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4-7
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)
V
o
lts (V)
TTL Logic
High
TTL Logic
Low
Time (t)
V
o
lts (V)
