DAQ VXI-SC-1102 Bedienerhandbuch PDF herunterladen (Seite 21)

Chapter 1 MIO and AI Devices

DAQ Hardware Overview Guide 1-4 www.ni.com

You can combine both single-channel and multiple-channel acquisition

with any of the following additional modes:

• Posttrigger mode

• Pretrigger mode

• Double-buffered mode

• AMUX-64T mode

• SCXI mode

Note The 611X devices do not support the AMUX-64T or SCXI modes.

Posttrigger mode collects a specified number of samples after the device

receives a trigger. Refer to the stop trigger discussion in the appropriate

data acquisition timing section for your device later in this chapter for

details. After the user-specified buffer is full, the data acquisition stops.

Pretrigger mode collects data both before and after the device receives a

trigger, either through software or by applying ahardware signal. The

device collects samples and fills the user-specified buffer without stopping

until the device receives the stop trigger signal. Refer to the stop trigger

discussion in the appropriate data acquisition timing section for your device

later in this chapter for details. The device then collects a specified number

of samples and stops the acquisition. The buffer is treated as a circular

buffer—when the entire buffer has been written to, data is stored at the

beginning again, overwriting the old data. When data acquisition stops, the

buffer has samples from before and after the stop trigger occurred. The

number of samples saved depends on the length of the user-specified buffer

and on the number of samples specified to be acquired after receipt of the

trigger.

Double-buffered mode, like pretrigger mode, also fills the user-specified

buffer continuously. You can call

DAQ_DB_Transfer totransfer old data

into a second buffer before it is overwritten by new data.

DAQ_DB_Transfer transfers data out of one half of the buffer while the

other half is filled with new data.

In the AMUX-64T mode, you use one, two, or four external AMUX-64T

devices to extend the number of analog input channels available. You

connect the external signals to the AMUX-64T device pins, instead of

directly to the DAQ device pins.

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DAQ VXI-SC-1102 Bedienerhandbuch Seite 21