DAQ VXI-SC-1102 Manual de Instruções descarregar pdf (Página 22)

Chapter 1 MIO and AI Devices

National Instruments Corporation 1-5 DAQ Hardware Overview Guide

You can use SCXI modules as a data acquisition front end for the device to

condition the input signals and multiplex the channels. You can use all the

modes just described in conjunction with SCXI. The SCXI Modules and

Compatible DAQ Devices section in Chapter14, SCXI Hardware,

describes how to use the SCXI functions to set up the SCXI modules for a

data acquisition to be performed by a DAQ device.

Note The DAQPad-MIO-16XE-50 uses half-FIFO mode by default when doing interrupt

data transfer operations for analog input with rates faster than 256 samples per second. The

PCI ESeries and DAQCard ESeries devices use half-FIFO when performing interrupt data

transfers for analog input with rates faster than 1000 samples per second. You can override

the default setting and select between interrupt on every sample and interrupt on half-FIFO.

When using external conversions, you should select the mode appropriate for the

acquisition rate. To set the interrupt generation mode, see the

Set_DAQ_Device_Info

function in the NI-DAQ Function Reference Online Help or the

Set_DAQ_Device_Info.vi in the LabVIEW DAQ Online Reference.

ESeries Data Acquisition Timing

The following DAQ-STC counters are used for data acquisition timing and

control:

• The scan counter is used to control the number of scans you will

acquire. If you want to perform pretriggered acquisition, this counter

will ensure that you acquire selected number of scans before the stop

trigger is recognized.

• The scan timer is a counter that you can use for start scan timing.

• The sample-interval timer is a counter that you can use for conversion

timing.

The DAQPad-6020E uses half-FIFO mode when doing interrupt data

transfer operations for analog input rates of > 256 samples per second.

Data acquisition timing involves the following timing signals:

•A start trigger is a signal that initiates a data acquisition sequence.

Youcan supply this signal externally through a selected I/O connector

pin, through a RTSI bus trigger line, or by software.

•A start scan signal initiates individual scans. This signal can be

supplied from the onboard programmable scan timer, externally

through a selected I/O connector pin, through a RTSI bus trigger line,

or by software.

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DAQ VXI-SC-1102 Manual de Instruções Página 22