Functional Details; Analog Input Acquisition Modes; Software Paced Mode; Hardware Paced Mode - Measurement Computing USB-1208HS-2AO User Manual

Functional Details

Analog input acquisition modes

The USB-1208HS-2AO can acquire analog input data in two basic modes – software paced and hardware
paced.

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 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 can acquire data from up to eight channels in hardware-paced mode. The analog data is continuously
acquired, converted to digital values, and written to an onboard FIFO buffer on the USB-1208HS-2AO until
you stop the scan. The FIFO buffer is serviced in blocks as the data is transferred from the USB-1208HS-2AO
FIFO buffer to the memory buffer on your computer.
The maximum sample rate is 1 MS/s aggregate over 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-1208HS-2AO has the following external components, as shown in Figure 2.

Screw terminal banks

LED indicators

USB connector
1 Screw terminal pins 1 to 28
2 Screw terminal pins 29 to 56
3 Status LED
Figure 2. External components
9
4 Activity LED
5 USB connector
Chapter 3