Raw data acquired from the analog outputs of a Delsys Trigno Wireless EMG System is amplified by a factor of 909 and output over a ± 5 Volt range. Additionally, the EMG signal has a time delay of 48 milliseconds, and the accelerometer signal has a time delay of 96 milliseconds. The correction for these delays and the amplification factor can be performed with the Arithmetic Channel Calculation in LabChart. To access the Arithmetic Channel Calculation feature, left mouse click the Setup menu, and select the Channel Settings option. In the Channel Settings dialog window that appears, left mouse click in the Calculation column for the desired channel, and select the "Arithmetic..." option.
In the Arithmetic dialog that appears, you will need to enter one of the following equations depending on the signal you are recording from the Trigno system:
EMG Data
shift(Ch1, -.048)/909
Accelerometer Data
shift(Ch1, -.096)/909
In these example equations, it is assumed that we are working with channel 1 (Ch1). For other channels, you would simply change the channel statement to reflect the appropriate channel, e.g. channel 2 would be Ch2. Finally, the correct units of amplitude can be applied by selecting them the drop down menu in the lower right hand corner of the Arithmetic dialog window.
For additional information about the Arithmetic Channel Calculation feature in LabChart, please review its LabChart Help Menu topic.
Note: These delays are only visible with the older "legacy" sensors and base stations. Newer "Avanti" sensors should have any delay with the USB base station connection to LabChart. Further information on the Anati sensors can be seen in the user guide here .
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE.