DAPL IFM (IIR Filter Module)
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Filter your data: DAPL IFM
DAPtools Standard Package includes... |
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The DAPL IFM is a DAPL IIR filter module: an onboard digital implementation of the five classic filter types (Bessel, Butterworth, Chebyshev, Inverse Chebyshev, and Elliptic). The product, DAPL IFM (IIR Filter Module), forms an optional additional command module to DAPL 2000: a 32-bit multitasking real-time operating system that runs on every DAP board. A user normally controls DAPL 2000 through Windows, either locally or over a network. Every standard DAP model in current production also will run under Linux.
The new DAPL IFM command module extends the range of DAPL 2000 by giving a user a simple means to specify onboard IIR filters that run in real time and continuously filter the sampled data stream. A single command, named for the filter type, specifies the filter in just one line:
CHEBYSHEV(IPIPE0, 8, 0.20, 0.1, $BINOUT)
 1) Output from the CHEBYSHEV command in the text, superimposed on the random input waveform
 2) FFT of the output in (1) superimposed on the FFT of the input, showing high frequency attenuation |
The above command operates on the data stream from channel 0 (input pipe 0); it applies an eighth-order Chebyshev filter, with a cutoff at 20% of the Nyquist frequency (Nyquist frequency = half of the sample rate) and allows a 0.1 decibel passband ripple. It streams the filtered data to the PC through the system binary output pipe, $BINOUT.
The four other commands, BUTTERWORTH, BESSEL, CHEBYINV, ELLIPTIC, for the four other filter types, have the same simple user interface: source, order, cutoff, ripple levels, and destination. Any data pipe, not just those shown, may act as source or destination.
A single DAP board, with external rack-mounted expansion hardware, can handle up to 512 analog inputs. With the new DAPL IFM (IIR Filter Module), DAPL 2000 now can filter the data on any channels using any mix of these filter types. The filters operate independently, and each filter may have different parameters. The new IIR filters complement the existing FIR filters built into DAPL 2000.
Microstar Laboratories includes DAPL IFM in the DAPtools Standard software package. Contact us to order. For audio applications, download the free IIR-based IEC651 A-Weight Audio Filtering Software. This software, based on the same simple interface to advanced IIR filtering as the DAPL IFM, allows A-Weight filtering on any number of channels.
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