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Overview: Demonstrates on enabling digital filtering on any PFI line on an M Series DAQ Device by using a Dummy Counter.
Descriptions: When acquiring digital signals in an industrial or otherwise electromagnetic noisy environment, it is common to see some bounces on the acquired signals whenever the signal changes state. These bounces appear as extra pulses close to the actual transition of a digital signal. When processing digital signals for pulse counts such as a quadrature encoded value, it is desirable to avoid theses bounces or eliminate them before processing the signal. This type of filtering or processing is commonly called debouncing as it removes the bounces from the digital signal.
Digital filters (digital debounce filters) can be implemented on the device's PFI line(s) to eliminate noise, unexpected, inaccurate, or incorrect counts on any counter tasks with sensors like the encoder.
On National Instruments M Series (62xx) DAQ Devices it is possible to enable digital debouncing filters on PFI lines used in Counter tasks. This example program configures a Dummy Task for the purpose of enabling the debouncing filter. The PFI Line will continue to use the filter until the device is reset or the filter is disabled explicitly (due to the "Lazy Uncommit" behavior of NI-DAQmx).