A 256 channel digital filter for a data acquisition system

The TRIUMF Central Control System (CCS) employs several data acquisition systems to monitor its operational parameters. Each system multiplexes 256 analog channels into one analog to digital converter. Space constraints on the multiplexer cards prohibit the installation of adequate anti-alias filters which allows 60 Hz and other noise to corrupt the measurements. The new system overcomes this problem by sampling each channel at a 160 samples/second rate and using a DSP microcomputer to lowpass filter the data. The multiplexer and analog-digital converter operate at 256 times the channel sample rate. The channel filter bandwidth is restricted to approximately 1 Hz due to the rate at which the CCS reads the data. One DSP microcomputer is able to filter the 256 channels in a multiplexed system at a cost less than that of the anti-alias filters which would otherwise have been required. (Author) 4 refs., 3 figs