Owner's manual

Chapter 3

Functional Details

Analog input modes

The OM-USB-1608FS-Plus can acquire analog input data in three modes – software paced, hardware paced,

and burst scan.

Software paced

You can acquire one analog sample at a time in software paced mode. You initiate the A/D conversion by

calling a software command. The analog value is converted to digital data and returned to the computer. You

can repeat this procedure until you have the total number of samples that you want from one channel.

The typical throughput sample rate in software paced mode is 500 S/s (system-dependent).

Hardware paced

You can acquire data from up to eight channels simultaneously in hardware paced mode. The analog data is

continuously acquired, converted to digital values, and written to an on-board FIFO buffer on the device until

you stop the scan. The FIFO buffer is serviced in blocks as the data is transferred from the device FIFO buffer

to the memory buffer on your computer. Data is transferred in blocks from the device to the memory buffer on

your computer.

The maximum sampling rate is an aggregate rate. The total sample rate using hardware paced mode is 400 kS/s

divided by the number of channels, with a maximum rate of 100 kS/s for any channel. You can acquire data

from one to four channels at 100 kS/s each, six channels at 66.7 kS/s each, and so on, up to eight channels at

50 kS/s each. You can start a hardware paced scan with a software command or an external hardware trigger

event.

Burst scan

In burst scan mode (BURSTIO), you can acquire data from the OM-USB-1608FS-Plus using the full capacity

of the 32 k sample FIFO. The acquired data is read from the FIFO and transferred to a user buffer in the

computer. You can initiate a single acquisition sequence of one to eight channels with either a software

command or an external hardware trigger event.

Burst scans are limited to the depth of the on-board memory, as the data is acquired at a rate faster than it can be

transferred to the computer. The maximum sampling rate is an aggregate rate. The total sample rate using burst

scan mode is 100 kS/s per channel for any or all channels. A data overrun may occur if you exceed the FIFO

capacity and sample 32,768 samples.