10
Chapter 3
Functional Details
Analog input acquisition modes
OM-USB-1208HS Series devices acquire analog input data in two modes – software paced and hardware
paced.
Software paced mode
You 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 throughput sample rate in software paced mode is system-dependent, and can range from 33 S/s to
4000 S/s.
Hardware paced mode
You acquire data from up to eight channels in continuous scan mode. The analog data is continuously acquired,
converted to digital values, and written to an onboard 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.
The maximum sampling rate is 1 MS/s aggregate from one to eight channels. You can start a continuous scan
with either a software command or external hardware trigger event.
External components
OM-USB-1208HS Series hardware have the following external components, as shown in Figure 2.
Screw terminals
USB connector
LEDs
1
Screw terminal pins 1 to 28
4
Activity LED
2
Screw terminal pins 29 to 56
5
USB connector
3
Status LED
Figure 2. OM-USB-1208HS Series components
USB connector
The USB connector pr5 V power and communication. No external power supply is required.
LEDs
OM-USB-1208HS Series devices have two LEDs –
Status
and
Activity
. The
Status
LED turns on when the
device is detected and installed on the computer.
