Trends in Temperature Calibration

1. Trends in Temperature Calibration David Southworth VP: Sales and Marketing Isothermal Technology Ltd, UK (Isotech) www.isotech.co.uk

2. Trends in Temperature Calibration • We see from Industry to Primary Metrology a demand for greater accuracy • A demand for more confidence • We have responded with innovative new technology

3. Introducing Isotech • David Southworth • David.Southworth@isotech.co.uk • Worked at Isotech since 1984 • Engineering Background • VP Sales and Marketing since 2006

4. UK Company • Isotech • Established in 1980 • Premier Supplier of Temperature Equipment • Premier UKAS Temperature Calibration Lab • Premier Source of Articles and Training

5. NTPL • NTPL – Isothermal Technology's Calibration Laboratory

6. NTPL • NTPL – Isothermal Technology's Calibration Laboratory • Best Measurement Capability, Gallium Fixed Point Cells • 0.000,07°C! • Within 4uK of NIST Reference Cell – 0.000004°C • +/-0.07mK 2 Sigma Uncertainty (NIST only National Lab with smaller uncertainties

7. National Metrology Institutes use Isotech equipment • Primary Standards • ITS-90 Fixed Points • Standard Thermometers • Associated Equipment Many Nations rely on Isotech for their Primary Temperature Standards

8. Secondary and Industrial • Secondary Calibration Equipment • Liquid Baths • Fluidized Furnace • High Temperature Furnaces • Thermometers • Instruments • Industrial Calibration Equipment • Dry Blocks • Liquid Baths • Probes, Indicators and Software

9. Introducing Isotech • Operated a Calibration Lab Since 1983 • Achieved Accreditation in 1985 • We regularly provide training courses

10. Introducing Isotech • Manufacture Calibration Equipment • Industrial, Scientific and Primary Laboratories • We Use What We Produce • Isotech Lab equipped with Isotech products

11. Introducing Isotech • NTPL equipped with Isotech Products • Industrial, Scientific and Primary Laboratories • UKAS Accreditation • Performance Claims Validated with regular audits

12. Trends in Temperature Calibration • Always a demand for greater accuracy • NEVER less accuracy – always better

13. Trends in Temperature Calibration • We see a demand to improve the accuracy of calibrating industrial sensors • For example Green Buildings • Calibrating Thermistors more accurately can save enormous amounts of money and protect the environment

14. Trends in Temperature Calibration • Isotech Response • Greater Accuracy with innovative fixed Point Solutions • ISOTower • Measuring Systems • milliK

15. Most calibrations are performed by comparing the unknown characteristics of the thermometer under test to a calibrated reference thermometer But how are the reference thermometers calibrated? Introduction

16. The answer is, in a series of known and fixed temperatures where pure substances (usually metals) melt or freeze Introduction

17. Three things are required before a thermometer can be calibrated at a fixed point A fixed point cell (an ingot of pure metal inside a specially shaped graphite crucible) An apparatus or furnace to melt and freeze the ingot of metal uniformly The thermometer must be sufficiently immersed so that the sensing element is at the cell’s temperature Introduction

18. Fixed point systems to National Laboratory standards are very expensive and are also inconvenient if the thermometer is short. So shorter and smaller fixed point systems were developed The shorter, smaller and cheaper fixed points are approximations to those in National Laboratories and they seldom provide sufficient immersion for the thermometer being calibrated Introduction

19. To offer the customer small uncertainties the smaller cells are calibrated in large furnaces and the user must make allowance for the stem conductance of his thermometer This is not very satisfactory Introduction

20. What if we throw the existing ideas out of the window and start again? What if the cell and furnace become one and inseparable? What if the immersion necessary is calculated and compensated? Might we end up with a novel but improved solution to fixed point calibration? A New Approach

21. The key to the new design is a heat siphon in the shape of a Dewar with elongated inner tube The key feature of the Siphonic Dewar is that it is gradient-free so a cell inside will melt and freeze uniformly Next the cell fits snugly inside and is sealed in place surrounded by 1 atmosphere of pure argon New Design (Patents Applied For)

22. The concept was patented and called a Siphonic Cell (S.C.) Combining Cell and Apparatus

23. The ideal apparatus to surround a cell is a heat pipe or heat siphon. If the outer wall of a metal clad fixed point cell also becomes the inner wall of the heat siphon then a very simple structure of ideal thermal profile would result Combining Cell and Apparatus

24. How Does it Work? • Two heaters are used, the main heater for the Siphonic Dewar, the second heats the immersion compensator to the same temperature as the cell

25. Immersion Compensator IC • The depth from metal surface to the bottom of the re-entrant tube is 180mm and this is inadequate for most SPRTs • The unit under test therefore needs to go through an isothermal zone above the cell set to the cell’s transition temperature

26. Immersion Compensator IC • The Immersion Compensator actively provides the Isothermal Zone

27. How Does it Work? • The control temperature is set above the melt temperature – the cell melts. 0.1°C above yields a 30 hours melt. 0.2°C above 15 hours melt etc • Setting the temperature 0.1°C below yields a 30 hour freeze etc

28. Results • A series of melt and freeze plateau graphs follow Slide: 28

29. Siphonic Sn Fixed Point Cell Melt Plateau

30. Siphonic Sn Fixed Point Cell Freeze Plateau

31. Siphonic Zn Fixed Point Cell Melt Plateau

32. Siphonic Zn Fixed Point Cell Freeze Plateau

33. Siphonic Al Fixed Point Cell Melt Plateau

34. Siphonic Al Fixed Point Cell Freeze Plateau

35. German Laboratory Invested in ISOTowers • KK set up a laboratory based on ISOTowers

36. ISOTowers in Germany • Achieved Daaks (formerly DKD accreditation • Tin 3mK • Zinc 3mK • Aluminium 5mK

37. Trends in Temperature Calibration • Always a demand for greater accuracy • As well as ISOTowers we have responded with new instrumentation

38. Trends in Temperature Calibration • Isotech Response for Higher Accuracy • Measuring Systems • milliK

39. milliK • High Accuracy Precision Thermometer • Why called milliK? • One thousandth of a ⁰C, 0.001 ⁰C is 1milli Kelvin, mK • milliK works to this level

40. milliK: Greater Accuracy • Resistance thermometers • 3mK at 0⁰C • 4mK over 1 year • Resolution of 0.0001⁰C, 0.1mK • Thermocouples • 2µV and 4µV over 12 months • For Type K – 4µV =0.1 ⁰C

41. milliK Logging • Other instruments can store up to several thousands of data points • The milliK has capacity to log time stamped data for up to six months internally, add a low cost USB Memory Drive and store a lifetime of data

42. milliK USB • On the same USB you can plug a Mouse / Keyboard to ease entering probe calibration data, Set Programs etc.

43. milliK Innovation • Colour Display • Choice of Strip Chart or Numeric • Includes simultaneous view of all three channels

44. milliK Innovation • Isolated Inputs • High Degree of Galvanic Isolation • Sensor Inputs Isolated from current input • Avoid Problems with high voltage pick up on TC inputs • Safety

45. milliK Innovation • Built in 24VDC PSU • Isolated • Power Transmitters

46. milliK Innovation • Connectivity • Two Serial Ports • For PC connections to PC and Dry Block • Easy to program SCPI Style Interface • Controls ISOTECH Dry Blocks and Baths

47. milliK Innovation • USB Host • Memory Stick / Mouse / Keyboard • Ethernet • Remote control over network

48. Expandable The millisKanner allows for more channels

49. Expanding the milliK • The millisKanner Channel Expander • Connect SPRT, PRT, Thermistor or Thermocouple on any channel • It is not just a scanner

50. So what is the millisKanner? • Expands milliK to have more inputs • Allows for an SPRT, PRT, Thermistor or Thermocouple on any channel