Digital Filter - Somat eDAQlite User Manual

Digital Filter Processing Notes
• In the steady-state, the taps coefficients are multiplied by the input data sample values and these products are summed
to form a single filtered data output value. This process is obviously computationally intensive if there are a large
number of taps.
• If the filter delay is greater than zero (which is typically the case), the first output samples cannot be fully filtered. The
lite backfills these first output samples using the first fully filtered data value. For example, if the delay is nine,
eDAQ
the first nine output samples are assigned the same value as the tenth output sample value.
154
Filter Length
Specify the desired length of the boxcar filter. The number must be an odd number
between 3 and 201.
7.4.6

Digital Filter

The Digital Filter computed channel generates an FIR digitally filtered output channel
based on an ASCII file. The file format conforms to the conventions used by MATLAB®
to generate ASCII filter files including the following:
• All fields are floating point values, using only whitespace delimiters (e.g.,
spaces, tabs, newlines etc.).
• The first field is the number of tap coefficients. There must be at least two taps.
• The second field is the filter delay which synchronizes the filtered output data
with the input data. The value can range from zero to the number of taps minus
one.
• The third field is the filter gain. This field is optional in the sense that TCE does
not use it directly. However, it does provide a check. If the gain value is not 0.0,
then TCE checks the gain value against the sum of the tap coefficients and
reports any significant conflict.
• The remaining fields are the ordered array of tap coefficients.
Numerous examples are available in the TCE installation kit. See the files in the hsfilter
and sfilter subdirectories under the main TCE install directory.
Input Channel
The input channel data type must be 32-bit float.
Output Data Type
The output channel data type is 32-bit float.
File
Specify the full path name of the ASCII file that defines the filter. Use the browse button
to select the desired file. Use the check file option to parse the ASCII file and verify that
the format is valid.
NOTE
Because TCE parses the ASCII file at test initialization, any changes to the file prior to
initialization are effective for subsequent test runs.
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