Analog Connections; Analog Inputs; Single-Ended And Differential Inputs; Single-Ended Inputs - Measurement Computing CIO-DAS6402/12 Manual

4.1

ANALOG INPUTS

The following section provides explanations and helpful hints regarding analog input connections. This section is designed to help
you achieve the optimum performance from your CIO-DAS6402 series board.
Prior to jumping into actual connection schemes, you should have at least a basic understanding of Single-Ended/Differential inputs
and system grounding/isolation. If you are already comfortable with these concepts you may wish to skip to the next section (on
wiring configurations).

4.1.1 SINGLE-ENDED AND DIFFERENTIAL INPUTS

The CIO-DAS6402 provides either 32 differential or 64 single-ended input channels.

4.1.2 SINGLE-ENDED INPUTS

A single-ended input measures the voltage between the input signal and ground. In this case, in single-ended mode the
CIO-DAS6402 measures the voltage between the input channel and LLGND. The single-ended input configuration requires only
one physical connection (wire) per channel and allows the CIO-DAS6402 to monitor more channels than the (2-wire) differential
configuration using the same connector and onboard multiplexor. However, since the CIO-DAS6402 is measuring the input voltage
relative to its own low level ground, single-ended inputs are more susceptible to both EMI (Electro Magnetic Interference) and any
ground noise at the signal source. Figure 4-1 shows the theory of single-ended input configuration
C H IN
LL G N D
I/O
C o n n e c tor
~
V s
g 1
A n y v oltage differential betw een grounds
g1 and g2 s how s up a s a n error signal
at the input am plifier
S in gle -e n de d inp ut w ith C o m m o n M od e Volta g e
+
In p ut
To A /D
A m p
-
S ingle-Ended Input
C H IN
+
In p u t
V s + Vg2 - Vg1
A m p
LL G N D -
g 2
Figure 4-1. Single-Ended Voltage Input Theory

4 ANALOG CONNECTIONS

To A /D
6