Noise peaks appear at regular intervals in BioSigRP recordings

Tech Note: TN0160
Product: BioSigRP
Version: All
Date Added: 2004-12-29


Noise peaks that occur at regular intervals can occur when the system is affected by 60 Hz electrical noise. You might not see the peak at 60 Hz if you have a 60 Hz notch filter in place, but harmonics can still be present.


There are three things you can do to minimize BioSigRP recording problems related to electrical noise:

  1. Record in an environment where the 60 Hz noise is limited (like a Faraday cage).

  2. Ensure that the electrode impedances are as close together as possible. If you are using a 2 kOhm electrode and a 4 kOhm electrode, you will only get a reduction in the 60 Hz noise and its multiples by half (as opposed to virtually eliminating it in the amplifier). A differential amplifier will eliminate signals that are common to both the recording and reference electrodes. If the impedances to these electrodes are different, the common signals will have different voltages and not be subtracted out.

  3. Set the stimulus presentation rate at something other than a multiple of 60 Hz. For example, if the presentation rate were 20 Hz, then it would line up perfectly on the 60 Hz noise, and the noise would not be averaged out. Instead, make the stimulus presentation rate something like 21 Hz (or 11 Hz, if you wanted to use a 10 Hz presentation rate).