QC IQ C IQuartz Crystal Immittance Measurement Software

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Intellect SFT.Potsdam, New York

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CONTENTS

1. Introduction ........................................................................................................... 22. System Requirements ........................................................................................... 33. Installation ............................................................................................................ 44. How to Start QCI Program .................................................................................. 6

Initial conditions ............................................................................................. 6The ways to start ............................................................................................ 6Start up procedure .......................................................................................... 6

5. Frequency Scan .................................................................................................... 8Main frequency scan parameters ................................................................... 8Communication with Model FG-906 generator ………………................... 9Number of points ............................................................................................ 10Averaging ....................................................................................................... 10RS-232C panel ............................................................................................... 11Start F-scan and data acquisition ................................................................... 11

6. Plot Scale .............................................................................................................. 12Variables ......................................................................................................... 12RANGE per Volt ............................................................................................ 13MIN%, MAX%: set plot scale in percentage of the RANGE per Volt ........ 14

7. Variables .............................................................................................................. 18DAQ channels: variables to be measured ..................................................... 18Changing units ............................................................................................... 19Adding and modifying variable names and symbols .................................... 19

8. Running an Experiment ....................................................................................... 21Set the program and other parameters first ................................................... 21Start experiment with the RUN button .......................................................... 21Analysis, Simulation, and Evaluation ............................................................ 22

9. Save and Load Operations ................................................................................... 2410. Ending the Session with QCI ............................................................................... 2611. Appendix .............................................................................................................. 27

QC equivalent circuit ..................................................................................... 27QCI graphs ..................................................................................................... 28

INTRODUCTION

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Chapter 1

INTRODUCTION

QCI is a powerful software package for real time data acquisitionand processing of complex quartz crystal resonator admittance data onDAQ-616SC Data Loggers. It features high resolution XGA or SVGAgraphics with user-friendly interface and an interactive dataacquisition allowing for convenient control of the measurements,display, and data storage. The data are stored on disk in a binary orASCII (text) format that can be exported directly to spreadsheetprograms, such as Microsoft EXCEL, which can be used for furtherdata processing and graphing purposes. The QCI Version 2.0 allowsone to convert and calibrate the rough admittance data from EQCN-900 series instruments to QC admittance modulus |Y|, QCconductance G, and QC susceptance B, as well as plot these functionsvs. frequency f or on complex plane plots of Y(im) vs. Y(re). The QCresonator characteristics can then be analyzed and values ofequivalent circuit elements evaluated, including motional armelements L1, C1, and R1, parallel shunt capacitance C 0, parallelresistance Rp, and series resistance Rs.

Running data acquisition experiments with QCI is extremelysimple. Just follow the simple rules described in this manual.

SYSTEM REQUIREMENTS

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Chapter 2

SYSTEM REQUIREMENTS

To run QCI, Version 2.0 program, the Data Logger DAQ-616SC orDAQ-716v with the following hardware and software are required:

• Intel Pentium , American Micro Devices K-6/2 , NationalSemiconductors Cyrix MII/686 , or higher compatiblemicroprocessor;

• 10 MByte RAM memory;

• XGA graphics adapter card with 256 colors or gray shade;

• hard disk with at least 10 MBytes of free memory available;

• Microsoft Windows-98/ME/2000/XP or higher, compatible;

• Data Logger compatible with the software version.

The software is optimized for XGA high resolution graphics. It isrecommended not to change the screen resolution set to XGA in factoryfor Data Loggers DAQ-616/716 series.

INSTALLATION Chapter 3

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Chapter 3

INSTALLATION

Turn the computer on and wait until Microsoft Windows-98/ME/2000/XP in your Data Logger boots up. If you already haveyour Data Logger turned on, exit from any program you might be inand close all other running programs. On the computer screen, youshould have only a desktop and no working windows open. The quicklaunch panel (the one with Windows START button) should indicatethat there are no running programs.

Press the button on the CD-ROM drive to open the drive door.Insert the QCI CD-ROM disk and close the door by slightly pushingthe drive drawer. Wait a few seconds (it can be, sometimes, up to aminute) until the installation program recorded on the QCI CD isloaded and shows up on the screen. If, for any reason, the auto-runfeature does not work and the auto-installation program does not startautomatically, use the Windows Explorer and go to the CD-ROM drive.Find the INSTALL.exe program in the main directory and double-clickon it to start the QCI installation manually.

The installation is self-explanatory and does not require anyadditional comments. After the software installation has successfullybeen completed, open the CD-ROM drive, remove the disk, and store itin a safe place free of dust and moisture. Restart the computer.

The following information may help you in further configuringyour data file structure.

The executable program files and binary files necessary foroperation of the main program are stored in:

c:\Program Files\Elchema\QCI 2.0\Bin

folder. Do not open or change any of the files included in these foldersas the program may not then run correctly or may not run at all.However, you can access the information stored in the folder:

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c:\Program Files\Elchema\manuals

which contains manuals for a potentiostat, quartz crystal nanobalance,QCI software, tips for setting up your experimental system, etc.

The user data files can be stored in any folder (directory). Thedefault folder is:

c:\data-QCI

You can create additional folders with names reflecting different seriesof experiments, e.g.:

c:\data\copperc:\data\silverc:\data\PPyetc.

or:

c:\My Documents\copperc:\My Documents\silverc:\My Documents\PPyetc.

If you are going to collect large amounts of files, you may considerstoring some data on removable floppy diskettes, recordable CD-Rcompact disks, IOmega ZIP-disks, Compact Flash cards, tapes, or othermedia. You can transfer some folders with data files to the removablemedia later on, for the purpose of proper storage or to make some morespace in the computer. Consider also saving copies of important datafiles on external media as a backup to prevent any accidental data loss.

The installation program creates also some icons, which arepainted onto the desktop. These are shortcuts to QCI data acquisitionprogram and to the data directory. They will help you to quickly startthe acquisition experiments and view data files.

After the installation has been completed, you can run QCI (referto the next Chapter). Be sure, your data acquisition board has driversinstalled and is inserted into the computer and connected to theinstrumentation. QCI based Data Loggers DAQ-616/716SC have D/Aand A/D converters assembled and tested and do not require anyfurther attention.

HOW TO START QCI PROGRAM Chapter 4

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Chapter 4

HOW TO START QCIPROGRAM

Initial conditions

Turn the Data Logger DAQ-616SC/716v and wait until MicrosoftWindows-98/ME/2000/XP boots up. If you are already working withthe Data Logger, exit from any program you are in. It is recommendedto close all other running programs as they may interfere with theData Logger timing functions. On the computer screen, you shouldhave only a desktop and no working windows open.

The ways to start

You can start QCI 2.0 Data Acquisition and Control program in atleast two ways:

(1) On the desktop, find an icon, which is marked QCI 2, and double-click on it. It will start QCI 2.0 program automatically.

(2) Click the Windows START button located on the Quick Launchbar at the bottom or at the side of the screen. Select PROGRAMSoption, and then ELCHEMA group, and QCI software. Click on theQCI program to start it.

Start up procedure

Right after the QCI program has been started, it displays abitmap picture with program name QCI, Version 2.0. When asked fora password, type it in and press the ENTER key. For Data Loggercomputers set up in the Elchema factory, the principal investigatorname is usually entered as the password, which is then remembered

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by the computer, and you need only to press the CONFIRM button.The program initialization routines load standard parameter sets fromdisk and then they load the last data recorded in previous session withQCI. These experimental data are stored in the file LastData.qci inthe folder:

c:\Program Files\Elchema\QCI 2.0.

These data are automatically scaled and plotted on the screen canvas.To prepare experimental parameters for a new experiment, click on thePARAMS button located on a Cool Bar in the upper part of the screen.This will activate the Tabbed Notebook with parameters to set. Followthe instructions to modify the frequency scan parameters (FSCAN), setvalue of the electrode potential (WAVE), plot scaling (SCALE), selectvariables to plot (VARS), etc., described in the next chapters.

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Chapter 5

FREQUENCY SCAN

To set parameters of the frequency scan, which controls thescanning generator Model FG-906, enter the Tabbed Notebook byclicking on the PARAMS button located on the Cool Bar in the upperpart of the screen. Select the page of the notebook named FSCAN byclicking the tab with that label. Alternatively, you can select F-scan inthe main menu, which will activate Notebook, if it is not active, andopen the page FSCAN.

Main frequency scan parameters

There are three main frequency scan parameters in QCI 2.0program:

(1) initial frequency,

(2) final frequency, and

(3) scan time.

The initial and final frequencies are expressed in kHz and are relatedto the main band frequency of 10 MHz by the formula:

fini = fini,set*1000 + f0

ffin = ffin,set*1000 + f0

where f0 = 10,000,000 Hz, f ini and f fin are the initial and finalfrequencies in Hz, fini,set and ffin,set are frequencies entered in edit boxesin kHz. This appears to be the most convenient way to enterfrequencies around 10 MHz, as the operator does not need to typemany leading or trailing zeros or 9's. For instance, the entry "50"means 50 kHz above 10 MHz, that is: 10,050,000 Hz. The negativeentry "-20" means 20 kHz below 10 MHz, that is: 9,9980,000 Hz. Non-integral entries are allowed, e.g. -40.123, 60.123456 (kHz).

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Typical frequency span (i.e. ffin – f ini) is 20 to 100 kHz. Whilesearching for the admittance peak, you can apply a wider frequencyspan. The iQC(f) and Y(f) spectra are very narrow for quartz crystalresonators in air. The spectra are peak-shaped. The initial frequencyshould be set before peak frequency (maximum admittance) and thefinal frequency slightly beyond the minimum (maximum impedance)which follows the peak.

NOTE: To evaluate correctly the equivalent circuit elements,select the frequency span such that the |Y |-f graphincludes both the admittance maximum and minimum.

For quartz crystals immersed in solution and/or with attached thickfilms, the admittance peak width is substantially increased and thepeak height is decreased. Therefore, wider frequency spans should beused in this case.

The scan time is an important parameter since it used in theautomatic calculation of the number of points (i.e. frequencies) in thescan. If a higher frequency resolution is necessary then a longer scantime should be selected. Typical scan time is 60 s.

Communication with Model FG-906 generator

The Data Logger communicates with the Model FG-906 scanninggenerator through a serial communication using the RS-232C protocol.The data structure is the following:

Communication port: COM1

Baud rate: 9600 bps

Data bits: 8

Parity bits: none

Stop bits: 1

These settings are established automatically during the boot-up of theData Logger DAQ-616SC. In case you changed these settings, pleaseread the following. Note that the MS Windows sets these controlsnormally for a lower data transfer rate (usually: 1200 bps) so you mustadjust the serial port settings. You can check the Windows setting byrunning the following batch program (there should be an icon Check-RS on the desktop so you can simply click on it):

C:\Program Files\Elchema\QCI\Bin\Check RS-232

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Close the window after checking the RS settings. You can change theRS-232C setting by running another batch program:

C:\Program Files\Elchema\QCI\Bin\Set RS-232

for which there should also be an icon Set-RS on the desktop so you cansimply click on it. If you click again on the check-RS icon, you shouldsee changed COM1 characteristics.

You can also change RS-232C settings using Windows Device Managerfacility. To do that, invoke Windows Control Panel and select:

System/Hardware/Device Manager/Ports/COM1/Port Settings.

Note that some remote devices may utilize indirectly COM ports andchange their settings. Check always the COM1 settings before youstart QCI program using the Check RS-232 utility by clicking on itsicon on the desktop.

Number of points

The default number of points, measured by QCI 2.0 in anexperiment, is 2000. However, the RS-232C serial communication andinternal conversions in FG-906 take approximately 16 ms to synthesizeeach frequency. Therefore, for faster scanning rates the number offrequencies has to be reduced. The QCI program does all thecalculations and displays summary of scan parameters on the FSCANpanel of the Tabbed Notebook. These parameters include scan rate[Hz/s], step [Hz per point], interval [ms per point], and number ofpoints. The scan time (total time) is adjusted, if necessary.

Averaging

During measurements, there is always some noise associated withmeasured values and analog to digital conversion. The experimentalnoise can be filtered out by employing analog filters and/or byaveraging and digital smoothing procedures. For instance, theELCHEMA potentiostat Model PS-605 has two analog filters (E and IFilters) that act on E and I output signals, and also the speed controlwhich can be used to reduce bandwidth and thus reduce noise. TheQCI outputs in EQCN-900 are also equipped with built-in analogoutput filters to provide smoothed output signals. Further noisereduction can be achieved by averaging, i.e. repeating themeasurements several times for each data point and calculating theaverages. The number of repeated measurements is set in theAVERAGING speed box, located on the FSCAN page of the

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Parameters Notebook. The number of samples for averaging can be setfrom 1 (no averaging) to 128. Note, however, that while the increasednumber of samples for averaging will decrease the high frequencynoise, it will also diminish the speed of acquisition. For normaloperation, set the number of samples to 1 or 2. If noise is notsubstantially reduced with 4 or, say 9, samples, then the type of noiseyou are experiencing may be better suited for analog filtering ratherthan averaging.

RS-232C panel

This panel provides the operator with a complete control over theserial communication with Model FG-906 scanning generator. Thebuttons START RS, STOP RS, SCAN Frequency, GOTO F-ini, andGOTO F can be used before the actual DAQ recording to set up thebest conditions for the experiment.

Start F-scan and data acquisition

To start frequency scanning and data acquisition, click on theCHECK F-scan button and then on the RUN button that appears on aseparate panel on the right-side of the screen.

After the f-scan and data acquisition are finished, save the data. Youcan repeat the experiment by clicking the RE-RUN button.

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Chapter 6

PLOT SCALE

Variables

There are up to nine variables recorded in each experiment. Youcan record the following variables:

VARIABLE # NAME SYMBOL UNITS 0 TIME t s 1 POTENTIAL E V 2 CURRENT i mA 3 MASS m ng 4 VQC V mV 5 IQC I mA 6 Phase shift fi deg 7 FREQUENCY f MHz 8 CHARGE Q mC

Variables #1 through #6 are measured with the data acquisitionsystem. Time t is determined on the basis of the system clock. Duringthe acquisition process, in real-time, the rough experimental data:VQC, IQC, and FI are converted, calibrated, and stored as the QCadmittance data: G, B, and |Y|, as shown below:

VARIABLE # NAME SYMBOL UNITS 0 TIME t s 1 POTENTIAL E V 2 CURRENT i mA 3 CONDUCTANCE G mS 4 SUSCEPTANCE B mS 5 |Y| modulus |Y| mS 6 Phase shift fi deg 7 FREQUENCY f MHz 8 CHARGE Q mC

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The data are stored in a QCI binary data format for quick access forfurther data processing and graphical analysis. The data are stored inthe order: eight variables shown above plus one extra variable(reserved, for instance, for charge), all for the first "data point", thenall variables values for the second "data point", and so on. The dataare preceded and followed by a list of variable names, symbols, andunits, number of points collected, etc. You do not need to know anydetails of the data format, or how many points have been collected. Itis all transparent to the user. Just keep track of the file names andexperimental conditions.

RANGE per Volt

The RANGE per Volt is the value set by the range selector on yourinstrument front panel.

For CURRENT, set the current range on your potentiostat withcurrent range selector. Usually, the recorder output will supply 1 Vsignal for a full scale current. In this case, simply enter the currentrange value as the RANGE per Volt in the PARAMETERS table ofQCI. For example, if you are using a potentiostat with the CURRENTRANGE set to 0.5 mA and the recorder output of the potentiostatsupplies 1 V signal for full scale current (0.5 mA), enter 0.5 mA (or: 500µA) as the RANGE per Volt in the PARAMETERS table of QCI. If,however, your potentiostat supplies 10 V signal on recorder output for0.5 mA, enter 0.05 mA (or: 50 µA) in the RANGE per Volt field forCURRENT (alternatively, you can set the GAIN = 0.1, instead of 1, forthe CURRENT channel in the OFFSET table, and CURRENT RANGE= 0.5 mA; you can do this since during the data conversion process theacquired value is multiplied by both the RANGE and GAIN).

For POTENTIAL, the recorder output usually supplies 1 V signalfor the real potential E of 1 V. Set the RANGE per Volt to 1000 mVper Volt if you want to have your graph scaled in mV, or 1 V per Volt ifyou want your graph to be scaled in Volts.

In the case of MASS change, the RANGE per Volt may be 1000 ngper 1 V of the recorder output signal from the Electrochemical QuartzCrystal Nanobalance Instrument. For larger mass changes (lesssensitive measurements), the RANGE per Volt may be 100 µg (or:

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100,000 ng) per Volt, as set on the front panel of the EQCN instrument(Model EQCN-900 has multiple mass change ranges.)

You must enter the instrumental RANGE per Volt to thePARAMETERS table whenever you change the range on yourinstrument.

NOTE: See the next paragraph, how to set the scale of yourmonitor plot.

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MIN %, MAX %:

Set the plot scale in percentage of the RANGE per Volt

The graph scaling in QCI works as follows. Since we are dealingwith instruments which have outputs selected with a range selector,and for each range the maximum voltage output is the same (e.g.: -1 Vfor -FS, and +1 V for +FS, where FS stands for Full Scale), it isconvenient to control our plot scaling in terms of percentage of theinstrument Full Scale and have a plot displayed with a scale in realworld numbers. The following examples illustrate how this isaccomplished in QCI.

Suppose, you change now the current range on your potentiostatto 10 mA. The only thing you need to change in your PARAMETERStable is:

RANGE per Volt: 10 mA

With real world numbers, you would need to enter both the minimumand the maximum value.

Example 2. Only positive currents.

Instrumental Range: 2 mA (as selected on your potentiostat)RANGE per Volt: 2 mA (set in PARAMETERS table of QCI)MIN %: 0 (set in PARAMETERS table of QCI)MAX %: 100 (set in PARAMETERS table of QCI)Plot range: 0 to +2 mA (resulting plot scale)

Example 3. Extended scale MASS change.

Instrumental Range: 1000 ng (as selected on your EQCN-600 instrument)RANGE per Volt: 1000 ng (set in PARAMETERS table of QCI)MIN %: -200 (set in PARAMETERS table of QCI)MAX %: 200 (set in PARAMETERS table of QCI)Plot range: -2000 ng to +2000 ng (resulting plot scale)

Usually, instruments provide output with good linearityextending over the nominal RANGE (sometimes up to twice the FS).You can use any number above 100 % (or below -100 %) to set theextended scale of your graph.

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Example 4. Recording very small MASS changes.

Instrumental Range: 1000 ng (as selected on your EQCN-600 instrument)RANGE per Volt: 1000 ng (set in PARAMETERS table of QCI)MIN %: -5 (set in PARAMETERS table of QCI)MAX %: 5 (set in PARAMETERS table of QCI)Plot range: -50 ng to +50 ng (resulting plot scale)

Since the signal-to-noise ratio decreases as the signal becomes asmall fraction of the FS, it is recommended to increase the DAMPINGtime constant (if the signal dynamics allow) and/or to include moremeasurements in averaging procedure (set REPEAT = 128 inPARAMETERS table, if possible).

While the RANGE per Volt is clearly needed to convert the valuesof the measured signal to real world numbers, scaling of the plotrequires the MIN %, MAX % values. This information is sufficient ifthe instrument outputs a signal of 1 V for the FS measurable.However, occasionally, the instrument may output a signal, S,different than 1 V, to the recorder, for the FS measurable. In this case,the MIN and MAX values should be set higher to be able to plot fullscale outputs. In general, the settings:

MIN % = -S*100 andMAX % = +S*100,

should be used, to set the plot scale from -FS to +FS. This isillustrated in the next example.

Example 5. Recorder output voltage different than 1 V for FS current.

Instrumental Range: 50 mA FS (as selected on your potentiostat)Output Voltage: 10 V for FS current (i.e. 50 mA)RANGE per Volt: 5 mA (set in PARAMETERS table of QCI)MIN %: -1000 (set in PARAMETERS table of QCI)MAX %: 1000 (set in PARAMETERS table of QCI)Plot range: -50 mA to +50 mA (resulting plot scale)

With the potential scale, the situation is slightly different thanwith other variables. Usually, the operator changes the upper andlower potential limits very often, and also, these limits have to beentered in the PROGRAM field of the PARAMETERS table to designthe potential waveform. Therefore, having the waveform parametersat hand, QCI searches automatically for the lowest and highest

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potential limits, and sets the potential scale of the plot accordingly.The MIN % and MAX % values still appear to be useful. QCIcalculates the potential range as a difference between the highest andthe lowest potential limit. This potential range is assumed to 100 %,so if you set MIN % = -100, and MAX % = +100, exactly this potentialrange will appear on the plot on the potential axis. By changing theMIN %, or MAX %, you can reduce or expand the potential scale interms of percentage of the potential range. The following exampleillustrates how to make a 5 % clear zone on the lefthand-side and therighthand-side of the potential range. With settings shown below youmay never need to change them.

Example 6. Allow for a clear zone at the graph edges.

Instrumental Range: 1 V (potential output from your potentiostat)RANGE per Volt: 1000 mV (set in PARAMETERS table of QCI)MIN %: -105 (set in PARAMETERS table of QCI)MAX %: 105 (set in PARAMETERS table of QCI)

This setting allows for 5 % of the potential range for a clear zoneon the lefthand-side and the righthand-side of the plot. It increasesclarity. If you set MIN and MAX to -95 % and +95 %, respectively, 5 %of the potential range would be lost on each side of the plot (would notbe displayed but the data in memory would not be affected).

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Chapter 7

VARIABLES

The selection of variables to be plotted, both during anexperiment as well as during a post-experiment inspection, is done bymeans of the variables table and pull-down boxes available on the pageVARIABLES in the Parameters Notebook. With the pull-down boxes,which list all variable symbols currently used by the system, you canselect variables for two ordinates (left and right) and for abscissa. Ifonly one ordinate is desired, select NONE for the variable for secondordinate.

DAQ channels: variables to be measured

The six variables recorded in each experiment are digitized usingchannels 0-5 of the Data Logger, as follows:

CHANNEL VARIABLE NAME SYMBOL UNITS - 0 TIME t s 0 1 POTENTIAL E V 1 2 CURRENT i mA 2 3 MASS m ng 3 4 VQC V mV 4 5 IQC I mA 5 6 Phase shift fi deg - 7 FREQUENCY f MHz - 8 CHARGE Q mC

The first variable, time t, is determined on the basis of the systemclock. As mentioned in Chapter 6, during the data acquisition process,in real-time, the rough experimental data: VQC, IQC, and FI areconverted, calibrated, and stored as the QC admittance data: G, B,|Y|, and FI, in variables #3...#6. The data are stored in the QCI

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binary data format for quick access for further data processing andgraphical analysis. The data are stored in the order: nine variables,shown above, all for the first 'data point', then nine variables values forthe second 'data point', and so on. The data are preceded and followedby a list of variable names, symbols, and units, number of pointscollected, etc. You do not need to know any details of the data format,or how many points have been collected. It is all transparent to theuser. Just keep track of the file names and experimental conditions.You can load this set of variables by clicking on the LOAD DEFAULTVARIABLES button located on the VARIABLES page of theParameters Notebook.

Changing units

If it is necessary to change the units of any variables, it can bedone by simply replacing the old units with new ones. To do that, clickon the appropriate cell of the VARIABLES table to gain focus on thatcell and type in the new units. The new units will appear on any graphdrawn during the real-time data acquisition or when reviewing thedata from finished experiment or from disk.

Adding and modifying variable names and symbols

In the same way, as for the units, described above, you canbasically add or change variable names and symbols for othervariables. However, if do attempt to change the six measuredvariables, since they are assigned to the DAQ channels, as describedearlier in this chapter, the system will not work correctly or not workat all. Also, the time and frequency are used as the system variablesand in principle can be placed in any order with other variables, aslong as the QCI program can find their symbols, t and f.

After any addition or change, click on the CONFIRM button to acceptchanges and transfer the new data into the pull-down boxes for Y1, Y2,and X axes.

You can save a frequently used set of variables and units byclicking on the button SAVE VARIABLES. This set of variables canreadily be retrieved later on, by clicking on the button LOADVARIABLES. This set of variables will be automatically stored on ahard disk and, thus, can be retrieved in subsequent sessions with QCI.

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RUNNING AN EXPERIMENT Chapter 8

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Chapter 8

RUNNING AN EXPERIMENT

Set the f-scan and other parameters first

Before you start an experiment, make sure you set all theparameters in the frequency scan, electrode potential, scale, andvariables to be displayed in real-time during the experiment. Thus,the frequency scan parameters should be set by visiting the FSCANpage of the tabbed Parameters Notebook. The electrode potentialshould be set on the WAVE page of the Notebook. Then, the plot scaleshould be set on the SCALE page of the Notebook. Finally, thevariables to be plotted and their units should be set on page VARS ofthe Notebook. If you perform a series of experiments with the sameparameters, you do not need to invoke the Parameters Notebook andset the parameters again. Just save the data and click on the RE-RUNbutton to repeat the experiment. The program waveform isautomatically loaded and read when you start the experiment.

Start experiment with the RUN button

To start an experiment, go to the FSCAN page of the ParametersNotebook and click on the CHECK F-SCAN button. A plot with theprogram waveform will appear on the screen canvas and the Notebookwill deactivate. However, another panel will appear on the right-sideof the screen with a RUN button. Click on it to start the experiment.

Make sure that your scanning generator, nanobalance, andpotentiostat, if any, are properly connected to the data logger and theprogram waveform is supplied to the potentiostat analog input. Beforestarting the program sequence execution, the CELL toggle switch in

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potentiostat should be switched to ON and the program input switchedto ON.

The parameters from the Parameters Notebook are used toinitialize the data acquisition board. A prescaled plot is displayed onthe screen at the beginning of an experiment, after you click on theRUN button. Since the initialization of the DAQ board takes ca. 1-2seconds, the data do not show up on the graph immediately, but onlyafter this initialization period. The initialization is performed at thebeginning of each experiment.

During the acquisition, a message "Acquisition in progress" isdisplayed on the screen, on a Cool Bar. Do not interrupt theacquisition process. When the experiment is finished, another messageis displayed: "Acquisition finished". At that time, you can inspect thedata collected, replot them, autoscale, change variables, etc. But, mostimportantly, you must save the data on a hard disk or removablemedia before a new data set takes its place in the computer RAMmemory.

If you are going to use the same set of data acquisition parametersfor the next experiment, as in the preceding experiment, you do notneed to invoke the Parameters Notebook again before clicking on theRE-RUN button. The program waveform and other parameters arestored in computer memory and read automatically when you startnew experiment.

Analysis, Simulation, and Evaluation

ANALYSIS

After the experiment is finished, you can analyze the |Y| magnitudevs. f plot by clicking on the ANALYZE button on the cool bar. Itperforms first analysis by searching for maximum and minimumadmittance, characteristic frequencies, etc., and attempting to estimatethe values of total series resistance R1 (the equivalent circuit ispresented in Appendix; R1 = Rm + Raq + Rf), shunt capacitance C0, andthe product L1C1. The values of L1 and C1 are shown only as a guide(although their product should be correct).

SIMULATION

On the basis of the tentative analysis, you can now try to simulate theequivalent circuit by changing values of the passive elements andplotting the admittance characteristics: |Y |, G , and B versus f,complex plane plots Y(im)–Y(re), or log|Y| versus f. The simulation is

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simplified by using the SIMULATE function invoked by clicking on thebutton SIMULATE on the cool bar. If unsuccessful, you can try usingthe QCI automatic EVALUATE function, which evaluates theequivalent circuit elements for you. You may still improve theevaluation by continuing the simulation procedures. Note thatdifferent admittance graphs put more attention to different aspects ofthe overall QC immittance characteristic.

EVALUATION

As mentioned above, the EVALUATE function, invoked by clicking onthe EVALUATE button on the cool bar, can evaluate the equivalentcircuit elements for quartz crystal resonators. Remember, that theseries resistance sealed inside the Faraday Cage is 20.00 Ω. So, if youadd externally another series resistor, you should increase the value ofRs by this external resistance in order to obtain correct R1 estimate.For the proper evaluation of QC characteristics, it is imperative thatthe admittance spectrum recorded spans the whole resonance region,i.e. from a frequency below the admittance maximum to a frequencybeyond the admittance minimum. The wide-scan spectrum puts some"perspective" into the evaluation and usually allows to obtain goodvalue of C0. This value can be used later in SIMULATE function fornarrow-scan spectra which give better estimates for R1 and L1 providedthat C0 is known.

See Appendix for equivalent circuit for QC resonators and typicaladmittance plots.

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Chapter 9

SAVE AND LOAD OPERATIONS

The save and load operations in QCI conform to the MicrosoftWindows standards and do not require any detailed descriptions.However, it is important to introduce the user to the special formatsthe experimental data can be stored in for further processing. Theseinclude two file formats:

(1) binary format,

(2) ASCII (or: text) data format.

The basic data format is the QCI 2 binary data format. Thebinary files store the measured data, variable specifications, and allthe experimental conditions. Retrieving a binary file is, therefore,equivalent to loading the corresponding experimental conditions,which may be useful for future reference. The binary files are alsomore compact and are saved and loaded faster than text files.

The QCI 2 ASCII data files contain the information about thenumber of variables (by default: 6) and the number of data points.This information is followed by the specification of variables and theirunits. The following measured data are organized in this way: first,the values for each of the six variables corresponding to the firstexperimental point are listed and separated by the tab characters; thenthe values for each variable corresponding to the second experimentalpoint are listed, followed by those for the third point, and so on. Thedata for each point are separated by the line feed and carriage returncharacter. The ASCII data files are larger and so they occupy more ofthe disk storage space. Also, the saving of these files is slower.

While the normal operation of QCI 2, and also earlier versions, isbased on the binary data format, at the stage of data processing, theASCII format is useful, since it allows the user to utilize plotting andprocessing capabilities of software packages available from othervendors, e.g. Microsoft EXCEL, Microcal ORIGIN, etc.

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NOTE: QCI 2 is compatible with earlier version of QCI (Ver.1), which used a different file structure. The earlier binaryformat was based on 32-bit (6-byte) real numbers and reducedspecification of experimental conditions. The QCI 2 binary fileformat is now based on double-precision 64-bit (8-byte) realnumbers. However, QCI 2 program can recognize the old fileformat and load data from these files without operatorintervention. The file name extension, both in the old files andthe new files, are not essential. This means that you can addan extension .qci to the QCI files but the file can be retrievedwith any other extension too, e.g., .123, .dat, etc. This is notthe case, however, with the ASCII files, since Microsoft'sEXCEL will not be able to import data from a text file, whichhas an extension different than .txt. Therefore, when saving afile in an ASCII format, do not force QCI to make a differentextension than the default .txt extension, which is addedautomatically by QCI.

NOTE: QCI 2.0 data file format .qci is not compatible with thegeneral purpose Voltscan file format .vv5. The specificinformation about variables, calibration, and representation ofQC immittance data cannot be reproduced in Voltscan 5.0.

The data collected during an experiment are stored in thecomputer RAM (volatile) memory. If you are satisfied with theexperiment, the data should be saved on disk.

You can save data after experiment by using one of the twopossible routes:

(a) by clicking on one of the SAVE AS buttons on the Cool Bar (onebutton is for saving data in a binary format and one for saving data inan ASCII format), or

(b) by a proper selection in the main menu:

alt/File/Save, or alt/File/Save as.

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Chapter 10

ENDING THE SESSION WITH QCI

Be sure that your data set present in the volatile computer RAMmemory is saved on hard disk or removable storage media, such as thefloppy diskette, CD-R optical disk, ZIP disk, solid state flash memorycard, etc. To leave the program, it is essential to follow the exitprocedure. It is important because various operating parameters mustbe saved and all open files closed before the program is terminated.Otherwise, some system data may be lost and the program may notwork properly next time the computer is turned on.

The exit procedure includes activation of the ParametersNotebook (click on the PARAMS button, if it is not in an active state),selecting the EXIT page, and clicking on the QUIT button.Alternatively, you can go through the main menu and select:

alt/File/Exit.

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Cm

Rs Lm Rm

C0

Rp

Lf RfLaq Raq

Chapter 11

APPENDIX

Quartz Crystal Resonator equivalent circuit

where:

Lm - motional inductanceCm - motional capacitanceRm - motional resistance

Laq - liquid loading inductanceRaq - liquid loading resistance

Lf - film inductanceRf - film resistance

C0 - shunt capacitanceRs - series resistance, Rs = 20.00 Ω (sealed inside Faraday Cage)Rp - parallel resistance

QCI evaluates:

L1 = Lm + Laq + LfC1 = Cm

R1 = Rm + Raq + Rf

C0

Rs, Rp – can be entered to aid analysis

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In solution, the QC admittance maximum is lower and Q-values are also lower.

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Additional examples are included in C:\data-QCI folder in the Data Logger.