5901 Series User`s Guide.vp
Contents
1. lt TPW Cell Figure 2 Freeze mantle using a Quick Stick 13 5901 Series Triple Point of Water Cells User s Guide A WARNING Always use extreme care when using liquid nitrogen Contact can burn skin or damage eyes 4 2 3 Metal Pre cooled In Liquid Nitrogen Freezing Process 14 4 3 Pre cool a few metal rods in liquid nitrogen Insert the pre cooled metal rods into the heat transfer liquid in the reentrant well successively Several insertions will be needed to form an adequate ice mantle The Inner Melt A very pure ice water interface surrounding the reentrant well is formed by melting a thin layer of ice next to the well This interface is referred to as the inner melt The inner melt is formed first by pouring a small amount of pre cooled water or alcohol below 2 C into the reentrant well to a level just above the top of the ice mantle A glass rod at room temperature is then in serted into the reentrant well The glass rod is left in place long enough a few seconds to melt the ice mantle free from the reentrant well Test that the mantle is free by gently rotating the cell and observing that the mantle freely rotates about the axis of the reentrant well If the mantle does not rotate warm the rod to room temperature and repeat the process The inner melt should be done each time the cell is used and the test for the existence of a free mantle should be carrie2. Hart Scientific 9 5901 Series Triple Point of Water Cells User s Guide Rev 580501 ENG Limited Warranty amp Limitation of Liability Each product from Fluke s Hart Scientific Division Hart is warranted to be free from defects in material and workmanship under normal use and service The warranty period is one year for the TPW Cell The warranty period begins on the date of the shipment Parts product repairs and services are warranted for 90 days The warranty extends only to the original buyer or end user cus tomer of a Hart authorized reseller and does not apply to fuses disposable bat teries or to any other product which in Hart s opinion has been misused altered neglected or damaged by accident or abnormal conditions of operation or handling Hart warrants that software will operate substantially in accor dance with its functional specifications for 90 days and that it has been prop erly recorded on non defective media Hart does not warrant that software will be error free or operate without interruption Hart authorized resellers shall extend this warranty on new and unused prod ucts to end user customers only but have no authority to extend a greater or dif ferent warranty on behalf of Hart Warranty support is available if product is purchased through a Hart authorized sales outlet or Buyer has paid the applica ble international price Hart reserves the right to invoice Buyer for importation costs of
3. This design has a wide mouth to facilitate the use of crushed dry ice to freeze the mantle The rubber foot allows the cell to rest on the bottom surface of a Dewar vessel when maintained in an ice bath or holding fixture for extra stability and protection while the cell is in use The shell mate rial of the 5901D G is borosilicate glass and the shell material of 5901D Q is fused silica glass Model 5901A G and 5901 A Q Cell are designed after the original NBS cell with a glass support arm While the arm does not impact performance in any ES g g B E o g 3 8 38 39 N N N 8 mm H g g ke S m i 60 mm 60mm 30 mm 5901C G 5901C Q 5901D G Q 5901B G Figure 1 Triple point of water cell designs and dimensions 2 Introduction way some users prefer this design because it facilitates lifting and carrying the cell The arm can be used as a hook for supporting the cell in an ice bath or used as a McLeod gauge for a strictly qualitative check of trapped air in the cell The shell material of the 5901A G is borosilicate glass and the shell mate rial of the 5901A Q is fused silica glass Model 5901B G Cell is a smaller cell that is easy to handle accommodates shorter sensors and can be maintained in an automatic maintenance device such as
4. LOSS OF DATA WHETHER ARISING FROM BREACH OF WARRANTY OR BASED ON CONTRACT TORT RELIANCE OR ANY OTHER THEORY Since some countries or states do not allow limitation of the term of an implied warranty or exclusion or limitation of incidental or consequential damages the limitations and exclusions of this warranty may not apply to every buyer If any provision of this Warranty is held invalid or unenforceable by a court of compe tent jurisdiction such holding will not affect the validity or enforceability of any other provision Fluke Corporation Hart Scientific Division 799 E Utah Valley Drive American Fork UT 84003 9775 USA Phone 1 801 763 1600 Telefax 1 801 763 1010 Email support hartscientific com www hartscientific com Subject to change without notice Copyright 2005 Printed in USA Table of Contents 1 Before Yon Start wise aco oe ew RS we ES 1 1 1 Symbols Used o oce testura eo cR 1 1 1 1 Warnings ps x Baa a EUR EOS 3 2 1 1 2 CAUTIONS xa y Meow DOR ENCWUM ee HEED Hee NS 2 2 Introduction ID HA 5 3 Specifications eee Ro Ux 9S OOS 9 4 Freezing an Ice Mantle inthe Cell 11 4 1 Preparations x a oce Si Bik el a Be V Se RS 11 4 2 Freezing s rey wd dhe heehee See E 11 4 2 1 Dry Ice Freezing PrOGeSS o o xo A RA A 11 4 2 2 The Heat Pipe Freezing
5. Process ae 12 42 3 Metal Pre cooled In Liquid Nitrogen Freezing Process 14 4 3 The Inner Melt Ree a 14 5 Maintenance and Life Time of a TPW Realization 15 6 Using the Cell cessen cesson we 17 7 Isotopic Composition ee eee 19 8 Careof Your TPW Cell 2 nics ieee eee wee was 23 9 REFERENCES 5x95 o9 ee Rw RS RO 25 Figures Figure 1 Figure 2 Triple point of water cell designs and dimensions Freeze an ice mantle using a Quick Stick Tables Table 1 International Electrical Symbols s lii 1 Before You Start Symbols Used 1 1 Before You Start Symbols Used Table lists the International Electrical Symbols Some or all of these symbols may be used on the instrument or in this manual Table 1 International Electrical Symbols Symbol Description No AC Alternating Current A9 AC DC Battery CE Complies with European Union Directives P DC Double Insulated Electric Shock Fuse PE Ground Hot Surface Burn Hazard Read the User s Manual Important Information Off On 5 5901 Series Triple Point of Water Cells User s Guide Symbol Description Canadian Standards Association US OVERVOLTAGE Installation CATEGORY II Pollution Degree 2 per IEC1010 1 re CATI fers to the level of Impulse Withstand Volt
6. degas we should pay attention not only to the isotopic composition of the original water but also to the manufacturing technique Now we are glad to announce that the isotopic composition of water in Hart TPW cells is nearly identical to V SMOW The actual isotope ratios of water in a Hart TPW cell are as the follows dD 0 0 010 10966 0 0 001 1 0960 The uncertainty from the isotopic deviation and variation of water in Hart TPW cells is estimated to be less than 7 uK 0 007mK An isotopic composition analysis report sampling analysis is attached in the TPW certificate The wa ter sample used for the analysis was directly taken from the final TPW cell after 7 Isotopic Composition degas and sealing process As a matter of course the water used in TPW cell manufacturing process is analyzed every month In order to reduce the uncertainty further an individual isotopic composition analysis for a TPW cell is available Hart provides two options 1 When you order a TPW cell you can order a water sample about 10 ml in an ampoule at the same time The water sample was directly taken from the final TPW cell after the degas and sealing process So the isoto pic composition of the water sample is exactly the same as the one in the TPW cell You can send the water sample to the laboratory of your choice to get an isotopic analysis The actual isotopic composition of the water in the TPW cell will be known more accurat
7. ice Neither the SI definition of the Kelvin the unit of the thermodynamic temperature as 1 273 16 of the thermodynamic temperature of the triple point of water nor the official ITS texts ITS 90 and IPTS 68 spec ify the isotopic composition of water for the TPW Some suggest that docu ments published by BIPM such as Supplementary Information for the International Temperature Scale of 1990 4 and Supplementary Information for the IPTS and EPT 76 specify that the isotopic composition of water for TPW should be substantially the same as ocean water The followings excerpts are taken directly from Supplementary Information for the International Temperature Scale of 1990 An operating triple point cell contains ice water and water vapor all of high purity and of substantially the isotopic composition of ocean water Variations in the isotopic content of naturally occurring water can give rise to detectable differences in the triple point temperature Ocean water contains about 0 16 mmol of per mole of H 0 4 mmol of 7 and 2 mmol of per mole of O this proportion of heavy isotopes is almost never exceeded in naturally occurring water Continental surface water normally contains about 0 15 mmol of per mole of H water coming from polar snow or glacial ice may occasionally contain as little as 0 1 mmol of per mole of H The purifying of water may slightly modify its isotopic composition distill
8. repairs replacement parts when product purchased in one country is submitted for repair in another country Hart s warranty obligation is limited at Hart s option to refund of the purchase price free of charge repair or replacement of a defective product which is re turned to a Hart authorized service center within the warranty period To obtain warranty service contact your nearest Hart authorized service center or send the product with a description of the difficulty postage and insurance prepaid FOB Destination to the nearest Hart authorized service center Hart assumes no risk for damage in transit Following warranty repair the product will be returned to Buyer transportation prepaid FOB Destination If Hart de termines that the failure was caused by misuse alteration accident or abnormal condition or operation or handling Hart will provide an estimate or repair costs and obtain authorization before commencing the work Following repair the product will be returned to the Buyer transportation prepaid and the Buyer will be billed for the repair and return transportation charges FOB Shipping Point THIS WARRANTY IS BUYER S SOLE AND EXCULSIVE REMEDY AND IS IN LIEU OF ALL OTHER WARRANTIES EXPRESS OR IMPLIED IN CLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABLILTY OR FITNESS FOR A PARTICULAR PURPOSE HART SHALL NOT BE LIABLE FOR ANY SPECIAL INDIRECT INCI DENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES INCLUDING
9. 0003799 8 Variations in isotope ratios are conventionally reported as deviations from V SMOW 8 50 180 160 sample 180 150 V 85MOW 150 150 V S5MOW and similarly for D and 6 7O Usually the results are in the parts per thousand range so are expressed as per mil per thousand c For isotopic compositions near V SMOW the effect of the isotopes can be ap proximated by a liner function of the delta values Tmeas TV SMOW AD D A 708 70 A 806 80 There are few measurements of the isotopic depression constants The most precise are by Kiyosawa 1991 who measured the melting point elevation of samples of water enriched with D and The depression constants were found from Kiyosawa s data to be AD 628 6 uK and A 502641 23uK The value of A O is inferred as 57 uK The delta values 6D 6 7O and 6 O for precipitation meteoric waters are highly correlated Approximate relationships are 5D 8 6 80 0 01 and 1 6 70 1 6 80 0 528 Therefore the temperature correction can be predicted from measurements of D only according to Tmeas TV SMOW uK 712 X 0 8 A great effort has been made at Hart to reduce the uncertainty of TPW due to variations in the isotopic composition of water We try to make the final isoto pic composition of water in a Hart TPW as close to V SMOW as possible Be cause the isotopic composition of water will change during each operation of the manufacturing process distill and
10. a tion normally entails a decrease in the H content and the isotopic composi tion at an ice water interface is very slightly dependent on the freezing technique A decrease of 10 umol of H per mole of H corresponds to a decrease of tem perature of the triple point of about 40 uK this is the difference between the triple points of ocean water and the normally occurring continental surface wa ter An extreme and quite atypical difference in the triple point temperatures of naturally occurring water is about 0 25mK and is that between sea water and water obtained from melted polar ice Recently D R White et al has made a deep investigation on the effect of isoto pic content on triple point temperature of water 12 The follows are some in formation from White s paper The international science community through the International Atomic Energy Agency uses a defined Standard Mean Ocean Water SMOW as a point of reference for studies in the isotopic composition of waters Measurements of isotopic composition are made with respect to V SMOW Vienna SMOW and SLAP Stand Light Antarctic Precipitation two standard reference materials waters 19 5901 Series Triple Point of Water Cells User s Guide 20 that span the isotopic range of naturally occurring waters Absolute measure ments of the isotope ratios for V SMOW give D H V SMOW 0 00015576 5 180 160 V SMOW 0 00200520 45 and 70 150 V SMOW 0
11. a Hart Scientific Model 9210 Despite this cell s diminutive size it is made with the same materials and technology used to make larger cells The 5901B has an expanded uncertainty of 0 0002 C and a reentrant well diameter of 8 mm The shell material of 5901B G is borosilicate glass Model 5901C G and 5901C Q cell are identical to models 5901 G and 5901 Q cells with the exception of the reentrant well diameter which is 13 6 mm and 14 4 mm respectively rather than the standard 12 mm The larger reentrant well diameter is designed to accommodate larger diameter thermometers The shell material of the 5901C G is borosilicate glass and the shell material of the 5901C Q is fused silica glass Water impurities and remnant gas are the two primary sources of error for the TPW cell therefore Hart Scientific cells are designed to minimize the effects of these two errors Both factors lower the equilibrium temperature within the cell A higher equilibrium temperature in an inter comparison usually indicates a higher quality cell High quality borosilicate glass and fused silica glass are used in the construc tion of the shell material for TPW cells The contamination rate of impurities from or through the glass into water is extremely low for these types of glass The TPW cell must be assembled with scrupulous attention to the requirement that the water remain free of impurities Meticulous cleaning of all parts is ex tremely important in the manufac
12. age protection provided Equipment of OVERVOLTAGE CATEGORY II is energy consuming equipment to be supplied from the fixed installation Examples include household office and laboratory appliances C TIC Australian EMC Mark The European Waste Electrical and Electronic Equipment WEEE Directive 2002 96 EC mark Sz 1 1 1 A Warnings Always use extreme care when using liquid nitrogen Contact with liquid nitro gen can cause frost bite or severe freezer burns Use extreme caution when using dry ice Contact with dry ice can cause frost bite or severe freezer burns 1 1 2 Cautions Read section entitled Care Of Your TPW Cell before removing the cell from the case Incorrect or improper handling of the cell can damage or break the cell DO NOT shake the cell DO NOT invert the cell too fast as the cell can break due to the water ham mer explained in Section 8 Care of Your TPW Cell If the cell does not produce a water hammer the cell may be broken even though there are no visible cracks DO NOT allow the entire cell to freeze as the cell will break Avoid the formation of an ice bridge from the reentrant well across the surface to the outer glass cylinder of the cell while freezing the ice mantle This may cause sufficient pressure to break the glass While freezing the ice mantle the mantle should never become so thick that it comes in contact with the outer glass shell or the cell will break The Cell
13. and Quick Stick if used need to be well supported during the freez ing process or the cell may be damaged or broken DO NOT drop probes into the reentrant well of the cell The cell and or probe will be damaged or broken 1 Before You Start Symbols Used It is suggested that the TPW cell be kept in the vertical position during transportation The cell must be transported at temperatures above 0 C Avoid vibration and jarring during transportation The effect of the water ham mer can break the cell Store the cell in temperatures above 0 C DO NOT allow the water in the cell to freeze too quickly Rapid freezing of the water in a TPW cell will break the cell 2 Introduction Introduction The temperature of the TPW is the intrinsic temperature of pure water with the three phases of water ice and water vapor in thermal equilibrium The tempera ture of the TPW 273 16K 0 01 C is 0 01 C above the melting point of ice the ice point The ice point was historically one of the defining fixed points of the Thermodynamic Temperature Scale and the International Temperature Scale ITS 27 and ITS 48 The equilibrium temperature of three phases of a pure material is unique The equilibrium of three phases of a pure material can only exist at a unique pressure Whereas the equilibrium temperature between two phases i e melting point and boiling point varies with pressure There fore a special pressure must be assigned to
14. d out regularly during the course of a use of the Cell Once the mantle has been aged and the ice water interface created the triple point of water cell is ready to make measurements 5 Maintenance and Life Time of a TPW Realization Maintenance and Life Time of a TPW Realization After a short period of time the ice mantle will reattach to the reentrant well Pressure can build up in this layer and observed temperatures can be low by as much as 0 0001 C The mantle must of course again be freed by the tempo rary insertion of a warm rod in the well as described in section 4 3 The cell should be prepared at least two days prior to its use The equilibrium temperature in a TPW cell is a little low 0 0005 C immediately after freezing The reason for this low initial temperature and the subsequent gradual increase during one or two days to a steady value is believed to be connected with struc tural strains that are produced when the ice is first frozen Presumably the strains are relieved with time as the ice anneals The magnitude of the lower initial temperature and the rate of increase to a steady temperature value is de pendent upon the specific technique that is employed in freezing the cell A TPW cell with an ice mantle can be preserved for a few months in a well controlled bath or in a Dewar filled with crushed ice with a plastic container be tween the Dewar and the TPW cell The temperature uniformity and stability of the bat
15. ely A mini correction for the isotopic composition can be made if necessary In this way the uncertainty component from the isotopic composition might be reduced to about 3 uK Model No 5901 SMPL 2 You can order an analysis report with a TPW cell Hart will send a water sample water is taken same as option 1 to a laboratory of our choice for the isotopic analysis the report will be delivered along with the cell Model No 5901 ITST 21 8 Care of Your TPW Cell Care of Your TPW Cell The TPW cell is an extremely delicate device Great care must be taken in han dling using and transporting the cell The glass outer shell is easily broken It is suggested that the TPW cell be kept in the vertical position during transporta tion Avoid violent vibration and jarring during transportation because TPW cells can be broken by the shock of the water hammering against the cell walls The lack of cushioning air in the cell allows the water vapor to convert instantly to liquid water such that the glass receives the full impact of the liquid mass in motion This explains the typical clicking sound of an airless cell as the water in the cell is gently rocked back and forth If the cell does not produce a water hammer the cell may have a leak The surrounding temperature during trans portation and storage should be above 0 C It is very hazardous to the TPW cell to be exposed to an area where the temperatures are or can be below 0 C Rapid fre
16. ete visibility of the cell Use dry ice that is ground or crushed to 2 mm diameter granules which is the consistency of snow Introduce small amounts into the dry well until a mantle is formed at the bottom and then introduce more dry ice until the level is near the top of the cell As the dry ice sublimates continue to refill the reentrant well so that the level is maintained at the water level If the dry ice level be comes too low before more is added the mantle may crack which will require additional annealing time Formation of an ice bridge from the reentrant well across the surface to the outer glass cylinder of the cell while freezing the ice mantle may cause sufficient pressure to break the glass The bridging can be prevented by warming that portion of the cell with the hand while shaking it gently sideways to agitate the surface of the water and allow it to wash over the ice The mantle should never become so thick that it comes into contact with the outer glass or breakage could occur In the vertical position the mantle will appear larger than it actually is due to the magnification created by the cylindri 11 5901 Series Triple Point of Water Cells User s Guide 4 2 2 cal container and the water If the cell is carefully inverted the true mantle size can be observed through the portion of the cell containing only vapor This pro cedure should only be performed while the mantle is still attached to the reentrant wel
17. ezing of the water in a TPW cell will break the cell Never allow an ice bridge ice freezes completely across the top surface in the cell to form across the top surface of water in the cell If an ice bridge forms on the top in a TPW cell it should be melted immediately otherwise the pres sure built from water freezing below the top will break the cell Check the TPW cell regularly during maintenance in a bath or Dewar If a TPW cell is pre served in very cold environment the ice mantle will grow As soon as the ice mantle touches the outer shell the cell will rupture in a short period of time 23 9 REFERENCES REFERENCES 10 11 12 13 10th General Conference on Weights and Measures 10th CGPM 1954 3th General Conference on Weights and Measures 13th CGPM 1967 1968 Resolutions 3 and 4 p 104 Preston Thomas H The International Temperature Scale of 1990 ITS 90 Metrologia Vol 27 p 3 10 1990 ibid p 107 BIPM Supplementary Information for the International Temperature Scale of 1990 1990 Mangum B W Furukawa G T Guidelines for Realizing the Interna tional Temperature Scale of 1990 ITS 90 NIST Technical Note 1265 U S Government Printing Office Washington D C 20402 Aug 1990 Schooley James F Thermometry CRC Press Boca Raton Florida 33431 Chap 3 p 40 1986 Riddle J L Furukawa G T and Plumb H H Platinum Resistance Thermometry NBS Monograph 126 U S Govern
18. h used to maintain TPW cells should be 0 003 C or better Hart s 7012 and 7312 baths are designed for this purpose The 7012 bath can accommodate up to four TPW cells and the 7312 bath up to two According to our experience the bath temperature should be set at about 0 003 C below the TPW about 0 007 C in order to maintain the TPW for a few months If the bath temperature is too low more water in the cell will freeze If the bath tem perature is too high the ice mantle in the cell will melt gradually During the first month a bath is used to maintain TPW cells the ice mantle should be checked daily Adjust the bath set temperature a little if necessary to obtain the optimal maintenance situation If an ice bridge is found across the top surface of water in the cell it must be melted immediately Otherwise the pressure cre ated from water freezing on the surface might break the cell After initial ad justments of the bath the TPW cells in the bath can be used for a few months with little care Hart s 2028 Dewar can be used to maintain TPW cell When a TPW cell is maintained in Dewar with crushed ice ice will form on the surface of the water in the cell as a result of heat transferred via the vapor to the cold glass which is often at 0 C When a cell is not disturbed for several days the ice will freeze completely across the top surface and must be melted back e g by warming with the hands before the cell ruptures Care must be
19. hanol approximately 100ml The Quick Stick must be cooling before inserting it into the TPW Once the cooling cycle has begun insert it to the bottom of the reentrant well the radius at the bottom helps cen ter it in the well 4 After the Quick Stick is inserted carefully into the cell the gap is filled with ethanol until it is a little below the water level in the cell about 1 cm This helps to prevent ice from bridging across the top during mantle formation A special heat sink is provided that fits around the TPW cell that also helps prevent bridging Slide the heat sink onto the cell up to the level of the water Room heat is absorbed and transferred to the water at the surface Adjust the centering bushing until the heat pipe is centered in the reentrant well The cell and Quick Stick need to be well supported during this process Care must be taken not to break the reentrant well during this process or the cell will be ruined The cell and Quick Stick must be supported separately The Hart Scientific model 2067 P support kit is available for this purpose The freezing process takes care of itself beyond this point Be sure that there is no ice bridging at the top One fill of dry ice forms a good mantle in 40 to 60 minutes 4 Freezing an Ice Mantle in the TPW Cell Freezing Dry Ice and Alcohol E Centering Bushing Heat Sink and Strap Alcohol 1 cm below water lt Ice Mantle
20. he cell or invert the cell vigorously To realize the triple point of water temperature an ice mantle must be formed from the reentrant well outward Preparations It is important that the reentrant well is cleaned and dried before attempting a freeze of the cell If this precaution is not taken water inside the reentrant well will freeze during the mantle formation creating a less uniform mantle which will not last as long A drop of alcohol in the bottom of the reentrant well be fore freezing will help prevent ice formation from moisture which may be in troduced during the process Remove any foreign material from the outside of the cell to prevent contamination of the bath In order to provide more uniform mantles and reduce coolant required for freezing pre chill the cell by immers ing it into an ice bath or maintenance bath until it is no more than a few degrees above the ice point Freezing The cell should be frozen by refrigerating the inside of the reentrant well so that water freezes from the reentrant well outward to form a mantle of ice around the well A variety of refrigeration methods are used to freeze a cell such as refrigerated cold fingers heat pipes LN2 chilled rods and dry ice Dry Ice Freezing Process A simple and fast method of freezing an ice mantle is to pour crushed Dry Ice solid CO directly into the dry reentrant well Support the cell during freezing in arack which will prevent breakage but allow compl
21. ive melting of the ice mantle Insertion into the maintenance bath or separate ice bath is an excellent way to pre cool the thermometer The Hart Scientific maintenance bath Models 7012 7312 and ice bath Dewar Model 2028 have holes for pre cooling Ambient Radiation Ambient room radiation to the thermometer can elevate its temperature by sev eral tenths of a milli Kelvin above the temperature of the inner melt even when the cell is completely packed in ice To provide sufficient radiation shielding and to insure that the desired accuracy is obtained use an opaque insulated covered container Hydrostatic Pressure Effects At a depth 1 meters below the liquid surface where the true triple point temper ature exists the equilibrium temperature t at the solid liquid interface is given by t Bl where A 0 01 C and B 7 3 X 10 4 m 1 C Since the ther mometer sensor is not located at the surface the effects of hydrostatic pressure must be corrected For example in the case of an SPRT with the sensor at 242 mm below the surface the correction is computed as shown below T 2 0 01 C 7 3 X 10 4 m 1 C x 0 242m 0 00982334 C 17 7 Isotopic Composition Isotopic Composition Variations in the isotopic content of naturally occurring water can cause detect able differences in the TPW temperature A difference as large as 0 25 mK in TPW temperatures has been found between ocean water and water obtained from melted polar
22. l When the ice mantle becomes sufficiently thick 4 to 10 mm with at least 5 mm at the bottom the cell may be carefully moved to the main tenance bath to evaporate the remaining dry ice Allow the mantle to anneal for at least two days to remove the strains since strains in the ice may depress the actual triple point temperature about 0 2 mK Applications that do not require as stringent a level of accuracy will not require this delay If the mantle cracks it takes at least two days to anneal the mantle The Heat Pipe Freezing Process Hart Scientific has developed a Quick Stick to facilitate the formation of an ice mantle with greater ease Please refer to Model 2031 Quick Stick User s Guide for details The instructions for use of the Quick Stick in the formation of an ice mantle are as follows Figure 2 1 Dry ice is broken into small chunks less than 1 4 inch appropriate for fit ting into the cup 2 TPW reentrant well is dried with alcohol and a 1 4 inch of alcohol is placed into the bottom Next approximately 2 cc of finely crushed dry ice is dropped into the bottom of the reentrant well This helps start the freeze process and prevents super cooling of the water A small forma tion of ice is frozen onto the end of the reentrant well initially before the heat pipe is inserted which helps thicken the ice mantle at the bottom 3 dry ice is loaded into the Quick Stick cup and the spaces are filled with et
23. ment Printing Office Washington D C 20402 Apr 1972 McLaren E H The Freezing Points of High Purity Metals as Precision Temperature Standards I Precision Measurements with Standard Resis tance Thermometers Can J Phys Vol 35 78 1957 Berry R J The Temperature Time Dependence of the Triple Point of Water Can J Phys Vol 37 1959 Furukawa G T and Bigge W R Reproducibility of Some Triple Point of Water Cells the American Institute of Physics Vol 5 Part 1 p 291 1982 Stimson H F Precision Resistance Thermometry and Fixed Points Temperature Its Measurement and Control in Sci and Ind Reinhold Pub Corp New York NY Vol 2 Chap 9 p 141 1955 White D R Dransfield T D Strouse G F Tew W L Rusby R L and Gray J Effects of Heavy Hydrogen and Oxygen on the Tri ple Point Temperature of Water Temperature Its Measurement and Control in Science and Industry Volume 7 edited by Dean C Ripple American Institute of Physics p 221 226 2002 Hill K D Is there a long term drift in triple point of waters Metrologia 38 79 82 2001 25
24. taken to warm the water as little as possible so as not to melt too much of the mantle The above effects are much reduced by insulating the cell from the ice bath As mentioned above this can be done by using a plastic container with foam spacers to ensure that there is an air gap of about cm between the cell and the container wall A cell stored in this way can be used for many months with very little attention be yond maintaining the ice bath 15 6 Using the Cell Using the Cell The following recommendations will improve accuracy and extend the life and usefulness of the cell Shock Protection By placing a small foam rubber sponge in the bottom of the re entrant well the shock created when placing the SPRT or other sensor into the re entrant well will be reduced Heat Transfer Medium There should be fluid in the re entrant well such as water or alcohol to act as a heat transfer medium from the ice and water interface to the thermometer in the well A sufficient volume of fluid must be in the re entrant well to bring the level above that of the cell water when the thermometer is inserted If desired a brass or aluminum bushing about 5 cm long may be used to increase the ther mal conduction between the thermometer and the ice water interface which will also reduce external self heating of the thermometer Thermometer Pre cooling The thermometer should be pre cooled for at least 5 minutes before insertion to avoid excess
25. ted by its surrounding environment but the sealed TPW cell protects the water in the cell from contamination for many years For these reasons in 1954 CGPM General Conference of Weights and Measures adopted the TPW as the sole point defining the unit of Thermodynamic Temperature instead of the combina tion of the ice point and the boiling point of water This is similar to the method proposed by the famous physicist W T Kelvin in 1848 In order to accommodate the broad application of the TPWs Hart Scientific has developed a series of TPW cells including Models 5901D G 5901A G 5901B G 5901C G 5901D Q 5901A Q and 5901C Q Figure 1 Hart Scien tific TPW cells and technology make it easy to realize the TPW All Hart Scien tific TPW cells constructed with a high quality Pyrex envelope or fused silica envelope are described in this User Manual The Variations in the isotopic con tent of naturally occurring water can cause detectable differences in the TPW 5901 Series Triple Point of Water Cells User s Guide 450 mm 265 mm 50mm 5901A G Q N 13 6 mm 14 4 mm 12 mm 7 4 f J z J J Y 4 N KY N l temperature The isotopic composition of water in Hart TPW cells is substan tially the same as one of Standard Mean Ocean Water We will discuss this is sue in more detail in the manual Model 5901D G and 5901D Q Cell are of the design used by national tempera ture labs around the world
26. the melting point or boiling point which is usually standard atmospheric pressure 101 325 kPa The triple point of water TPW is the only thermometric fixed point used in definitions of both the thermodynamic temperature and the international tem perature scale 1 3 The unit of thermodynamic temperature Kelvin is defined as the fraction 1 273 16 of the thermodynamic temperature of the TPW It is also a defining fixed point on the International Temperature Scale of 1990 ITS 90 According to the ITS 90 the temperatures between 13 8033 K and 961 78 C are determined in terms of the ratio of the resistance at a temperature T R T90 and the resistance at the TPW RTPW of a standard platinum resis tance thermometer SPRT The ratio W T90 is W T90 R T90 RTPW 1 The Triple Point of Water Cell is an important instrument in temperature cali bration labs TPW cells are the most commonly used and hence one of the most important temperature fixed points The triple point of water temperature is the most reliable and repeatable temperature point available Room pressure desolved gases in water especially CO2 and other factors have detectable effects on the equilibrium temperature between water and ice Therefore it is very difficult to obtain an expanded uncertainty of 0 1 mK for the ice point Although it is very easy to obtain an expanded uncertainty of 0 1 mK for the TPW The water in an ice point apparatus is easily contamina
27. ture of TPW cells Recent research 13 shows that a decrease of 4 microK per year has been ob served in borosilicate glass TPW cells due to the dissolution of glass of the cell The borosilicate glass may be a less than ideal container as it is the most likely source of the contamination elements As a result of this concern Hart has in troduced TPW cells with fused silica glass containers The fused silica glass may be a more ideal container material for a TPW cell than borosilicate glass More research results may be reported 3 Specifications 3 Specifications 5901A G 5901A Q 5901C G 5901C Q 5901D G 5901D Q 5901B G Expanded Uncertainty k 2 lt 0 0001 C 0 0002 C Reproducibility 0 00002 C 0 00005 C Dimensions 50 mm OD 60mm OD 60mmOD 60 mm OD 30 mm OD 12 mm ID 13 6 mmID 14 4mm ID 12 mm ID 8 mm ID 450 mm long 420 mm long 420 mm long 420 mm long 180 mm long Immersion Depth water 265 mm 118 surface to well bottom Material Borosilicate Fused Silica Borosilicate Fused Silica Borosilicate Fused Silica Borosilicate Glass Quartz Glass Quartz Glass Quartz Glass Water Source Ocean 0 10 1 20 5180 5 1 5 0 15 3 Effect of devaiation from 7 x14yK VSMOW 4 Freezing an Ice Mantle in the TPW Cell Preparations 4 4 1 4 2 4 2 1 Freezing an Ice Mantle in the TPW Cell A CAUTION DO NOT shake t
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