CUSTOMER: CUSTOMER ORDER: ITL REFERENCE: DESCRIPTION: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell. IDENTIFICATION: DATE OF CALIBRATION: From 6th October 2009 to 10th October 2009 BASIS OF CALIBRATION: The Isothermal Tower has been inter-compared to one of the Laboratory Reference cells. The temperature scale in use in this Laboratory is the International Temperature Scale of 1990 (ITS 90). This laboratory is accredited in accordance with the recognised International Standard ISO/IEC 17025:2005. This accreditation demonstrates technical competence for a defined scope and the operation of a laboratory quality management system (refer joint ISO-ILAC-IAF Communiqué dated January 2009). The Joint Communique is available on the ILAC website at www.ilac.org on the publications and resources page.

CERTIFICATE OF CALIBRATION ISSUED BY: ISOTHERMAL TECHNOLOGY LIMITED. DATE OF ISSUE: 14th October 2009 CERTIFICATE NO:

Approved Signatory Name: Signature:

Page 1of 7

The Northern Temperature Primary Laboratory is the Calibration Laboratory of Isothermal Technology Limited

This certificate is issued in accordance with the laboratory accreditation requirements of the United Kingdom Accreditation Service. It provides traceability of measurement to recognized national standards and to units of measurement realized at the National Physical Laboratory or other recognized national standards laboratories. This certificate may not be reproduced other than in full, except with the prior written approval of the issuing laboratory.

MEASUREMENTS:

1. The fixed point cell within the Isothermal Tower comprises an ingot of 99.9999 (6N) pure metal in a very high purity graphite crucible, all sealed in metal.

Melt and freeze plateaux were observed, using a Standard Platinum Resistance Thermometer (SPRT) to investigate the slopes of the melt and freeze curves (ref. Isotech Journal of Thermometry Volumes 7.1 and 8.1).

2. The cell was also compared to one of the Laboratories reference cells. For this, a monitor SPRT was placed in each cell. The reference cell was melted and held at 5˚C above the melt temperature overnight whilst the Isothermal Tower was melted and held at 2˚C above the melt temperature overnight. The following day both cells were put onto their freeze plateau in the prescribed manner at the same time. The plateau temperatures of the test and reference cells were recorded for a period of 20 minutes after stabilisation. The SPRT’s were then exchanged and the readings of temperature difference between the test cell and the reference cell recorded for 20 minutes. The SPRT’s were exchanged once more and readings of temperature recorded as before. Finally the remainder of the freeze plateau for both the test and reference cells was recorded to establish that the measurements of temperature difference had been made on the first 25% of the freeze plateau. Each freeze plateau lasted in excess of 10 hours. The inter-comparison was repeated again on subsequent days using separate freezes.

CERTIFICATE OF CALIBRATION Description: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 2 of 7

RESULTS:

The temperature of the test cell has been compared to that of the Isotech Open Primary Reference Aluminium cell which has traceability to the reference cell of NIST, and for which an uncertainty of ± 0.80 mK (2s) has been established. The equilibrium temperature of the calibrated cell differed from that of the reference cell as follows;

INTER-COMPARISON TEST CELL – REFERENCE CELL

(mK)

1 -1.622

2 -1.749

Mean Difference = -1.686 mK Standard Deviation = +/- 0.127 mK (2s)

CERTIFICATE OF CALIBRATION Description: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 3 of 7

UNCERTAINTIES: The principle components of uncertainty in the inter–comparison of the cells were: TYPE A: (statistical)

1. The short term reproducibility of the SPRT in the cells and the effects caused by thermal shock during transfer from one cell to the other.

2. Statistical uncertainties in the resistance measurements, particularly those due to electrical interference from the furnace heater and controller.

TYPE B:

3. The effects of impurities. 4. The effects of different thermal conditions in the furnaces used (ie. temperature gradients) 5. Uncertainties resulting from the bridge measurements.

Reproducibility of the SPRT and the measurements, and interference effects (1 & 2 above) cause Type A (statistical) uncertainties. Impurities contribute to the Type B uncertainty in the freezing point and are estimated from the quality of the freezing plateau obtained. The uncertainty estimates at approximately 95 % confidence (2 standard deviations) for the inter-comparison are given in Table 1. The uncertainty of the inter-comparison was obtained by combining the component uncertainties in quadrature (ie. by calculating the square root of the sum of the squares), and is also at 2 standard deviations. Table 1.

Type A 1 & 2 ± 0.421 mK

Type B 3, 4 & 5 ± 1.775 mK

Uncertainty of Inter-comparison (2s) ± 1.824 mK

CERTIFICATE OF CALIBRATION Description: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 4 of 7

The uncertainty of the equilibrium temperature of the calibrated cell is ±2 mK. (2s), this does not include the mean temperature difference of the calibrated cell to the reference cell. The reported expanded uncertainty is based on a standard uncertainty multiplied by a coverage factor k = 2, providing a level of confidence of approximately 95%. The uncertainty evaluation has been carried out in accordance with UKAS requirements.

NOTES:

1. There is a temperature variation with depth below the metal surface where the ITS 90 defined temperature applies.

2. In the calibrated cell the distance from the metal surface to the bottom of the re entrant

well is 180 mm ± 5 mm. 3. The hydrostatic temperature variation of this cell is 0.0016 mK per mm. 4. The correction should be calculated using the distance between the metal surface and the

mean sensing position of the thermometer in the re entrant well. 5. The ambient temperature was 20 ˚C ± 2 ˚C throughout the calibration.

6. Throughout the inter-comparison the Zone Controller of the Isothermal Tower was set to

12.0.

CERTIFICATE OF CALIBRATION Description: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 5 of 7

29418/3 Isothermal Tower Aluminium Fixed Point Cell MELT PLATEAU 4 17th September 2009 (S.P. 660.8 Deg C, Zone 12.0)

85.1658

85.1659

85.166

85.1661

85.1662

85.1663

85.1664

85.1665

85.1666

85.1667

85.1668

85.1669

85.167

85.1671

85.1672

85.1673

85.1674

85.1675

85.1676

85.1677

85.1678

899600 903200 906800 910400 914000 917600 921200

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670SQ/002 Resistance/Ohms 29418/3 Isothermal Tower Aluminium Fixed Point Cell FREEZE PLATEAU 4

18th September 2009 (S.P. 660.2 Deg C, Zone 12.0)

85.1654

85.1655

85.1656

85.1657

85.1658

85.1659

85.166

85.1661

85.1662

85.1663

85.1664

85.1665

85.1666

85.1667

85.1668

85.1669

85.167

85.1671

85.1672

970000 973600 977200 980800 984400 988000 991600 995200 998800

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670SQ/002 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 6 of 7

29418/3 Isothermal Tower Aluminium Fixed Point Cell MELT PLATEAU 52nd October 2009 (S.P. 661.4 Deg C, Zone 12.0)

85.0742

85.0743

85.0744

85.0745

85.0746

85.0747

85.0748

85.0749

85.075

85.0751

85.0752

85.0753

85.0754

85.0755

85.0756

171000 174600 178200 181800 185400 189000 192600 196200 199800

TIME/SECS

RE

S/O

HM

S

670SQ/014 Resistance/Ohms 29418/3 Isothermal Tower Aluminium Fixed Point Cell FREEZE PLATEAU 5

5th October 2009 (S.P. 660.0 Deg C, Zone 12.0)

85.0731

85.0732

85.0733

85.0734

85.0735

85.0736

85.0737

85.0738

85.0739

85.074

85.0741

85.0742

85.0743

85.0744

85.0745

85.0746

85.0747

85.0748

85.0749

419500 423100 426700

TIME/SECS

RE

S/O

HM

S

670SQ/014 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 493 Isothermal Tower Aluminium Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 7 of 7

CUSTOMER: CUSTOMER ORDER: ITL REFERENCE: DESCRIPTION: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell. IDENTIFICATION: DATE OF CALIBRATION: From 24th September 2009 to 1st October 2009 BASIS OF CALIBRATION: The Isothermal Tower has been inter-compared to one of the Laboratory Reference cells. The temperature scale in use in this Laboratory is the International Temperature Scale of 1990 (ITS 90). This laboratory is accredited in accordance with the recognised International Standard ISO/IEC 17025:2005. This accreditation demonstrates technical competence for a defined scope and the operation of a laboratory quality management system (refer joint ISO-ILAC-IAF Communiqué dated January 2009). The Joint Communique is available on the ILAC website at www.ilac.org on the publications and resources page.

CERTIFICATE OF CALIBRATION ISSUED BY: ISOTHERMAL TECHNOLOGY LIMITED. DATE OF ISSUE: CERTIFICATE NO:

Approved Signatory Name: Signature:

Page 1of 8

The Northern Temperature Primary Laboratory is the Calibration Laboratory of Isothermal Technology Limited

This certificate is issued in accordance with the laboratory accreditation requirements of the United Kingdom Accreditation Service. It provides traceability of measurement to recognized national standards and to units of measurement realized at the National Physical Laboratory or other recognized national standards laboratories. This certificate may not be reproduced other than in full, except with the prior written approval of the issuing laboratory.

MEASUREMENTS:

1. The fixed point cell within the Isothermal Tower comprises an ingot of 99.9999 (6N) pure metal in a very high purity graphite crucible, all sealed in metal.

Melt and freeze plateaux were observed, using a Standard Platinum Resistance Thermometer (SPRT) to investigate the slopes of the melt and freeze curves (ref. Isotech Journal of Thermometry Volumes 7.1 and 8.1).

2. The cell was also compared to one of the Laboratories reference cells. For this, a monitor SPRT was placed in each cell. The reference cell was melted and held at 5˚C above the melt temperature overnight whilst the Isothermal Tower was melted and held at 2˚C above the melt temperature overnight. The following day both cells were put onto their freeze plateau in the prescribed manner at the same time. The plateau temperatures of the test and reference cells were recorded for a period of 20 minutes after stabilisation. The SPRT’s were then exchanged and the readings of temperature difference between the test cell and the reference cell recorded for 20 minutes. The SPRT’s were exchanged once more and readings of temperature recorded as before. Finally the remainder of the freeze plateau for both the test and reference cells was recorded to establish that the measurements of temperature difference had been made on the first 25% of the freeze plateau. Each freeze plateau lasted in excess of 10 hours. The inter-comparison was repeated again on subsequent days using separate freezes.

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 2 of 8

RESULTS:

The temperature of the test cell has been compared to that of the Isotech Open Primary Reference Tin cell which has traceability to the reference cell of NIST, and for which an uncertainty of ± 0.29 mK (2s) has been established. The equilibrium temperature of the calibrated cell differed from that of the reference cell as follows;

INTER-COMPARISON TEST CELL – REFERENCE CELL

(mK)

1 -0.448

2 -0.426

Mean Difference = -0.437 mK Standard Deviation = +/- 0.022 mK (2s)

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 3 of 8

UNCERTAINTIES: The principle components of uncertainty in the inter–comparison of the cells were: TYPE A: (statistical)

1. The short term reproducibility of the SPRT in the cells and the effects caused by thermal shock during transfer from one cell to the other.

2. Statistical uncertainties in the resistance measurements, particularly those due to electrical interference from the furnace heater and controller.

TYPE B:

3. The effects of impurities. 4. The effects of different thermal conditions in the furnaces used (ie. temperature gradients) 5. Uncertainties resulting from the bridge measurements.

Reproducibility of the SPRT and the measurements, and interference effects (1 & 2 above) cause Type A (statistical) uncertainties. Impurities contribute to the Type B uncertainty in the freezing point and are estimated from the quality of the freezing plateau obtained. The uncertainty estimates at approximately 95 % confidence (2 standard deviations) for the inter-comparison are given in Table 1. The uncertainty of the inter-comparison was obtained by combining the component uncertainties in quadrature (ie. by calculating the square root of the sum of the squares), and is also at 2 standard deviations. Table 1.

Type A 1 & 2 ± 0.317 mK

Type B 3, 4 & 5 ± 0.673 mK

Uncertainty of Inter-comparison (2s) ± 0.744 mK

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 4 of 8

The uncertainty of the equilibrium temperature of the calibrated cell is ±0.80 mK. (2s), this does not include the mean temperature difference of the calibrated cell to the reference cell. The reported expanded uncertainty is based on a standard uncertainty multiplied by a coverage factor k = 2, providing a level of confidence of approximately 95%. The uncertainty evaluation has been carried out in accordance with UKAS requirements.

NOTES:

1. There is a temperature variation with depth below the metal surface where the ITS 90 defined temperature applies.

2. In the calibrated cell the distance from the metal surface to the bottom of the re entrant

well is 180 mm ± 5 mm. 3. The hydrostatic temperature variation of this cell is 0.0022 mK per mm. 4. The correction should be calculated using the distance between the metal surface and the

mean sensing position of the thermometer in the re entrant well. 5. The ambient temperature was 20 ˚C ± 2 ˚C throughout the calibration.

6. Throughout the inter-comparison the Zone Controller of the Isothermal Tower was set to

4.0.

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 5 of 8

29418/1 Isothermal Tower Tin FixedPoint Cell MELT PLATEAU 2 (S.P. 231.6 Deg C, Zone 4.0) 14th August 2009

47.7511

47.7512

47.7513

47.7514

47.7515

47.7516

47.7517

47.7518

47.7519

47.752

47.7521

47.7522

47.7523

47.7524

182500 186100 189700 193300 196900 200500 204100 207700 211300 214900 218500 222100

TIME/SECONDS

RE

SIS

TA

NC

E/O

HM

S

670SQ/002 Resistance/Ohms 29418/1 Isothermal Tower Tin Fixed Point Cell FREEZE PLATEAU 2

(S.P. 231.0 Deg C, Zone 4.0) 15th August 2009

47.7505

47.7506

47.7507

47.7508

47.7509

47.751

47.7511

47.7512

47.7513

47.7514

47.7515

47.7516

47.7517

47.7518

252600 256200 259800 263400 267000 270600 274200 277800 281400 285000 288600 292200 295800 299400

TIME/SECONDS

RE

SIS

TA

NC

E/O

HM

S

670SQ/002 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 6 of 8

29418/1 Isothermal Tower Tin Fixed Point Cell MELT PLATEAU 3 (S.P. 231.6 Deg C, Zone 4.0) 16th August 2009

47.7511

47.7512

47.7513

47.7514

47.7515

47.7516

47.7517

47.7518

47.7519

47.752

47.7521

47.7522

47.7523

47.7524

336000 343200 350400 357600 364800 372000 379200 386400 393600 400800

TIME/SECONDS

RE

SIS

TA

NC

E/O

HM

S

670SQ/002 Resistance/Ohms 29418/1 Isothermal Tower Tin Fixed Point Cell FREEZE PLATEAU 3

(S.P. 231.0 Deg C, Zone 4.0) 17th August 2009

47.7505

47.7506

47.7507

47.7508

47.7509

47.751

47.7511

47.7512

47.7513

47.7514

47.7515

47.7516

47.7517

47.7518

428200 431800 435400 439000 442600 446200 449800 453400 457000 460600 464200 467800 471400 475000

TIME/SECONDS

RE

SIS

TA

NC

E/O

HM

S

670SQ/002 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 7 of 8

29418/1 Isothermal Tower Tin Fixed Point Cell MELT PLATEAU 421st September 2009 (S.P. 232.8 Deg C, Zone 4.0).

47

47.0001

47.0002

47.0003

47.0004

47.0005

47.0006

47.0007

47.0008

47.0009

47.001

47.0011

364300 367900 371500

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670/113 Resistance/Ohms

29418/1 Isothermal Tower Tin Fixed Point Cell FREEZE PLATEAU 4 22nd September 2009 (S.P. 230.0 Deg C, Zone 4.0).

46.9985

46.998646.9987

46.9988

46.9989

46.99946.9991

46.9992

46.999346.9994

46.9995

46.999646.9997

46.9998

46.9999

4747.0001

47.0002

47.000347.0004

47.0005

47.0006

449000 452600 456200 459800

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670/113 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 491 Isothermal Tower Tin Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 8 of 8

CUSTOMER CUSTOMER ORDER: ITL REFERENCE: DESCRIPTION: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell. IDENTIFICATION: DATE OF CALIBRATION: From 14th October 2009 to 20th October 2009 BASIS OF CALIBRATION: The Isothermal Tower has been inter-compared to one of the Laboratory Reference cells. The temperature scale in use in this Laboratory is the International Temperature Scale of 1990 (ITS 90). This laboratory is accredited in accordance with the recognised International Standard ISO/IEC 17025:2005. This accreditation demonstrates technical competence for a defined scope and the operation of a laboratory quality management system (refer joint ISO-ILAC-IAF Communiqué dated January 2009). The Joint Communique is available on the ILAC website at www.ilac.org on the publications and resources page.

CERTIFICATE OF CALIBRATION ISSUED BY: ISOTHERMAL TECHNOLOGY LIMITED. DATE OF ISSUE: 20th October 2009 CERTIFICATE NO:

Approved Signatory Name: Signature:

Page 1of 7

The Northern Temperature Primary Laboratory is the Calibration Laboratory of Isothermal Technology Limited

This certificate is issued in accordance with the laboratory accreditation requirements of the United Kingdom Accreditation Service. It provides traceability of measurement to recognized national standards and to units of measurement realized at the National Physical Laboratory or other recognized national standards laboratories. This certificate may not be reproduced other than in full, except with the prior written approval of the issuing laboratory.

MEASUREMENTS:

1. The fixed point cell within the Isothermal Tower comprises an ingot of 99.9999 (6N) pure metal in a very high purity graphite crucible, all sealed in metal.

Melt and freeze plateaux were observed, using a Standard Platinum Resistance Thermometer (SPRT) to investigate the slopes of the melt and freeze curves (ref. Isotech Journal of Thermometry Volumes 7.1 and 8.1).

2. The cell was also compared to one of the Laboratories reference cells. For this, a monitor SPRT was placed in each cell. The reference cell was melted and held at 5˚C above the melt temperature overnight whilst the Isothermal Tower was melted and held at 2˚C above the melt temperature overnight. The following day both cells were put onto their freeze plateau in the prescribed manner at the same time. The plateau temperatures of the test and reference cells were recorded for a period of 20 minutes after stabilisation. The SPRT’s were then exchanged and the readings of temperature difference between the test cell and the reference cell recorded for 20 minutes. The SPRT’s were exchanged once more and readings of temperature recorded as before. Finally the remainder of the freeze plateau for both the test and reference cells was recorded to establish that the measurements of temperature difference had been made on the first 25% of the freeze plateau. Each freeze plateau lasted in excess of 12 hours. The inter-comparison was repeated again on subsequent days using separate freezes.

CERTIFICATE OF CALIBRATION Description: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 2 of 7

RESULTS:

The temperature of the test cell has been compared to that of the Isotech Open Primary Reference Zinc cell which has traceability to the reference cell of NIST, and for which an uncertainty of ± 0.52 mK (2s) has been established. The equilibrium temperature of the calibrated cell differed from that of the reference cell as follows;

INTER-COMPARISON TEST CELL – REFERENCE CELL

(mK)

1 0.767

2 0.808

Mean Difference = 0.788 mK Standard Deviation = +/- 0.041 mK (2s)

CERTIFICATE OF CALIBRATION Description: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 3 of 7

UNCERTAINTIES: The principle components of uncertainty in the inter–comparison of the cells were: TYPE A: (statistical)

1. The short term reproducibility of the SPRT in the cells and the effects caused by thermal shock during transfer from one cell to the other.

2. Statistical uncertainties in the resistance measurements, particularly those due to electrical interference from the furnace heater and controller.

TYPE B:

3. The effects of impurities. 4. The effects of different thermal conditions in the furnaces used (ie. temperature gradients) 5. Uncertainties resulting from the bridge measurements.

Reproducibility of the SPRT and the measurements, and interference effects (1 & 2 above) cause Type A (statistical) uncertainties. Impurities contribute to the Type B uncertainty in the freezing point and are estimated from the quality of the freezing plateau obtained. The uncertainty estimates at approximately 95 % confidence (2 standard deviations) for the inter-comparison are given in Table 1. The uncertainty of the inter-comparison was obtained by combining the component uncertainties in quadrature (ie. by calculating the square root of the sum of the squares), and is also at 2 standard deviations. Table 1.

Type A 1 & 2 ± 0.360 mK

Type B 3, 4 & 5 ± 0.773 mK

Uncertainty of Inter-comparison (2s) ± 0.853 mK

CERTIFICATE OF CALIBRATION Description: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 4 of 7

The uncertainty of the equilibrium temperature of the calibrated cell is ±1 mK. (2s), this does not include the mean temperature difference of the calibrated cell to the reference cell. The reported expanded uncertainty is based on a standard uncertainty multiplied by a coverage factor k = 2, providing a level of confidence of approximately 95%. The uncertainty evaluation has been carried out in accordance with UKAS requirements.

NOTES:

1. There is a temperature variation with depth below the metal surface where the ITS 90 defined temperature applies.

2. In the calibrated cell the distance from the metal surface to the bottom of the re entrant

well is 180 mm ± 5 mm. 3. The hydrostatic temperature variation of this cell is 0.0027 mK per mm. 4. The correction should be calculated using the distance between the metal surface and the

mean sensing position of the thermometer in the re entrant well. 5. The ambient temperature was 20 ˚C ± 2 ˚C throughout the calibration.

6. Throughout the inter-comparison the Zone Controller of the Isothermal Tower was set to

13.0.

CERTIFICATE OF CALIBRATION Description: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 5 of 7

29418-2 Isothermal Tower Zinc Fixed Point Cell MELT PLATEAU 12th October 2009 (S.P. 420.0 Deg C, Zone 13.0)

63.787

63.7871

63.7872

63.7873

63.7874

63.7875

63.7876

63.7877

63.7878

63.7879

63.788

63.7881

63.7882

63.7883

63.7884

63.7885

63.7886

63.7887

1044500 1048100 1051700 1055300 1058900 1062500 1066100 1069700 1073300

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670/113 Resistance/Ohms 29418-2 Isothermal Tower Zinc Fixed Point Cell FREEZE PLATEAU

13th October 2009 (S.P. 419.0 Deg C, Zone 13.0)

63.786

63.7861

63.7862

63.7863

63.7864

63.7865

63.7866

63.7867

63.7868

63.7869

63.787

63.7871

63.7872

63.7873

63.7874

63.7875

63.7876

63.7877

63.7878

63.7879

63.788

1109000 1112600 1116200 1119800 1123400 1127000 1130600 1134200

TIME/SECS

RE

S/O

HM

S

670-113 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 6 of 7

29418-2 Isothermal Tower Zinc Fixed Point Cell MELT PLATEAU 2 15th October 2009 (S.P. 420.0 Deg C, Zone 13.0)

63.787

63.7871

63.7872

63.7873

63.7874

63.7875

63.7876

63.7877

63.7878

63.7879

63.788

63.7881

63.7882

63.7883

63.7884

63.7885

63.7886

63.7887

1299700 1303300 1306900 1310500 1314100 1317700 1321300 1324900 1328500 1332100 1335700

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670-113 Resistance/Ohms 29418-2 Isothermal Tower Zinc Fixed Point Cell FREEZE PLATEAU 2

16th October 2009 (S.P. 419.0 Deg C, Zone 13.0)

63.786

63.7862

63.7864

63.7866

63.7868

63.787

63.7872

63.7874

63.7876

63.7878

63.788

1366000 1369600 1373200 1376800 1380400 1384000 1387600 1391200

TIME/SECS

RE

SIS

TA

NC

E/O

HM

S

670-113 Resistance/Ohms

CERTIFICATE OF CALIBRATION Description: Isotech Model 492 Isothermal Tower Zinc Fixed Point Cell Identification: UKAS Accredited Calibration Laboratory No. 0175 N.T.P.L. Northern Temperature Primary Laboratory, Southport, England Tel. +44 (0) 1704 543830 / 544611 Fax. +44 (0) 1704 544799

CERTIFICATE NO:

Page 7 of 7

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