National Instruments SCB-68A - PFI 0 Lowpass Filtering Applications

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NI SCB-68A User Manual
PFI 0 Lowpass Filtering Applications
Lowpass filters can function as debouncing filters to smooth noise on digital trigger input
signals, thus enabling the trigger-detection circuitry of the DAQ device to understand the signal
as a valid digital trigger.
Figure 4-10. Digital Trigger Input Signal with a High-Frequency Component
Apply a lowpass filter to the signal to remove the high-frequency component for a cleaner digital
signal, as Figure 4-11 shows.
Figure 4-11. Lowpass Filtering of Digital Trigger Input Signals
Note Due to the filter order, the digital trigger input signal is delayed for a specific
amount of time depending on the filter you use before the DAQ device senses the
signal at the trigger input.
Time (t)
Volts (V)
TTL Logic
High
TTL Logic
Low
Time (t)
Volts (V)