5944-45-46-47 Users Guide 6C0
Contents
1. 5944 5945 5946 5947 Fixed Point Cell User s Guide inner liquid solid interface that is measured by the thermometer Sometimes the inner liquid solid interface is called the defining temperature interface Shell gt Graphite Crucible Liquid Sample t Solid Sample Reentrant Tube Melting State Freezing State Figure 4 Typical freeze point cell design showing the liquid solid interfaces It is extremely important for the process described here that there is a very uni form stable and controlled temperature environment enclosing the fixed point cell We have developed several designs of fixed point furnaces to satisfy these requirements The Model 9114 furnace has three independent heaters and con trollers designed to be used for a temperature range up to 680 C as shown in Figure 5 16 6 Realization of the Fixed Point Background Information SPRT Thermal Guard Assembly Main Controller SET DOWN UP EXIT ne Po SPRT Equilibration PRT Sensor Block Top Zone Heater lt Top Zone Controller TOP END ZONE SET DOWN UP em VA y Differential TCs Main Heater Freeze Point Cell PRIMARY ZONE Differential TCs Cell Support Container Thermal Block Bottom Zone Controller MY y 3 zone subdi2. Hart Scientific 5944 5945 5946 5947 Mini Metal Fixed Point Cells User s Guide Rev 6C0601 Rev 6C0601 Limited Warranty amp Limitation of Liability Each product from Fluke Corporation Hart Scientific Division Hart is warranted to be free from de fects in material and workmanship under normal use and service The warranty period is one year for the Mini Metal Fixed Point Cell The warranty period begins on the date of the shipment Parts product re pairs and services are warranted for 90 days The warranty extends only to the original buyer or end user customer of a Hart authorized reseller and does not apply to fuses disposable batteries or to any other product which in Hart s opinion has been misused altered neglected or damaged by accident or abnor mal 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 properly recorded on non defective media Hart does not warrant that software will be error free or operate without interrup tion Hart does not warrant calibrations on the Mini Metal Fixed Point Cell Hart authorized resellers shall extend this warranty on new and unused products to end user customers only but have no authority to extend a greater or different warranty on behalf of Hart Warranty support is available if product is purchased through a Hart authorized sales outlet or Buyer h
3. 6 9260 furnace interior with freeze point cell cross sectional view 19 5944 5945 5946 5947 Fixed Point Cell User s Guide 20 6 2 6 2 1 Table 6 The furnaces for fixed points and their temperature uniformity Fixed Point The Equipment Used Temperature Uniformity The freezing point of indium Model 9114 furnace three zones 0 01 C The freezing point of tin Model 9114 furnace three zones 0 015 C The freezing point of zinc Model 9114 furnace three zones 0 02 C The freezing point of indium Model 9260 furnace three zones 0 05 C The freezing point of tin Model 9260 furnace three zones 0 08 C The freezing point of zinc Model 9260 furnace three zones 0 10 C The cell should be put into the cell containment vessel before insertion into any furnace Ideally each cell would be kept in its own unique vessel Fiber ceramic insulation is placed in the bottom of the cell basket to protect the cell Insula tion is also placed on top of the cell for protection and to reduce heat loss Vertical Temperature Gradient and Controller Accuracy Adjustment Vertical temperature gradient adjustment The vertical temperature gradient has to be within the required specification be fore a fixed point cell sample is melted Otherwise the cell may break There fore the vertical temperature gradient should be measured each time the cell is installed in a furnace and checked at least every six months The Model 9114 an
4. SHALL NOT BE LIABLE FOR ANY SPECIAL INDIRECT INCIDENTAL OR CONSE QUENTIAL DAMAGES OR LOSSES INCLUDING 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 com petent jurisdiction such holding will not affect the validity or enforceability of any other provision Fluke Corporation Hart Scientific Division 799 E Utah Valley Drive e American Fork UT 84003 9775 USA Phone 1 801 763 1600 Telefax 1 801 763 1010 E mail support hartscientific com www hartscientific com Subject to change without notice e Copyright 2005 e Printed in USA Table of Contents 1 Before You Start 0 0c00000000e0e00001 1 1 Symbols Used o cu ee we eee bni undid wee e a 1 1 2 Safety Information o e se go a ale ae oe e ee ee ee 2 1 2 1 War PS ar ae RS gs EE neces aah a dai 00 e at a Bi 07 ai Ge eg 2 1 22 CAUTIONS d aag see sek ee 2a ot at sak sd a Mota dE d sd zach ada E tty seeds he rd cae NE 2 1 3 Authorized Service Centers 0 02020004 3 2 Introduction 0200 cece eevee eee vee S 3 Specifications and Environmental Conditions 7
5. duced freezing technique was found to fit the purpose best The detail of the technique will be described a little later A very slow freeze allows enough time to calibrate a number of SPRTs in the beginning part of a single freeze 13 5944 5945 5946 5947 Fixed Point Cell User s Guide 14 Table 5 Summary of the 1st Cryoscopic Constants and the Estimated Effects of Impurities 1st Cryoscopic Deviation from Pure Substance Constant Impurity Level Liquidus Point Indium 0 00732 K 99 99999 0 01 mK Tin 0 00329 K 99 9999 0 3 mK Zinc 0 00185 K 99 9999 0 5 mK Aluminum 0 00149 K 99 9999 0 7 mK Silver 0 000891 K 99 9999 1 1 mK Gold 0 000831 K 99 9999 Copper 0 000857 K 99 9999 660 38 660 36 660 34 660 32 660 28 Temperature C 2 e 3 660 26 660 24 660 22 10 12 14 Time hours 16 18 20 Theoretical freezing curve of an ideal pure metal without supercool Freezing curve of an ideal pure metal with supercool a Freezing curve of a real high purity metal Figure 3 Freezing curve comparison of one cell The highest accuracy realizations are greatly facilitated by establishing a sec ond essentially static solid liquid interface immediately surrounding the re en trant well The induced technique mentioned above can generate two liquid solid interfaces in the cell When the pure metal has been melted thor 6 Realization of the Fix
6. is less than 5 PPM All of the graphite parts are subjected to a high temperature high vac uum treatment before loading the metal sample It is important to avoid any possible contamination to the surface of the graphite parts during the manufac turing process The assembled graphite crucible with the high purity metal is then enclosed in a metal cased outer case and connected to a high vacuum sys tem The cell is drawn down to a proper pressure at a temperature near the freezing point for several days During this period the cell is purged with high purity argon repeatedly to remove any contaminants Finally the cell is filled with 99 999 pure argon and permanently sealed at the freezing point The pressure of the argon in the cell at the freezing point is closely adjusted to 101 325 Pa and the actual value of the pressure recorded A small temperature correction for the pressure difference can be made using the information in Section 7 The Correction for the Pressure Difference The metal cased cell is design to be used not only in primary fixed point fur nace Model 9114 but also in small portable furnace Model 9260 The total depth of a portable furnace is only about 270 mm 10 6 inch allowing short probes to be calibrated by fixed point On the top the space above the fixed point cell of the furnace a minimum of fifty mm of thermal insulation is required to maintain good vertical temperature uniformity in the cell That means that
7. point of total immer sion during a freezing plateau in the cell is calculated using Equation 2 Equation 2 Calculation of the Actual Temperature f ti t At Therefore t 419 527 C 0 000301 C 419 5267 C where is the defining fixed point temperature i e 419 527 C for the freezing point of zinc 7 The Correction for the Pressure Difference The resistance ratio W for the particular cell exactly at the freezing point of zinc can be calculated using the following equation The value for dW dt is taken from Table 7 Equation Calculation of Wz for the exact defining fixed point temperature dW Wzn Ww t kt A e Substituting values 2 568917300 0 00301 3 495 x 10 Thus the W for the cell is Wz 256891835 Zn 27
8. the total length of the cell is limited to about 220 mm Therefore a total immersion depth into the pure metal is 156 mm Figure 2 The total im mersion depth 156 mm is a slightly more than is available in the 591X quartz glass cell 140 mm but less than that of 590X quartz glass cell 195 mm We pay special attention to decreasing or eliminating thermal conduction error during calibration at fixed points Very thin metal tubing 0 01 inch thickness as the re entrant well decreases the conductivity along the well to a minimum The tight match between the metal well and the graphite well improves thermal conductivity in the radial direction and decreases the thermal conduction error 5944 5945 5946 5947 Fixed Point Cell User s Guide H 7 82 mm PURE METAL GRAPHITE CRUCIBLE METAL OUTER SHELL 156 mm 222 mm m 41 28mm Figure 2 The Model 5944 5945 5946 5947 metal cased fixed point cell 10 5 Care and Handling Guidelines Care and Handling Guidelines The 5944 5945 5946 5947 fixed point cell is a delicate device Great care must be taken in handling using and transporting the cell The metal case is very sturdy however the graphite crucible is brittle It is suggested that the cell be kept in the vertical position as shown in Figure 2 for safety However putting a cold cell in horizontal orientation for a short period of time will not cause any damage Up side down orientation might
9. using the following equation Equation 1 Pressure Dependent Temperature Correction 25 5944 5945 5946 5947 Fixed Point Cell User s Guide 26 At P P xk hx k P the actual pressure of argon in the cell exactly at the fixed point temperature P the standard atmospheric pressure i e 101 325 Pa gait dP dT VAn dh h the immersion depth of the midpoint of the sensor of a SPRT into the matal used for the fixed point The immersion depth of the midpoint of a SPRT sensor in a Hart 5944 5945 5946 5947 fixed point cell is approximately 0 131 m the distance from the bottom of the central well to the surface of liquid metal is about 0 156 m The actual pressure of the argon at the freezing point in the cell p is pro vided in the Report of Test or Certification The temperature correction Af can be calculated using Equation 1 Example The pressure of argon at the freezing point in the zinc freezing point cell S N Zn 45001 is 86 100 Pa 86 10 kPa as given in the Report of Test k and k for the freezing point of zinc can be found in Table 7 k 4 3 10 5 mK Pa and k 2 7 mK m The average immersion depth is 0 131 m for most of standard platinum resistance thermometers Therefore use Equation 1 to calculate At Substituting values into Equation 1 5 86100 Pa 101325Pa C K 40131m 0 65mK 0 35mK a Consequently At 0 301mK Hence the actual temperature of a sensor of a SPRT at the
10. 3 1 Speciications e se e eBay a eee EE ERR Ee He ee eS 7 3 2 Environmental Conditions a aooo a a 7 4 Construction ss see seces rers ewww eee eee ee 9 5 Care and Handling Guidelines 11 6 Realization of the Fixed Point 6 13 6 1 Background Information 0 13 6 2 Vertical Temperature Gradient and Controller Accuracy Adjustment 20 6 2 1 Vertical temperature gradient adjustment o oo 20 6 2 2 Controller display accuracy adjustment o oo o a 21 6 3 Procedure for Realizing the Freeze 2 2 21 6 4 Procedure for Realizing the Melting Point 22 6 5 Special notes for freezing point of aluminum 23 7 The Correction for the Pressure Difference 25 Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 The metal cased freezing point cell 2 2 222 000 The Model 5944 5945 5946 5947 metal cased fixed point cell Freezing curve comparison of one cell Typical freeze point cell design showing the liquid solid interfaces 9114 Furnace Interior with Freeze Point Cell Cross Sectional View 9260 furnace interior with freeze point cell cross sectional view A typical freezing curve for the Zinc Cell 2 ee Tables Table1 International Electrical Symbols 0 Table 2 The defining metal freezing points of the ITS 90 pressure constants and re
11. FP Sn and FP Zn 0 C 231 928 C FP In and FP Sn 0 C 156 5985 C FP In 3 Specifications and Environmental Conditions Specifications 3 Specifications and Environmental Conditions 3 1 Specifications Table 4 Specifications Model Number 5944 5945 5946 5947 ITS 90 Assigned Temperature C 156 5985 231 928 419 527 660 323 Expanded Uncertainty C k 2 Cell Itself 0 0006 0 0008 0 001 0 002 Expanded Uncertainty C k 2 Used in 0 0012 0 0016 0 002 0 004 9260 Melting Curve Metal Purity gt 99 9999 gt 99 9999 gt 99 9999 gt 99 9999 Quantity of Metal 9 660 655 648 200 Outer Diameter of the Cell mm 41 3 41 3 41 3 41 3 Overall Height of the Cell mm 222 222 222 222 Inner diameter of the Re entrant Well mm 7 8 78 78 7 8 Total Immersion Deptht mm 156 156 156 156 The distance from the bottom of the re entrant well to the upper surface of the pure metal 3 2 Environmental Conditions Although the instrument has been designed for optimum durability and trou ble free operation it must be handled with care The instrument should not be operated in an excessively dusty or dirty environment 4 Construction Construction The 5944 5945 5946 5947 metal freezing point cell is shown in Figure 2 An appropriate quantity of metal See Table 4 Specifications on page 7 for de tails with a purity of 99 9999 is melted into a graphite crucible with a graphite lid and re entrant well The impurity in the graphite
12. as paid the applicable international price Hart reserves the right to invoice Buyer for importation costs of 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 re pair or replacement of a defective product which is returned 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 au thorized service center Hart assumes no risk for damage in transit Following warranty repair the prod uct will be returned to Buyer transportation prepaid FOB Destination If Hart determines 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 EXCLUSIVE REMEDY AND IS IN LIEU OF ALL OTHER WARRANTIES EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IM PLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE HART
13. d 9260 Furnaces are three zone furnaces and their temperature gradient can be adjusted through the top zone and the bottom zone heater Vertical temperature gradient test method Set the furnace temperature 5 C below the melting point of the sample For ex ample the melting point temperature of Zinc is 419 527 C the furnace temper ature should be set to 414 5 C Maintain the temperature for at least 4 hours stabilizing after the display temperature of the furnace reaches the set point temperature The SPRT is moved up 120 mm from the bottom of the thermom eter well and then back to the bottom The SPRT was moved in 40 mm incre ments and measurements taken at each depth After every move and before each measurement a two minute stabilization period was allowed The vertical temperature should meet the specification of the furnaces Ideally the temperature uniformity of 9114 and 9260 should meet the uniformity listed in Table 6 If the furnace does not meet the requirement the vertical tempera ture gradient should be adjusted through the top and bottom heater 6 Realization of the Fixed Point Procedure for Realizing the Freeze 6 2 2 6 3 Controller display accuracy adjustment The absolute accuracy of the instrument might change after adjusting the tem perature gradient therefore it is important to check it after performing the verti cal gradient adjustment The offset in accuracy should be considered or corrected during
14. damage the cell Store the cell in the vertical position and in a safe place Always handle the cell with care The cell can be shipped by commercial carrier with the following preparation e Keep the cell in the vertical direction during transportation e Put the cell into the wooden case specially designed for fixed point cell first and then place the wooden cell case into a large package with foam around the wooden cell case e Avoid bumping shock and strong vibration during transportation Utilize Shock Watch and Tilt Watch indicators If the instructions in this manual are carefully followed the Model 5944 5945 5946 5947 fixed point cell will provide many years of accurate use 11 6 Realization of the Fixed Point Background Information 6 1 Realization of the Fixed Point As was mentioned in Section 2 Introduction it is not difficult to realize a freezing point by using a Hart completely sealed metal freezing point cell In order to get the highest possible accuracy a general understanding of the freez ing process of an ideal pure metal is helpful Background Information Theoretically the melting and freezing temperatures for an ideal pure metal are identical However with the introduction of impurities in the metal the melting and freezing equilibrium points are usually slightly lower The freezing plateau of an ideal pure metal is conceptually flat The only exception is during the supercool Impurities in the m
15. ed Point Background Information oughly maintain the furnace at 2 C above the freezing point overnight The next morning decrease the furnace temperature to about 2 C below the freez ing point at a rate of 0 5 C per minute A SPRT inserted into the cell is used to monitor the pure metal temperature As soon as the recalescence indicated temperature stops to decrease and starts to rise occurs take the SPRT out of the furnace and insert two cold quartz glass rods into the cell in succession each rod remains in the cell for about two minutes Set the furnace to a temper ature of about 0 5 C below the freezing point The cold quartz glass rods ab sorb heat from the pure metal and a thin film of pure metal is frozen around the re entrant well immediately A continuous liquid solid interface as nearly as is practical encloses the sensor of the SPRT being calibrated Another liq uid solid interface is formed on the wall of the graphite crucible In this a situa tion the outer interface advances slowly as the liquid continues to solidify Ideally this generates a shell that continues to be of uniform thickness com pletely surrounding the liquid which itself surrounds the inner liquid solid in terface that is adjacent to the thermometer well Figure 4 The inner interface is essentially static except when a specific heat extraction process takes place e g the insertion of a cool replacement thermometer It is the temperature of the 15
16. etal generally introduce a slightly negative slope to the plateau Most of the different types of impurities will cause a drop in the freezing plateau e g gallium impurities in tin will cause a drop in the freezing plateau A few of the types of impurities can cause an increase in the plateau e g gold impurities in silver will cause the freezing plateau to increase An ex tremely high purity metal 99 9999 or higher behaves very closely to an ideal pure metal Figure 3 shows the difference between a freeze of an ideal pure metal and a high purity metal The approximate effect of the impurity on the equilibrium point can be calculated using the first cryoscopic constant This calculation is discussed in the Guidelines for Realizing the International Tem perature Scale of 1990 ITS 90 For general uncertainty comparisons the first cryoscopic constant the metal purity requirement and the difference in the liquidus point are outlined in Table 5 In a modern temperature standard labora tory using a SPRT a temperature change as low as 0 01 mK 0 00001 C can be detected Therefore the best technique for realizing the freezing point with a real sample is one that measures a temperature nearest to the freezing point of the ideal pure metal The beginning of the very slow freezing curve of a high purity metal is the closest temperature to the ideal freezing point which can be obtained in a modern temperature standard laboratory A so called slow in
17. fixed installation Examples include household office and laboratory appliances N The European Waste Electrical and Electronic Equipment WEEE Directive 2002 96 EC mark E 1 2 Safety Information Use this instrument only as specified in this manual Otherwise the protection provided by the instrument may be impaired The following definitions apply to the terms Warning and Caution Warning identifies conditions and actions that may pose hazards to the user Caution identifies conditions and actions that may damage the instrument be ing used 1 2 1 A Warnings To avoid possible personal injury follow these guidelines DO NOT use this instrument for any application other than calibration work DO NOT use this instrument in environments other than those listed in the user s guide Follow all safety guidelines listed in the user s guide Calibration Equipment should only be used by Trained Personnel 1 2 2 A Cautions To avoid possible damage to the instrument follow these guidelines Read the section entitled Care and Handling Guidelines before removing the fixed point cell from the case Incorrect handling can damage the cell The fixed point cell must be kept in a vertical position Placing the cell in a horizontal position can damage the cell and void the warranty DO NOT place the fixed point cell upside down 1 Before You Start Authorized Service Centers 1 3 Authori
18. he actual pressure in the cell exactly at the fixed point was measured at Hart This actual argon pressure in the cell at the freezing point is provided on the Report of Test or Certification enabling calculation of correc tion for the difference in pressure During measurement at a fixed point the sensor of a SPRT is usually placed at a height which is h meters lower than the upper surface of the pure metal and where the pressure is higher than that at the surface due to the static head ITS 90 gives all of the necessary coefficients for the calculation of the correction caused by the pressure difference which are summarized in following table Table 7 Coefficients for the Pressure Difference of Some Defining Fixed Points Assigned Value of Temperature with Equilibrium Temperature Pressure p k1 Variation with depth Approximate Substance T Kelvin K dT dp 10 5 mK Pa k2 dT dh mK m dW dt 1 K Argon T 83 8058 25 3 3 0 004342 Mercury T 234 3156 5 4 74 0 004037 Water T 273 16 7 5 0 73 0 003989 Gallium M 302 9146 2 0 1 2 0 003952 Indium F 429 7485 4 9 3 3 0 003801 Tin F 505 078 3 3 2 2 0 003713 Zinc F 692 677 4 3 2 7 0 003495 Aluminum F 933 473 7 0 1 6 0 003205 Silver F 1234 93 6 0 5 4 0 002841 Gold F 1337 33 6 1 10 Copper F 1357 77 3 3 2 6 T Triple Point M Melting Point F Freezing Point The correction of temperature caused by the difference in pressure can be cal culated by
19. he variance among different realizations of a freezing point should be well within 1 0 mK for the freezing points of indium tin and zinc and within a few millikelven for the freezing points of aluminum silver gold and copper For your convenience Hart has developed a sealed cell design and new technique for the realization of the freezing points which has made it easy to realize these fixed points Model 5944 5945 5946 5947 metal cased fixed point cells are members of the Hart fixed point cell family see Figure 1 The 5944 5945 5946 5947 fixed point cells not only retain the merit of the lowest uncertainties of Hart fused silica fixed point cells 590X and 591X but also provide a much stron ger more durable case You will never worry about breaking the cell case 5944 5945 5946 5947 Fixed Point Cell User s Guide again The new cell can be shipped by conventional carrier eliminating the in convenience of hand carrying the cell from one place to another Figure 1 The metal cased freezing point cell These freezing points are indispensable for the calibration of a standard plati num resistance thermometer SPRT Different sub ranges require different sets of freezing points as summarized in Table 3 Table 3 Some sub ranges of the ITS 90 and freezing points required for calibration Subrange Freezing Points Required 0 C 961 78 C FP Sn FP Zn FP Al and FP Ag 0 C 660 323 C FP Sn FP Zn and FP Al 0 C 419 527 C
20. ls melt and freeze at a unique temperature through a process involving the absorption or liberation of the latent heat of fusion A metal freezing point is the phase equilibrium be tween the liquid phase and solid phase of a pure metal at a pressure of one stan dard atmospheric pressure 101 325 Pa The freezing points of indium tin zinc aluminum silver gold and copper are the defining fixed points of the ITS 90 The temperature values of these freezing points assigned by the ITS 90 the pressure effect constants and the resistance ratios at these fixed points according to the ITS 90 SPRT reference function are listed in Table 2 Table 2 The defining metal freezing points of the ITS 90 pressure constants and resistance ratios Pressure Effect of Fixed Points Assigned Temperature dt dP dt dh Wr T90 dW dt Fixed Point Too K toy C 10 8K Pa t 10 3K m x 0 001 FP In 429 7485 156 5985 4 9 3 3 1 60980185 3 801024 FP Sn 505 078 231 928 3 3 2 2 1 89279768 3 712721 FP Zn 692 677 419 527 4 3 2 7 2 56891730 3 495367 FP Al 933 473 660 323 7 0 1 6 3 37600860 3 204971 FP Ag 1234 93 961 78 6 0 5 4 4 28642053 2 840862 FP Au 1337 33 1064 18 6 1 10 FP Cu 1357 77 1084 62 3 3 2 6 t Equivalent to millikelvins per standard atmosphere All of these fixed points are intrinsic temperature standards according to the definition of the ITS 90 Under controlled conditions these freezing points are highly reproducible T
21. nutes 6 Set the furnace at a stable temperature of 0 5 C below the freezing point 7 Insert the preheated SPRT to be calibrated into the cell Preheat the SPRTs to be calibrated at a temperature of about 2 C above the freezing point for thirty minutes before inserting them into the cell 8 It will take 30 40 minutes to get equilibrium between the SPRT sensor and pure metal sample After equilibrium reached you can start measurements This procedure provides a very stable long freezing plateau that typically lasts for more than twenty hours The changes in temperature in the first half of the plateau are usually within 0 2 0 3 mK A typical freezing curve is shown in Figure 7 Many SPRTs can be calibrated in a single freezing plateau When multiple 21 5944 5945 5946 5947 Fixed Point Cell User s Guide SPRTs are to be calibrated from a single freeze preheat of SPRTs to be cali brated is very important 0 6552574 0 6552569 lt a ee GRAAL OA AAA OO 0 5 mK 0 6552564 0 6552559 0 6552554 e 0 6552549 0 6552544 6552530 e eS F18 Bridge reading Rt Rs 0 6552534 0 6552529 T T T T T T T T 10 8 10 8 10 8 10 8 10 8 10 9 10 9 10 9 10 9 10 9 10 00 13 00 16 00 19 00 22 00 1 00 4 00 7 00 10 00 13 00 Date and time Figure 7 A typical freezing curve for the Zinc Cell 6 4 Procedure for Realizing the Melting Point The melting point of metal ca
22. sed cells are realized manually in a similar way A NOTE In order to optimize the Melting Point Realization it is recom mended to preheat all probes before inserting them into the metal cased cell Probes can be preheated in a preheat well not available on all fur naces or annealing furnace operating at the same temperature of the metal cased cell A NOTE For new setup or installation it is recommended that the melt pla teau be monitored with an SPRT and recorded throughout the entire pla teau Doing so establishes the length of the plateau 1 Set the temperature of the furnace about 5 C below the freezing point 2 After the furnace temperature reaches the setting temperature wait for 30 min for stabilization and equilibration 3 Set the temperature of the furnace 0 8 C higher than the freezing point with a scan rate of 1 5 C per minute 22 6 Realization of the Fixed Point Special notes for freezing point of aluminum 6 5 After the furnace temperature reaches the set temperature insert the check standard SPRT if available into a pre heat well or annealing fur nace see note above Wait for 30 min for the fixed point cell to equilibrate and transition into the melt plateau Insert the check standard SPRT into the cell It will take 30 40 minutes to achieve equilibrium between the SPRT sen sor and the pure metal sample After equilibrium is reached measure ments can be made It is recommended to mea
23. sistance ratios o oe cea ee Table 3 Some sub ranges of the ITS 90 and freezing points required forcalibratioin esa Ae BS Eee GY ER Sh week og ee Table 4 Specifications i0 ae Geek ee edb the eee ee eed ae Table 5 Summary of the Ist Cryoscopic Constants and the Estimated Effects of Impurities oasis a aie ee Ae ee Se 3 3 Table 6 The furnaces for fixed points and their temperature uniformity Table 7 Coefficients for the Pressure Difference of Some Defining Fixed Poms 4 0 gah eG ae Ap Bee Re eS He n iii 1 Before You Start Symbols Used 1 1 Before You Start Symbols Used Table 1 lists the International Electrical Symbols Some or all of these symbols may be used on the instrument or in this manual Table1 International Electrical Symbols Symbol Description IN AC Alternating Current IN AC DC Battery Complies with European Union directives N N DC Double Insulated Electric Shock Fuse PE Ground Hot Surface Burn Hazard Read the User s Manual Important Information Off On O I ei 5944 5945 5946 5947 Fixed Point Cell User s Guide Symbol Description Canadian Standards Association US Australian EMC Mark OVERVOLTAGE Installation CATEGORY II Pollution Degree 2 per IEC1010 1 refers to CATI the level of Impulse Withstand Voltage protection provided Equipment of OVERVOLTAGE CATEGORY II is energy consuming equipment to be supplied from the
24. sure the check standard again to end the plateau Special notes for freezing point of aluminum The cell for freezing point of Al is very easy to be damaged since the fused sil ica is very sensitive to aluminum and the aluminum is strongly adhesive to graphite crucible To prevent the cell from damage a specific procedure has to be followed 1 After the realization of freezing point of Al the furnace temperature should be decreased to room temperature through a rate of 1 8 C per minute Anytime if you would like to remove the cell out of furnace the cell should not be taken out until the furnace temperature fully reach the room temperature 22 C If the furnace temperature could not reach room temperature the power cord of the furnace should be unplugged for one day 23 7 The Correction for the Pressure Difference The Correction for the Pressure Difference This is the procedure used in the Hart metrology lab with the Hart sealed fixed point cells Other procedures are sometimes employed in industry Except for a few triple points the values of temperature assigned to the defin ing fixed points by ITS 90 correspond to the temperatures at the standard atmo spheric pressure 101 325 kPa The actual pressure in a cell may be not exactly the standard value During the course of manufacture of a fixed point cell it is easier to seal the cell if the pressure in the cell is a slightly lower than the room pressure T
25. the realization of fixed points The controller accuracy should be checked after the sample is fully melted in every realization of a fixed point Please refer to the respective furnace Users Guide for a calibration procedure A calibrated SPRT should be used to measure the controller accuracy Procedure for Realizing the Freeze All of the freezing points of metal cased cells are realized manually in a similar way 1 Insert the cell with the cell containment vessel carefully into the furnace Place as much thermal insulation material as possible onto the top of the fixed point cell in the cell containment vessel and on the top of the vessel 2 Set the temperature of the furnace about 5 C higher than the freezing point Allow all of the metal to melt completely 3 After all metal is completely melted the furnace is set at a stable temper ature about 2 C above the freezing point overnight 4 The next morning the furnace temperature is decreased slowly about 0 1 C per minute In order to monitor the pure metal sample tempera ture a SPRT is inserted into the cell The temperature of the metal sam ple decreases to less than the freezing point before recalescence The amounts of supercool are different from metal to metal 5 After recalescence remove the thermometer from the furnace immedi ately and insert two cold room temperature quartz rods or tubes into the fixed point cell one by one keep each rod in the cell for two mi
26. vision BOTTOM END ZONE INWY VYY VY VY WVV VY VVN AAA VVV VVV WVV VVV VVV VVV VIV 5 5 MMMMMMMMMMMMMMMMMMMMMWIMMMM MMM VV VVV YV VVV VVV VVV A Bottom Zone Heater Water Cooling Coils Supercooling Figure 5 9114 Furnace Interior with Freeze Point Cell Cross Sectional View Gas Supply Argon 17 5944 5945 5946 5947 Fixed Point Cell User s Guide The 9260 small portable fixed point furnace is much shorter than traditional furnaces and can easily be used on a table or bench Figure 6 The furnace has a total height of 489 mm and an outer diameter of 209 mm and it weights about 17 kg The 9260 permits simplified realization of either freezing or melt ing curves Probes shorter than 430 mm 17 cannot be calibrated in the 9114 furnace Probes at least 220 mm 9 in length can be calibrated in the 9260 furnace Three heaters are used to obtain uniform temperatures around the fixed point cell The main heater covers the furnace s entire length while the top and bottom zone heaters cover only the upper and lower parts of the fur nace respectively Only one controller is used in 9260 Software within the unit s controller is used to adjust the ratios of the three heaters Using this tech 6 Realization of the Fixed Point Background Information nique we can achieve temperature uniformity of 0 1 C or better within the cell Figure
27. zed Service Centers Please contact one of the following authorized Service Centers to coordinate service on your Hart product 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 E mail support hartscientific com Fluke Nederland B V Customer Support Services Science Park Eindhoven 5108 5692 EC Son NETHERLANDS Phone 31 402 675300 Telefax 3 1 402 675321 E mail ServiceDesk fluke nl Fluke Int l Corporation Service Center Instrimpex Room 2301 Sciteck Tower 22 Jianguomenwai Dajie Chao Yang District Beijing 100004 PRC CHINA Phone 86 10 6 5 12 3436 Telefax 86 10 6 5 12 3437 E mail xingye han fluke com cn Fluke South East Asia Pte Ltd Fluke ASEAN Regional Office Service Center 5944 5945 5946 5947 Fixed Point Cell User s Guide 60 Alexandra Terrace 03 16 The Comtech Lobby D 118502 SINGAPORE Phone 65 6799 5588 Telefax 65 6799 5588 E mail antng singa fluke com When contacting these Service Centers for support please have the following information available e Model Number e Serial Number e Complete description of the problem 2 Introduction Introduction The International Temperature Scale of 1990 ITS 90 is based on a series of defining fixed points At temperatures above 273 16 K most of the fixed points are the freezing points of specified pure metals Pure meta
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