LNE

Workshop « Towards more accurate fixed points » – St Denis – 23-24 November 20061

LNECenter for Scientific and

Industrial Metrology (CMSI)Thermal & Optical Division29, avenue Roger Hennequin

78197 Trappes , France

( [email protected] ),

R. Morice, J.C. Barbaras, N. Fleurence, V. Le Sant, P. Ridoux, J.R. Filtz

G. Bonnier

Temperature Fixed Points Temperature Fixed Points and Thermal Effectsand Thermal Effects


Within the frame of the EUROMET project 732, LNE have shared its activity in two parts :

1. LNE-INM (Saint-Denis) realizes new cells and take in consideration the effects of impurities

2. LNE-CMSI (Trappes is concerned with the thermal environment set up to realize the fixed point.

The present paper deals uniquely with the point 2


Typical uncertainty Budget Calibration of SPRT at the Zinc freezing point

Type A method Repeatability

Standard deviation si = 0.25 mK

Type B method Upper limit of the error

t(mK) ui = t / K

B0 : uncertainty propagated from the triple point

of water : u zn = Wzn*uo,o1

B1: Electrical Measurements 0.35 0.12 B2 : Self heating 0.1 0.03 B3 Internal gas pressure 0.05 0.017 B4 : Spurious effects on the SPRT - Moisture -Electrical noise

0.015 0.005

B5 : Hydrostatic effects 0.02 0.007 B6 : Heat losses 0.5 0.1 7 B7 : Chemical impurities 0.2 0.07 Combined uncertainty :

0,49 mK (at 1 standard deviation level)

Component of uncertainty linked with heat exchanges with the surrounding can be large


In association with a permanent heating process, a customary metal temperature fixed point is designed for :

Maintaining an enclosure at a stable temperature

Realizing uniform temperature enclosure

Affecting a known temperature value


Melting Freezing

Permanent heat flux process

Time

Temperature

Schematic representation of melting and freezing process


Aluminium Freezing UME Cell

Data:

1,986

1,988

1,99

1,992

1,994

1,996

1,998

2

2,002

2,004

0 100 200 300 400 500 600 700 800


03.11.2006 Hart Scientific 1ppm bridge

1,9976001,9976051,9976101,9976151,9976201,9976251,9976301,9976351,9976401,9976451,997650

180 280 380 480 580 680 780 880 980

Aluminium Freezing UME Cell


100% 75% X1 X2 15% 0%

Freezing Point T1

T2

Percentage of remaining liquid


Al Freeezing Point Plateau

Results obtained by my Mai-Huong Vallin at LNE-INM

-3

-2,5

-2

-1,5

-1

-0,5

0

0,5

0 2 4 6 8 10

Thermometer depth of immersion (cm)

Tx-

Tb

ott

om

(mK

)

Tx-Txfond (à 1h30' soit 8% du palier) en mK

Tx-Txfond (à 2h35' soit 13,9%du palier) en mK

Tx-Txfond (à 4h35' soit 24,6% du palier) en mK

Tx-Txfond (à 3h25' soit ~40% du palier) en mK




Variation liée à la pression hydrostatique en mK

Results obtained by my Mai-Huong Vallin at LNE-INM

Tx-Txbottom ; f= 0,08







Hydrostatic pressure effect


Indium cell

Indium guard

Thermometer

Heat fluxsensor

ThermocoupleAirpulsedfurnace

Heaters

Where is located the liquid/solid interface ?


Temperature fixed point

Design of a sealed cell


Percentage of remaining liquid100% 80% 60% 50% 40% 30% 15% 0%


Experimentally observed behaviour Possible effect of an overheating

Melting Point T1

T2

Percentage of formed liquid


Percentage of liquid formed increases

Melting process


Materialization of a temperature fixed point Freezing /melting and permanent heating

• Both freezing and melting are a function of time

• Effect of impurities

• Thermal effects

Phase transition observed through calorimetric process• The result is, in principle, independent of time


Schematic representation of a melt observed in a cryogenic sealed triple-point cell


Cryogenic sealed cell placed in adiabatic calorimeter


Hydrogen (13,8033 K)Deuterium (18,724 K)Neon (24,5561 K)Oxygen (54,3584 K)Nitrogen (63,151 K)Nitrogen (83, 8058 K)Carbon Dioxide (216, 592 K)mercury (234,3156 K)Water (273,16 K)

Multicells


Realisation of the Silver point using a calorimetric method

Simplified scheme :

1, Silver cell 2, thermal insulating material 3, positioning system 4, ceramic tube 5, radiation shields 6, heat pipe 7,cell-holding system 8, heater


Therm om eter

Environm ent

G uard cell

F ixed point ce ll

Heater

Heater

Principle of the adiabatic method used at LNE to realize ITS-90 metal fixed points


BNM-INM/CNAM

Heating constant(for a short while)

Solid Phase Liquid Phase Thermometer

Wall of the cellStainless Steel

Temperature

Distance

Temperature profile in the cell during heating time


Temperature profile in the cell during heating time

Solid Phase Liquid Phase Thermometer

Temperature

Distance

CRTh


Change in Temperature = f (1/F)

0

0,0005

0,001

0,0015

0,002

0,0025

0,003

0,0035

0,004

0 2 4 6 8 10 121/F

F percentage of metal in liquid phase

Ch

an

ge

in

Te

mp

era

ture

in

°C

Melting

Freezing

Aluminium freezing point, constant heat flux method


Change in Temperature T = f(1/F)

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

0 5 10 151/F

F is the percentage of liquid

Ch

an

ge

in T

em

pe

ratu

re

in m

K melting

freezing

Aluminium freezing point. Calorimetric method


Indium cell

Indium guard

Thermometer

Heat fluxsensor

ThermocoupleAirpulsedfurnace

Heaters

Design of the guard cell


In summary:

The principle of using the calorimetric method at any metal fixed point is established.

The actual design has to be improved in order to get a final design.

The final design must be easy to use.

Using calorimetric method induces a better definition of a fixed point temperature.

LNE

Documents

conglation adia2 avec

accurate fixed points

heating timeworkshop

th sorti

temperature t

sans compensation1

sans compen300

sans compensationfr