114Magtrol Model DSP7000 Dynamometer ControllerChapter10 – TheoryMAINTENANCE10.3 filter parametersThe Digital Filters of the DSP7000 are used to remove undesired noise from the TSC inputs. Thisnoise could be conducted from an undesired measured signal such as mechanical vibration or otherelectrical sources.The input to the A/D converter internal to the DSP7000 has a traditional analog filter that is comprisedof the following characteristics:• -3db Point: 3.8 KHz• A/D Sample Rate: 7812.5 Hz• 16 Acquired and Averaged Samples: Average applied to filter 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 filter• Transposed Direct Form II Architecture: The diagram below shows this architecture.Z-1+Z-1+-a 1b 0+b 1b 2 -a 2x(n) y(n)w1w2Transposed Direct Form IIFigure 10–2 Transposed Direct Form II ArchitectureWith a Digital Filter, the DSP7000 is able to solve the following equations:y(n) = b 0 * x(n) + w1w1 = b1 * x(n) + a1 * y(n) + w2w1 = b 2 * x(n) + a2 * y(n)The equations are applicable to each channel, occurring every 2.48 milliseconds.
