detectable signal is being received (no noise
or other signal is present)
whether the power of the main Receiving Unit
is turned "on". The green LED power
indicator should be lit.
the main transmission cable for proper connections.
whether the Portable unit has the battery pack
the voltage and the POLARITY of the batteries
in the power pack (the most likely cause of
60 (50) Hz hum or heavy clipped signal is being
sure that a grounded pre-amp is used (i.e. pre-amplifier
with the green ground lead).
sure that the ground lead is connected to a
reference pellet electrode in a suitable position.
Also check that the electrode is adequately
attached to the bony reference site. If necessary,
apply a new reference electrode or re-attach
the reference pellet elsewhere.
the "ground" pellet electrode on the
skin of a bony region of the body, but as close
to the recording electrode as possible. Use
conductive gel to improve the electrical contact
between the skin and the pellet electrode.
of the EMG signals is not present
quality of contact is likely bad for one or
both of the electrode sites. This can be quickly
diagnosed using a skin/electrode impedance meter,
like the BISIM device offered as an accessory
by Bortec. Please contact us for further details.
Remove the electrode(s), re-prepare the skin
and attach a new electrode. If this does not
solve the problem please contact us.
are artifacts in the signal or the baseline
is jumping when I am trying to record the EMG
are generally two sources behind recording problems
with the EMG signal; the AMT-8 hardware or the
acquisition hardware and software. As a general
rule, if you are having problems with recording
signals with your computer, test the outputs
from the AMT-8 directly to an oscilloscope or
other display device. If the signals display,
then the problem is with the acquisition hardware
or software, otherwise there is a problem with
the set-up or function of the AMT-8. Ensure
that the system is set-up properly and re-evaluate.
type of Electrodes can be used with the AMT-8?
type of disposable or re-usable EMG electrode
that is combined with an electrolytic gel and
has a pellet attachment. However, in accordance
with the SENIAM
guidelines, Bortec recommends the use of
a disposable pregelled Ag/AgCl (silver - silver
chloride) electrode, as used in approximately
80% of surface EMG recordings. For more information
Factors in Surface EMG Measurement.
offers a bipolar disposable EMG electrode (BIPOLE),
meeting all of the specifications of the SENIAM
I use the AMT-8 to measure Intra-muscular EMG?
Bortec AMT-8 provides complete subject isolation,
ensuring subject safety. Bortec offers a pre-amplifier
with a robust spring connector attachment allowing
the attachment of wire leads (IPE
accessories). This can be used with surface
EMG electrodes with bare wire ends as well as
with wire electrodes.
Bortec does not assume any responsibility for
the use of wire electrodes, and their use is
at the discretion of licensed practitioners
is the maximum distance that the subject can
be away from the main amplifier and recording
maximum recording distance with the AMT-8 is
50m. The standard transmission cable length
is 10m, but any length can be ordered between
3 and 50m.
contact Bortec for pricing information.
what situations are the high gain pre-amplifiers
high gain pre-amplifiers (APE-2000)
are used when recording from deep lying muscles
and/or when the level of muscle contraction
(activity) is very low; basically in conditions
where the signal is quite faint.
aspect of the EMG signal should be noted. As
the distance from the electrode to the muscle
area of interest increases, the signal strength
decreases, due to a phenomenon called tissue
filtering. For more information see Important
Factors in Surface EMG Measurement.
contact Bortec to see if high gain pre-amplifiers
would benefit your EMG measurement application.
the AMT-8 be used with other physiological measurement
AMT-8 is commonly used in conjunction with other
measurement equipment such as but not restricted
to, force plates/mats/arrays, treadmills, electrical
and magnetic stimulators, motion capture, video,
goniometers, accelerometers, skin impedance,
ECG, EEG and respiration equipment.
the specifications of your data acquisition
hardware to see if it has 10 A/D channels for
EMG and footswitch inputs from the AMT-8. Configure
your software to record and display the EMG
and footswitch signals.
consult the user manuals for your particular
data acquisition hardware and software package.
I expand the 4 or 8 channel EMG systems?
4 channel system can be fully expanded to an
8 channel system, as the 4 and 8 channel systems
use the same main amplifier and Portable unit
16 channel system can be configured by coupling
two 8 channel systems in a sturdy table top
case. Wearing two Portable units is the only
complication, but customer reports indicate
that this is only problematic with recordings
in small children. The benefit is that the two
8 channel systems can be used independently.
For example, when less than 9 channels of EMG
are to be measured in a research study, the
second 8 channel AMT-8 system can be used in
a teaching lab.
the reference pre-amplifier need to be inserted
into the 1st channel of the Portable unit?
The rule is that the reference pre-amplifier
must be connected into the Portable unit, provided
that there are no other pre-amplifiers connected
to a Portable unit channel with a smaller channel
number. Most users find it convenient to consistently
connect the reference pre-amplifier into channel
1 on the Portable unit.
is the SENIAM initiative and how can I get more
- Surface EMG for the Non Invasive Assessment
of Muscle was a recent concerted action funded
by the European Community to better standardize
EMG recordings. 9
countries were represented with 60 leading researchers
in the field of surface EMG research. For more
information see SENIAM
I use a notch filter to remove 50Hz or 60Hz
There is no need for notch filtering with the
Bortec AMT-8, or any other system using differential
pre-amplification of the EMG signal. Differential
pre-amplification allows for the rejection of
50Hz or 60Hz hum (power-line noise) and other
external noise sources by rejecting common signal
components that are measured from two closely
spaced (e.g. 2 cm) electrode sites. One important
measure of how well noise components are suppressed
is what is termed the common mode rejection
are the differences between fixed cable signal
transmission and radio telemetry?
cable systems use a transmission cable between
the subject and main amplifier and data acquisition
system, whereas, radio telemetry systems transmit
the signal from the subject to a receiving unit
advantage of radio telemetry is that the subject
can freely ambulate over a certain area, however,
this technology is much more expensive than
a fixed cable system. The latest method (i.e.
LAN based) of telemetry is more reliable than
the old form of radio frequency telemetry, which
is susceptible to interference from other equipment
and breaks in the transmission (i.e. producing
holes in the EMG data).
do I best record EMG in conjunction with electrical
consult your stimulator manual for instructions
on its operation. For a more detailed description
Factors in Surface EMG Measurement.
types of recording systems can be used with
AMT-8 system can be used with any analog or
digital display or recording device. Outputs
from the AMT-8 are analog with an output maximum
peak to peak voltage of 4V.
output signals are available on the back of
the main amplifier and are accessed via standard
BNC connectors. You should determine the type
of connection on the display or recording equipment
and attach a suitable cable to this device.
For further information consult the appropriate
are the characteristics of the outputs from
EMG outputs are in analog form with a maximum
peak to peak voltage of 4V, so for digital storage
the signals need to be converted from analog
to digital form (i.e. A/D converted).
footswitch outputs are digital and can either
be attached to the digital or analog input channel
on your A/D card.