National Instruments 6368, Руководство пользователя

Страница: 67 / 278

4-24
|
ni.com
Chapter 4 Analog Input
• AI Hold Complete Event Signal
• AI Start Trigger Signal
*
• AI Reference Trigger Signal
*
• AI Pause Trigger Signal
*
Signals with an
*
support digital filtering. Refer to the PFI Filters section of Chapter 8, PFI , for
more information.
Aggregate versus Single Channel Sample Rates
MIO X Series devices are characterized with maximum single channel and maximum aggregate
sample rates. The maximum single channel rate is the fastest you can acquire data on the device
from a single channel and still achieve accurate results. The maximum aggregate sample rate is
the fastest you can acquire on multiple channels and still achieve accurate results. For example,
NI 6351 devices have a single channel maximum rate of 1.25 MS/s and aggregate maximum
sample rate of 1 MS/s so they can sample one channel at 1.25 MS/s or two channels at 500 kS/s
per channel, as shown in Table 4-5.
AI Sample Clock Signal
Use the AI Sample Clock (ai/SampleClock) signal to initiate a set of measurements. Your MIO
X Series device samples the AI signals of every channel in the task once for every AI Sample
Clock. A measurement acquisition consists of one or more samples.
You can specify an internal or external source for AI Sample Clock. You can also specify
whether the measurement sample begins on the rising edge or falling edge of AI Sample Clock.
Table 4-5. Analog Input Rates for MIO X Series Devices
MIO X Series Device
Analog Input Rate*
Single Channel Multi-Channel (Aggregate)
NI 6320/6321/6323 250 kS/s 250 kS/s
NI 6341/6343/6345 500 kS/s 500 kS/s
NI 6351/6353/6355 1.25 MS/s 1 MS/s
NI 6361/6363/6365 2 MS/s 1 MS/s
NI 6375 3.846 MS/s 1 MS/s
* On several devices, the single channel rate is higher than the aggregate rate because while the ADC
can sample at that rate, the PGIA cannot settle fast enough to meet accuracy specifications.