Actiwave User Guide - Issue 2.0.18
Page 26
8 Preparing for an EMG recording
8.1
Electrodes
There are two main types of electrode for measuring EMG:
surface and needle. The needle electrodes give a small
very local signal from within the muscle. Surface
electrodes are the more common type and give a larger
‘averaged’ signal. For measuring surface EMG the
electrodes tend to be smaller than the ECG types although
some pads are dual use.
8.2
Pad
placement
Generally the EMG is measured along the muscle and the
signal level will vary according to distance between the
pads. There are many different sites and placements for
the electrodes and there is a huge amount of information
available on this subject. For measuring impulse response
along fibre we recommend that the common be used for
the
central
point.
The
signals
are
measured
synchronously so they can be summed or differenced in
your PC software. This also allows the measurement of
transit time.
8.3
Signal level
& Sampling
The level of EMG varies and the Actiwave unit has a high
signal mode (8mV) and a low signal mode (500uV). The
user selects which range to use when setting up. The
expected signal level depends on the placement of the
EMG electrodes. If in doubt try a short recording on the
low range; if the signal is too large then switch to the high
range.
It has also been found that a sampling rate of below 256Hz
for EMG recording may provide poor results (again
depending upon the location from which the signal is being
recorded). It is suggested that a short test recording is
performed to verify the suitability of the sampling frequency
before engaging in a full test.
Important!
In the European Union the Actiwave is
not
a
medical device and is intended for
research only
. Please
contact CamNtech UK for further clarification on suitability
of application.
WARNING!
Care should be taken when electrodes are applied to the
subject to ensure that unconnected leads or parts are not
accidentally shorted to other conductive paths or to earth
(ground).
