%rh)
35°C: MI70
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts)
© NMISA 2010
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.
-3
-2
-1
0
1
2
3
0 25 50 75 100
Co
rrecti
on
(%
rh)
Relative humidity (%rh)
55°C: MI70
MIKES Feb-09 NMISA (salts) Dec-09 NMISA (salts)
NMISA (2-P generator) NMISA (generator: modified)
© NMISA 2010
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
© NMISA 2010
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
© NMISA 2010
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
•
© NMISA 2010
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
© NMISA 2010
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
