An FPGA correlator for continuous real-time measurement of particulate flow

This paper describes an FPGA based system for monitoring the flow rate of pneumatically conveyed particulates by calculating the cross-correlation of signals generated by a pair of electrostatic sensors embedded in a pipeline. The architecture is capable of calculating a delay in the range of 0 to 20.48 ms with a resolution of 20.48 μs at the sampling rate of 48.8 kHz. The circuit is implemented using a Xilinx Spartan3 device operating at a frequency of 50 MHz and uses a novel logarithmic based arithmetic circuit for calculating normalized cross-correlation data at a rate 1000x higher than previously published microcontroller based solutions. The architecture is easily extensible to accommodate systems with more than 2 sensing elements and can operate at higher sampling rates as required. The current system uses just 12 multipliers, 12 BRAMS and 34% of the logic resources available on a XC3S700A device.