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SOFTWARE MANUAL

DILATOMETER SYSTEM

Version 10.1

August 2002

ANTER CORPORATION1700 Universal Road

Pittsburgh, PA 15235-3998

Phone: (412) 795-6410www.anter.com

Anter Corporation Dilatometer Software Manual 1

1.0 GENERAL SOFTWARE DESCRIPTION

This section describes procedures that are common to all Anter made dilatometersystems. It is possible that numerical examples may not match the values onewould encounter with this particular model.

Test parameter input and data acquisition is achieved with a Windows™ based programvia the computer system. The program also permits viewing data collected from pasttests, printing hard copy outputs from tests, and graphical representations of the data.All standard Windows™ techniques for navigating through the program are valid, bothvia mouse and keyboard.

Since the instrument’s control requires constant communication between the systemand the computer program, it is recommended that no other programs should be usedwhile the dilatometer software is operating.

The computer system is loaded with the operating software at the factory. The initialscreen has eight menu items to choose from: OPERATION, WINDOW, RESULTS,GRAPHS, ANALYSIS, OUTPUT, SETUP, and ABOUT. Each of these can beaccessed using the mouse, or by simultaneously pressing the ALT key and thecorresponding underlined letter. The screen also has a tool bar with the standardWindows™ icons for working with documents. Each of the menu choices and theirrespective menus will be discussed in the following sections.

Text conventions used will be that items located in a window are identified in brackets[character], and items selected during an operation are identified using a <<character>>notation.


2.0 OPERATION

Starting procedures and test parameter entries are accomplished through theOperation Menu.

Selecting the Operation menu will display the menu as shown in Figure AA.

Figure AA

The choices in this menu are for establishing and changing operational sequences,such as initial input of test information, beginning and ending a test, terminating thecurrent segment and moving to the next one, resetting the gauges prior to a test, andexiting the program to return to the Windows™ desktop.

2.1 START UP INFORMATION

Selecting Startup Information will automatically guide the operator to cyclethrough the following five choices (Test Type, Test ID Information, SampleInformation, Initial Delay and Temperature Program), in succession. One canalso modify an entry from any one of these menu items by simply selecting itfrom this menu. All inputs are into sub-levels, each of which is presentedsequentially, or accessed individually if needed. It should be noted, however,that once the automatic sequence has been broken, it is never restored and allfurther remaining entries must be made in the individual access mode.


2.1.1 Test Type

This screen permits the operator to choose between a standard thermalExpansion Test or a Calibration Run. It defaults to the expansion test, asshown below in Figure AB.

Select one <OK>.

With special application systems, some of the unique functions are availablefor selection in this dialog box.

[Differential] – Selection of this option will operate a dual/differentialconfiguration system in the differential mode, whereby sample 1 isconsidered the reference, and sample 2 is the unknown material. This isonly available when the optional software is installed. Without thissoftware, the function is not accessible.

After selecting [Differential], a dialog box appears and the appropriatereference file must be selected, much the same way a reference file mustbe selected for a calibration run (see Figure AC).

[Sintering] – Selection of this option will designate the test as a sinteringtest. This is only available when the optional software is installed. Withoutthis software, the function is not accessible.

[Softening] – Selection of this option will designate the test as a softeningpoint determination test. This is only available when the optional softwareis installed. Without this software, the function is not accessible.

Figure AB


2.1.2 Temperature Program

The next screen is the Select a Program input entry box screen, whichallows the operator to view existing (saved) temperature programs, select oneof the previously saved programs, or input a new temperature program.Figure AD shows this screen.

Depending on the type of test selected a slightly different dialog window boxwill appear. Expansion, calibration, and differential operation are identical tothis point.

Figure AD

Figure AC


2.1.2.1 Expansion Test

For demonstration purposes, the path of generating a new program will befollowed, which includes all possible steps one may encounter in thisprocess.

2.1.2.1.1 Generating A New Program

Choosing the [New] option (<<New>>) will display the Heating Rate &Dwell Time auxiliary dialog box (Figure AE) to prompt inputting a uniformheating rate and dwell time for a multiple step program. It is aconvenience item eliminating the need for entering the same rate anddwell information several times. The default values are set at “99oC/min”and “0 minute dwell”.

− Controlled rates can be selected within the bounds the instrument isable to follow. These limits are factory set and automatically appear inthis window. Rates may be entered in 0.1oC increments.

Pick the most likely rate and dwell time for the desired program.

Example: (highlight [99.0]) <<5.2>>, then (highlight [0]) and <<10>>.

Note: Selecting [Cancel] will return to previous screen without any of thefields being filled. Choosing [OK] without any data entries will fill the fieldswith the default values shown. Figure AF demonstrates the aboveexample.

Figure AE


Figure AF

At this point the dwell temperatures have to be entered into theTemperature field. Any combination of temperatures are allowed;however, one must keep in mind the practical limitation of the furnace andsample to change Temperature. For a single up-ramp program only thefirst segment is filled in. See Figure AG.

Figure AG


Once the last desired temperature segment is entered, the programtermination point is signaled with no entry into the next Temperature field.It is unnecessary to remove the unused entries from the Rate and DwellTime fields facing no temperature entries.

To alter any of the Rate or Dwell Time entries, simply highlight and writeover, such as it is shown below in Figure AH.

Another shortcut that may be useful is the uniform temperature stepoption. <<UNIFORM Temperature>> will prompt the Uniform Segmentsscreen, an auxiliary dialogue box show in Figure AI, where the lowesttemperature point (other than ambient) is entered under Start. Thehighest temperature point is entered under End and the size of thetemperature increments is entered under Increment.

Figure AH

Figure AI


After <OK> this will automatically fill the Temperature fields in theSegment Information, as shown in Figure AJ.

The new program can be saved immediately at this point by selecting<<SAVE exit>>. This action brings up a dialog box, Segment ProgramTitle where the program can be given a descriptive Title (shown in FiguresAK and AL). The Program Number is automatically assigned.

Figure AJ

Figure AL

Figure AK


<OK> will proceed to the {Test Information} dialog box AM. <Cancel> willalso proceed to the same point but without saving the program.

2.1.2.1.2 Recalling an Existing Program

All saved programs are listed in the Title List area of the SegmentInformation dialog box shown previously in Figure AD. Simply highlight aprogram and its content will fill the appropriate fields. Double clicking adesired program or choosing <OK> will select the program and insert itinto Segment Information (shown in Figure AN). From this point in theprogram, the inputs may be altered by the methods described inGenerating a New Program (section 2.1.2.1.1). If changes are made, thedialog box shown in Figure AK will appear prompting to save it in thealtered form, and to assign a title as in Figure AL.

Figure AN

2.1.4 Test Information

The next window to appear is the Test Information screen, which permitsinput of a Test Title, a description of the Sample Material, a Test Number, andthe Operator’s initials. This information will be displayed in the Statuswindow while the test is running, and is stored in the results file for the test.


Figure AO

− Test Title is a descriptive entry used to describe the nature, purpose,or intent of the test in its entirety. This Title will appear on all dataoutputs such as tables and graphs. It is editable in the data file. It isnot a mandatory entry.

− Sample Material is a generic description of the sample being tested. Itis not a mandatory entry.

− Test Number is an automatically assigned number, incremented everytime a new test is started. If desired it may be overridden.

− Operator is not a mandatory entry, provides the operator’s name forrecord.

<OK> will progress to the next input section. <Cancel> will also continue tothe next input window, but without any of the entries.

2.1.5 Sample Information

After entering the test information, the Sample Information screen (FigureAP) appears. It is used to define the file name and the initial length of eachsample being tested. If the instrument is able to test two samples this windowmay be selected twice, once for each sample. Use the <ANOTHER> macro


button to start entering the information for the second sample. Then, click onthe <FINISHED> button to continue.

Figure AP

− File ID is a designation under which the data will be stored. Inselecting a designation one should choose a meaningful one which willaid when a directory search is made to recall completed tests for futureanalysis. All restrictions for file names imposed by Windows must beobserved (no /, . etc.) If two samples are being tested in the sametime, each one will be given a discrete file extension, so the file IDname may remain the same, without problems of overwriting the files.

− Length is the externally measured sample dimension in unitsdisplayed.

− Title is a more specific description of this particular sample. Oftenprocess or batch numbers, formation numbers or narrative type text isused.

If only one sample is to be tested, then after the entry of the inputs for sample1, select <FINISHED>. If two samples are to be tested, then after the entry ofthe inputs for sample 1, select <ANOTHER>. This will automatically display aSample Information box for the second sample.


2.1.6 Initial Delay

After completion of all Sample Information the Initial Delay dialog box shownin Figure AR appears. The primary use of the initial delay is to permit thesample(s) and dilatometer to equilibrate with the ambient environment, or toallow time to cool off and restart unattended. Two types of initial delay maybe employed: a timed delay or a temperature limit delay. The time delay is inhours, and may be any value from 0 to 99. When the test is started, in realitya count down of the delay starts and heating will begin only after this delaytime has expired. The temperature of the system is not a limiting factor at anytime during the delay period. The temperature delay will not permit thedilatometer to begin heating until all temperatures are below the input value.This is monitored with no regard to the length of time it may take to satisfy.

Figure AR

<OK> will progress to the next input step, as well will <Cancel> but with thedefault None choice.


2.1.7 Number of Repeats

The Number of Repeats screen (Figure AS) allows the user to programrepetitive tests for the dilatometer. The repeat tests input may be from 0 to 8,yielding a maximum of 9 tests from any one program. If repeats areemployed, a screen for delay between the repeats is then displayed.

Figure AS

<OK> will progress to the next input step, as will <Cancel> but with thedefault “0” choice.

2.1.8 Start Test

Once all the information has been entered, the Start Test screen will bedisplayed. Selecting <<YES>> begins the testing program, while <<NO>>retains the data input without beginning the test. If NO was selected, the testmay be started by using the START TEST option in the menu group.


Once all information is entered, the STATUS window (AU) will appear. Thiswindow will be displayed while the test is running. It shows all the informationentered by the operator, plus the current status of the dilatometer, samplelength change and temperature.

Several dialog boxes appear with working and informational messages.Acknowledge and act upon each as required.

Figure AT

Figure AU


3.0 WINDOW

By choosing the window command, the menu listed below will be shown:

This menu has the standard Windows™ arrangement for the desktop, enabling the userto cascade or tile windows, close them or arrange icons. It also permits the selection ofthe aforementioned status window, the temperature window, and real time data plots oftemperature and sample’s length change versus time for the test.

3.1 TEMPERATURE

The temperature window shows the sample’s temperature while tested. It ismovable and sizable as needed.

Figure AV


3.2 REAL TIME PLOTS

The real time plots AY display the temperatures (set point, furnace, and sample)versus time, as well as the samples’ length changes versus time, during the test.

Figure AX

Figure AY


The real time data graph AY can be adjusted as follows.

3.2.1 Scales

Right clicking the mouse over the graph will bring up the graph parameterwindow, where the x and y axis scales can be changed.

Since the right y scale for expansion is different from the left y scale fortemperature, its value can be adjusted by <<RIGHT CLICK>> on the dL1button and changing values in the scale window.

3.2.2 Traces

Each macro button on the upper left toggles to turn on/off the correspondingtrace.

TARG denotes the final desired temperature for the segment.SETP denotes the progress of the control set point.RATE is the heating rate for the furnace.Smp is the sample temperature.DL1 expansion of sample 1 (dL2, sample 2, etc.).DJ cold junction temperature.

3.2.3 Other Operations

<RIGHT CLICK> will bring up a sub-menu for other self explanatoryoperations.

3.2.4 Update

The graph automatically re-scales itself in 10 minute intervals, and updates in10 second intervals.


4.0 RESULTS

The results menu is used for tests which are currently running, to display the results filefor each run. See Figure AZ.

Each file has the header information that was input at the beginning of the test, thecorrection coefficients for the dilatometer, and a listing of time, temperature, gaugedisplacement and corrections as saved during the test. This is shown in Figure BA.

Figure AZ

Figure BA


For obtaining tables of percent expansion and coefficients of thermal expansion versustemperature, the Tabulated Data option should be chosen from the Result screen. Thiswill bring up another dialog box, asking for order of curve fitting, minimum and maximumtemperature limits and increment for tabulating the data. See Figure BB.

Figure BB


5.0 GRAPHS

The graph display gives the operator the ability to view plots for the samples, andchange the graph scales with graph parameters. The menu is shown below in FigureBC:

Figure BC


6.0 ANALYSIS

Post analysis for previous tests can be done from this menu, as well as editingcalibration or expansion data immediately after completing a tests.

The Post Analysis option offers the capability to view the test results as data files, tablesof percent expansion and coefficients of thermal expansion versus temperature, andgraphs, for both calibration and thermal expansion tests.

Figure BE

Figure BD


The files can also be corrected and reanalyzed, in case the initial test information wasentered erroneously.


7.0 OUTPUT

The output menu is standard for all Windows™ applications. This permits printing hardcopies of test results and plots for later viewing.

The menu is shown below in Figure BF:

Figure BF


8.0 SETUP

Setup has several specific commands to determine the computer/dilatometerconnections. This window offers the capability to change the port and baud rate, toaccess the diagnostics and demonstration tests, to tune the instrument and to alter theequilibrium criteria, if needed (these are preset at the factory and it is advised that theyare left unchanged). The input units can be chosen as English (in.) or Metric (mm) fromthis window as well. In case any hardware error appears on the status screen, it can becleared and the test may proceed by using the Clear Hardware Error choice from thismenu.

Figure BG


9.0 ABOUT This menu shows program version information.

UNITHERMTM MODEL 1161 HIGH TEMPERATUREDILATOMETER SYSTEM

OPERATING AND MAINTENANCE MANUAL

Version 4.0

January 2001

ANTER CORPORATION1700 Universal Road

Pittsburgh, PA 15235-3998

(412) 795-6410 Phone(412) 795-8225 Fax

E-mail: [email protected]://www.anter.com

Table of Contents

1.0 INSTALLATION 21.1 UNPACKING INSTRUMENT 21.2 INSTRUMENT SETUP AND INSTALLATION 2

1.2.1 LOCATION 21.2.2 POWER 21.2.3 ELECTRICAL CONNECTIONS 21.2.4 WATER 31.2.5 INERT GAS ATMOSPHERE 31.2.6 VACUUM OPERATION (Optional) 4

2.0 THEORY OF OPERATION 53.0 GENERAL HANDLING 13

3.1 PUSH ROD CHECK 133.2 OPENING AND CLOSING 133.3 LOADING AND UNLOADING 133.4 NONSTANDARD SAMPLES 14

3.4.1 SMALL SAMPLES 143.4.2 SOFTENING POINT STUDY SAMPLES 14

3.5 PROTECTIVE ATMOSPHERE 143.5.1 EVACUATIN PROCEDURE 143.5.2 VACUUM OPERATION (Optional) 15

4.0 OPERATION 165.0 ADJUSTMENTS AND MAINTENANCE 17

5.1 PUSHROD TRACKING PRESSURE 175.2 CHANGING SAMPLE TESTING LENGTH 17

5.2.1 PRE ADJUSTMENT PREPARATIONS 185.2.2 ADJUSTMENT 185.2.3 ZERO RESET (Optional Procedure) 185.2.4 TRAVEL CHECK 195.2.5 SPACERS 19

5.3 TUNING THE FURNACE (Tune Utility) 195.3.1 SET UP 195.3.2 THE PROCESS 19

5.4 PERIODIC RECALIBRATION OF SYSTEM COMPONENTS 205.5 CALIBRATION TEST 205.6 VERIFICATION TESTS 21

6.0 TESTING CONSIDERATIONS 226.1 CONTROL STRATEGY 22

6.1.1 FURNACE CONTROL 226.1.2 TARGETING 22

6.2 THERMAL CYCLE PROGRAMMING 236.3 SAFETY INTERLOCKS 23

6.3.1 WATER INTERLOCK 236.3.2 TEMPERATURE INTERLOCKS 24

6.3.2.1 OVERTEMPERATURE DETECTION 246.3.2.2 OPEN THERMOCOUPLE MONITOR 24

6.3.3 DEAD COMPUTER DETECTION 24

Table of Contents

7.0 DIGITAL TRANSDUCER 257.1 OPERATION AND RESET 25

7.1.1 GENERAL OPERATION 257.1.2 INITIAL RESET AND BATTERY CHARGING 257.1.3 PRECAUTIONS 267.1.4 OPERATIONAL SETTINGS 26

7.2 FUNCTIONAL DESCRIPTION 277.2.1 POWER SWITCH 277.2.2 RESET SWITCH 277.2.3 DIRECTION SWITCH 277.2.4 MODE SWITCH 277.2.5 INCH/MM SWITCH 287.2.6 RESET SWITCH 287.2.7 DIRECTION SWITCH 297.2.8 MODE SWITCH 297.2.9 INCH/MM SWITCH 29

. 7.3 POWER SUPPLY CONSIDERATIONS 307.3.1 NORMAL OPERATIONS 307.3.2 RESTARTING AFTER CHARGE UP 307.3.3 BATTERY OPERATION 30

APPENDIX

Anter Corporation 1161v4.0 1

1.0 INSTALLATION

1.1 UNPACKING INSTRUMENT

Exercise care when removing the instrument and the interfaced devices from thecrate(s). The instrument is highly sensitive and carelessness in handling couldaffect the instrument's performance. It is recommended to let the instrument andinterfaced devices reach an equilibrium at room temperature before installation.Damages, if noticed, must be communicated to the carrier, and all packingmaterials retained for inspection.

1.2 INSTRUMENT SETUP AND INSTALLATION

1.2.1 Location

Place the dilatometer away from high traffic areas. Since the instrument is ahighly accurate measuring device, it will be very sensitive to wide temperaturefluctuations. For this reason air drafts and areas near frequently opened doorsshould be avoided. Air-conditioned space is preferred. Some general guidelinesfor the operating environment are as follows:

Temperature: 60o to 90oF (15o to 35oC)Humidity: 20% to 80% (Non-condensing)

The unit is designed to require minimum workspace. About 2 ft. workspace infront and behind the unit is required, with at least 1 ft. on each side.

1.2.2 Power

The Installation and Utility Requirements sheet in the Appendix contains specificdetails concerning voltage, current, and connector requirements.

WARNING:

PROPER GROUNDING MUST BE OBSERVED AT ALL TIMES.

To properly connect the power to the computer, monitor, and printer, it isnecessary to have at least three grounded 120 VAC outlets available (total fusedcurrent of at least 15 A). In all situations, a line filter with surge protection shouldbe installed. For 220 or 208V installations, a line voltage adjusting transformermay be required with these outlets.

1.2.3 Electrical Connections

Turn the power switches on both the computer and the instrument to 'OFF'.Insert the male ends of the power cords into a power outlet. Connect cable tocomputer.


Connect the cables for the printer, keyboard, and display monitor to the I/O ports(labeled PRINTER, KEYBOARD, and MONITOR, respectively) on the computer.Insert the opposite end of the printer cable to the input port located on the side ofthe printer. Then, with the printer, computer, and monitor power switches in the'OFF' position, plug the power cord from each into a properly grounded outlet.

1.2.4 Water

The cooling water should have a pressure and volume flow rate as specified inthe Installation and Utility Requirements in the Appendix.

WARNING:

The water INLET and OUTLET are NOT interchangeable.

A flexible hose hook up is recommended. An interruption of the water flow willlead to warming of the water cooled dilatometer parts, and cause prematureending of the test when the water interlock drops out.

1.2.5 Inert Gas Atmosphere

Inert gas is not required for operation of the Model 1161 since it can be operatedin air. It is recommended that an air purge (with desiccator and filter) be run toavoid possible moisture condensing in the unit. If the sample being testedrequires an inert purge, provisions are made to allow supplying the samplechamber with a purge gas.

Connect the pressure regulated inert gas to the purge gas inlet hose at the rearof the instrument (Maximum pressure and flow rates are specified in theInstallation and Utility Requirements in the Appendix). All gas controls, includingvalves and flow meters must be supplied and installed externally.

An outlet is also provided for collecting the effluent purge gas. If a bubbler issupplied with the instrument it should be installed on the purge gas outlet. Thelower chamber of the bubbler should be filled with enough water or oil to coverthe bottom of the bubbler tube. The bubbler must be operated in the verticalposition to allow the upper check valve to seal properly. This prevents air frombeing sucked back into the instrument (which could occur when cooled rapidly, orwhen vacuum is pulled on the instrument).

Argon is the preferred purge gas, since it is inert to well above 1800oC. Nitrogencan also be used. Any purge gas must be high grade DRY gas. Moisture in thepurge gas will condense on the dilatometer parts, and possibly result in crackingor other related damage to the muffle tube and dilatometer tube. For safetyreasons, potentially explosive purge gases are not recommended, except in casewhen hydrogen service option is supplied (see addendum dealing with thisoption). If non-inert purge gases are used in any quantity or mixture, allwarranties on the equipment will be void, unless the unit is specifically configuredfor these purge gases.


The standard furnace and the connected head chamber are NOTDESIGNED FOR INTERNAL PRESSURIZATION. Internal pressure build updue to excessive purge gas flow must be limited to less than 2 psig forsafety reasons.

1.2.6 Vacuum Operation (Optional)

If equipment is supplied with vacuum option, it will require a shut off on the purgegas inlet line, mounted on the top of the instrument. A large diameter tube(extending out the rear of the equipment, from the dilatometer head) is connectedto a vacuum pump. When it is desired to pull vacuum in the instrument, thepurge gas shutoff valve must be closed. When backfilling the instrument with apurge gas prior to a test, this valve can be used to adjust the flow rate of theincoming gas.

Flow rate can be judged by the rapidity and size of the bubbles as they emergefrom the bottom tube into the liquid. Although actual flow cannot be quantitativelydefined by only using a bubbler, experience will show that a steady, even flow ofbubbles is usually adequate to keep a positive pressure inside the furnace whenheating or cooling.


2.0 THEORY OF OPERATIONPRINCIPLES OF PUSH-ROD DILATOMETRY

A DILATOMETER measures the expansion of a material when it is heated. Asmall sample of the material is placed into the instrument and then heated (orcooled) according to a schedule picked by the investigator.

1.) PRINCIPLE OF OPERATION

Pushrod dilatometry, as its name implies, involves intermediary machinemembers to transmit the dimensional change caused by subjecting a sample to achange in temperature. The need for these members is a practical one, since thetransducer that registers this change cannot normally be subjected to the sametemperature excursion as the sample. The closer the transducer can be coupledto the sample, the less the transmission member can influence the results, and,consequently, the more ideal the dilatometer becomes. Specifically, the moreone can reduce the contributions made by any such intervening machinemembers, the more purely the data will represent true values.

In principle, one can devise a simple arrangement in which the movement istransmitted out of the controlled environments and into the ambient by holdingthe sample between two rods which extend outside of the heated region asshown on Figure 1. The sample pushes the two rods (A and B) as it is beingheated, hence the name "pushrod". The sample will expand an amount shown bythe shaded area, ∆LS. By examining the experimental model, it becomesimmediately clear that this configuration will not produce the desired ∆LS. Sinceportions of both rods A and B are in the controlled environment, it is inevitablethat they themselves will also expand (∆LA and ∆LB respectively). Thus, themeasured value of (∆XA+∆XB) will contain (∆LA+∆LB) in addition to ∆LS. Thesample’s length change, ∆LS, can therefore be written as:

(Eq. 1) ∆LS = (∆XA - ∆LA)+( ∆XB - ∆LB)

Unless one can assign values to ∆LA and ∆LB, the true magnitude of ∆LS cannotbe determined from the measured values of ∆XA and ∆XB alone. Obviously, if ∆LAand ∆LB are not present at all, the measurement becomes absolute, but as longas this is not the case, the measurement is, in principle, a relative one.

The most tempting prospect is to minimize the magnitudes of ∆LA and ∆LB incomparison to ∆LS and then to neglect them. If the material of rods A and B donot expand appreciably compared to the sample, or not at all, the conditionsbecome favorable to obtain results with reasonable accuracy. A good example ofthis would be to use light beams that do not expand when entering the controlledenvironment in place of rods A and B. More frequently, very low expansionmaterials such as fused silica are used for rods A and B, and, for manyapplications, this is enough to reduce inaccuracies to a small fraction of themeasured values when high expansion materials such as plastics are tested.


In general usage, however, one must determine the magnitude of ∆LA and ∆LBaccurately. Most commonly, one tests a sample from a material already well-defined by some other absolute method (twin telescopes, interferometer, etc.),which then leaves only the combined values of ∆LA and ∆LB unknown. Thisprocess is known as "calibration" for the dilatometer; the well-defined material isreferred to as a "standard" or "reference;" and the combined value of ∆LA and∆LB and is known as "system correction." Upon closer examination, it is clear thatthe correction obtained with a standard will be true only if this sample is of thesame length, ensuring that the protruding lengths of rods A and B into thecontrolled environment region are identical during the calibration and during thetest. Furthermore, what may be true at one value of temperature T may not betrue at another. To ensure that a calibration is indeed applicable:

− the sample and reference lengths must be close to each other.− the calibration thermal cycle must closely approximate the test cycle

(or vice versa).− the reference's expansion must be close to the expected expansion of

the sample.

(The last criterion is often difficult to visualize as being important, yet experiencebears it out to be true.)

A more common variation of this device involves both rods' entering thecontrolled environment from the same side (Figure 2). For sake of continuity inthis discussion, rod B, now longer than before, is divided into two sections: thepart that is equal in length with A and as before noted to expand ∆LB, and theportion that happens to be equal to and running alongside of the sample, C, thatexpands ∆LC. When heated, both legs (A+sample) and (B+C) will expand. Sincethey move in the same direction, the transducer will register ∆X, the differencebetween the two movements. Thus:

(Eq. 2) ∆X = (∆LS + ∆LA) - (∆LB + ∆LC)

By fabricating A and B from identical material and keeping them close to eachother, it is reasonable to postulate that they will behave identically under mostconditions. This assumption makes ∆LA = ∆LB, reducing Equation 2 to:

(Eq. 3) ∆X = ∆LS - ∆LC

which states that a dilatometer of this configuration always measures thedifference between the expansion of the sample and that of its own materialpassing alongside the sample. As with the previous configuration before, thevalue of ∆LC can be determined by first calibrating the dilatometer with astandard. (The criteria discussed earlier for a valid calibration are still holdingtrue.)


A natural extension of the above model is another configuration known as a"differential" dilatometer. In this design, sections B and C are indeed twoseparate pieces. B is made of the same material as A, so ∆LA cancels out ∆LB.Section C can be made of any benchmark material usually referred to as the"reference", often the same type used for calibrating an ordinary dilatometer.Equation 3 established earlier that the measured value is the difference inexpansion between the sample and section C. This arrangement can offeradvantages in certain applications where:

− direct comparison of two samples is desired, when it is more importantto know their relative performance than their absolute expansion (forexample, screening studies, quality control testing, formulationevaluation, etc.).

− absolute expansion determination in case C is actually a standard.− the effects of non-uniform heating, and inaccurate temperature (T)

measurement are to be minimized.

Differential dilatometers usually measure very small differences with highmagnification. A major drawback of this configuration is its susceptibility to errorsdue to transducer gain misadjustments or malfunctions. As an extreme condition,one can obtain seemingly valid data (that is, the sample appears to expandexactly at the same rate as the reference) with the transducer literally turned off.Additionally, the high magnification severely restricts the range of measurabledisplacement. For these reasons, the use of differential dilatometers should belimited to applications in which the advantages clearly outweigh thesedrawbacks. If a temperature change from TO

to T has caused this expansion in asample of initial length LO, the average coefficient of linear thermal expansioncan be calculated as:

(Eq. 4) α= (∆LS/LO)/(T-TO)

This coefficient, often referred to as CTE, is only true for the temperature rangeTO to T. (Note that the word "linear" should never precede the word "coefficient",as it always implies uniaxial expansion rather than linearity of the coefficient.)

2.) Definitions

Linear Thermal Expansion -- The change in length of a material resulting from atemperature change. Linear thermal expansion is symbolically represented by∆L/L0, where ∆L is the observed change in length (∆L = L1 - L0), and L0 and L1are the lengths of the specimen at reference temperature T0 and testtemperatures T1. Linear thermal expansion is dimensionless, it is often expressedas a percentage, or in parts per million (such as µm/m) units.

Mean Coefficient of Linear Thermal Expansion -- The linear thermal expansionper change in temperature. The mean coefficient of linear thermal expansion, α,is defined as:

α = 1/L0 [(L1 - L0) / (T1 - T0)] = [1/L0 (∆L/∆T)]


(It is customary to designate the coefficient of thermal expansion with the greekletter alpha (α). For the mean coefficient, a bar is placed over it, and is referred toas alpha-bar. In industry, frequently the whole process is referred to as “CTEtesting”.)

The value of the mean coefficient must be accompanied by the values of the twotemperatures.

Instantaneous Coefficient of Linear Thermal Expansion -- The slope of the linearthermal expansion curve at temperature T. Instantaneous coefficient of linearthermal expansion is represented by:

αT = (1/L0) dL/dT

The value of the instantaneous coefficient must be accompanied by thetemperature at which it is determined.

3.) Types of Dilatometers

There are two basic types:

Standard Dilatometer

It is the basic device (described earlier in section 1). To calibrate this kind ofdevice, a Standard or Reference sample is tested repeatedly first and acalibration factor for the tube is then computed from these tests. The calibrationfactor is used when unknown materials are tested.

b.) Differential Dilatometer

This device always measures the difference between two samples. The twosamples are placed into the dilatometer tube, side-by-side, and two push-rodsare used to track each sample independently. Since the measurement is one vs.the other sample, the tube has no other purpose than to support the samples. Adifferential dilatometer can be calibrated similarly to the standard dilatometer, butmost frequently it is operated with the Reference in place of one sample. Thistype of instrument has been greatly overrated for its sensitivity, disregardingdrawbacks such as short stroke. Often the device is favored purely on personalpreference with not much fundamental reasoning behind it.

4.) Common Configurations

There are two configurations that are most common among commercial devices.Researchers frequently come up with clever new seemingly differentconfigurations, but on close scrutiny, they all fall within the two basic ones or arenot practical due to complexity, cost, or requiring very high skills from theoperator.


a.) Horizontal Dilatometers

As the name implies, this device has a horizontal tube with the sample laying onits side. Advantage of this configuration is better thermal uniformity along thesample. Disadvantage, especially for samples with large shrinkage, is the highpush-rod pressures needed to slide the sample along to keep it in contract withthe end-plate of the tube. Usually no provision available for push-rodcounterbalancing (see later).

b.) Vertical Dilatometers

The sample stands up on the end-plate of the dilatometer tube with the push-rodresting on it. It does not suffer from the tracking problems noted with horizontalinstruments, and therefore is especially useful for measuring large shrinkages(sintering, etc.). As with every vertical system, thermal uniformity is not as goodas in a horizontal device, however, one can limit sample size to be still within anearly uniform thermal zone. Counterbalancing with dead weight is possible.Tracking pressures can be greatly reduced, but not below a minimum needed forsmooth and continuous movement.

The UnithermTM line is structured so that almost any dilatometer can beconfigured either as a Standard or as a Differential device. There are bothhorizontal and vertical units available in every model.

5.) Advanced Configurations

a.) Multi Sample Dilatometers

Unique to the UnithermTM line is the ability to test several samples concurrently inthe same furnace and to run several devices parallel with the same computer.This greatly increases testing capacity at a fraction of the cost of multipleinstruments. (It is often possible to add further testing capacity to an alreadyexisting system at a later date.)

b.) Large Sample Dilatometers

Frequently the need arises to test materials that are not homogeneous, andtherefore necessitating samples larger than ordinary dilatometers canaccommodate. Natural substances (rocks, mineral deposits, food stuffs), plasticfoams, certain ceramics, large grain carbon and graphites, etc. fall into thiscategory. Sometimes it is the poor load bearing ability, at other times it is the sizeof the particles in a mix (concrete, for example), or grain size that necessitatesthe size increases.

The UnithermTM line contains several models that are also available in the largesample configuration.


6.) Test Procedure

a.) Expansion Measurement

The sample is placed into a holder, usually called the dilatometer tube. This maybe horizontal or vertical. A rod in the axis of the tube contacts the sample totransmit the size increase. This is called the push-rod. The sample, when itexpands, pushes the tube and the push-rod in opposite directions. Thismovement is sensed by a transducer. The tube and the transducer are fixed tothe same reference surface with the moving member of the transducer coupledto the push-rod. The transducer may be an ordinary dial indicator, an LVDT, orsome other type of displacement sensor. The UnithermTM line only uses digitaltransducers which have very high accuracy and do not require periodicrecalibration. This is unique among all dilatometers made anywhere in the world.

b.) Temperature Control and Measurement

Usually thermocouples are used, except for the Ultra High Temperature systemwhich employs a pyrometer. It is imperative to know the temperature of thesample region (not only the sample itself) well, and to control the furnace toprovide uniform sample temperature. It is often promoted that the sampletemperature must be determined closely and investigators have even attachedthermocouples or embedded the couples into the sample. This is not a goodpractice, as it will interfere with the free movement of the sample and will totallyignore the temperature of the dilatometer tube running along the sample. A bestsolution is to keep the thermocouple in between the two.

c.) Calibration

Since the push-rod movement is always the difference between the expansion ofthe sample and the dilatometer tube, the latter one must be defined accurately.This is done by using a well characterized sample whose expansion is known,called a Standard or Reference.

d.) Heating Programs

There are no right and wrong heating schedules. Very often they resemble aschedule used in production, other times they are designed to bring about anexpected change. Generally there are two major kinds: ramp heating andstepwise heating. With a ramp, the sample is heated continuously to maintain aconstant rate of temperature rise. With stepwise heating, the sample is allowed tocome to thermal equilibrium at selected temperatures. UnithermTM dilatometerscan do both kinds of heating programs or even a mixture.

7.) Sample Considerations

a.) Machining

It is unimportant to finish machining the entire sample. Only the ends contactingthe end-plate of the dilatometer tube and the tip of the push-rod must be flat(RMS 60 or better) and parallel (+0.001 inch; +0.025mm).


b.) Soft Samples

Foams, plastics, thermal insulators, and other materials having a low loadbearing capacity are difficult to test because the push-rod tends to indent into thesample. Two solutions can be used either separately or together.

1) Reduction of push-rod pressure. It helps but is can also result in jerkymovement (ratcheting) when very low tracking force is used. It is better to limitthis action and to rely on (b). Vertical dilatometers (such as the Model 1161)with static weight counterbalancing lend themselves best to this approach.

2) Using a pressure distribution plate. This is a thin sheet of very stiff material,similar in nature to the material of construction for the dilatometer itself.Quartz plates for quartz dilatometers, alumina plates for alumina dilatometers,etc. Often stainless steel is used where temperature limitation permits it.When a dissimilar material is used, its contribution to the results must becomputed first. If the plate is kept thin, it is usually insignificant.

3) Pressure distribution plates for Model 1054. This is a special case, for thismodel uses flat plate samples and thin strips on the ends by themselveswould not be stiff enough to do the job. The strips are bent into small anglesand these are placed over the two end faces of the sample where the push-rod and the back-up rod make contact. With high expansion materials (suchas plastics), plate thickness up to 0.010 inch were found to be insignificant.

c.) Stacking of Samples

Often samples are available in short sections only. To build up a reasonablesample length, several short sections can be stacked up. Vertical dilatometeresare best to accommodate this condition.

d.) Thin Films (flexible)

(1) Auxiliary Fixturing

In some instances, if the film has a stiff nature, it is possible to test it flat in theModel 1054 with an aluminum pressure bar resting on it. This bar is made slightlyshorter than the sample, so the push-rod and the back-up rod are only contactingthe ends of the sample. For higher temperatures, jigs can be made out of twobars with a present gap between them to accommodate the sample. Horizontaldilatometers are better suited to deal with this configuration.

(2) Shaping

Rolling up the film to produce a cylinder has been used with success. Alsofolding a crease into the sample may help to stiffen it.

(3) Combination

Combination of (a) and (b) may be used, such as folding up both lengthwiseedges of a foil sample and also placing a weigh-down bar on the center section.


e.) Yarns or Thin Filaments

These can be tested only in tension and therefore it requires special fixturing.Vertical dilatometers with counterbalancing can be adapted readily to this task.

8.) Furnace Construction

Depending on the temperature range alone (not the model number), differenttypes of furnaces can be employed even in the same instrument. These are:

a) Cryogenic to 500oC maximum, aluminum alloy block furnace. Advantage isvery good temperature uniformity, superior control, and fast heat up. Veryoften the sample is not isolated from the furnace block for enhancedtemperature uniformity and heat transfer.

b) Ambient to 1200oC maximum, Nichrome wire heaters in coiled form are used.These are supported on ceramic half-shells. (Although these are rated to1200oC, it is preferred to run them to 1000oC and no higher.) Surrounding thehalf-shells is fiberous insulation. These are the least attractive furnaces in theentire instrument line. They are comparatively slow, and less uniform than thealuminum alloy block furnace.

c) High speed IR radiant furnaces. Fast heating system, limited to 1200oC.

d) Ambient to 1700oC range is serviced by Kanthal Super S hairpin heaterssuspended in a cavity formed by high temperature fiberous insulation. Thisfurnace is very fast heating and somewhat slow cooling due to the excellentinsulator shell.

e) Ambient to 3000oC range is serviced by graphite furnaces that are builtintegrally with the dilatometer.

9.) Temperature Sensors

Depending on the maximum temperature, a device will have:

a) up to 1000oC, Type K thermocouple (Chromel/Alumel).

b) up to 1700oC, Type S thermocouple (Platinum/Platinum-10% Rhodium). up to3000oC, optical pyrometers.


3.0 GENERAL HANDLING

The dilatometer is a precision measuring instrument and should be handledcarefully. The quality of the data obtained and the life of the dilatometer parts aredirectly proportional to the care and the lightness of touch with which theinstrument is handled.

NOTE: Some dilatometers are equipped with two pushrods, each one connecteddirectly to a separate digital gauge. References in this section are for single pushrod systems, but apply equally to dual pushrod systems as well.

3.1 PUSH ROD CHECK

The dilatometer should be inspected for free movement of the pushrod by slowlylifting it and then releasing it. The sample cavity should be kept clean at all times.Use a vacuum cleaner with a small nozzle for cleaning. Do not use an air gun.Do not bump the dilatometer tube, or the pushrod.

3.2 OPENING AND CLOSING

The two snap locks on either side of the head latch the head into place. Afterunlatching, the platform tends to rise, lifting the dilatometer out of the furnace.

CAUTION: Do not open furnace unless it is completely cooled to roomtemperature. This usually occurs about 5-6 hours after it is shut down,depending on the highest temperature reached during the test beforeshutdown. Water flow must be maintained until the furnace is completelycool.

3.3 LOADING AND UNLOADING

With the dilatometer exposed:

1) Place a piece of paper or cloth over the furnace cavity, to prevent pieces fromfalling into the furnace.

2) Actuate the pushrod lifting mechanism under the base of the instrument head.Lift pushrod.

3) Place sample into dilatometer tube. Standard sample size 1.50 to 2.50 inchlength, up to 0.375 inch in diameter, unless a unit is instrumented for smalleror larger samples.

NOTE: It is possible to change overall sample length range of the dilatometertube/pushrod assembly. See 5.2 Changing Sample Testing Length for moreinformation.


4) Lower pushrod. Depress the plunger to raise the pushrod, and release it tolower the pushrod. Gently repeat this a few times to seat the sample and thepushrod in the dilatometer tube.

5) Lower dilatometer and lock latching ears.

3.4 NONSTANDARD SAMPLES

3.4.1 Small Samples

Samples smaller in diameter than 0.25 inch should be inserted into a suitablesupport (slightly shorter than the sample) to form a cylinder 0.375 inch indiameter, with a hole in the axis loosely fitting over the sample. The supportpiece must be slightly shorter than the sample to allow for expansion orcontraction of the sample.

3.4.2 Softening Point Study Samples

For tests where the softening point is being determined, an enclosure tube andend plates should be utilized. These can be purchased from Anter. The purposeof the sample container is to minimize the risk of damage to the instrument whichcould result from the sample softening and then reforming around the pushrod.This container is also used to minimize the potential for damage to the sample.When this type of testing is being carried out, it is also advisable to add weight tothe counterbalance. This reduces the force of the pushrod even further andreduces the possibility of the pushrod aiding the deformation of the sample.

3.5 PROTECTIVE ATMOSPHERE

The Model 1161 dilatometer can be operated in air, therefore it does not requirea protective atmosphere, or vacuum. However, sample requirements maydictate using a protective atmosphere, vacuum, or (sequentially) both.

Keep in mind that valves and fittings are generally the responsibility of the user tosupply.

3.5.1 Evacuation Procedure

Prior to start up, the system may be evacuated using a mechanical vacuumpump, back filled with inert gas, then evacuated and back filled again, in order toremove traces of oxygen. The gas inlet and outlet valves (if equipped) must beshut off during evacuation. The vacuum valve (if equipped) leading to the pumpmust be shut off during the test run. In configuring external valving, always allowfor gas outflow as a default condition. This is to prevent complete isolation of thefurnace. If the furnace is completely sealed during heat up, very rapid expansionof gasses can lead to dangerous pressure building up inside.


3.5.2 Vacuum Operation (Optional)

It is possible to operate the system in moderate vacuum. However, thermalresponse of the system will be greatly slowed, so much so that it may be almostimpossible to avoid overshoot unless extremely slow heating rates are employed.If the system is supplied with a high vacuum option, a specific instruction sheetfor the operation of the high vacuum diffusion pump system will be included withthe manual.


4.0 OPERATIONConsult Software Manual for testing procedure.


5.0 ADJUSTMENTS and MAINTENANCE

The following adjustments may be made to customize the performance of thedilatometer.

5.1 PUSHROD TRACKING PRESSURE

Pushrod tracking pressure can be adjusted by varying the weight of thecounterbalance. Although it is possible to equalize the weight of the pushrod,extremely low tracking pressures can result in “ratcheting”, since the static frictionof the counterbalancing system is slightly greater than the dynamic friction. Noisyor outright erroneous data may be generated, so it may be practically better tohave a slight force on the pushrod to allow it to track the sample movement moresmoothly.

For soft samples, or samples that may soften during heating, the recommendedpractice is to place a pressure distribution plate on top and maintain a normalpushrod pressure. The pushrod’s normal contact area is about 0.25 mm2.Consequently, when a plate of only 5mm diameter is used, the effective pressureon the sample is reduced by a factor of nearly 80, a change that is impossible toachieve with mere counterweight reduction.

CAUTION: The pressure distribution plates must be fabricated from theexact same stock as the dilatometer, otherwise substantial errors will beintroduced. Matched plates are available from Anter.

The counterbalance supplied with the instrument is optimized for the equipment(as shipped) for normal dilatometer expansion tests. Modification of thecounterbalance is possible by adding or removing washers held on by a 1/4-20bolt inserted into the bottom of the counterbalance. If the system is supplied withwashers in place, and if all additional washers are removed, and thecounterbalance is still too heavy, lighter weight counterbalances can be obtainedfrom Anter.

5.2 CHANGING SAMPLE TESTING LENGTH

The dilatometer head and gauge assembly allows for an extremely largevariation in sample size. There are two factors which determine sample size. Thefirst is the overall position of the gauge assembly, and the second is the variationfrom sample to sample that is allowed for a given position.

Sample size can be varied by approximately +0.5 inches, without making anychanges in the position of the gauge assembly. This means, for example, that theuser can select a nominal sample size of 1 inch, but can actually run samplesthat are as small as 0.5 inches, or as large as 1.5 inches.


NOTE: In practice, it is important to remember that these limits are ultimate limitsof travel, and actual sample size may have to be a bit smaller than the maximumto allow for sample expansion, or a bit larger than the minimum to allow forsample shrinkage. If the anticipated change in length of the sample would causethe gauge assembly to go out of range (at either extreme), then the sample sizeor the gauge assembly position should be adjusted so that the initial samplelength is about halfway between each of the extremes of travel on the gaugeassembly.

CAUTION: Not allowing movement for the expected expansion will lead tobreakage of the dilatometer or the gauge.

In addition to the near 1 inch sample size variation (without adjustment), theoverall nominal sample size can be varied by moving the whole gauge assemblyup or down. This adjustment is comparable to installing a longer or shorterpushrod. It takes only a few minutes to do and requires no disassembly of thedilatometer head or pushrod.

5.2.1 Pre Adjustment Preparations

Remove samples from dilatometer. Remove head cover. Locate two smallthumb-screws on the front of the mounting column (chrome plated) of the gaugestructure. Note the position of the gauge head as it is presently (note the numberand position of mounting holes exposed behind the mounting column). Locatethe lifter pin(s) and note the insertion position.

NOTE: It is recommended that a written note of these is made, to avoid laterconfusion.

5.2.2 Adjustment

Knowing the current sample capacity and the desired capacity, determine thedirection of the gauge head movement needed to accomplish the change.(Moving the gauge head upward will increase the capacity.) Changes can bemade in 1/2 inch (12 mm) increments. Translate the change into changes in themounting hole positions exposed behind the mounting bar. (For example, ifpresently one hole is exposed and the edge of the column intersects with thehole below it, a 1/2 increase in sample size will necessitate having two holesexposed and the third to intersect, etc.) Remove the thumb-screws while grippingthe gauge assembly, move to new position and reinstall thumb-screws. Observeposition of guide channel for proper alignment.

5.2.3 Zero Reset (Optional Procedure)

Depress gauge Reset Button (gauge tip is not in contact with top of slide). Inserta piece having a length of roughly midrange. Observe gauge reading. Properlydone, the display should show 0.4 to 0.6 inch or 10 to 14 mm, depending whichscale is active. If position is not satisfactory, rework and readjust.


5.2.4 Travel Check

With the sample out of the dilatometer, lift the pushrod by hand (moving thecounterbalance anchor point on the slide until it just contacts the tip of thegauge). Insert pin into lifter mechanism just below the position that would makecontact with the slide. Release pushrod. It should drop just a little before beingheld up by the lifter. Actuate lifter. In its uppermost position, there must be aslight gauge travel left, otherwise every lifting cycle will put a stress on the gauge.

5.2.5 Spacers

If these adjustments still do not satisfy the user’s requirements, customizedpushrods, or spacers, can be obtained from Anter, which would allow testing ofintermediate sample sizes.

5.3 TUNING THE FURNACE (Tune Utility)

This procedure must be performed only after installation of a new heater or ifperformance in approaching set temperatures degenerates. It is also neededwhen new atmosphere mixes are introduced.

Since each furnace installation has its own unique thermal characteristics, whichare dependent on the heater resistances, thermocouple positioning, andconstruction details, the thermal response of a system will vary slightly from onesystem to another. These differences are usually not large, and are partiallycompensated for by the software control algorithms as the test progresses. Butin an effort to even further refine the control system (primarily to avoidunnecessary undershoot and overshoot when targeting a temperature), anadditional automatic tuning algorithm is used.

The most apparent symptom of need for retuning is significant undershoot orovershoot (greater than 50oC) when ramping to a temperature. Retuning of thefurnace should improve the tuning constants to a point where the undershoot orovershoot is less than this value at all temperatures (and all heating rates). Thereare some exceptions, but this is a good rule of thumb.

5.3.1 Set Up

Access tuning from “Setup” on the Menu Bar.

To do a tune, a sample needs not be in place.

Proceed with the instructions in the dialog box. All normal protections(atmosphere) of a test must be present.

5.3.2 The Process

This algorithm will generate a set of equations that are stored in a text file for useby the dilatometer test program. The steeping, control, and sample temperaturesare recorded at a fixed interval over the entire temperature range.


The standard tuning program supplied with the equipment will successivelyrecord the temperatures from the low end of the temperature range, to about thehigh end of the operating temperature range, in even 1000C intervals. It willrecord the temperatures after a suitable time period has elapsed at eachtemperature.

This procedure should be repeated any time the furnace performance shows asignificant drift.

5.4 PERIODIC RECALIBRATION OF SYSTEM COMPONENTS

Periodic recalibration of displacement sensors, amplifiers, thermocouples, etc. isNOT RECOMMENDED (with the exception of differential dilatometer heads thatemploy analog displacement transducers). The inherent long term stability ofthese components and the interpretation schemes used require no periodicadjustments. The overall performance of the instrument is to be checked byperforming verification tests (5.6 Verification Tests).

5.5 CALIBRATION TEST

To determine the contribution of the system's expansion to the measuredexpansion, it is necessary to test well characterized materials with knownexpansion. Usually one of the several Standard Reference Materials (SRM)issued and certified by the National Institute of Standards and Technology (NIST)or its predecessor, the National Bureau of Standards (NBS), is used for thepurpose. It is recommended that the standard is to have a coefficient of thermalexpansion in the range where most of the tested materials will fall.

Unfortunately, this is not always possible, due to the limited number of referencesissued. Another practical approach is to use a standard that is genericallyidentical to the dilatometer material. Thus, fused silica for fused silicadilatometers, sapphire for alumina dilatometers, and graphite for graphitedilatometers would be appropriate. The dilatometer calibration software canaccommodate any reference material that is usable in the temperature range ofthe equipment.

The test of a standard is no different than that of any other material. It should bedone with extra care and deliberation, as its results will affect all data that isgenerated thereafter.

Procedurally this is done in the following fashion. The raw data is sorted andselected, normalized to unit length of sample, fitted to a curve, and thecoefficients of the best fit polynomial determined. If this sample were a knownmaterial, the tabular data on its true expansion could be also fitted to apolynomial of the same order and the difference between the two equations thenwould represent the system’s contribution. Consequently, when an unknown istested later, it is reasonable to assume that the system’s contribution is the sameas long as the test parameters were reasonably identical. Thus, one would takethe equation obtained from the test data and add to it the equation representingthe system’s contribution.


Statistical considerations dictate that multiple tests are in order. At least 3(perhaps as many as 7) tests should be performed for a single calibration. Notethat it is preferable to perform an odd number of tests. The tests should cover theentire temperature range of the dilatometer, with 8 to 10 soaks about equallydistributed, each with ample dwell time to ensure good equilibration. Since thesystem can perform repeat runs, a large calibration program can beaccomplished essentially unattended.

Alternately, one may opt for a continuous ramp test, if that is the type that will beused in regular operations. The ramp rate should be reasonably low, but certainlycomparable to the rate(s) that will be used for subsequent testing. It should benoted that any ramp rate that is found to be too fast for calibration is also too fastfor testing.

In either type of calibration (ramp or equilibrium), the most accurate calibrationwill be obtained by designing the calibration test sequence to take into accountthe types of tests that will be performed later.

5.6 VERIFICATION TESTS

Periodic verification of overall performance can be done by testing the standardsample that was used for calibration and comparing the resultant analyzed datawith good values. These tests should not be used to enter new calibrationfactors, although one may use them to modify the existing factors to furtherimprove calibration. In that case it is imperative to run these tests identically tothe program with which unknown samples are to be tested, and follow theappropriate procedure.


6.0 TESTING CONSIDERATIONS

6.1 CONTROL STRATEGY

The control strategy employed is a combination of time or phase angleproportioning of the electrical power to the heater, and digital adaptivetemperature control. Understanding its operation will help in designingtemperature cycles and produce better data.

The heaters are equipped with a thermocouple that rapidly responds totemperature change in the heaters. The sample temperature on the other handis measured near the sample and away from the heater.

It is simply not possible to control from the sample thermocouple because ofthermal lag. To combat the problem, a combination control was developed usingtwo basic elements, furnace control and targeting.

NOTE: These controls may be implemented in a variety of ways, which aremodel-dependent, but the general theory behind the different configurationsremains the same.

6.1.1 Furnace Control

The heaters are always controlled based on the output of the controlthermocouple. The control used is a time or phase angle proportioning type inwhich the temperature difference between the actual thermocouple temperatureand the setpoint is computed. For every degree temperature difference, a certainportion of a predetermined duty cycle is turned on.

After the furnace has entered a DWELL period, the first comparison of thesample to the setpoint occurs within the “adjustment period”. The setpoint is thenadjusted by the difference. Once this new effective setpoint is presented to thefurnace, the furnace will then control to the new setpoint, just as if it were thenominal setpoint. Further adjustments are made in subsequent intervals, thus atotal response effect is achieved. However, always only the nominal setpoint isprinted or displayed. During the ramp portion of a program, no adaption takesplace after the commencement of the ramp.

6.1.2 Targeting

For step heating, an initial adaptation is made immediately at the commencementof the step. This is done to hasten the process of reaching the final sampletemperature. The amount of this adaptation is determined by the setpointtemperature. Targeting for ramps is determined by the setpoint and the ramprate.

Tuning of the thermal response of the furnace, sample, and controlthermocouples is accomplished by the TUNE automatic tuning function.


This feature allows characterization of the thermal response of a particularfurnace. This information, once generated, is automatically stored, and will berecalled each time a test is performed. The overall result is that the software isable to more accurately predict the response of the furnace, significantly reducingthe undershoot or overshoot of the control.

Since this tuning process can be performed at any time, it allows retuning tocompensate for insulation changes over time, thermocouple positioningdifferences, and overall physical changes unique to each system.

6.2 THERMAL CYCLE PROGRAMMING

The dilatometer is physically limited by its thermal mass, the power available tothe heaters, the lags introduced by the mass of the sample, and the thermalimpedance of the gaps around the sample. Therefore, it is prudent to design thetemperature excursions with this in mind. Normally, a minimal overshoot isunavoidable in every system, therefore, caution should be exercised to take intoconsideration the possible material changes such overshoots may cause. Theamount of overshoot is governed by the mass and conductivity of the samplemore than anything else, so no general rule can be given, however, overshootcan be minimized by using a ramped heating rather than step heating betweenequilibrium points.

For safety reasons, most high temperature dilatometers have a built in undershoot, especially as the temperature becomes closer to the operating limit of theinstrument. This under shoot may appear before beginning a dwell period, andwill be partially compensated for by initial adaptation parameters. Given severalminutes, the setpoint will be adapted based on the sample temperature, so thatthe desired target will be reached.

During the execution of a thermal cycle, if the program is interrupted foralteration, one should keep the following in mind: Alteration can not affect anycompleted segments, or the present segment being executed. The onlysegments which may be altered are those ahead of the one presently beingexecuted. (If the test has not been started, then ALL segments can be edited.)

6.3 SAFETY INTERLOCKS

6.3.1 Water Interlock

Upon turning the cooling water flow on, a thermal switch will activate the watertemperature sensing circuit, which then enables actuation of the HEAT ON powerrelay. While water is flowing, power to the furnace can then be turned on. Loss ofadequate water flow may lead to gradual warming and ultimate test stoppagedue to the excessive heat on the water cooled components.


6.3.2 Temperature Interlocks

6.3.2.1 Overtemperature Detection

Overtemperature detection is made by checking the temperature of both thesample and control thermocouples every time a reading is taken. If the output ofthe signal conditioning circuit exceeds the programmed limits, the power controlwill be shut down. If the control thermocouple temperature reaches the setmaximum, an overtemperature warning will be displayed until the temperaturefalls below the maximum user-specified temperature.

6.3.2.2 Open Thermocouple Monitor

Open thermocouple detection is employed on the hardware level also. An openthermocouple will result in a full scale signal from the conditioning circuit, whichthen results in a power shut down as described above.

6.3.3 Dead Computer Detection

To ensure the sound operation of the Control/Data system during a test, theactivity of the computer/equipment interface is continuously monitored. If, for anyreason, the computer fails to maintain the proper communication with theequipment, a Dead Computer interlock will shut down the power to the system.Software and/or complete system restart is necessary to restore normaloperation.

This condition will occur if there is a malfunction in the computer system, if thecomputer is shut off, or if the computer is reset. If detection of a computermalfunction is sensed, an automatic timer starts, and if proper communication isnot restored within a given time (typically 3 to 4 minutes), the system is shutdown. This shut down will automatically account for any setpoints that may havebeen in effect at the time of the failure, and all power to the furnace will bedisabled.


7.0 DIGITAL TRANSDUCER

7.1 Operation and Reset

This section describes general operation of the digital transducer used tomeasure pushrod movement. For specific situations not covered here, pleasecontact Anter personnel for guidance and advice.

NOTE: It may be necessary to remove the clear cylindrical cover to perform all orpart of the digital gauge operation and reset procedures. This is done byremoving the four clamps securing the cover to the head plate, removing theclear cover, and lifting it clear of the equipment. Removal of the cover is notnormally necessary when operating the equipment, as long as the gauge is fullycharged, and the main power to the dilatometer is active.

7.1.1 General Operation

The digital transducer used to measure movement of the push rod is acompletely self-contained unit, and employs no analog signals. The position ofthe push rod is translated directly into a digital signal, and is then transmitted tothe computer. The transducer has a linearity and resolution of + 1micron (0.001mm) over its approximately 25mm total range of travel. Statistical treatment in thesoftware improves this to about 4x interpolation.

Normally, the digital transducer should be set to mm (millimeters). If for somereason the transducer is displaying in inches, it must be reset by holding both thepower button and the reset button for a minimum of 30 seconds. The defaultdisplay is in the mm mode.

Normal display contains the + or – sign, the ^ (up arrow triangle), along with areading with the format: XX.XXX mm. If any additional symbols or letters aredisplayed (MAX, MIN, B, AB, HOLD, etc.) or if the transducer does not displayanything, it may be necessary to perform an initial reset of the transducer asdescribed in the above paragraph.

The transducer does not need to be reset to zero prior to a test. The computerwill automatically determine the initial position, and offset the data accordingly.

7.1.2 Initial Reset and Battery Charging

When installing the equipment for the first time, or when the power to the unit hasbeen turned off for a period longer than approximately 12 hours, the internalbattery of the transducer may be discharged, causing it to turn on, thenimmediately back off when power is first applied. To solve this problem, thebattery must be recharged.


In order to recharge the battery (if the B indicator appears, or the display doesnot show any reading), the POWER switch on the gauge must be depressed untilthe transducer turns off (blank display). Power must be applied to the dilatometer(main power) for a period of about 1-hour to charge the battery enough to allowthe transducer to function. Complete charging will occur in about 16 hours.

NOTE: It may not be necessary to completely charge the battery for normaloperation, however this complete charging allows brief shutdown or interruptionof the dilatometer power supply without performing initial reset of the systemeach time the power is restored.

Quick start up of the transducer is possible, even if the battery is completelydischarged. This is accomplished by turning the main power to the dilatometeron and waiting about a minute before turning the power on to the transducer.Then, perform a system reset by holding down both the POWER and the RESETbuttons at the same time, for about 30 seconds. The display should return to thenormal display in the format: +0.000mm.

This reset can also be used to clear the transducer of any abnormal display orerror conditions.

7.1.3 Precautions

Over-discharge can occur during shipment, so first charge the battery sufficientlyby having the system left with the main power ON for 24 hours.

When using the device for the first time, press the power switch and reset switchsimultaneously to perform a system reset.

When the voltage of the internal rechargeable battery falls below a referencelevel (approx. 4.7V), “B” will appear on the LCD display. If operation is continuedin this condition, when the voltage falls below approximately 4.6V, “B” will appearon the LCD display and the power will switch off automatically. In this condition, ifthe power is switched on once again, “B” will appear for approximately twoseconds and the power will be switched off once again. If “B” appears, thebattery should be recharged. (Do this with the power switch off.)

In addition, when the battery is fully discharged, even if the power is switched on,nothing will appear on the LCD display. In such case, after charging the battery,press the power switch simultaneously with the reset switch to perform a systemreset before beginning measurements.

7.1.4 Operational Settings

POWER: ONin/mm: mm+/-: +MODE: Normal (no legend above displayed values)RESET: Disregard


7.2 FUNCTIONAL DESCRIPTION

In this application, the digital gauge is used in a dedicated mode. It is notintended as a stand alone device and therefore it should be kept in a certainprescribed operating mode for the overall system to function properly. Thedescription below is given only to aid in recognizing setup errors or malfunctions.

7.2.1 Power Switch

When the power switch is pressed, the device is powered and measurement ispossible. When this is done, the LCD display reads “0”.

7.2.2 Reset Switch

When this reset switch is pressed and then released (within two seconds), thedisplay value is reset to “0”. When this happens, the output is “no data” when thereset switch is pressed and the display is blank, and is “0” when the reset isreleased and the display changes to “0”.

When the switch is allowed to return to its original position, “0” is indicated on thedisplay and the current spindle position is the zero point.

7.2.3 Direction Switch

The measured value is incremented or decremented, depending upon thedirection of spindle movement. The counting direction can be selected either toadd or subtract when the spindle is pressed in, depending upon the setting of thedirection switch. The counting mode is indicated by the E or F mark on thedisplay.

↑ : Addition (+ direction) when spindle is pushed in.↓ : Subtraction (- direction) when spindle is pushed in.

7.2.4 Mode Switch

Each time the mode switch is pressed within two seconds, the mode issequentially changed from the normal measurement mode to the maximumvalue, the minimum value display mode, then the (R) range (maximum tominimum) display mode, and finally back to the normal measurement mode.

(1) In the normal measurement mode, the measured value is continuouslydisplayed. The gauge should be left in this mode for proper system operation.

(2) If the mode switch is pressed once (within two seconds), “MAX” appears inthe display, indicating that the maximum value display mode has been reached.

In this mode, read-in measured values are continuously compared and themaximum value measured is displayed.


(3) If the mode switch is pressed a second time (within two seconds), “MIN”appears in the display, indicating that the minimum value display mode has beenreached.

In this mode, measured values are continuously compared and the minimumvalue is displayed.

(4) If the mode switch is pressed a third time (within two seconds), “R” appears inthe display, indicating that the range value display mode has been reached.

In this mode, the maximum and minimum values are internally registered inaccordance with the up-down movement of the spindle, with the range value(maximum-minimum value) displayed continuously.

(5) If the mode switch is pressed once more (within two seconds), “R” isextinguished from the display and return is made to the normal measurementmode.

The initial value for the MAX, MIN, and R display mode is the value displayedwhen a switch is made to the MAX mode from the normal mode. Once set, theinitial value is held until the reset switch is pressed (within two seconds) and thenreleased. If it is necessary to set initial value once again, perform a reset. Theprevious initial value will then be canceled and the displayed value when a switchis made from the normal mode to the MAX mode will be set as the initial value.

(When a reset is performed, the data output is “no data” when the reset switch ispressed and the display is blank, and is “0” when the reset switch is released andthe display changes to “0”.)

7.2.5 Inch/mm Switch

This switch selects either “inch” or “mm” as the units for display of the measuredvalue. The units are alternately selected each time the switch is pressed. Theselected mode is maintained even when the power is switched off. This switchshould always be left in the “mm” position for proper system operation.

7.2.6 Reset Switch

<Absolute zero function>

If the normal function is set, and the RESET switch is pressed for more than twoseconds and released, the display will indicate “AB”, indicating that the absolutezero function has been selected. If the RESET switch is pressed once again andreleased, return is made to the normal function.

If the switch is pressed further, the absolute zero and normal functions will beselected alternately. In the absolute zero function, the RESET switch cannot beused to set the display value to zero.

<Preset function>


When this function is selected, the RESET switch has two functions:

1 If the RESET switch is pressed for less than two seconds and released, thedisplayed value in the NORMAL, MAX, MIN mode will be the preset value and, inthe R mode, the preset value will be 0.

2 If the RESET switch is pressed for more than two seconds and released, returnis made to the normal function. After this, if the switch is pressed further, theabsolute zero function will be selected.

7.2.7 Direction Switch


In this function, the direction cannot be changed. It is fixed as the direction.

<Preset function>

In this function, the direction cannot be changed. It is fixed as the directionselected in the normal function.

7.2.8 Mode Switch


In this function, mode switching is not possible (i.e., it is protected).

<Preset function>

In the normal function, if the MODE switch is pressed for longer than twoseconds, the “P” mark appears in the display and the preset function is ready foruse. In this function, the MODE switch has two functions:

1 If the mode switch is pressed for less than two seconds, the preset mode isreached and the sequence normal--MAX--MIN--R is switched through, afterwhich return is made to the normal mode.

2 If the mode switch is pressed for more than two seconds, switch is made to thepreset setting procedure. The preset value setting is also made using this modeswitch.

7.2.9 Inch/mm Switch


In this function, it is not possible to perform inch/mm switching. In this function,the unit is fixed at the position selected in the normal function.

<Preset function>


In this function, it is not possible to perform inch/mm switching. In this function,the unit is fixed at the position selected in the normal function.

7.3 POWER SUPPLY CONSIDERATIONS

When the voltage of the internal rechargeable battery falls below a referencelevel (approx. 4.7V), “B” appears on the display. If operation is continued in thiscondition, when the voltage falls below approximately 4.6V, “B” will appear on thedisplay and the power will be switched off automatically. In this event, if thepower is switched on once again, “B” will appear for approximately two secondsand the power will be switched off once again. If “B” appears, the battery shouldbe recharged for 16 hours. This should be done with the power switched off.

7.3.1 Normal Operations

The gauge is powered from the main system power supply, therefore the systemmust be left on continuously to prevent the gauge from discharging.

7.3.2 Restarting After Charge Up

If the self-contained rechargeable battery is completely discharged (i.e., if eventhe “B” does not appear when the power is switched on), turn system power onand charge for approximately 30 seconds. Then perform a system reset toenable the display and make possible operations from the AC line.

7.3.3 Battery Operation

The gauge has a self-contained rechargeable battery. In order to recharge thebattery, turn system power on for 16 hours with the power switch OFF. Whenused in this fully charged condition, the battery will give continuous operation for8 hours.

APPENDIX

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