Multichannel Systems MC_Rack Manual - Manual (Page 189)

183
8 Glossary
A
aliasing: Frequencies (noise) that are above half the sampling rate (for example above 2.5 kHz
at a 5 kHz sampling rate) will be transformed into lower frequencies.
anti-aliasing: Using an analog Low Pass filter for removing high frequency noise, which would
lead to aliasing if a sampling frequency lower than twice the bandwidth of the input signal is
used.
B
Bandstop Resonator: In signal processing, a bandstop filter is a filter that passes most
frequencies unaltered, but attenuates those in a specific range to very low levels. A bandstop
filter with a high Q factor has a narrow stopband.
Bessel Filter: A Bessel filter is a type of linear filter with a maximally flat group delay (maximally
linear phase response). Analog Bessel filters are characterized by almost constant group delay
across the entire passband, thus preserving the wave shape of filtered signals in the passband.
bit: A bit is a binary digit, taking a value of either 0 or 1. The digital data stream of the MC_Card
has 16 input and 16 output bits. A single bit can be used, for example, to trigger the recording
(based on a TTL output of a stimulator) or an external device. Multiple bits can be used to set up
more complex trigger patterns (where several requirements need to be met) or to encode a
decimal number, for example, from an external measuring instrument. In a number, bits are
always counted starting with 0, i. e. the 16 bits are numbered from 0 to 15.
Bitmap (BMP): Standard Windows bitmap image format, file extension *.bmp
Butterworth Filter: The Butterworth filter is one type of filter design. The frequency response
of the Butterworth filter is maximally flat (has no ripples) in the passband, and rolls off towards
zero in the stopband. For a second-order Butterworth filter, the response decreases at -12 dB per
octave.
C
Chebyshev Filter: Chebyshev filters are analog or digital filters having a steeper roll-off than
Butterworth filters. Chebyshev filters have the property that they minimize the error between
the idealized filter characteristic and the actual over the range of the filter, but with ripples in
the passband. Because of the passband ripple inherent in Chebyshev filters, filters which have a
smoother response in the passband but a more irregular response in the stopband are preferred
for some applications.
continuous recording: Opposite of triggered recording. Recording is started once and the data
is saved continuously to the hard disk until the recording is stopped. Note that a triggered data
analysis or display (online or offline) is possible independent of the recording mode.
D
Device Independent Bitmap (DIB): Windows clipboard format, , file extension *.dib
Digital Data: The Digital Data stream is the input data stream from the 16-bit digital input of the
MC_Card. In a standard MEA- or ME-System, only three of the 16 digital input bits are available
via BNC connectors. A digital in/out extension is available as an accessory for accessing all 16 input
and output bits. The Digital Data stream can only have values of 0 and 1. It can be displayed with
the Digital Data Display.
Downsampling: The downsampling feature offers the possibility to generate raw and filtered
data streams with different sampling frequencies to avoid huge amounts of resulting data when
recording more than one data stream.