EMG Signal Conversion to mV
Quote from patricia.bayer on 17 November 2025, 4:18We would like to measure CMAPs (M-wave) after nerve stimulation of the peroneal nerve using the USB-2+ (bipolar EMG; gain: 1000). The values for the CMAPs (peak-to-peak) that we read in the software (OTBioLab+) during the measurements are approximately in the range of 2 mV. When we retrieve the same values offline in the software (OTBIOLAB25), they suddenly amount to 60-70 mV. In Matlab and after conversion using the equation from the software manual, they are 1-1.5 mV. In the literature, values of 5-10 mV are considered normal. We suspect that there are errors in the conversion to mV. Could you please let us know why this might be that we have three different ranges of values and what we can do to obtain the correct mV values?
We would like to measure CMAPs (M-wave) after nerve stimulation of the peroneal nerve using the USB-2+ (bipolar EMG; gain: 1000). The values for the CMAPs (peak-to-peak) that we read in the software (OTBioLab+) during the measurements are approximately in the range of 2 mV. When we retrieve the same values offline in the software (OTBIOLAB25), they suddenly amount to 60-70 mV. In Matlab and after conversion using the equation from the software manual, they are 1-1.5 mV. In the literature, values of 5-10 mV are considered normal. We suspect that there are errors in the conversion to mV. Could you please let us know why this might be that we have three different ranges of values and what we can do to obtain the correct mV values?
Quote from Simone on 17 November 2025, 11:26Hi patricia,
Thank you for reaching out.
This may be related to how the conversion factor is being read from the .otb+ file.
Could you please send me one of the recordings so I can check it and identify where the mismatch comes from?Write to me at: s.posella@otbioelettronica.it
Kind regards,
Simone
Hi patricia,
Thank you for reaching out.
This may be related to how the conversion factor is being read from the .otb+ file.
Could you please send me one of the recordings so I can check it and identify where the mismatch comes from?
Write to me at: s.posella@otbioelettronica.it
Kind regards,
Simone
