ASCD-424A

The ASCD-424A is used to condition and digitize up to 24 analog differential-ended channels. Single-ended configurations are possible by enabling programmable pull-down resistors on any of the negative inputs.

At the heart of the ASCD-424A is a hard-wired state machine that oversamples all channels at a rate between 40 ksps and 80 ksps and digitally filters any noise above the user-programmable cutoff frequency. This is achieved using cascaded, 15-tap FIR filters with output rate decimation, followed by a final FIR or IIR filter. If IIR filtering mode is selected, the last digital filter in the filtering chain is an 8th or 16th order (selectable) Butterworth filter. If FIR mode is selected, the last digital filter in the filtering chain is a 49-tap Kaiser window, Beta 6 filter.

There are three independently configurable output streams per channel, allowing different sample rate, cutoff, and filter type to be selected for each output stream.

All signals are sampled simultaneously. When several channels are sampled at different sampling rates, at the start of an acquisition cycle all channels are aligned.