National Instruments NI USB-621x User Manual

Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices
NI USB-621x User Manual 5-4 ni.com
In the single-ended modes, more electrostatic and magnetic noise couples
into the signal connections than in DIFF configurations. The coupling is the
result of differences in the signal path. Magnetic coupling is proportional
to the area between the two signal conductors. Electrical coupling is a
function of how much the electric field differs between the two conductors.
With this type of connection, the NI-PGIA rejects both the common-mode
noise in the signal and the ground potential difference between the signal
source and the device ground.
Refer to the Using Referenced Single-Ended (RSE) Connections for
Floating Signal Sources section for more information about RSE
connections.
When to Use Non-Referenced Single-Ended (NRSE) Connections with
Floating Signal Sources
Only use NRSE input connections if the input signal meets the following
conditions.
• The input signal is high-level (greater than 1 V).
• The leads connecting the signal to the device are less than 3 m (10 ft).
DIFF input connections are recommended for greater signal integrity for
any input signal that does not meet the preceding conditions.
In the single-ended modes, more electrostatic and magnetic noise couples
into the signal connections than in DIFF configurations. The coupling is the
result of differences in the signal path. Magnetic coupling is proportional
to the area between the two signal conductors. Electrical coupling is a
function of how much the electric field differs between the two conductors.
With this type of connection, the NI-PGIA rejects both the common-mode
noise in the signal and the ground potential difference between the signal
source and the device ground.
Refer to the Using Non-Referenced Single-Ended (NRSE) Connections for
Floating Signal Sources section for more information about NRSE
connections.

National Instruments NI USB-621x Specifications

General

Model	NI USB-621x
Category	Computer Hardware
Interface	USB
Analog Input Resolution	16 bits
Analog Input Sample Rate	250 kS/s (aggregate)
Analog Output Channels	2
Analog Output Resolution	16 bits
Digital I/O Channels	8
Counter/Timers	2
Operating System Compatibility	Windows, Linux
Power Supply	USB powered
Device Type	Data Acquisition Device
Analog Input Channels	16 single-ended or 8 differential
Analog Input Range	±10 V
Operating Temperature	0 °C to 50 °C

Summary

Chapter 1 Getting Started

Installing NI-DAQmx

Details on installing the NI-DAQmx software, including step-by-step instructions for setup and configuration.

Installing the Hardware

Non-software-specific information for installing USB DAQ devices.

Chapter 2 DAQ System Overview

Programming Devices in Software

How to program DAQ devices using NI-DAQ driver software, functions, and VIs.

Chapter 3 Connector Information

I/O Connector Signal Descriptions

Details the signals found on the I/O connectors, including AI, AO, and PFI signals.

Chapter 4 Analog Input

Analog Input Ground-Reference Settings

Describes supported ground-reference settings (DIFF, RSE, NRSE) for analog input.

Multichannel Scanning Considerations

Issues to consider for accurate multichannel scanning, such as settling time and channel order.

Analog Input Data Acquisition Methods

Explains software-timed vs. hardware-timed acquisitions and buffered vs. non-buffered modes.

Analog Input Digital Triggering

Details the support for start, reference, and pause triggers for analog input.

Analog Input Timing Signals

Summarizes the various timing signals used for analog input operations.

Getting Started with AI Applications in Software

Guidance on using M Series devices for analog input applications in software.

Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices

Connecting Floating Signal Sources

How to connect floating signal sources, including when to use differential or single-ended configurations.

Connecting Ground-Referenced Signal Sources

How to connect ground-referenced signal sources and common connection configurations.

Using Differential Connections for Floating Signal Sources

Diagrams and explanations for differential connections with floating signal sources.

Using Non-Referenced Single-Ended (NRSE) Connections for Floating Signal Sources

Chapter 6 Connecting AI Signals on the USB-6215/6218 Devices

Chapter 7 Analog Output

Analog Output Data Generation Methods

Explains software-timed vs. hardware-timed generations for analog output.

Analog Output Digital Triggering

Details the support for start and pause triggers for analog output operations.

Analog Output Timing Signals

Chapter 8 Digital I/O

I/O Protection

Connecting Digital I/O Signals

Getting Started with DIO Applications in Software

Chapter 9 Counters

Counter Input Applications

Frequency Measurement

Explains various methods for measuring frequency using the device's counters.

Counter Output Applications

Details applications for counter outputs, including pulse and train generation.

Counter Timing Signals

Counter Triggering

Describes arm start, start, and pause triggers for counter operations.

Duplicate Count Prevention

Chapter 10 PFI

Using PFI Terminals as Timing Input Signals

Exporting Timing Output Signals Using PFI Terminals

Using PFI Terminals as Static Digital I/Os

Chapter 11 Isolation and Digital Isolators

Chapter 14 Triggering

Triggering with a Digital Source

How to generate triggers using digital signals, specifying source and edge.

Appendix B Troubleshooting

Analog Input

Analog Output

Appendix C Technical Support and Professional Services

Support