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Page 1

5924/5925/5926

5927/5928/5929

Metal Freeze Point Cell

Users Guide

2004, Rev. 1, 12/11

All product names are trademarks of their respective companies.

Page 2

Limited Warranty & Limitation of Liability

Each Fluke product is warranted to be free from defects in material and workmanship under normal use and service. The warranty period is one year and begins on the date of shipment. Parts, product repairs, and services are warranted for 90 days. This warranty extends only to the original buyer or end-user customer of a Fluke authorized reseller, and does not apply to fuses, disposable batteries, or to any product which, in Fluke’s opinion, has been misused, altered, neglected, contaminated, or damaged by accident or abnormal conditions of operation or handling. Fluke warrants

that software will operate substantially in accordance with its functional specications for 90 days and that it has been

properly recorded on non-defective media. Fluke does not warrant that software will be error free or operate without interruption.

Fluke 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 Fluke. Warranty support is available only if product is purchased through a Fluke authorized sales outlet or Buyer has paid the applicable international price. Fluke reserves the right to invoice Buyer for importation costs of repair/replacement parts when product purchased in one country is submitted for repair in another country.

Fluke’s warranty obligation is limited, at Fluke’s option, to refund of the purchase price, free of charge repair, or replacement of a defective product which is returned to a Fluke authorized service center within the warranty period.

To obtain warranty service, contact your nearest Fluke authorized service center to obtain return authorization

information, then send the product to that service center, with a description of the difculty, postage and insurance

prepaid (FOB Destination). Fluke assumes no risk for damage in transit. Following warranty repair, the product will be returned to Buyer, transportation prepaid (FOB Destination). If Fluke determines that failure was caused by neglect, misuse, contamination, alteration, accident, or abnormal condition of operation or handling, including overvoltage

failures caused by use outside the product’s specied rating, or normal wear and tear of mechanical components, Fluke

will provide an estimate of 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 IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. FLUKE SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF DATA, ARISING FROM ANY CAUSE OR 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 or other decision-maker of competent jurisdiction, such holding will not affect the validity or enforceability of any other provision.

Fluke Corporation Fluke Europe B.V. P.O. Box 9090 P.O. Box 1186 Everett, WA 98206-9090 5602 BD Eindhoven U.S.A. The Netherlands

11/99

Page 3

Title Page

Introduction ................................................................................................................... 1

Before You Start ............................................................................................................ 3

Symbols Used ........................................................................................................... 3

Safety Information .................................................................................................... 4

How to Contact Fluke ............................................................................................... 4

Specications ................................................................................................................ 5

Calibration Process Overview ...................................................................................... 5

Care of Your Metal Freezing Point Cell ....................................................................... 6

General Information .................................................................................................. 6

Devitrication of Quartz Glass ................................................................................. 6

Unpacking ..................................................................................................................... 7

Assembly Guide ............................................................................................................ 7

Background Information ............................................................................................... 9

Maintaining the Cell with Argon .................................................................................. 15

Vertical Temperature Gradient Adjustment .................................................................. 15

Controller Display Accuracy Adjustment ..................................................................... 16

Procedure for Realizing the Freeze (In, Zn, Al, Ag, and Cu Fixed Points) .................. 17

Realization of the Freezing Point of In .................................................................... 17

Realization of the Freezing Point of Sn .................................................................... 18

Realization of the Freezing Point of Zn .................................................................... 19

Realization of the Freezing Point of Al .................................................................... 20

Realization of the Freezing Point of Ag .................................................................... 21

Realization of the Freezing Point of Cu .................................................................... 22

SPRT Care At High Temperatures ................................................................................ 23

The Correction for the Pressure Difference .................................................................. 23

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5924/5925/5926/5927/5928/5929

Users Guide

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List of Tables

Table Title

Table 1. The Dening Metal Freezing Points of the ITS-90, Pressure Constants,

and Resistance Ratios ........................................................................................................... 1

Table 2. Subranges of the ITS-90 and Freezing Points Required for Calibration .............................. 2

Table 3. International Electrical Symbols ........................................................................................... 3

Table 4. The Specication of Metal Freezing Point Cells. ................................................................. 5

Table 5. Summary of the First Cryoscopic Constants and the Estimated Effects of Impurities ......... 9

Table 6. The Furnaces for Fixed Points and their Temperature Uniformity ....................................... 15

Table 7. Hydrostatic Head Correction Coefcients ............................................................................ 23

Page

List of Figures

Figure Title Page

Figure 1. The Metal Freezing Point Cell............................................................................................. 2

Figure 2. The Fluke Open Metal Freezing Point Cell ......................................................................... 8

Figure 3. Freezing Curve Comparison of One Cell ............................................................................ 10

Figure 4. 9114 Furnace Interior with Freeze Point Cell, Cross Sectional View ................................. 11

Figure 5. 9115A/9116A Furnace Interior with Freeze Point Cell, Cross Sectional View ................... 12

Figure 6. The Metal Freezing Point Cell in the Cell Containment Vessel (Basket) ........................... 13

Figure 7. Two Liquid-solid Interfaces in the Cell ............................................................................... 14

Figure 8. A Typical Freezing Curve for the Zinc Cell ........................................................................ 20

iii

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Users Guide

Page 7

Introduction

The International Temperature Scale of 1990 (ITS-90) is based on a series of dening xed points. At temperatures above 273.16 K, most of the xed points are the freezing points of specied pure metals. Pure metals 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 between the liquid phase and solid phase of a pure metal at a pressure of one standard atmospheric pressure (101.325 kPa). The freezing points of indium, tin, zinc, aluminum,

silver, gold, and copper are the dening xed points of the ITS-90. The temperature values of

these freezing points are assigned by the ITS-90. The pressure effect constants and the resistance ratios of the ITS-90 are listed in Table 1.

Table 1. The Dening Metal Freezing Points of the ITS-90, Pressure Constants, and Resistance Ratios

Fixed Point T90 (K) t90 (°C)

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 -- --

[1] Equivalent to millikelvins per standard atmosphere.

Pressure Effect of Fixed Points

Assigned Temperature

dt/dP

(10-8 K/Pa)

[1]

dt/dh

(10-3 K/m)

(T90)

dWr/dt

( x 0.001)

The xed points in Table 1 are intrinsic temperature standards according to the denition of the ITS-90. In certain conditions, these freezing points are highly reproducible, obtaining almost the same temperature where and when a freezing point is realized. The difference among realizations of a freezing point of indium, tin and zinc might be well within 1.0 mK. For aluminum and silver, the difference among realizations of a freezing point might be within a few millikelven.

The 5900 series and 5910 Series Fixed-point Cells are fully sealed cells that simplify the

realization process. The 5920 series of open xed-point cells include stainless steel caps and ports

for use with argon gas.

Fluke has open xed-point cells for those who require traditional xed-point cells. Contact Fluke

for more information.

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Users Guide

gpv001.jpg

Figure 1. The Metal Freezing Point Cell

To calibrate a Standard Platinum Resistance Thermometer (SPRT), you must be able to reach the xed-point temperatures in Table 1. When working with subranges, the freezing points change depending on the metal. Refer to Table 2 for subrange freezing points.

Table 2. Subranges of the ITS-90 and Freezing Points Required for Calibration

Subrange Freezing Points Required

0 °C to 961.78 °C FP Sn, FP Zn, FP Al, and FP Ag

0 °C to 660.323 °C FP Sn, FP Zn, and FP Al

0 °C to 419.527 °C FP Sn and FP Zn

0 °C to 231.928 °C FP In and FP Sn

0 °C to 156.5985 °C FP In

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Before You Start

Symbols Used

Table 3 lists the International Electrical Symbols. Some or all of these symbols may be used on the instrument or in this manual.

Symbol Description Symbol Description

Metal Freeze Point Cell

Before You Start

Table 3. International Electrical Symbols

X : W

CAT II

Hazardous Voltage

Hot Surface (Burn Hazard)

Risk of Danger. Important information. See manual.

AC (Alternating Current)

AC-DC

Double Insulated

PE Ground

CAT II equipment is designed to protect against transients from energy-consuming

equipment supplied from the xed installation, such as TVs, PCs, portable tools, and

other household appliances.

;

)



Off

Fuse

Battery

Conforms to Relevant Australian EMC Requirements.

Conforms to Relevant North American Safety Standards.

Conforms to European Union Directives.

Do Not Dispose of this Product as Unsorted Municipal Waste. Go

to Fluke’s Website for Recycling

Information.

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Users Guide

Safety Information

Use this instrument only as specied in this manual. Otherwise, the protection provided by the

instrument may be impaired.

The following denitions apply to the terms “Warning” and “Caution”.

• “Warning” identies conditions and actions that may pose hazards to the user.

• “Caution” identies conditions and actions that may damage the instrument being used.

To avoid 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 Users Guide.

• Follow all safety guidelines listed in the Users Guide.

• Avoid leaving a PRT installed for an extended period of time which can cause the PRT handle to become hot.

• Calibration Equipment should only be used by trained personnel.

• Use the Product only as specied, or the protection supplied by the Product can be compromised.

• Do not use and disable the Product if it is damaged.

• Use this Product indoors only.

• Have an approved technician repair the Product.

Warning W

To avoid possible damage to the instrument, follow these guidelines:

• Keep the cell clean and avoid contact with bare hands, tap water, or contaminated PRTs. If there is any chance that the cell has been contaminated, clean the quartz with reagent grade alcohol before inserting it into a furnace.

• Use the product in the vertical orientation only.

How to Contact Fluke

To contact Fluke, call one of the following telephone numbers:

• Technical Support USA: 1-877-355-3225

• Calibration/Repair USA: 1-877-355-3225

• Canada: 1-800-36-FLUKE (1-800-363-5853)

• Europe: +31-40-2675-200

• Japan: +81-3-6714-3114

• Singapore: +65-6799-5566

• China: +86-400-810-3435

• Brazil: +55-11-3759-7600

• Anywhere in the world: +1-425-446-6110

To see product information and download the latest manual supplements, visit Fluke Calibration’s website at www.ukecal.com.

To register your product, visit http://ukecal.com/register-product.

Caution W

Page 11

Metal Freeze Point Cell

Specications

Table 4. The Specication of Metal Freezing Point Cells

Model Number 5924 5925 5926 5927 5928

Fixed Point FP In FP Sn FP Zn FP Al FP Ag FP Au FP Cu

Reproducibility (mK) 0.15 to 0.30 0.2 to 0.4 0.2 to 0.4 0.6 to 1.0 1.0 to 2.0 -- 2.0 to 4.0

Expanded Uncertainty (mK), k = 2

Metal Purity 99.9999 % 99.9999 % 99.9999 % 99.9999 % 99.9999 % 99.9999 % 99.9999 %

Quantity of metal (kg) 0.97 0.96 0.95 0.35 1.35 -- 1.13

Outer Diameter of the Cell (mm)

Overall Height of the Cell (mm)

Inner Diameter of the Well (mm)

Total Immersion

[1]

Depth

[1] The distance from the bottom of the re-entrant well to the upper surface of the metal

(mm)

0.7 0.5 0.9 1.3 2.4 -- 10.0

50 50 50 50 50 50 50

596 596 596 596/696 696 696 696

8 8 8 8 8 8 8

195 195 195 195 195 195 195

Contact

Fluke

5929

Calibration Process Overview

A typical 592X Fluke Metal Fixed-Point Cell is shown in Figure 1. To calibrate a Metal FixedPoint Cell, a proper quantity of metal 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 must be less than 5 ppm. All of the graphite parts are then subjected to a high-temperature, high-vacuum treatment before loading the metal sample. A graphite disk is put on top of the crucible. The assembled graphite crucible, with the high-purity metal, is then enclosed in a long quartz cell. Pure silica wool insulation is interspersed between graphite disks to act as a thermal barrier.

Next, the cell is sealed with a specially designed stainless steel cap with a port and vacuum valve.

The cell is connected to a pumping and lling system and then 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 absorption gas on the surface of all parts in the

cell. Finally, the cell is lled with 99.999 % pure argon at a pressure close to 101.325 kPa at room

temperature and the vacuum valve closed.

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Users Guide

Care of Your Metal Freezing Point Cell

General Information

The metal freezing point cell is an extremely delicate device. Great care must be taken when working with or transporting the cell. The quartz glass outer shell is fragile and can be easily broken. Fluke suggests that the cell be kept in the vertical position for safety.

Note

Putting a cool cell in the horizontal orientation for a short period of time is not a typical cause of cell damage.

Transporting the cell on a general freight carrier will damage the cell beyond repair. To prevent damage, hand carry the cell from location to location. It is extremely important to keep the outer

surface of the cell clean to prevent devitrication of the quartz glass. Never touch the cell with

bare hands. When you have to handle the cell, always wear clean cotton gloves and use clean ashless paper. If there is a chance that the outside of the cell has been touched with bare hands, clean the quartz glass with alcohol before inserting it into a furnace.

Devitrication of Quartz Glass

Devitrication is a natural process with quartz glass. The quartz glass is utilized in a glass state. The most stable state for quartz is crystalline. Therefore, devitrication is the tendency

of the quartz to return to its most stable state. If the quartz is kept extremely clean and free of

contamination, devitrication will occur only at high temperatures. The process occurs more

rapidly and at lower temperatures when the glass has become contaminated by alkaline metals (Na, K, Mg, and Ca). The alkalis found in normal tap water can cause the process to start.

Caution W

Removal of the devitrication is not practical as it requires drastic measures and is potentially dangerous to the instrument and/or the user.

Devitrication starts with a dulling or opacity of the quartz. It develops into a rough and crumbling surface. Devitrication ultimately weakens the glass/quartz until it breaks or is

otherwise no longer useful.

The best cure for contamination and devitrication is prevention. Be aware of the causes and

signs of contamination which will help you take the steps necessary to control contamination of the cell. Keep your cell clean and avoid contact with bare hands, tap water, or contaminated SPRTs.

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Unpacking

Since it is difcult to hand carry or deliver an assembled 592X xed point cell, the 592X xed

point cell must be delivered as a kit. The kit is comprised of the following parts:

1. Crucible assembly (sealed in a Pyrex vessel in dry pure argon atmosphere)

2. High-purity graphite disks, 6 pieces, sealed in a Pyrex vessel in dry pure argon atmosphere, same Pyrex vessel as for crucible assembly

3. Pure fused silica (quartz glass) wool disks (in a Pyrex tube)

4. Fused silica (quartz glass) outer shell, 1 piece

5. Fused silica (quartz glass) reentrant well, 1 piece

6. A clean Pyrex tube or rod (used as tool, and will not be assembled into the cell)

7. Extra-clean ash less lter papers (used during assembling)

8. Stainless steel (SS) cap assembly, 1 set, including the following parts:

• SS top cover, 1 piece

• SS well clamp, 1 piece

• SS cover clamp ring, 1 piece

• Silicone O-ring 1.862 ID x 0.103 w, 1 piece

• Silicone O-ring 0.424 ID x 0.103 w, 1 piece

• Silicone seal washer (64.0 mm/50.6 mm x 5.0 mm), 1 piece

• High vacuum bellow valve, NUPRO SS-4H, 1 piece

• SS valve support bracket, 1 piece

• Screw, 8-32 x 1 SKTHD CAP, 4 pieces

• Screw, 4-40 x 1⁄4 SKTHD CAP SST, 3 pieces

• Screw, 8-32 x 5⁄16 PPHD, 2 pieces

Metal Freeze Point Cell

Unpacking

Assembly Guide

1. Assembly should be performed in a clean and suitable work area. Wear new clean gloves during assembling and only place the crucible assembly on clean ash-less paper (provided).

To prevent contamination of the crucible, do not break open the Pyrex vessel until you are ready to work with it.

2. Carefully break the top of the Pyrex vessel containing the crucible assembly and graphite disks with a clean metal tool. Remove the graphite disks from the Pyrex vessel and put them

on a piece of ash-less lter paper. Complete the entire assembly process without interruption

in order to avoid contamination and oxidation to pure metal.

3. Keep the fused silica outer shell (outer shell) at an angle of 10 degrees relative to the horizontal direction. Let the crucible assembly slide slowly and gently to the bottom of

the outer shell. Use a piece of ash-less lter paper to hold the crucible assembly during the

process. Put one piece of graphite disk on the top of the crucible assembly.

4. Carefully take pure fused silica wool disks from the Pyrex tube and put them into the outer shell using the Pyrex tube as a guide. Put more pure fused silica wool disks into the outer shell until their height is approximately 80 mm.

5. Put a graphite disk into the outer shell on the top of the pure fused silica wool disks. Push down the graphite disk until the height of pure fused silica wool disks decreases to approximately 40 mm using the Pyrex tube and fused silica well as guides (keep the surface of fused silica well clean during the entire assembling process). Insert the fused silica well through the holes of graphite disks and pure fused silica wool disks into the well of the crucible assembly to check the assembly. Next, take the fused silica well out of the outer shell.

6. Repeat steps 4 and 5 until ve graphite disks and enough pure fused silica wool disks are assembled into the outer shell as shown in Figure 2.

Caution W

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Users Guide

7. Carefully assemble the stainless steel (SS) cap onto the top of the Purge Gas Connection Assembly as shown in Figure 2.

8. Keep the outer surface of the fused silica cell clean to prevent devitrication. Clean the outer surface of the cell and the cell support container (basket) before assembling the cell into the container. Use only clean tissue and Reagent Grade alcohol for the cleaning. Put pure fused silica (quartz glass) wool felt with a thickness about 1 inch on the inner bottom of the container as cushion.

9. Insert the cell into the cell basket in the furnace.

Purge Gas Connection

Cooling Water Ports

Valve Support Bracket

Cooling Flange

Reentrant Tube

Graphite Crucible

High Purity Metal Sample

gpv002.eps

Figure 2. The Fluke Open Metal Freezing Point Cell

10. Connect the outlet of the vacuum valve to the pumping and lling system according to the attached Swagelok tube tting instructions.

11. Open the vacuum valve and pump the cell using a mechanical vacuum pump. The vacuum pressure will decrease to about 0.01 Torr. If the pressure does not decrease, check and tighten all of the screws.

Page 15

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 at.

The only exception is during the supercool. Impurities in the metal generally introduce a slightly negative slope to the plateau. Most of the different types of impurities will cause a drop in the freezing plateau. For example, gallium impurities in tin will cause a drop in the freezing plateau.

Different types of impurities can cause an increase in the plateau. For example, gold impurities in silver will cause the freezing plateau to increase. An extremely 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 rst cryoscopic constant. This calculation is

discussed in the Guidelines for Realizing the International Temperature Scale of 1990 (ITS-90).

For general uncertainty comparisons, the rst cryoscopic constant, the metal purity requirement,

and the difference in the liquidus point are outlined in Table 5. In a modern temperature standard laboratory 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 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 slow induced freezing technique

was found to t the purpose best (the details of the technique are described in the section

Procedure for Realizing the Freeze). A very slow freeze allows enough time to calibrate a number of SPRTs at the initial portion of a single freeze.

Metal Freeze Point Cell

Background Information

Table 5. Summary of the First Cryoscopic Constants and the Estimated Effects of Impurities

Substance 1st Cryoscopic

Constant

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 % -1.2 mK

Copper 0.000857/K 99.9999 % -1.2 mK

Impurity Level Deviation from Pure

Liquidus Point

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660.38

Temperature (° C )

Users Guide

660.36

660.34

660.32

660.30

660.28

660.26

660.24

660.22

0246 8101214161820

Theoretical freezing curveofanideal pure metalwithout supercool

Freezing curve of an ideal pure metalwithsupercool

Freezing curve of a realhigh-purity metal

Time (hours)

Figure 3. Freezing Curve Comparison of One Cell

gpv003.eps

The induced technique generates two liquid-solid interfaces in the cell. A continuous liquid-solid interface that, as nearly as is practical, encloses the sensor of the SPRT being calibrated. Another liquid-solid interface is formed on the wall of the graphite crucible. In such a situation, the outer interface advances slowly as the liquid continues to solidify. Ideally this generates a shell that continues to be of uniform thickness completely surrounding the liquid, which itself surrounds the inner liquid-solid interface that is adjacent to the thermometer well (Figure 4). The inner interface

is essentially static except when a specic heat-extraction process takes place. For example,

the insertion of a cool replacement thermometer. It is the temperature of the inner liquid-solid interface that is measured by the thermometer. Sometimes the inner liquid-solid interface is called

the dening temperature interface.

Page 17

Top Zone

Heater

Top Zone

Controller

419.03 C

SET

DOWN

Dierential TCs

SPRT Equilibration

EXIT

Block

Metal Freeze Point Cell

Background Information

Main Controller

PRT Sensor

419.03 C

SET DOWN UP EXIT

TOP END ZONE

Main Heater

Dierential TCs

Bottom Zone

Controller

419.03 C

SET

DOWN

EXIT

Bottom Zone

Heater

Freeze-P oint

Cell

PRIMARY ZONE

Cell Support

Container

Thermal Block

(3 zone subdivision)

BOTTOM END ZONE

Water Cooling

Coils

Supercooling

Gas Supply

(Argon)

Figure 4. 9114 Furnace Interior with Freeze Point Cell, Cross Sectional View

gpv005.eps

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Users Guide

Top Support

Cooling Water Port

Block

Retaining Plate

Entrant W ell

Purge Gas Connection

Cooling Flange

Top Cover

Cutout Thermocouple

Cooling Coils

Heating Element

Control and Cutout

Thermocouple

Metal Freeze Point Cell

Heat Pipe

Ceramic Fiber

Insulation

Air Gap

(Circulating Air)

Bottom Support

Figure 5. 9115A/9116A Furnace Interior with Freeze Point Cell, Cross Sectional View

Block

gpv006.eps

Page 19

Fiber Ceramic Insulation

Cell Containment Vessel or “Basket”

Metal Freeze Point Cell

Background Information

Fiber Ceramic Paper to Center Cell in Basket

Metal Freeze Point Cell (Cell Interior Construction Shown)

Fiber Ceramic Cushion

gpv010.eps

Figure 6. The Metal Freezing Point Cell in the Cell Containment Vessel (Basket)

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Users Guide

Shell

Graphite Crucible

Liquid Sample

Solid Sample

Reentrant Tube

Melting Stat

Figure 7. Two Liquid-solid Interfaces in the Cell

reezing State

gpv004.eps

It is extremely important to follow the instructions in this manual to ensure that there is a

uniform, stable, and controlled temperature environment when you enclose the xed point cell. Fluke has developed three designs of xed point furnaces to help you create this stable controlled

environment. The Model 9114 furnace has three independent heaters and controllers designed to be used for a temperature range up to 680 °C as shown in Figure 4.

The Model 9115A Furnace with a sodium-in-inconel heat-pipe is designed for a temperature range from 500 °C through 1000 °C. Although the 9115A furnace can be used up to 1100 °C, the longevity of the heat pipe may be shortened if used above 1000 °C for an extended period of time.

The Model 9116A furnace (Figure 5) has a higher temperature range and is designed for extended

use above 1000 °C, or more specically, the freezing point of copper (1084.62 °C).

Page 21

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 ±0.02 °C

The freezing point of tin Model 9114 furnace, three zones ±0.02 °C

The freezing point of zinc Model 9114 furnace, three zones ±0.02 °C

The freezing point of aluminum Model 9114 furnace, three zones ±0.03 °C

The freezing point of aluminum Model 9115 furnace, heat pipe ±0.03 °C

The freezing point of silver Model 9115 furnace, heat pipe ±0.05 °C

The freezing point of copper Model 9116 furnace, single zone ±0.2 °C

The cell should be placed into the cell containment vessel before insertion into any furnace.

The ideal conguration is to keep the cell in its own unique vessel. The cell containment vessel

(basket) for the Model 9114 furnace is shown in Figure 6. The 9115A and 9116A furnaces use a fused silica glass (quartz) cell basket to support and enclose the freezing point cell. A minimum of

50 mm (2 in) ber ceramic insulation is placed in the bottom of the cell basket to protect the cell.

Maintaining the Cell with Argon

It is recommended to maintain the cell in argon which will increase the life span of the cell. To maintain the cell with argon:

1. Connect the cell to a pumping and lling system.

2. Check all of the connections to make sure they are in good condition.

3. Check the seven screws on the cap to see if they are tight enough and tighten a little, if necessary.

4. Start pumping by using a mechanical vacuum pump. When the pressure reaches approximately 1e-2 Torr, open the vacuum valve slowly. If the pressure reaches approximately

-2

Torr again (it might take about 30 minutes), it indicates that all the connections and seals

are in good condition. If not, check all connections and sealing one-by-one.

5. Pump the cell using a diffusion pump or molecular pump for at least 4 hours. Rinse the cell

with 99.999 % pure argon three or four times and ll the cell with pure argon to a pressure

that is slight higher than local atmosphere pressure.

6. Close all valves.

Metal Freeze Point Cell

Maintaining the Cell with Argon

Vertical Temperature Gradient Adjustment

The vertical temperature gradient has to meet the requirement before the sample is to be melted. Otherwise, the cell may be broken. Therefore, the vertical temperature gradient should always be measured after the cell is installed and checked at least every six months. The 9114 furnace is a three-zone furnace whose gradient can be adjusted through the top and bottom zone heaters. The

9115A/9116A furnaces incorporate sodium heat pipes that distribute heat sufcient and uniform

enough that temperature a gradient adjustment is not required.

Vertical temperature gradient test method (9114 only):

1. Set the furnace temperature 5 °C below the melting point of the sample. For example, the melting point temperature of Zinc is 419.527 °C; the furnace temperature should be set to

414.5 °C. After the display temperature reaches the set point temperature, allow the furnace and cell to stabilize for 4-hours before proceeding.

2. Starting with the SPRT fully immersed at the bottom of the cell, record temperature measurements along the vertical axis of the cell in increments of 50 mm, up to 180 mm from the bottom of the cell. Allow a stabilization time of 2-minutes at each point before recording a measurement.

The vertical temperature requirements are listed in Table 6. If the furnace does not meet the requirement, the vertical temperature gradient should be adjusted through the top and bottom

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Users Guide

heater, see the sections named “End Zone Controllers” and “Nulling the Zone Controllers” in the

9114 Users Guide.

For installation of the 592X xed point cells, you must combine the process of vertical

temperature gradient measurement and the process of pressure adjustment in the cell (see

“Maintaining the Cell with Argon” in this manual).

Controller Display Accuracy Adjustment

The Controller Display does not have to be veried for accuracy when maintaining a cell with an

external temperature display instead of the Controller Display. If you are not using an external temperature display, there are instances where display accuracy is important and needs to be

veried for accuracy. Those instances are:

• The controller accuracy should be checked to know the offset using a calibrated SPRT (for

9114 and 9115) or a thermocouple (for 9116). The offset should be considered or corrected

during the realization of xed points.

• The controller accuracy should be corrected after the vertical temperature gradient is adjusted.

The accuracy can change after temperature gradient is adjusted.

• The controller accuracy should be checked after the sample fully melted in every realization of xed point. Please refer to the 9114/9115/9116 Furnace Users Manual for the accuracy

adjustment method.

To check the accuracy of the Controller Display, A calibrated SPRT or thermocouple should be

used. Thermocouple accuracy is not sufcient for the realization of the copper cell.

Use the this procedure to get the realization of the copper cell:

1. Raise the furnace to a temperature of 5 °C to 6 °C above the melting point with a ramp of

0.5 °C/min. Record the emf E(Cu) of the thermocouple during the melting plateau.

2. After the copper is melted, decrease the furnace to 2 °C above the freezing point. Maintain the furnace at this temperature for at least 4 hours or longer.

3. Check the accuracy of the furnace at the set temperature. When the temperature stabilizes at this temperature, record the emf E1. The actual temperature t can be calculated using the following equation:

t = 1084.62 °C + (E1 – E(Cu)) / dE/dt

dE/dt is 13.6 µV/°C for a Type R thermocouple, and 11.8 µV/°C for a Type S thermocouple.

4. Compare the calculated actual temperature and the furnace set temperature. Example: The furnace set temperature is 1085.6 °C and the calculated actual temperature is

1086.0 °C, the correction is 0.4 °C. Fluke recommends that this be performed each time.

Page 23

Metal Freeze Point Cell

Procedure for Realizing the Freeze (In, Zn, Al, Ag, and Cu Fixed Points)

Warning W

Due to different vapor pressure at the freezing points, the pumping and lling procedures are different for different xed-points.

This is the recommended procedure to realize the freezing point of 592X xed point cells. Other

procedures are sometimes employed in industry. These procedures provide a very stable, long freezing plateau that typically lasts for more than ten hours. The changes in temperature in the

rst half of the plateau are usually within ±0.2 mK to ±0.3 mK. A typical freezing curve is shown

in Figure 8.

Realization of the Freezing Point of In

1. Connect a mechanical vacuum pump and start pumping. When the pressure reaches approximately 1e-2 Torr, open the vacuum valve slowly. If the pressure reaches approximately 1e-2 Torr, again (it might take about 30 minutes), it indicates that all the connections and seals are in good condition. If not, check all connections and sealing one-by-one.

2. Turn-on the high vacuum system (diffusion pump or molecular pump), and open high vacuum valve to pump cell. The vacuum should be at 1e-5 Torr or lower.

3. Insert an SPRT into the reentrant well of the cell to monitor the temperature of the cell.

4. Make sure the vertical temperature gradient of the furnace with the cell is good enough. The

furnace vertical temperature gradient should be checked and adjusted if necessary at rst

operation and therefore every 6 months, refer to the 9114 Users Manual.

5. Turn-on the power to the furnace, and raise the temperature to 162 °C with a rate of 3 °C/min, while pumping continually. During this period, rinse the cell with pure argon (99.999 %) two or three times.

6. As soon as the indium is melted, change furnace temperature down to 2 °C higher than freezing point temperature of indium (158.6 °C). Rinse the cell with pure argon (99.999 %) two or three times. Fill the argon to the cell. Adjust the pressure close to the standard atmosphere and record the actual pressure in order to make the correction for the pressure

differences as shown in the section “The Correction for Pressure Difference”.

7. Stabilize the temperature for two hours.

8. Set the furnace temperature to 3 °C below the freezing point temperature (153.6 °C) decreasing at a rate of 0.1 °C/min.

9. When recalescence is observed, remove the SPRT. Insert a room temperature quartz rod for 1

minute or quartz tube for 2 minutes (creates “double freeze”).

10. Set the furnace to 1 °C below the freezing point temperature (155.6 °C)

11. The rst SPRT (check SPRT) to be calibrated is inserted into reentrant well and measurements

are made after the cell and SPRT are in the equilibrium. The rst SPRT is at room temperature

at the time of insertion. The furnace temperature is kept at a stable temperature of 1°C below the freezing point.

12. After all SPRTs are measured, set the furnace temperature at 20 °C with a rate of 2 °C/min.

13. The cell should be pumped for 10 minutes in the second day. At that time, the furnace temperature should close to room temperature. Fill pure argon to a pressure that is slightly higher than local atmosphere pressure.

14. Close all valves and turn-off the furnace.

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Realization of the Freezing Point of Sn

1. Connect a mechanical vacuum pump and start pumping. When the pressure reaches approximately 1e-2 Torr, open the vacuum valve slowly. If the pressure reaches approximately 1e-2 Torr again (it might take about 30 minutes), it indicates that all the connections and seals are in good condition. If not, check all connections and sealing one-by-one.

2. Turn-on the high vacuum system (diffusion pump or molecular pump), and open the high vacuum valve to pump cell. The vacuum should decrease to 1e-5 Torr or lower.

3. Insert an SPRT into the reentrant well of the cell to monitor the temperature of the cell.

4. Make sure the vertical temperature gradient of the furnace with the cell is good enough. The

furnace vertical temperature gradient should be checked and adjusted if necessary at rst

operation and every 6 months after, refer to the 9114 manual.

5. Turn-on the power to the furnace, and raise the temperature to 238 °C with a rate of 3 °C/min, while pumping continually. During this period, rinse the cell with pure argon (99.999 %) two or three times.

6. As soon as the tin is melted, decrease the furnace temperature to 2 °C higher than freezing point temperature of tin (233 °C). Rinse the cell with pure argon (99.999 %) two or three times. Fill the cell with argon. Adjust the pressure close to the standard atmosphere and record the actual pressure in order to make the correction for the pressure differences as shown in Chapter 7.

7. Stabilize the temperature for two hours.

8. Set the furnace temperature to 3 °C below freezing point temperature (228 °C) with a decrease rate of 0.1 °C/min.

9. When the temperature indicated by a thermometer immersed in the tin sample reaches the

freezing point, using the Model 9114 furnace, introduce a cold gas ow upward around the outer surface of the cell until recalescence. “Cold gas ow” means compressed air at an

approximate rate of 5-20 liter/min. (0.2 CFM to 0.7 CFM) and roughly 200 kPa (29 psia).

10. When recalescence is observed, turn-off the cold gas ow. Remove the SPRT and insert two

room temperature quartz rods one-by-one for 2 minutes each (creates “double freeze”).

11. Set the furnace to 1 °C below freezing point temperature (230.9 °C)

12. The rst SPRT (check SPRT) to be calibrated is inserted into reentrant well and measurements

are made after the cell and SPRT are in the equilibrium. The rst SPRT is at room temperature

at the time of insertion. The furnace temperature is kept at a stable temperature of 1 °C below the freezing point.

13. After all SPRTs are measured, set the furnace temperature at 20 °C with a rate of 2 °C/min.

14. The cell should be pumped for 10 minutes in the second day. At that time, the furnace temperature should close to room temperature. Fill the cell with pure argon to a pressure that is slightly higher than local atmosphere pressure.

15. Close all valves and turn-off the furnace.

Page 25

Realization of the Freezing Point of Zn

1. Connect a mechanical vacuum pump and start pumping. When the pressure reaches approximately 1e-2 Torr, open the vacuum valve slowly. If the pressure reaches approximately 1e-2 Torr again (it might take about 30 minutes), it indicates that all the connections and seals are in good condition. If not, check all connections and sealing one-by-one.

2. Turn-on the high vacuum system (diffusion pump or molecular pump), and open the high vacuum valve to pump cell. The vacuum pressure should decrease to 1e-5 Torr or lower.

3. Insert an SPRT into the reentrant well of the cell and monitor the temperature of the cell.

4. Make sure the vertical temperature gradient of the furnace with the cell meets the criteria described in Table 6. The furnace vertical temperature gradient should be checked and

adjusted if necessary at rst operation and every 6 months after, refer to the 9114 Users

Manual.

5. Turn-on the power to the furnace, and increase the temperature to 250 °C with a rate of 3 °C/ min, while pumping continually.

6. The furnace should be maintained at 250 °C for 2 hours, while pumping continually.

7. Rinse the cell with pure argon (99.999 %) two or three times. Fill the cell with argon to a pressure of 80 kPa.

8. Increase the furnace temperature to 425 °C with a rate of 3 °C.

DO NOT pump the cell for more than 10 seconds.

9. As soon as the temperature of the monitor SPRT reach 419.527 °C (melting point), pump the cell for 10 seconds using a mechanical pump. Fill the cell with pure argon. Adjust the pressure close to the standard atmosphere and record the actual pressure in order to make the

correction for the pressure differences as shown in the section “The Correction for Pressure Difference”.

10. As soon as the zinc is melted, decrease the furnace temperature to 2 °C higher than the freezing point temperature of zinc (421.5 °C).

11. Stabilize the temperature for two hours.

12. Set furnace temperature 2 °C below freezing point temperature (417.5 °C) with a decrease rate of 0.1 °C/min.

13. When recalescence is observed, remove the SPRT and insert a quartz rod at room temperature

for 1 minute or quartz tube for 2 minutes (creates “double freeze”).

14. Set the furnace 1 °C below freezing point temperature (418.5 °C).

15. Insert the rst SPRT (check SPRT) to be calibrated into the reentrant well measure after

the cell and SPRT are in equilibrium. The rst SPRT is at room temperature at the time of

insertion. Keep the furnace temperature at a stable temperature of 1 °C below the freezing point.

16. After all SPRTs are measured, set the furnace temperature at 20 °C with a rate of 2 °C/min.

17. Pump the cell for 10 minutes in the second day. At that time, the furnace temperature should close to room temperature. Fill the cell with pure argon to a pressure that is slightly higher than local atmosphere pressure.

18. Close all valves and turn-off the furnace.

Metal Freeze Point Cell

Procedure for Realizing the Freeze (In, Zn, Al, Ag, and Cu Fixed Points)

Warning W

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0.6552574

0.6552569

0.6552564

0.6552559

0.6552554

0.6552549

0.6552544

0.6552539

F18 Bridge reading (Rt/Rs)

0.6552534

0.6552529

10/8