Chapter 3 Functional Details; Analog Input Acquisition Modes; Components; Usb Connector - Measurement Computing USB-7204 User Manual

Functional Details

Analog input acquisition modes

The USB-7204 can acquire analog input data in software paced and continuous scan modes.
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 for each channel desired until you have the total number of samples that you want
from each channel. 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 and converted to digital values until you stop the scan. Data is transferred in blocks of up
to 32 samples from the USB-7204 to the memory buffer on your computer.
The maximum continuous scan rate of 50 kS/s is an aggregate rate. You can acquire data from one channel at
50 kS/s, two channels at 25 kS/s, and four channels at 12.5 kS/s. You can start a continuous scan with either a
software command or with an external hardware trigger event.

Components

The USB-7204 components are shown in Figure 2.

USB connector

The USB connector provides +5 V power and communication. The voltage supplied through the USB connector
is system-dependent, and may be less than 5 V. No external power supply is required.
This connector operates in parallel with the OEM connector — do not connect to both the USB connector and
the OEM connector.
Figure 2. USB-7204 external components
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Chapter 3