Signal Connections; Analog Input - Measurement Computing USB-231 User Manual

USB-231 User's Guide

Signal connections

Analog input

You can connect up to eight single-ended inputs or up to four differential inputs to screw terminals
through . The input voltage range is ±10 V. Figure 6 shows the USB-231 analog input circuitry.
CH3H/CH3L
The main analog input circuitry blocks are as follows:
—The multiplexer (MUX) routes one AI channel at a time to the mode selector multiplexer
MUX

(DIFF/SE MUX).
—The mode selector MUX selects between DIFF mode and SE measurement mode.
 DIFF/SE MUX
— The instrumentation amplifier (IA) removes the common mode signal and buffers the analog input
 IA
signal before it is sampled by the analog-to-digital converter (ADC).
—The ADC digitizes the AI signal by converting the analog voltage into digital code.
 ADC
—The DAQ device can perform both single and multiple analog-to-digital conversions of a fixed or
 AI FIFO
infinite number of samples. A first-in-first-out (FIFO) buffer holds data during AI acquisitions to ensure no
data is lost.
—The ADC control circuitry sets the conversion rate of the ADC, sets the input
 ADC Control
configuration, drives the scanning sequence, and starts acquisitions synchronous with the TRIG or CTR
signal
Single-ended configuration
When configured for SE input mode, the input signal is referenced to analog ground (
through two wires:
Connect the wire carrying the signal to be measured (

Connect the second wire to

The input range for single-ended mode is ±10 V. The single-ended mode pinout is shown in Figure 5 on page
13.
Figure 6. USB-231 analog input circuitry
.
AGND
14
or ).
CHxH CHxL
Functional Details
CH0H/CH0L
) and delivered
AGND