National Instruments Data Acquisition Device NI USB-621x - Page 6

Contents
NI USB-621x User Manual vi ni.com
Chapter 4
Analog Input
Analog Input Range....................................................................................................... 4-2
Analog Input Ground-Reference Settings ..................................................................... 4-3
Configuring AI Ground-Reference Settings in Software................................ 4-5
Multichannel Scanning Considerations......................................................................... 4-5
Analog Input Data Acquisition Methods....................................................................... 4-8
Analog Input Digital Triggering.................................................................................... 4-10
Field Wiring Considerations.......................................................................................... 4-10
Analog Input Timing Signals ........................................................................................ 4-11
AI Sample Clock Signal.................................................................................. 4-14
Using an Internal Source .................................................................. 4-14
Using an External Source ................................................................. 4-14
Routing AI Sample Clock to an Output Terminal............................ 4-14
Other Timing Requirements ............................................................. 4-14
AI Sample Clock Timebase Signal ................................................................. 4-15
AI Convert Clock Signal................................................................................. 4-16
Using an Internal Source .................................................................. 4-16
Using an External Source ................................................................. 4-16
Routing AI Convert Clock to an Output Terminal ........................... 4-16
Using a Delay from Sample Clock to Convert Clock ...................... 4-17
Other Timing Requirements ............................................................. 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 Source...................................................................... 4-20
Routing AI Start Trigger to an Output Terminal.............................. 4-20
AI Reference Trigger Signal ........................................................................... 4-21
Using a Digital Source...................................................................... 4-22
Routing AI Reference Trigger to an Output Terminal ..................... 4-22
AI Pause Trigger Signal.................................................................................. 4-22
Using a Digital Source...................................................................... 4-22
Getting Started with AI Applications in Software ........................................................ 4-22
Connecting Analog Input Signals on USB-6210/6211/6212 Devices .......................... 4-23
Connecting Floating Signal Sources ............................................................... 4-25
What Are Floating Signal Sources?.................................................. 4-25
When to Use Differential Connections with Floating
Signal Sources ............................................................................... 4-25
When to Use Referenced Single-Ended (RSE) Connections
with Floating Signal Sources ......................................................... 4-25
When to Use Non-Referenced Single-Ended (NRSE)
Connections with Floating Signal Sources .................................... 4-26
Using Differential Connections for Floating Signal Sources ........... 4-27