This article will describe the TDAS Control SIF settings to correct an ankle potentiometer (or the chest/crux angle potentiometers) to provide the true angle of the sensor.
This will require an initial test of the potentiometer to determine the offset voltage and actual angle.
- Set the potentiometer to 0.0° or set the foot to and maintain a known angle
- Lock the foot into a fixed position and record the angle of the foot
- Setup TDAS Control (TDC) with the SIF for the potentiometer
- The SIF must have the minimum settings
- Remove Offset?=No
- Zero Method=Equals 0 mV
- It is desirable to set the following
- The correct sensitivity in mV/V/°
- Excitation Voltage=5.0
- Perform a data collection run without moving the foot during the calibration or the collection of data
- View the data from the static test
- Note the the average angle that is reported.
- The .TLF from the test will contain the actual values that can be used but the data as seen will be an expedient method
- Subtract the recorded angle from the physical angle and not that result
- Go into Post-->Modify TLF and enter the result of the 'angle offset' into the 'Initial Engineering Unit Value' and use the ENTER or TAB key to receive the TDC prompt that the data will be re-written and choose OK
- Review the data again and verify that the baseline data is now showing the physical angle of the foot
- You can now write this value to the SIF and the real-time and collected EU data will have the angle corrected for true zero
In the example SIF shown here (and attached below)
- The electrical offset from 0.0V of the potentiometer is recorded as 243.36229mV during the TDC calibration with the example foot set to 0.0°
- This result gives 243.36229mV/-3.12805mv/5.0V=-15.56°
- The opposite value of the result or 15.56 is entered in the SIF to and the value is added to the data when viewing or exporting the data