- Force Tube - Rate Tube - Table Data - Any of these three data displays can be hidden through these options. The tubes, when hidden, disappear completely from sight, but the table stays visible while its
data section is covered up (62 KB png file).
- Show Raw Force Voltage - This option displays the Analog to Digital converter raw voltage of whichever sensor is currently being displayed before any translation to Gram or Newton. This option can be used when
calibrating the "Calibration Load Cell". During calibration, the values thus displayed go into the X column of the calibration data, and the actual weight into the Y
column. (See Thimble Calibration for more info).
- Current Calibration Data - This option gives the user a chance to inspect the current calibration: the actual
log function for the FSR, and, for the Load Cell, the X (A to D voltage) and Y (actual pressure in kilograms) values and the calculated linear
function associated with each pair of points (See Thimble Calibration for more info).
- Thimble -
- Calibration Load Cell -
- Thimble Calibration History - Every time the program is started, the application (Algometer.exe) folder is checked for the existence of a sub-folder called: "CalibrationHistory". If the folder does not exist it is created
and a file bearing the initials: "A-C-H-" (Algometer Calibration History) and the current date as a name is also created in this sub-folder, in which all the calibration data will be recorded until the program is exited. When the program is started again, the new
calibration data are appended to the same file if on the same date. A new file with the new date for name is created if on a different day (calibration history file sample).
- Displayed Sensor - The same tube is used to display either the Thimble or the Load Cell. When displaying the Thimble the tube "liquid" is red by default. When displaying the Load Cell the tube liquid is green by default.
The color of the tube and the liquid can be changed by clicking on the empty part of the tube to change the color of the tube or on the liquid to change the color of the liquid for the sensor currently displayed.
- Calibrate the Load Cell - See Load Cell Calibration below.
- Check Load Cell Calibration - Lets the user place any weight on the load cell to check its output (See main window). You can use the "Escape" key to exit this mode.
- Reset Load Cell Calibration - This should probably never be used except if the load cell calibration cannot be achieve. It will result in a non-usable, far off, load cell output.
- Check Thimble Calibration - Lets the user press the thimble onto the load cell, as when performing a thimble calibration, to check whether the thimble and load cell outputs are close enough. (See main window).
The thimble output is displayed in thimble "liquid" color and the load cell output in load cell "Liquid" color where the rate is normally displayed. Notice how changing the angle of the thimble on the load cell can greatly modify its output. You can use the "Escape" key to exit this mode.
- In Edit Mode when Checked - This menu option is set by the software when a variety of conditions do not permit to run an experiment. When clicked, the software will switch to "Test" Mode if the Thimble Controller is found and powered up.
- Force Range - Selects the range displayed by the tube. It has no effect on the range of the sensor or its calibration.
- Help on the WEB - Sends you to this WEB page.
Test Setup Options
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.
- 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.
Note that only the sites selected for the tests will be displayed in the oval site locator at te left of the panel.
When this option is checked the sites in the selected group are randomized.
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 Test" and Test#2 was repeated "by Trial"
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.
Load Cell Calibration
The load cell is an Omega LC8100-200-10
Before performing a load cell calibration it is recommended to check and make sure that it does need calibration:
- Load Cell Calibration Check -
- Set the software to display the Load cell force in the tube display. To do this, click on: Menu/View/Displayed Sensor/Calibration Load Cell.
By default the "liquid" in the tube should turn to a green color. The liquid is green by default when the load cell output is displayed, and red when the
thimble output is displayed.
- Click on the "Newton" label below the tube to display the strain in kilogram force.
- Place a known calibration weight on the load cell, or apply a force by means of a trusted hand held algometer, and check whether the
displayed value is the same as the applied force/weight.
- Only perform the calibration of the load cell if the reading is not acceptable.
- When done set the software back to display the Thimble output.
- Load Cell Software Calibration -
The load cell is a linear precision load cell, therefore a two point calibration to correct software offset and factor should be sufficient. However, the
software was designed to handle calibrations with any number of points should it be judged necessary to do so.
- Click on Menu/Tools/Calibrate the Load Cell
- The front panel will then change somewhat (See the calibration front panel):
- The strain tube will be displaying the load cell output.
- The rate tube will be hidden.
- A calibration table will replace the trial table.
- Step by step instructions will be presented at the top left corner of the front panel.
- You will then be presented with an editable list of weights from which to chose (at right).
- Follow the step by step instructions at the top left corner of the front panel.
- Once the calibration is completed, we recommend performing another "Calibration Load Cell Check" just in case something unexpected had happened.
- Load Cell Hardware Calibration -
- Set the menu "Tools/Check Load Cell Calibration".
- Set the menu "View/Show Raw Force Voltage".
- Remove the top of the unit (two philips screws on each side.
- Locate the only trimmer pot on the front panel board.
- Adjust the trimmer until the displayed voltage is as close to zero as possible.
- Put the unit back together.
- Load Cell Calibration Results -
Typical load cell calibration data are shown at right, as displayed by the software when using the menu:
"View >> Current Calibration Data >> Load Cell", and below as recorded in the defaults file: "AlgometerDFT.ini":
1=0.0100, 0.0000, 2.0795, -0.0208
2=0.4500, 0.9150, 0.0000, 0.0000
Both should be interpreted thus: the calibration function is a linear function passing through points (X = 0.01, Y = 0.0) and (X = 0.45, Y = 0.915)
which translates to the function:
Weight in kilogram = 2.0795 x the Voltage + (-0.02).
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
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.
Instead of using the "Best Fit" curve as previously, we now divide the translation table into equal sections. This results in a more accurate calibration specially that the FSR's seem to have lost some of their linearity.
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.
Should the calibration become impossible to perform, due to jumps in the outputs of the load cell or thimble or similar problems, we suggest the following procedure:
- Check that the output of the load cell is near zero volts when not loaded (Hardware calibration).
- Reset the load cell calibration through the menu "Tools/Reset Load Cell Calibration".
- Restart the program.
- Calibrate the load Cell.
- Calibrate the thimble.
- If unsuccessful send us an email to email@example.com
It seems that these problems are caused by an error while performing the load cell calibration.
Log & Data Files
Every time the [Start] button is clicked, a log file is created, in the application folder, with the name: ThimbleAlgometerLog#1.txt. 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.
Sample log file:
T H I M B L E A L G O M E T E R L O G
All timings start when the force reaches 0.5 Newton
Any force below 0.5 Newton results in invalid data.
The Rate = (Peak Force - 0.5N) / Peak Time
OR = (End Force - 0.5N) / Total Time (when not recording peaks).
Peak Peak End Total
Date Time Test Trial Site Force Time Rate Force Time User
11/11/2013 3:37:53 PM 1 1 6 9.72 0.77 12.01 0.16 5.02
11/11/2013 3:37:58 PM 1 2 6 6.26 0.99 5.81 4.55 1.31
11/11/2013 3:38:01 PM 1 3 3 3.27 0.34 8.23 1.92 0.77
11/11/2013 3:38:04 PM 1 4 3 3.26 0.45 6.15 2.70 0.66
11/11/2013 3:38:09 PM 1 5 9 9.58 2.06 4.40 2.52 2.51
11/11/2013 3:38:13 PM 1 6 9 9.33 1.33 6.65 0.10 1.76
11/11/2013 3:38:18 PM 2 1 9 9.40 2.29 3.89 0.01 2.83
11/11/2013 3:38:21 PM 2 2 3 2.97 0.43 5.73 0.00 0.98
11/11/2013 3:38:24 PM 2 3 6 3.86 0.45 7.49 0.01 0.99
11/11/2013 3:38:29 PM 2 4 6 6.00 1.20 4.58 0.01 1.63
11/11/2013 3:38:32 PM 2 5 3 3.39 0.34 8.59 0.05 0.66
11/11/2013 3:38:35 PM 2 6 9 10.37 0.54 18.15 0.21 0.98
11/11/2013 3:38:50 PM 2 3 6 6.24 1.76 3.26 0.41 2.18
- 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.
- The asterisk in the "User" column indicates that the trial was ended
using the "User" switch or the keyboard spacebar or that the "max. notification" was reached.
And its corresponding saved "Experiment Table" data file in text format:
Algometer Experiment Data
Subject ID: 9012
Types of Site:
Site# Test #1 Test #2
3 Type 1-3 Type 2-3
6 Type 1-6 Type 2-6
9 Type 1-9 Type 2-9
Test # 1 Test # 2
Site Force Rate Duration Site Force Rate Duration
1 6 9.72 12.01 0.77 9 9.40 3.89 2.29
2 6 6.26 5.81 0.99 3 2.97 5.73 0.43
3 3 3.27 8.23 0.34 6 6.24 3.26 1.76
4 3 3.26 6.15 0.45 6 6.00 4.58 1.20
5 9 9.58 4.40 2.06 3 3.39 8.59 0.34
6 9 9.33 6.65 1.33 9 10.37 18.15 0.54
And its corresponding saved "Experiment Table" data file in Excel format, as it will appear in Excel:
Date Subject Visit Experimenter Set Type Site Repetition Force Termination Rate Duration
11/11/2013 9012 4 5 6 Type1-6 6 1 9.72 0 12.01 0.77
11/11/2013 9012 4 5 6 Type1-6 6 2 6.26 0 5.81 0.99
11/11/2013 9012 4 5 6 Type1-3 3 1 3.27 0 8.23 0.34
11/11/2013 9012 4 5 6 Type1-3 3 2 3.26 0 6.15 0.45
11/11/2013 9012 4 5 6 Type1-9 9 1 9.58 0 4.4 2.06
11/11/2013 9012 4 5 6 Type1-9 9 2 9.33 0 6.65 1.33
11/11/2013 9012 4 5 6 Type2-9 9 1 9.4 0 3.89 2.29
11/11/2013 9012 4 5 6 Type2-3 3 1 2.97 0 5.73 0.43
11/11/2013 9012 4 5 6 Type2-6 6 3 6.24 0 3.26 1.76
11/11/2013 9012 4 5 6 Type2-6 6 2 6 0 4.58 1.2
11/11/2013 9012 4 5 6 Type2-3 3 2 3.39 0 8.59 0.34
11/11/2013 9012 4 5 6 Type2-9 9 2 10.37 0 18.15 0.54
Other Features and Notes
Units of Force Change
You can toggle between Newton and kilogram force by clicking on the displayed numbers under the tubes..
Reached Maximum Strain Notification
You can change the sound played when the specified maximum has been reached ("Reached max. notification"). The sound is saved as a "wav" file in the application folder under the file name of: "ReachedMax.wav". Any sound stored in this file will be played.
Tube and Liquid Color Changes
You can change the color of the tubes and their liquids by clicking the mouse on the portion to be changed.
- Empty portion of the force tube: click on the empty portion of the tube.
- Liquid portion for the Thimble: click on the liquid portion of the tube while displaying the thimble force.
- Liquid portion for the Load Cell: click on the liquid portion of the tube while displaying the load cell force.
- Empty portion of the rate tube: right click on the empty portion of the rate tube.
- Positive going liquid for the rate tube: click any portion of the tube over the + 10 N/sec mark.
- Negative going liquid for the rate tube: click any portion of the tube below the - 10 N/sec mark.
- Idle liquid for the rate tube: click any portion of the tube between the - 10 and + 10 N/sec marks.
Window not Visible
Should the main window not show on your screen while it is present on the Taskbar, select it from the Taskbar then press F2.
Pressing F2 will only work if the Algometer program window is in focus; make sure it is selected.
Load Cell Problems
The software will then put the system in "Edit Mode". To revert to "Test Mode" the condition must be cleared and the mode exited clicking the menu: "Tools/In Edit Mode when checked".
2012 September 1
Last update: 2014 March 6