Measurement Computing USB-1608HS - Manual (Page 13)

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Chapter 3
Functional Details
Theory of operation - analog input acquisition modes
The USB-1608HS can acquire analog input data in two basic modes – software paced and continuous scan.
Software paced mode
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.
The maximum throughput sample rate in software paced mode is system-dependent.
Continuous scan mode
You can acquire data from up to eight channels simultaneously in continuous scan mode. The analog data is
continuously acquired, converted to digital values, and written to an onboard FIFO buffer on the USB-1608HS
until you stop the scan. The FIFO buffer is serviced in blocks as the data is transferred from the USB-1608HS
FIFO buffer to the memory buffer on your computer.
The maximum sampling rate is 250 kS/s per channel for one-to-eight channels. You can start a continuous scan
with either a software command or with an external hardware trigger event.
External components
The USB-1608HS has the following external components, as shown in Figure 3.
 USB connector
 USB activity (ACT) LED
 Power connector
 Power (PWR) LED
 Screw terminals
Figure 3. USB-1608HS external components – front view
Screw terminal pins 1 to 54 USB active LED
Power LED