User`s manual

38
SETUP
4. Digital Filters
The Digital Filters of the DSP6001 are used to remove undesired noise from the TSC inputs. This
noise could be conducted from an undesired measured signal such as mechanical vibration or other
electrical sources.
4.1 FILTER PARAMETERS
The input to the A/D converter internal to the DSP6001 has a traditional analog filter that is comprised
of the following characteristics:
• -3dbPoint:3.8KHz
• A/DSampleRate:7812.5KHz
• 16AcquiredandAveragedSamples:Averageappliedtolteratarateof488.28125Hz
• FilterCutoffFrequencies:3Hz,10Hz,25Hz,50Hz
• FilterOutput:EquivalenttosecondorderButterworthanaloglter
• TransposedDirectFormIIArchitecture:Thediagrambelowshowsthisarchitecture.
Z
-1
+
Z
-1
+
-a
0
b
0
+
b
1
b
2
-a
1
x(n) y(n)
w1
w2
Transposed Direct Form II
Figure 4–1 Transposed Direct Form II Architecture
With a Digital Filter, the DSP6001 is able to solve the following equations:
y(n) = b
0
* x(n) + w1
w1 = b
1
* x(n) + a1 * y(n) + w2
w1 = b
2
* x(n) + a2 * y(n)
The equations are applicable to each channel, occurring every 2.48 milliseconds.