Measuring the time dependant properties of a drop

To make dynamic measurements you need to follow the 10 step setup procedure used for static measurements and make at least one static measurement to ensure that all the parameters are correctly set. In addition to this you need to enter the parameters on the remainder of the measurement board (to open click on measurement setup in the experiment dropdown menu) as follows:

Experiment parameters

Action: this determines whether the computer automatically starts the measurement (Automatic) or you start the measurement yourself (Manual). Manual Deposit is used when you form a drop and place it onto a sample for contact angle measurements

Initial Volume: Determines the volume of the drop to be formed before the measurement starts, after X drop defines the number of drops automatically expelled before the drop to be measured is formed.

Drop formation Click this button and you will be asked to enter a drop formation speed and tolerance these are by default 5 and 25 % respectively (the tolerance is a parameter which does nothing yet!). When you have entered the parameters click back to save them and return to the measurement board.

Deposit Setup Click this to enter parameters for manual deposits see action above.

Calculation With Volume? When this box is checked the software calculates the volume as the drop is formed (thus actively controlling the drop volume) , if it is not checked the motor is just driven to expel the volume requested from the syringe (and hence no correction is made for backlash bubbles in the syringe or any other factors effecting the drop volume.

Timing: this controls the time taken to form the drop on which the measurement is made and hence determines how accurately the drop’s initial volume is determined.

Syringe: Select the number of the syringe you have calibrated and its calibration parameter should appear adjacent to it’s number.

Control Parameters

Stop after X seconds: Defines the total time the measurement continues. If you enter 0 seconds the experiment will continue until you stop it.

No Stop: If this box is checked the experiment will continue even if an image is taken from which the software cannot calculate the interfacial tension (for example if the drop touched the edge of the cuvette). If it is not checked once the software experiences an error with a calculation the experiment will stop.

Stop On Eject: If this box is checked the experiment will not continue if the software detects the drop becoming detached from the needle. If it is not checked the experiment will continue even if the drop detaches

Others: If you click this you can get access to other Control and Experiment Parameters, generally these should not be adjusted consult the manual for further information

Saving

This region of the measurement board enables you to select whether you same the calculation results, the images or the calculation standard error (the difference between the calculated drop shape and that observed) or a combination of these. Select the boxes you want to record. When you start the measurement you will be asked for a .ITC file name. You can also choose when you save the information: Synchronize (the calculation results are saved continuously), Periodic Saving (The data is saved at a period specified below: "Data all 2 minutes" commands the software to save the buffered calculation results every 2 minutes), At the end (the calculation results are only saved at the end of the measurement) and Without saving (the results are displayed during the measurement but are then not saved at the end).

Sampling If you select images you can select to save an image periodically while continuously measuring the interfacial tension: "Images all 50 measurements" means that every 50 measurement an image is recorded.

Saving image on aberration If you check this box, when the software cannot calculate the interfacial tension the image is automatically saved.

Graphic Parameters

 Using the Select Graph box choose the number of graphs you want displayed during the measurement (on each graph you can plot two parameters against time). Select what you want to plot on each graph from their pull down menus. The zoom buttons allow you to select how the zoom occurs and the time scale buttons enable you to select whether the horizontal axis expands during the measurement (all measured on graph), it is partially compresses, it is displayed page by page or the whole scale is always displayed.

Dynamic Parameters

 Start Regulation with experiment If this is selected the dynamic experiment will start immediately the drop is formed.

The tagged panel enables you to select active control of the drops volume/area or interfacial tension. If none is selected no control is applied. If a parameter is to be controlled/changed several tags are available. Position, speed, automatic and PID allow you to actively fix one parameter during the measurement. Linear (you enter a fixed gradient which is applied from an initial condition), Sinusoid (a sinusoidal variation applied from the initial condition, you enter the amplitude, period, and initial phase shift), pulse (from the initial condition you enter an amplitude(A) and a time (t1) which define the first slope (A/t1), a second time (t2) which defines a wait (t2 - t1) at the initial condition + A, a third time (t3) which determines the return slope (A/( t3-t2)) which continues until –A the system then waits again for (t2 - t1) and the returns to the initial condition in t1, the whole cycle taking 2t3) or mixed periodic (a combination of the linear and sinusoidal profiles where you enter a gradient, amplitude, period, and initial phase shift) variation of the selected parameter to be applied. For the periodic variations you can enter a number of blank cycles before the active cycles start, and also the number of active cycles. After the active cycles are complete the blank cycles start again and the whole cycle repeats unless the measurement time elapsed. During these periodic variations you can control when the software measures the interfacial tension by entering an oscillating frequency (set this to 0 for the fastest sample rate).

Dynamic Data Acquisition

Once you have set all of the Experiment, Control, Saving, Graphic and Dynamic Parameters you are ready to start your measurement: Click on Run measurements in the experiment menu and a box titled Save ITC file select your directory and chose a suitable filename for the experiment you are about to run, then click Save and the experiment should start. (If the name you have selected has already been used you will be asked whether you wish to replace the existing file, if you reply no the experiment will not start). The main window will appear and will be updated as the experiment runs.

In the main part of the window the graphs are displayed, below them the sate of the memory of the PC and the name of the configuration file is given. Above the graphs the numerical data is displayed with buttons to start and stop regulation as well as shortcuts to other functions.

The measurement will finish when the time your have set elapses or you click the stop button, and the measurements results window will appear after a short period while the PC saves the data. You are now ready to process your data.

The regulation can be started at the beginning of the measurement by checking the start regulation box on the measurement board alternatively if this was not checked you can start the regulation during the measurement by clicking on the ‘cog’ button in the master window. To pause the regulation click the ‘cog’ button at anytime, clicking it again will restart the regulation.

The short cut buttons enable you mark an event (yellow cloud containing m on a black stick), change the drop volume (syringe) change the calculation frequency (graph), record a film (red button) and change the area (bar graph). These operations are fairly self explanatory, for further information see part C VII-5 of the manual. Other parameters can be changed during the measurement via the experiment menu; this enables you to change the parameters on the measurement board as well as direct access to the motor position via the manual motor command, an image capture via one measurement and frontier adjustment via Frontier setup.

Via the workshop menu, the optical parameters can be modified in the focus and histogram windows. Do not modify the parameters in the configuration file menu at any time.

The graphic display can be modified while the measurement is occurring or once the data is collected. In the windows menu you can select the number of charts displayed in the master window via the running chart dropdown menu, it is possible to display up to 4 graphs at any one time. The measured parameters displayed on the graphs are selected on the graphic parameters part of the measurement board, each graph can display up to two measured parameters.

To change the graph scales the following short cut buttons can be used:
A – Changes the horizontal scale so all data is displayed extending it as the data acquired
C – Compresses the horizontal scale by a factor of 2
P – Displays the data page by page as the data is acquired
F – Has a fixed horizontal scale showing the data over the total selected experimental time
A – Automatically scales the vertical scale to the maximum and minimum of the particular measured parameter
a – As above but with out points that are distinctly different from those around them (i.e. removes bad data points)
F – Allows you to manually set the vertical scale
D – When this is on both the curves are scaled to full height on the vertical axis, when it is off the curve representing the data on the left axis is displayed on the top half of the graph and the curve representing the data on the right axis is displayed on the bottom half.

Processing Dynamic Data

Only a brief description of the possible data analysis is described here, for further information see Part D of the manual.

The results window will appear when an experiment ends or if you open an ITC file using the file menu in the master window. At the top of the results window are 5 menus (Files, Curves, Shot, Data Analysis and Help). The help menu does nothing! The purpose of the other 4 are given below.
The graphs in the center of the window display the data; these can be resized using the mouse at the junction between graphs. To change the appearance of the graphs click on a vertical axis, a box will appear that allows you to change the data type displayed, the marker and colour of the data points, the axis scales (select zoom in the options box) and also allows you to fit a curve to the data. The time scale can be adjusted by dragging the mouse over a region of interest with the shift key held down.

It is also possible to display all of the measured parameters at a particular point on the graphs by selecting any point on the curve using the left mouse button; the data is given at the bottom of the results window. If at the bottom of the window Image Stored appears that means you have an image of that point saved if you wish to re-analyse it.

Files
The file menu enables you to save the .itc file after you have modified it either over the original file or as a new file using the save and save as commands respectively (the cut out function is the same as save as). The export option enables you to export the data to other programs such as excel. Alternatively by selecting the print option the data graph can be printed.

Curves
The curves menu consists of the following options:
Data: If this option is selected a spreadsheet of the data appears in a new window. Using the edit menu of the spreadsheet it is possible to select all the data and copy it to another program (such as Excel)
Header File:This option enables the user to attach all the measurement parameters to a chart. The tagged window that appears when you select this option enables you to check the values of all parameters used for the calculation, however only the parameters defined in the view panel can be changed as these control the format of the charts.
Comment: By selecting this option it is possible for you to display and write comments about the experiment or data processing you have completed
Fit Manager: This enables you to be able to view the results of any fits you have completed using the procedure detailed above.
Movie: This option enables you to play the video you have recorded and then select single image and analyse it using the one image view board (in the same way as for a static drop). To play the image choose the speed using the slider on the bottom right and then click the play button (an arrow and line) for the direction you wish the film to play alternatively move through the film image by image by using the arrow buttons. The film can be paused using the pause button (2 lines) or stopped using the stop button (a square). The image number is displayed above the control buttons. It is possible to change the optical threshold and frontier on the video image using the mouse or the buttons below the image. Select one image analysis and the one image board appears. At the top left of this is the image you were viewing in the movie when you selected one image analysis with the frontiers superimposed on it along with some of the other image parameters (which can be adjusted). As well as the light bulbs there is a zoom button to enable you to view a magnified part of the image. Select standard error display and the click go. On the top right the results will appear and on the bottom right an error graph is shown. If the error graph shows a random scatter around zero the drop is a good Lapalcian drop if not the instrument is not set up well or the needle was vibrating when the image was taken (try a second image, if it still does not fit well repeat the Setup).
Calculation: If this is selected the calculation parameters window appears. This contains the parameters (material properties, drop configuration, calculation precision) and the type of data to be displayed on each of the graphs produced) which if you proceed will be used to calculate results from a movie. The option “set up on first image” enables you to adjust the optical threshold and frontier on the first image. With the saving check boxes you can select what you wish to save. If you select tout you can gain access to all other parameters. If you select go a calculation proceeding window appears this shows you which image is being processed. When all images have been processed or when the stop button is pressed a new results window appears which is saved as originalfilename_1.itc in your default directory. This file can be reprocessed and modified in the same way as the original file.


Shot
The select function in the shot menu enables you to choose and then analyse a single using the one image view board (in the same way as for a static drop).

Data Analysis
The Data analysis menu has one option – elasticity. It enables you to determine parameters defining rheological characteristics of the interface. These include the complex interfacial elasticity (presented as real and imaginary parts or by a modulus and phase angle) and viscosity (it is possible to obtain both a point viscoelasticity and a dynamic viscoelasticity). The dynamic drop elasticity window that appears when elasticity is selected from the Data analysis window displays the data on the top left a graph of the data on the top right the calculation results on the bottom left and a harmonic plot on the bottom right. Select the time period you wish to perform the calculation for using the markers (vertical lines with a diamond on the top) on the graph then to start a calculation click the blue and red graph button the results will be displayed in the bottom left of the window. To smooth the data select the yellow and blue graph button and the smoothing window will appear. If you wish to do a point by point calculation select the go button and choose a file name for the .etl file to be produced. If during the calculation you wish to stop it click the exclamation mark button. The .etl file can be loaded into any spreadsheet program such as excel.

 
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