National-instruments Data Acquisition Device NI USB-621x Manual de usuario descargar pdf (Pagina 155)

Appendix B Troubleshooting

NI USB-621x User Manual B-2 ni.com

are various methods of achieving this reference while maintaining a high

common-mode rejection ratio (CMRR). These methods are outlined in the

Connecting Analog Input Signals on USB-6210/6211/6212 Devices and

Connecting Analog Input Signals on USB-6215/6216/6218 Devices

sections of Chapter 4, Analog Input.

AI GND is an AI common signal that routes directly to the ground

connection point on the devices. You can use this signal if you need a

general analog ground connection point to the device. Refer to the When to

Use Differential Connections with Ground-Referenced Signal Sources

section of Chapter 4, Analog Input, for more information.

How can I use the AI Sample Clock and AI Convert Clock signals on a

USB-621x device to sample the AI channel(s)?

USB-621x devices use AI Sample Clock and AI Convert Clock to perform

interval sampling. As Figure B-1 shows, AI Sample Clock controls the

sample period, which is determined by the following equation:

1/sample period = sample rate

Figure B-1. AI Sample Clock and AI Convert Clock

AI Convert Clock controls the convert period, which is determined by the

following equation:

1/convert period = convert rate

This method allows multiple channels to be sampled relatively quickly in

relationship to the overall sample rate, providing a nearly simultaneous

effect with a fixed delay between channels.

Channel 0

Channel 1

Convert Period

Sample Period

1 2 ... 150 151 152 153 154 155 156 157 158 159 160 ... 184 185

Sin comentarios

National-instruments Data Acquisition Device NI USB-621x Manual de usuario Pagina 155