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Bio Amp Owner’s Guide
38
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 effect.
• Turn off pieces of unnecessary equipment to try and isolate the cause, then
either leave the equipment off, or, if possible, move the subject or
equipment outside the area of any interfering field.
• At the lowest ranges you may have to shield, shorten, or even replace the
Bio Amp leads, since they will tend to act as radio receptors.
The signal appears to be unusual, very weak, clipped, or distorted in some
way
This may be a problem of technique: the sampling rate, range, or filter settings
may be inappropriate for the signal you are recording.
• Make sure the settings are appropriate for the expected signal.
You may be using the wrong Bio Amp cable for the type of input. The single
Bio Amp and Dual Bio Amp have different pin arrangements, so their Bio
Amp cables are not interchangeable.
• Use the correct, supplied Bio Amp cable: a 3-lead cable for the single Bio
Amp and a 5-lead cable for the Dual Bio Amp.
Refer
Recording Technique, p. 18