Measurement Computing CIO-DAS160x/1x - Manual (Page 12)

5 ANALOG CONNECTIONS
5.1 ANALOG INPUTS
Analog signal connection is one of the most challenging aspects of applying a data acquisition board. If
you are an Analog Electrical Engineer then this section is not for you, but if you are like most PC data
acquisition users, the best way to connect your analog inputs may not be obvious. Though complete
coverage of this topic is well beyond the scope of this manual, the following section provides some
explanations and helpful hints regarding these analog input connections. This section is designed to help
you achieve the optimum performance from your CIO-DAS1600 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).
5.1.1 Single-Ended and Differential Inputs
The CIO-DAS1600 provides either eight differential or 16 single-ended input channels.
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-DAS1600 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-DAS1600 to monitor more channels than the (2-wire) differential configuration using the same
connector and onboard multiplexor. However, since the CIO-DAS1600 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 5-1a and 5-1b show the
theory of single-ended input configuration
Figure 5-1a. Single-Ended Voltage Input Theory
8
+
-
In p ut
A m p
To A /D
S in g le-E n ded Inp ut
I/O
C o n n e c tor
LL G N D
C H IN