slide: 1 welcome measurement of temperature in sport, for health and safety john tavener : president...

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Welcome

Measurement of Temperature in Sport, for Health and Safety

John Tavener : President & Head of Laboratories

Isothermal Technology Ltd, UK (Isotech)

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Introduction

In health care all surgical items are regularly sterilised for the health and safety of all patients.Hundreds and thousands of thermometers are used world-wide to measure and control temperatures that save lives by killing bacteria and other pathogens.But what if they are measuring incorrectly?

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IntroductionIn the past, good old liquid-in-glass thermometers were used extensively in all aspects of human endeavour to gauge the condition of a human being by their temperature.Now we use more sophisticated devices such as thermal imaging, tympanic thermometers and radiation pyrometry to measure what is going on around us.The two pandemics of swine and bird flu forced airport authorities to scan the temperature of all passengers for example.

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Other ExamplesIn one example a company making medical products had to withdraw 1 million pounds worth of medical products because his sterilisation process took the product to 120.5°C instead of 121°C.A wrong temperature measurement can mean a patient will not be operated on which could be life-threatening.There are refrigerators in most supermarkets to keep food fresh. If the temperature inside the refrigerators is wrong bacteria can multiply causing the food to be harmful to us humans.

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SolutionThe solution is regular calibration of each and every thermometer. The easiest quickest and cheapest way to calibrate is to compare the thermometers to another thermometer that has been calibrated to a higher standard, in a comparison bath

The company that had to destroy a million pounds of medical supplies used to work this way. Unfortunately calibration by comparison has a number of limitations. The comparison bath can have temperature gradients, the reference thermometer can drift – the cost of this can be 1 million pounds!

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Absolute CalibrationFortunately there is another way to calibrate, for example pure ice and water give an absolute temperature of 0°C. Water boils close to 100°C at sea level. Thermometers can be calibrated at these temperatures without reference to other thermometers or comparison baths

They are called absolute temperaturesI persuaded the medical company in the above example to move from comparison to absolute calibration on basis that bugs die at absolute rather than comparison temperatures

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ITS-90

The temperature scale that applies to everyone around the world specifies a number of absolute temperatures at which pure substances (such as water) melt and freeze This is called the International Temperature Scale of 1990 (ITS-90)

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Some ITS-90 Absolute Points-38.8344°C Triple Point of Mercury

+0.01°C Triple Point of Water

29.7646°C Melting Point of Gallium

156.5985°C Freezing Point of Indium

231.928°C Freezing Point of Tin

419.517°C Freezing Point of Zinc

660.323°C Freezing Point of Aluminium

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Absolute Calibration

Absolute calibration is much easier and more accurate than comparison calibrationCalibration at these temperatures once the substance is set up to be half-liquid, half-solid is extremely fast and very accurate.The down-side of absolute calibration has been cost.

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ISOTowersHowever, recently, by combining the individual components of fixed point cell, and surrounding apparatus the cost of fixed points has tumbled to one third of the previous cost and the new “ISOTowers” can be easily automated to give its absolute temperature all day, every day.In the future we can look forward to a healthier, safer lifestyle.Would you like me to explain how these new ISOTowers work?

Please say yes!

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The most accurate method of calibrating thermometers is in a series of fixed point cells as described in ITS-90.

ITS-90 Fixed Points

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To get the best results from the melt or freeze of a fixed point cell it needs to be placed in an apparatus which is gradient free. Unfortunately no fixed point cell is long enough to eliminate the stem conduction of the thermometer and so the apparatus and cell are designed with heat reflectors, thermal shunts and layers of insulation to reduce stem conduction in the thermometer during calibration

Introduction

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The result is a complicated and expensive compromise, without proper scientific basis. During 2007 an attempt was made to separate the components and recombine them into a more logical and scientific solution.

Introduction

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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 became the inner wall of the heat siphon then a very simple structure of ideal thermal profile would result.Firstly over 160 UKAS certificates evaluating quartz and metal clad cells were compared

Combining Cell and Apparatus

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The analysis showed no detriment occurred to the metal in the cell provided the metal cladding was properly preparedA heat siphon provider was approached who was prepared to share his manufacture process. Perhaps not surprisingly the metals and metal preparation procedures were almost identical to those we use in preparing metal cladding for fixed point cells


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


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Immersion Compensator IC

The depth from metal surface to the bottom of the re-entrant tube is 180mm and this is inadequate for most SPRT’sThe unit under test therefore needs to go through an isothermal zone above the cell set to the cells transition temperature

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Immersion Compensator IC

Called an Immersion Compensator this drilled and heated thermal block sits on top the Siphonic cell

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Working Fluids

ITS-90 Fixed Point Heat Siphon Fluid

Indium Water

Tin Water

Zinc Potassium

Aluminium Sodium

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Isothermal Tower

The Siphonic cells with their Immersion Compensator were assembled into simple desktop apparatus 400mm high with built-in controllers

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Results

CCT/2000-13 “Optimal Realisations of the Defining Fixed Points of the ITS-90 that are used for Contact Thermometry” was chosen as the standard to which the results would be compared, as this document describes “…techniques that should be used when it is desired to achieve realisations at the highest levels of accuracy and precision that can be expected with the best equipment presently available”

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Results

ITS-90 Isothermal Towers of In, Sn, Zn and Al have been evaluated. Eight to ten melts and freezes were made with various settings of the Siphonic Cell and also the Immersion CompensatorPlateau lengths could be varied by offsetting the Siphonic Cell’s temperature from 30+ hours (offset 0.1°C) to 4 hours (offset 0.7°C)

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Graph 1: Siphonic In Fixed Point Cell Melt Plateau (26th April 2008)

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Graph 2: Siphonic In Fixed Point Cell Freeze Plateau (6th May 2008)

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Graph 3: Siphonic Sn Fixed Point Cell Melt

Plateau (27th November 2008)

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Graph 4: Siphonic Sn Fixed Point Cell Freeze Plateau (27th November 2008)

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Graph 5: Siphonic Zn Fixed Point Cell Melt

Plateau (24th February 2009)

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Graph 6: Siphonic Zn Fixed Point Cell Freeze Plateau (25th February 2009)

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Graph 7: Siphonic Al Fixed Point Cell Melt Plateau (14th April 2009)

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Graph 8: Siphonic Al Fixed Point Cell Freeze

Plateau (15th April 2009)

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Indium

CCT/2000-13 Indium

In Siphonic Cell

Coincidence 0.1 to 0.2mK

Length of plateau 10H+

80% melt 1mK

50% freeze 0.5mK

Purity 99.9999% 99.9999%

Conclusion: the Indium Siphonic Cell complies to the requirements of CCT/2000-13 for Indium

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Tin

CCT/2000-13 Tin Sn Siphonic Cell



80% melt 1mK

50% freeze 0.3mK

‘O’ immersion effects btm 30mm

Purity 99.9999%

Conclusion: the Tin Siphonic Cell complies to the requirements of CCT/2000-13 for Tin

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Zinc

CCT/2000-13 Zinc Zn Siphonic Cell



80% melt 1mK

50% freeze 0.5mK


Purity 6N

Conclusion: the Zinc Siphonic Cell complies to the requirements of CCT/2000-13 for Zinc

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Aluminium

CCT/2000-13 Aluminium

Al Siphonic Cell



80% melt 1mK

50% freeze 0.6mK


Purity 99.9999%

Conclusion: the Aluminium Siphonic Cell complies to the requirements of CCT/2000-13 for Aluminium

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Accuracy Temperature Point Uncertainty ±

-38.8344°C Triple Point of Mercury 1mK

+0.01°C Triple Point of Water 0.5mK

29.7646°C Melting Point of Gallium 1mK

156.5985°C Freezing Point of Indium 2mK

231.928°C Freezing Point of Tin 2mK

419.517°C Freezing Point of Zinc 2mK

660.323°C Freezing Point of Aluminium 6mK

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Conclusion

Where Health & Safety are concerned regular absolute calibration of all sensors is to be recommendedIn the past this ideal would have been expensive, only national Laboratories could afford to calibrate this wayRecent developments have dropped the cost to one third of conventional fixed point systems

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Conclusion

The new table top devices are ideals for automating

Only a simple 24 hour timer is required togive the fixed point temperature

All Day – Every DAy

The future is lookingBrighterSaferSimpler

Than was thought possible only 3 years ago

slide: 1 welcome measurement of temperature in sport, for health and safety john tavener : president...

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