Fluke 5943 User guide

5943

Gallium Melting Point Cell

Users Guide

2004, Rev. 1, 5/11

© 2004 - 2011 Fluke Corporation. All rights reserved. Specications subject to change without notice.

All product names are trademarks of their respective companies.

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

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SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF
DATA, ARISING FROM ANY CAUSE OR THEORY.

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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

Table of Contents

Title Page

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

Before You Start .................................................................................................................. 2

Symbols Used .................................................................................................................2

Safety Information .......................................................................................................... 3

How to Contact Fluke ..................................................................................................... 3

Specications ......................................................................................................................4

Environmental Conditions ..................................................................................................4

Construction ........................................................................................................................ 4

Care and Handling Guidelines ............................................................................................6

Operation ............................................................................................................................6

Freezing of Gallium ........................................................................................................ 6

Slow Freeze Method ....................................................................................................... 6

Fast Freeze Method ......................................................................................................... 7

Automated Freeze Method ..............................................................................................7

Melting Plateau ...................................................................................................................8

Realizing the Melting Point in a Bath ............................................................................. 8

Realizing the Melting Point in the 9230 Maintenance System .........................................10

The Correction for the Pressure Difference ...................................................................... 11

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5943

Users Guide

ii

List of Tables

Table Title

Table 1. International Electrical Symbols ............................................................................................... 2

Table 2. 5943 Specications ................................................................................................................... 4

Page

List of Figures

Figure Title Page

Figure 1. Construction of the Gallium Melting Point Cell .....................................................................5

Figure 2. Maintenance Bath Model 7011 with Gallium Cell Insert .......................................................7

Figure 3. Idealized Liquid/Solid Equilibrium State of a Gallium Cell ................................................... 9

Figure 4. Typical Melting Curve of Gallium ........................................................................................10

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iv

Introduction

The melting point of gallium (MPGa) at 29.7646 °C is one of the dening xed points of the

International Temperature Scale of 1990 (ITS-90). The MPGa is the phase equilibrium between
the liquid phase and solid phase of pure gallium at a pressure of one standard atmospheric

pressure (that is, 101.325 Pa). The temperature of the MPGa is dened to be 29.7646 °C by the

ITS-90 making it an intrinsic temperature standard. The MPGa is highly reproducible. You can
get almost the same temperature wherever and whenever you realize the MPGa. The differences
among the different realizations might be well within a few tenths of a millikelvin if you carefully
follow the instructions given in Supplementary Information for the ITS-90, Comite Consultatif de
Thermometrie (CCT), and Bureau International des Poids et Mesures (BIPM) 1990.

For your convenience Fluke has developed a series of sealed cells and new techniques for the
MPGa, which make it easier to realize the MPGa. The Model 5943 Stainless Steel-cased MPGa
Cell is a new member of the Fluke MPGa sealed cells series. The Model 5943 reserves all of the

benets of the Model 5903, including extremely low uncertainty. Stainless steel is used as case

material in the Model 5943 instead of the Pyrex glass used in the Model 5903. Therefore, the
Model 5943 is much more durable compared with the Model 5903. The Fluke sealed cells will
assist you immensely in realizing the MPGa in your laboratory.

The MPGa is an important xed point for the calibration of a standard platinum resistance
thermometer (SPRT). The ITS-90 species two subranges (for example, from 0 °C to 29.7646 °C

and from -38.8344 °C to 29.7646 °C, in which SPRTs must be calibrated at the MPGa). Checking
the stability of a temperature probe used mainly near room temperature at the MPGa is very
convenient. There is widespread application for the melting point of gallium in biologic,
environmental, oceanographic, geological, and energy research.

1

5943

Users Guide

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

Table 1. International Electrical Symbols

X
:
W

B

D

F

T

.

CAT II

Hazardous Voltage

Hot Surface (Burn Hazard)

Risk of Danger. Important
information. See manual.

AC (Alternating Current)

AC-DC

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.

o

I

M

;

)

P



Off

On

I

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.

2

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.

• Gallium is caustic. Consult the metal manufacturer’s MSDS (Material Safety

Data Sheet).

• Federal law prohibits carrying this cell in the passenger section of a
commercial airline. See MSDS in the back of this manual.

Gallium Melting Point Cell

Before You Start

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: [phone]

• Japan: [phone]

• Singapore: [phone]

• China: [phone]

• Brazil: [phone]

• Anywhere in the world: [phone]

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

3

5943

Users Guide

Specications

See Table 2 below for the Model 5943 Gallium Melting Point Cell specications.

Table 2. 5943Specications

Item Range

Reproducibility 0.05 mK (0.00005 °C)

Cell Uncertainty (k = 2) 0.08 mK to 0.15 mK (0.00008 °C to 0.000015 °C)

Certication (k = 2) 0.1 mK

Purity of Gallium 99.99999 %

Cell Outer Diameter 38.1 mm

Cell Overall Height 250.1 mm

Entrant Well Inner Diameter 8.2 mm

Immersion Depth

[1] Depth is measured from the bottom of the entrant well to the upper surface of the gallium.

[1]

Environmental Conditions

Although the instrument has been designed for optimum durability and trouble-free operation, it
must be handled with care. The instrument should not be operated in an excessively dusty or dirty
environment. The instrument operates safely under the following conditions:

• Temperature range: 5 °C to 35 °C (41 °F to 95 °F)

• Ambient relative humidity: 15 % to 50 %

• Pressure: 75k Pa to 106 kPa

• Mains voltage within ±10 % of nominal

• Altitudes less than 2,000 meters

168.0 mm

Construction

The Model 5943 Gallium Melting Point Cell consists of a stainless steel outer shell, a stainless

steel cap with an entrant well, a Teon® cell body containing the high-purity gallium and a nylon

lid with nylon entrant well (see Figure 1). Gallium expands on freezing by 3.1 % requiring the

cell to have exible walls. Teon® is a suitable material from this point of view, but Teon® is
gas-permeable over time. Over a four-year period, completely sealed Teon® cells drift about

0.5 mK under normal use. Therefore, a stainless steel outer case is used to keep gas tight in the
cell.

All of the parts and material used to construct the cell were carefully cleaned to avoid any

contamination to the high purity gallium. The high purity gallium was rst sealed into the Teon-

nylon body in a pure argon (99.999 %) atmosphere. The pressure of argon in the body was
adjusted to approximate 101,325 kPa at the melting temperature. The actual value of this pressure
was recorded and is reported on the Report of Test for the cell. The correction for pressure
difference from the standard value of 101,325 kPa is calculated according to the actual pressure in

the cell (see the section “Correction for Pressure Difference”). The assembled Teon®-nylon body

was then encased into the stainless steel outer shell. The stainless steel top with the entrant well
was joined to the stainless steel outer case using argon-arc welding. The assembled cell was then
connected to a vacuum system and pumped for more than ten hours. During the pumping period,

the cell was purged with high purity argon many times. Finally, the cell was lled with 99.999 %
pure argon and sealed at almost the same pressure as that in the Teon®-nylon body.

Note

Vibrations in the calibration environment should be minimized.

4

Gallium Melting Point Cell

Construction

Figure 1. Construction of the Gallium Melting Point Cell

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5943

Users Guide

Care and Handling Guidelines

The Model 5943 Gallium Melting Point Cell is a delicate device. Care must be taken in handling,
using, and transporting the cell. Keep the gallium in the cell in a solid state whenever possible.

Use and store the product in the vertical orientation only.

The surrounding temperature should be at least 4 °C below the melting point (for example, 25 °C
or lower).

Special care must be taken during transportation of the cell:

• Keep the gallium in the solid state.

• Store the cell in a vertical position.

• Keep the surrounding temperature lower than 25 °C.

If the instructions in this manual are carefully followed, the Model 5943 Gallium Melting Point
Cell will provide years of accurate use.

Operation

Caution W

Freezing of Gallium

The three methods for freezing the gallium cell, slow freeze, fast freeze, and automated freeze,
are described in the following sections.

Slow Freeze Method

In order to freeze all the gallium in the cell, immerse the cell in an ice bath (or a bath, with a
temperature close to the ice point). First, immerse only 1⁄4 of the cell in the bath, 30 minutes later
immerse 1⁄2 of the cell in the bath and another 30 minutes later immerse the 3⁄4 of the cell in the
bath. Because of the large super cool of gallium, even though the temperature of the gallium in
the cell declines to a temperature near 0 °C, all gallium might still remain in the liquid state for
a period of time. Therefore, monitor the temperature in the cell by using an SPRT. When the cell

is placed in an ice bath, the temperature indicated by an SPRT in the cell decreases fast at rst

and then decreases slowly, at last the temperature stops decreasing. After a period of time the
temperature raises, a signal that the gallium starts freezing. Finally, the temperature decreases
again and all of the gallium is frozen. Once frozen, the cell may be transferred to a maintenance
bath such as the Fluke Model 7011 (see Figure 2).

6

Gallium Melting Point Cell

Operation

Figure 2. Maintenance Bath Model 7011 with Gallium Cell Insert

Fast Freeze Method

The fast freeze method is based on the National Institute of Standards and Technology (NIST)

Technical Note 1265. Start with the xed point cell at room temperature. Use liquid nitrogen to

super cool two or three solid copper rods for insertion in the entrant well. The copper rods should
be only slightly smaller than the inside diameter of the entrant well. For example, the Fluke
Model 5943 Gallium Cell has an entrant well with an inside diameter of 8.2 mm. The solid copper
rods should have a diameter of approximately 7.0 mm. Insert the two or three super cooled copper
rods into the entrant well successively to induce nucleation. As soon as the rods have been used to
induce nucleation, place the cell in an ice bath for at least one hour or longer. Monitor the freeze
with an SPRT. Once the freeze has been achieved, place the cell in a maintenance bath such as the
Fluke Model 7011 (see Figure 2).

Automated Freeze Method

The Fluke Model 9230 Maintenance System is specically for the Model 5943 Gallium Cell. The

Model 9230 has a fully automated system for maintenance of the Model 5943. Refer to the Model
9230 Users Guide for complete information on how to use the maintenance device with the Model
5943 Gallium Cell.

gqu002.eps

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5943

Users Guide

Melting Plateau

Realizing the melting point can be performed in a bath or in the Model 9230 Maintenance System
as described below.

Realizing the Melting Point in a Bath

A stable and long (a few days) melting plateau, during which a great amount of thermometers can
be calibrated, is easy to obtain if you follow the instructions described below.

Put the cell into the maintenance bath at a temperature of 0.5 °C below the melting point. Fluke
manufactures a Model 7011 bath with a special cell support and SPRT preheat holder for the
purpose of maintaining the gallium cell (see Figure 2). Use silicone oil, 200.05 or 200.10,

as the bath uid. Light mineral oil, Fluke Model 5011 oil, can be used instead of silicon oil.

Use the same oil in the entrant well to provide adequate heat transfer between the cell and the
thermometer. The oil level in the well should be approximately the same level (52 mm below the
top of the cell) as that of the gallium in the cell when the thermometer is in place in the well.

With some care, distilled water can be used instead of oil as the bath uid and heat transfer

medium. Distilled water is cleaner and the viscosity of water is much lower than that of oil. The
water must be kept as clean as possible. Long-term direct contact between stainless steel and dirty
water causes the cell case to rust. The user should take the cell out of the bath and wipe the cell
surface dry using clean tissue. When the cell is not used for a period of time, store the cell in the
vertical position and in a clean place. The surrounding temperature should be below 25 °C. Before
freezing the cell, remove all of the water from the entrant well using an injector or other tool.
Never tilt the cell if you are not sure all of the gallium is frozen. If the temperature of the cell
goes below 0 °C during freezing, the water in the entrant well freezes and might break the entrant
well.

The procedure for realization of a melting curve in a bath is as follows. Make sure that all gallium
is frozen before starting. Maintain the bath at a temperature of 0.5 °C below the melting point
for at least 30 minutes. Raise the temperature to 1 °C above the melting point at a rate of 0.2 °C
per minute. Maintain the bath at this temperature for 20 minutes. Then insert an 8 watt heater
into the entrant well for four minutes. After the four minutes, decrease the bath to a temperature
of 0.01 °C to 0.1 °C above the melting point. Take the heater out of the entrant well and insert a
preheated thermometer into the well. When the thermal equilibrium between the thermometer and
pure gallium is reached (approximately 20 minutes), start the measurements. See Figure 3 for the
idealized liquid/solid equilibrium state of a gallium cell at the start of the melt. A typical melting
curve is shown in Figure 4. If the bath temperature is set at 0.1 °C above the melting point, the
melting curve will last for more than ten days. If the bath temperature is set at 0.01 °C above the
melting point, the melting curve will last for more than two months.

8

Gallium Melting Point Cell

Melting Plateau

Figure 3. Idealized Liquid/Solid Equilibrium State of a Gallium Cell

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5943

Users Guide

gqu003.eps

Figure 4. Typical Melting Curve of Gallium

Realizing the Melting Point in the 9230 Maintenance System

The user should be familiar with the following details before using the Model 9230 Maintenance
System. The Model 9230 is designed to automate the gallium cell melting process.

This melting process is accomplished through the use of the Auto Program, a microprocessor­controlled program that determines set temperatures, scan rates, duration times, Peltier module

congurations, and melt heater controls. By controlling these parameters in the proper order,
a temperature prole can be maintained in the block assembly that assures a uniform melt,

maintains the melt over long periods of time, properly refreezes the cell and keeps the cell ready
for the next melt cycle. The only attempt in describing the melting process in this manual is
to provide a simple overview. For complete details on realizing the melting point in the 9230
Maintenance System see the Model 9230 Users Guide. In the Auto Program, the Model 9230
stabilizes at 29.27 °C to allow the gallium cell to equalize. After equalization, the program
initiates the melt. The block temperature is set to initiate a melt on the outer surfaces of gallium

within the cell. At the appropriate time the unit beeps and the display ashes “Htr on” to indicate

that the inner melt heater has been turned ON. This allows the user to place the inner melt heater
in the entrant well of the cell to initiate the inner melt. Once the inner melt is initiated, the
heater is removed from the cell. The unit automatically de-energizes the heater at the appropriate
time. After the outer melt of the cell has been appropriately initiated, the unit changes into the
maintenance mode and the block temperature resets to 29.86 °C. After 30 to 60 minutes of
stabilization time, the unit is ready for use. The duration of the melt plateau varies depending on

usage, but lengths of ve days or longer is achievable.

10

The Correction for the Pressure Difference

()

t

()

t

()

The melting point of gallium, as mentioned earlier, is dened as the phase equilibrium between

the liquid phase and solid phase of pure gallium at a pressure of 101,325 Pa (P0). The actual
pressure, P, in a gallium cell may not be exactly the standard value. During the course of

manufacturing the xed-point cell, it is easier to seal the cell if the pressure in the cell is a

little lower than room pressure. The actual pressure value in the cell just at the melting point
is measured at Fluke so that the correction for the difference of the pressure can be made later

Table 2. of the ITS-90 gives the data of dT/dP for all the dening xed points. For the melting

point of gallium dT/dP = -2.0 x 10-8 °C/Pa. Therefore, the actual equilibrium temperature t′ can be
calculated using the following equation.

Actual Equilibrium Temperature Equation

−



=°−

t

29 7646

.

′

C

20 10






Furthermore, during the measurement at the melting point, the sensor of an SPRT is usually
placed at an average height, which is 0.143 m (0.168 m to 0.025 m) lower than the surface of
the gallium and where the pressure is higher than that at the surface due to the static head. The
correction, calculated according to the data given in Table 2 of the ITS-90, is -0.000172 °C. The
equilibrium temperature at an immersion depth of 0.143 m can be calculated using the following
equation.

Pressure Correction Equation



0 000172 20 10

′

=°−

29 7646

.

..

C






8

×−

.

PP

Pa

°− ×−

CC

Pa



°

C

0






−

8

PP



°

0






Gallium Melting Point Cell

The Correction for the Pressure Difference

Pressure Correction Example

The pressure of argon, P, at the melting point in the gallium point cell is 91,325 Pa as given on the

calibration certicate.

−

′

=°−

29 7646

.



0 000172 20 10 10000

C






°− ×−

..

CC

Pa

8

Pa



°






t′ = 29.7646 °C − 0.000172 °C

Thus:

t′ = 29.764428 °C

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