National Instruments USB-621 Series, User Manual

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Contents
NI USB-621x User Manual vi ni.com
Chapter 3
Connector and LED Information
I/O Connector Signal Descriptions................................................................................ 3-1
+5 V Power.................................................................................................................... 3-3
+5 V Power as an O u tp u t ................................................................................ 3-3
+5 V Power as an Inp u t................................................................................... 3-3
USB Chassis Gro u nd..................................................................................................... 3-4
USB Device F u se Replacement..................................................................................... 3-4
PWR/ACT LED Indicator ............................................................................................. 3-6
Chapter 4
Analog Input
Analog Inp u t Range....................................................................................................... 4-2
Analog Inp u t Gro u nd-Reference Settings ..................................................................... 4-3
Config u ring AI Gro u nd-Reference Settings in Software................................ 4-5
M u ltichannel Scanning Considerations ......................................................................... 4-5
Analog Inp u t Data Acq u isition Methods....................................................................... 4-8
Analog Inp u t Digital Triggering.................................................................................... 4-10
Field Wiring Considerations.......................................................................................... 4-10
Analog Inp
u t Timing Signals ........................................................................................ 4-11
AI Sample Clock Signal.................................................................................. 4-14
Using an Internal So u rce .................................................................. 4-14
Using an External So u rce ................................................................. 4-14
Ro u ting AI Sample Clock to an O u tp u t Terminal ............................ 4-14
Other Timing Req u irements ............................................................. 4-14
AI Sample Clock Timebase Signal ................................................................. 4-15
AI Convert Clock Signal................................................................................. 4-16
Using an Internal So u rce .................................................................. 4-16
Using an External So u rce ................................................................. 4-16
Ro u ting AI Convert Clock to an O u tp u t Terminal ........................... 4-16
Using a Delay from Sample Clock to Convert Clock ...................... 4-17
Other Timing Req
u irements ............................................................. 4-17
AI Convert Clock Timebase Signal ................................................................ 4-19
AI Hold Complete Event Signal ..................................................................... 4-19
AI Start Trigger Signal.................................................................................... 4-20
Using a Digital So u rce...................................................................... 4-20
Ro u ting AI Start Trigger to an O u tp u t Terminal .............................. 4-20
AI Reference Trigger Signal ........................................................................... 4-21
Using a Digital So u rce...................................................................... 4-22
Ro u ting AI Reference Trigger to an O u tp u t Terminal ..................... 4-22
AI Pa u se Trigger Signal .................................................................................. 4-22
Using a Digital So u rce...................................................................... 4-22