Multichannel Systems MC_Rack Manual - Manual (Page 133)

MC_Rack Features
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Digital Hardware Filter
In the "Digital Hardware Filter" tab, it is possible to switch the real-time feedback feature on
and off, and to define the characteristics of the digital hardware filter that gets applied to the
data before it goes through the signal detection algorithm. Using a filter is not obligatory
for real-time feedback. It needs Digital Signal Processor (DSP) resources and time for calculation.
The digital filter shifts the signal by some samples, so the real-time feedback is delayed about
eight times the sampling rate, for example 200 μs for 40 kHz sampling rate, compared to the time
without filter.
The filter is applied to all channels, whereas further processing is restricted to the channels
selected in the “Feedback Logic” tab.
Important: After selecting the filter parameters, you have to download the settings to the
DSP with the “Download” command. The “Download” button is available only if a download
is necessary. Pressing “Download” in any tab will send the settings from all tabs to the DSP.
The settings will also be automatically downloaded when the “Play” button in the main window
is activated.
With the "Feedback” button you can switch the tool on or off. With the command button
“Hide Display” it is possible to toggle the real-time feedback display.
Select the data stream you want to record. It is possible to generate feedback on a filtered data
stream, but still record the original, unfiltered data. The selected stream “Record Filtered Data”
or “Record Raw Data” will be sent to MC_Rack, and can be used for all other instruments.
If you select “Record Raw Data” the data is still filtered by the Digital Signal Processor (DSP)
for performing real-time feedback, but unfiltered data is sent to MC_Rack. With this option,
it is necessary to use a digital filter in MC_Rack to observe the data filtered in the same way
as it is used for real-time feedback processing.
Enable or disable the check box “High Pass Filter”. Select the high pass “Cutoff Frequency”
from the drop down menu in a range from 10 Hz to 2 kHz. Other frequencies may be directly
edited. 1 Hz is the smallest possible frequency, fractions of the unit are not allowed.
Enable or disable the check box “Low Pass Filter”. Select the low pass “Cutoff Frequency”
from the drop down menu in a range from 10 Hz to 2 kHz. Other frequencies may be directly
edited. 1 Hz is the smallest possible frequency, fractions of the unit are not allowed. If you apply
a high pass and a low pass filter the bandwidth of the resulting band pass filter is defined by the
cutoff frequencies of the high- and low pass filter. Select the first, second or third order of the
respective filter from the drop down menu. The setting of the filter order applies to all selected
filters.