Owner’s Guide
30
•
Reinstall the soft ware.
You are using an early version of LabChart.
•
Upgrade to the latest version of the soft ware. Contact your ADInstruments
representative for information.
The BNC or I
2
C cable is faulty.
•
Replace the cable and try again. Immediately label all cables proved faulty so
that you don’t use them again by accident.
The Bio Amp is faulty.
•
This is the least likely event. If the front-end will not work properly aft er the
previous measures, then try using it on another PowerLab. If the same problems
recur with a second PowerLab, the front-end may be faulty. Contact your
ADInstruments representative to arrange for repairs.
The trace will not zero properly when adjusting high-pass filtering
The Bio Amp is receiving signals at a level that has saturated the input amplifier,
resulting in a large off set. This is normally due to poor contact between the electrodes
and the subject.
•
Check the connections for proper contact and try again.
If you are using the Dual, Quad or Octal Bio Amps, with the 0.02 Hz high-pass filter, the
trace can take a long time to zero by itself.
•
Click the DC Restore button in the Bio Amp dialog to bring the trace back to zero
quickly.
The signal appears to display a constant amplitude oscillation
Frequency interference from power lines can become superimposed on the biological
signal being measured.
•
You can use the mains filter in the Bio Amp to remove excessive line voltage
frequency interference (use the checkbox in the Bio Amp dialog).
If you are using cables and leads that were not supplied with your Bio Amp, they may be
unshielded or of low quality.
•
Check to make sure that you are using high-quality shielded cables and high-
quality leads. Only the supplied Bio Amp cable and leads should really be used.
The signal is noisy at lower ranges
This is probably the amplified noise from the electrodes, not a fault as such. There is, in
addition, noise that cannot be avoided by any amplifier (called ‘thermal’ or ‘Johnson’
noise).
•
Set the low-pass filter to remove the noise. (But be careful, since important
components of the signal could also be attenuated.)
This could be due an electrically noisy environment, particularly if there is some
equipment that produces a radio frequency that interacts with the Bio Amp modulator,
giving a heterodyne eff ect.
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