PowerLab Teaching Series - Owner’s Guide
26
Setting the Range
T h e R a n g e p o p - u p m e n u l e t s y o u s e l e c t t h e i n p u t r a n g e , o r s e n s i t i v i t y , o f t h e
channel — the combined range of the PowerLab and Bio Amp. Changing the range in the
Bio Amp dialog is equivalent to changing it in the Chart window. The default setting (if
you have not loaded a settings file) is 20 mV, rather than 10 V, and the ranges go down to
100 μV in eight steps.
Filtering
Each of the Bio Amps in the PowerLab has low-pass, high-pass and mains filter circuitry
that can be adjusted to suit the recording. Note: the settings for one filter type may
restrict the possible settings for the other.
High-Pass Filtering. The High Pass pop-up menu gives a choice of two high-pass
filters: 0.5 and 10 Hz. The high-pass filter allows high frequencies in the signal to pass,
and removes frequency components below the filter frequency (including any DC
signal). These filters are useful for removing slowly moving baselines, such as motion or
respiration artifacts, particularly in ECG (EKG) recordings.
Low-Pass Filtering. The Low pass pop-up menu gives the choice of eight low-pass
filters: 10, 20, 50, 100, 200 and 500 Hz, and 1 and 2 kHz. These filters are useful for
removing high-frequency signals, such as noise.
DC Restore. Click DC Restore to reduce the time constant of the high-pass filter so that
the filter can rapidly adjust to an altered baseline value.
Figure 3-6
The Bio Amp dialog
for Windows
Signal amplitude
Click this to open the Units Conversion dialog
Filtering
options
Amplitude axis
Pause and Scroll buttons
Range pop-up
menu
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