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ThimbleAlgometer-05-11.exe Latest version.

Index:

Calibration
Load Cell
Thimble
Comparing Interlink to Tekscan FSR's
Excel(Sending to Excel)
File Menu
Installation
Log Files
Maintenance
Menu Options
Test Setup Options
Tools Menu
View Menu

Description

The Electronic Thimble Algometer is made of a force sensing resistor (FSR by INTERLINK ELECTRONICS, also distributed by:Trossen Robotics and Digi-Key or an other type FSR with totally different characteristics: FlexiForce Force Sensors by TekScan) taped to the user's index finger before putting on a surgical glove (Notes on Interlink vs Tekscan FSR's).  Any pressure applied to the finger is sensed by the resistor the resistance of which is sent to an IBM compatible computer through a USB port LabJack U12 data acquisition device.  A quick calibration by means of a second force sensor (a load cell mounted with a muscle mass simulating foam) permits the user to ascertain the validity of the force readout each time the FSR is repositioned on the finger (see Calibration below).

The software collects the data into a table and can send them simultaneously to Microsoft Excel. The data can also be saved to a disk file independently from Excel. New in 2008, the data are also automatically saved to log files with a preset name whether or not the user needs them.  In case of power failure or other malfunction, the data can be retrieved from these log files.

To zero the strain value before a measurement is made the user can press the computer keyboard 'Z' key, or set the "Automatic Zero" option to "on" ,which causes the strain reading to zero automatically at the end of each Inter Trial Interval (ITI).

The keyboard 'R' key can be used to reset any previous offset back to hardware baseline (not normally useful, but could be an indication of a malfunction or need for adjustment, should a large pressure reading result).

A "Subject" switch, a "User" switch or the computer keyboard space bar can be used to store the current strain value into the table on the program main window.  If the space bar or the "User" switch are used, an asterisk is added after the strain value to indicate that the subject did not respond to the applied pressure.

When starting, the software is in setup mode. A panel of setup controls is then visible. These controls must be used to edit three groups of options:

1 - The Session information.
The information entered in this panel is sent to Excel along with the experiment data when the "Send to Excel" feature is used (Excel report sample).

2 - The Experiment options: the "Site" columns of the table (for more info on setting up the test options).
3 - To change the switches, voice, auto zero options, and whether the peak force or current force is to be recorded. This panel can also be used to test the "User" and "Subject" switches: when the corresponding switch is depressed, its label background color turns green. If the FSR is made by Interlink, its plug has a code circuit to identify it. A label on the options panel will display: "FSR by Interlink". If no code is present the label will read: "FSR by Tekscan".
      This panel can also be used to enable or disable the "Maximum strain reached" audio notification feature, and set the value at which it is activated.

Clicking "START" switches to "Run" mode and after a delay equal to the set "Inter Trial Interval" and if the "Voice" option is checked on, a voiced prompt calls for the first site to be stimulated.
Pressing the subject switch (if the subject switch option is checked on), the user switch (if this option is checked on) or the computer space bar will cause the pressure reading to be stored into the "Test #" column of the table and the next ITI will start.  If the peak force option is selected the force stored is the highest force detected since the end of the last ITI.
The "Run" mode can be exited at any time. The experiment can then be restarted for test #1 trial #1, or resumed at any user selected trial.  To select the trial from which to start, click the table cell for this trial, and then "Resume" rather than "Start".

In order to perform a blind experiment, the display tubes can individually be hidden from sight and the table can be blacked out to hide the readings.  This is done through the menu "View" options

Maintenance

The "Force Sensing Resistor" (FSR) that fits on the finger has an estimated life of approximately 6 months depending on usage. Three FSR's are supplied with the unit but, once they are all used, it is the responsibility of the user to replace them. The FSR's can be purchased from the Digi-Key Corporation. Their part number is: 1027-1001
Anyone familiar with soldering can easily attach the new FSR to the existing cable making sure not to apply excessive heat to the FSR plastic backing (It is recommended to use a hemostat, some pliers, or a similar tool as a heat sink). It is also imperative to insulate the exposed conductors to avoid contact with the user's hand.

Menu Options

    File (more info)     View

    Tools (more info)

    Help

Test Setup Options (Order in which the test sites are tested)



Test # The number of the test being setup.  There are 2 tests per experiment.
Site Selection. Any number of the sites #3, #6 or #9 can be specified in any order (for more information).
Randomized. Specifies that the order, in which the selected sites are tested, should be randomized.
Repeat Mode. Specifies whether the sites to be tested should be repeated the certain number of times, by trial (each trial repeated) or by test ( the test sites are repeated as a group).
ITI. Inter Trial Interval or the amount of time in seconds between trials.

Menu Options

    File

    View

    Tools

    Help

Test Setup Options

Test #   The "Test #" specifies which test is being setup, or rather which test will be filled up with the setup selections when the "Enter" command bar is clicked. It automatically switches to the next test after the "Enter" command is used.
Site Selection
Site Selection
- Selecting a preset group: Click the down arrow to get access to a list of previously saved groups of sites to be tested. Click the desired group in the list. The selected group will be used by the program to define the trial sequence for the test being edited.
- Removing a group: Select the group to be removed, then click "Remove".
-Adding a new group: Type the new group into the text window above the list. You must separate the test sites with some character other than spaces and numerals, any character will stay in the list display but will be ignored when transferred to the table. The newly defined group can then be added to the list by clicking the "Add" button. If not "Added" to the list, this new group can be used but will not be saved for use at a later date. The groups are automatically placed in alphabetical order, and , if preceded with a name can more easily be retrieved if the list becomes long enough.
Randomized When this option is checked the sites in the selected group are randomized.
Repeat Mode Three options are available: 1-each trial is repeated , 2- the whole group is repeated as a unit, 3- no repetition, the sites are only tested once. In the example, Test#1 was repeated "by Trial" and Test#2 was repeated "by Test"
ITI Each test can have a different Inter Trial Interval that is specified by typing a time in seconds into the ITI text box.
Once all the options are selected, clicking the "Enter" bar will make the computer fill the trial sequence into the table and save the ITI.

Thimble Calibration.

Background Information.
    The FSR resistance is sensitive to the curvature as well as the pressure applied to the sensor. This is the reason a foam, simulating the tested object is used as an interface between the calibration load cell and the FSR.
   In order to properly use the algometer on a different surface, it is imperative that the foam be changed to one with characteristics closer to the new object to be tested It is the responsibility of the user to find such substitute and affix it to the calibration load cell apparatus.
    Attempting to test the system accuracy using any other force producing device such as another algometer or scales is futile unless the same type of interface is used between the two units.
    The accuracy of the "INTERLINK ELECTRONICS" force sensing resistors and their stability are somewhat questionable ( FSR publication p5 and FSR publication p6).In order to ascertain the validity of the measurement a quick re-calibration is needed each time the FSR is placed onto the finger or any time deemed necessary.  A second force sensor, an Omega  LC8100-200-10 load cell is fitted with a layer of plastic foam to simulate the muscle mass.  Pressing the FSR onto the load cell foam causes the software to take a series of samples of both, the thimble FSR and load cell force readings thus creating a translation table. The resulting best fit curve is subsequently used to translate the input voltage from the Thimble FSR into a force in Kgf or Newton. This calibration procedure takes no more than a couple of seconds.

    For this calibration to be accurate, it is necessary to ascertain that the precision load cell is itself properly calibrated.

Interlink vs Tekscan FSR's

The Tekscan A201-1 sensor  has a better size (1cm in diameter) than the Interlink sensors (choice between two diameters: 5mm and 13mm).  However the main difference between the Interlink and Tekscan FSR's is their impedances: while the Interlink FSR impedance is in the order of the Kilo-Ohms, the Tekscan FSR impedance is in the Meg-Ohms.  Insulation of the Tekscan leads and connectors is very important for the slightest touch will make the force reading jump around the whole usable range.  A jumper was added inside the Interlink plug to change the biasing of the FSR's (See schematics) depending on whether it is made by Interlink or Tekscan. Although the size of the Tekscan FSR is more appropriate for small fingers, the Interlink FSR has a more linear response and should probably be used whenever possible. The "Calibration Data" graph above is pretty much typical of the Interlink FSR's.  Two near perfect calibration graphs: Interlink and Tekscan

Sending to Excel

1- Open Excel and edit the sheet name to change the Excel default to whatever name you desire. We highly recommend changing the Excel default in order to avoid accidentally erasing valuable data. The Algometer program automatically sends the data to Excel without checking for proper transfer nor errors. Excel  Sheet Selection
2- "Copy" the name to the clipboard then press 'Enter' to validate the new name otherwise the data will not transfer from the Algometer program.
3- In the Electronic Thimble  Algometer program, select the menu option: "File/Rename Excel Sheet". The small window shown at right will appear. This File option is only available when the menu "View/Sending to Excel Option" is checked (the "Sending / Not Sending to Excel" command bar is then visible).
4- Select the whole text currently inside the text box, then "paste" the Excel sheet name previously saved to the clipboard (You can also edit the name without copying and pasting).  Click "Add" if you want to add it to the list for future use.
5- Clicking the 'Remove' button will delete the currently selected name from the list.
6- Clicking the 'OK' button will validate the selection and close the window. If you have selected the option of 'Sending to Excel' by clicking on the command bar, you will notice that the caption of the bar has changed to reflect the current name of the Excel sheet.
7- Clicking the 'Close' button will close the window without changing any previously selected name.
8- You should now make sure that the data are being sent to Excel before running the experiment.
a- Click the button bar with the caption: "Not Sending to Excel" which should change to: "Sending to Excel - " followed by the Excel sheet name to which the data will be sent.
b- Click the "S T A R T" button
c- Press the 'Subject' switch or the keyboard space bar and observe that whatever is being saved into the Algometer program table, also appears on the Excel sheet.
d- Clicking on the "Clear Test Results" will clear the data in Excel as well as the data in the table.

Log Files Table & sample Log file
Every time the [Start] button is clicked, a log file is created with the name: ThimbleAlgometerLog#1.txt ( or WagnerAlgometerLog#1.txt or VonFreyAlgometerLog#1.txt for the other types of Algometers).  If the file already exists it is renamed: ThimbleAlgometerLog#2.txt. If that one already exists it is also renamed with the #3, etc. up to #9 at which time the file that would be called #10 is deleted. So the latest log file is always #1.

Log File as of February 25, 2008
        T H I M B L E    A L G O M E T E R   L O G

All timings start when the strain reaches 0.5 Newton
The Rate = (Peak Strain - 0.5N) / Peak Time 

                                           Peak    Peak            End     Total
  Date       Time      Test# Trial#  Site  Strain  Time    Rate    Strain  Time   User

 2/25/2008 3:57:54 PM    1     1      6    6.26   11.82    0.47    6.11   11.92   *
 2/25/2008 3:58:07 PM    1     2      9    6.35    8.16    0.72    6.35    8.16   *
 2/25/2008 3:58:23 PM    1     3      3   10.46   10.33    0.96   10.46   10.33   *
 2/25/2008 3:58:34 PM    2     1      6    9.58    6.34    1.43    9.58    6.34   *
 2/25/2008 3:58:50 PM    2     2      3    8.58    4.20    1.92    8.58    4.20   *
 2/25/2008 3:58:59 PM    2     3      9   10.11    3.93    2.39   10.11    4.02   *

And its corresponding saved "Experiment Table" data
	 Algometer Experiment Data

  Subject ID: qwe

                   Test # 1                                 Test # 2                   
         Site    Strain     Rate   Duration      Site    Strain     Rate   Duration
02-25-2008    15:59:26
 1         6      6.1*      0.47     11.92         6      9.6*      1.43      6.34
 2         9      6.4*      0.72      8.16         3      8.6*      1.92      4.20
 3         3     10.5*      0.96     10.33         9     10.1*      2.39      4.02

- Blank rows are inserted to alert of the fact that the experiment was stopped and then resumed, and that the trial following the blank row may not necessarily be the next one showing in the table, as is the case for the second blank row in the sample above.
- The asterisk in the "User" column indicates that the trial was ended using the "User" switch or the keyboard spacebar.

2005 September 30
Last update: 2011 December 19