Measurement Computing USB-1208FS-Plus-OEM - Manual (Page 8)

8
Chapter 3
Functional Details
Analog input acquisition modes
The USB-1208FS-Plus-OEM can acquire analog input data in either software paced or hardware paced mode.
Software paced
The USB-1208FS-Plus-OEM acquires data one analog sample at a time using software paced mode. You
initiate the A/D conversion by calling a software command. The analog value is converted to digital and
returned to the computer. You can repeat this procedure until you have the total number of samples that you
want.
The maximum sample rate in software-paced mode is system-dependent.
Hardware paced
The USB-1208FS-Plus-OEM can acquire data from up to eight channels using hardware-paced mode. The
analog data is acquired and converted to digital values until you stop the scan. Data is transferred in blocks of
32 samples from the device to the memory buffer on your computer.
The A/D converter is paced by either an internal or external clock source.
The maximum sample rate is an aggregate rate. The total sample rate for all channels cannot exceed 50 kS/s.
The following table lists the sample rate when scanning from one to eight channels.
Maximum per channel sample rate
# channels
scanned
Sample rate
(kS/s)
1 50
2 25
3 16.70
4 12.50
5 10
6 8.30
7 7.14
8 6.25
You can start a hardware-paced scan with a software command. Optionally, hardware-paced scans can be
delayed by an external hardware trigger event.