Triggering With An Analog Source; Apfi <0..1> Terminals - National Instruments NI 6221 User Manual

Chapter 11 Triggering

Triggering with an Analog Source

Analog
Input
Channels
APFI <0..1>
APFI <0..1> Terminals
M Series User Manual
You also can program your DAQ device to perform an action in response to
a trigger from a digital source. The action can affect the following:
• Analog input acquisition
• Analog output generation
• Counter behavior
• Digital waveform acquisition and generation
Some M Series devices can generate a trigger on an analog signal. To find
your device triggering options, refer to the specifications document for
your device.
Figure 11-2 shows the analog trigger circuit.
+
PGIA
–
Mux
Figure 11-2. Analog Trigger Circuit
You must specify a source and an analog trigger type. The source can be
either an APFI <0..1> terminal or an analog input channel.
When you use either APFI <0..1> terminal as an analog trigger, you should
drive the terminal with a low-impedance signal source (less than 1 kΩ
source impedance). If APFI <0..1> are left unconnected, they are
susceptible to crosstalk from adjacent terminals, which can cause false
triggering. Note that the APFI <0..1> terminals also can be used for other
functions such as the AO External Reference input, as described in the
Offset and AO Reference Selection
ADC
Analog Comparison
Analog
Event
Trigger
(Analog Trigger
Detection
Circuitry Output)
section of Chapter 5,
11-2
AI Circuitry
AO Circuitry
Counter Circuitry
AO
Analog Output.
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