Data Translation DT9820 Series, Getting Started Manual

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Wiring Signals
41
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6
Connecting Analog Input Signals
You can connect analog input signals to the DT9820 Series modules in
the differential configuration only.
Figure 6A illustrates how to connect a floating signal source to a
DT9820 Series function module using differential inputs. (A floating
signal source is a voltage source that has no connection with earth
ground.)
Note:
For floating signal sources, it is recommended that you
provide a bias return path for the differential channels by adding
10 k
Ω
of termination resistance from the low side of the channel to
isolated analog ground.
For more information on configuring termination resistance, refer to
Chapter 4 starting on page 21 .
Figure 6B illustrates how to connect a nonfloating signal source to a
DT9820 Series function module using differential inputs. In this case,
the signal source itself provides the bias return path; therefore, you
do not need to provide bias return resistance through software.
R
s
is the signal source resistance while R
v
is the resistance required to
balance the bridge. Note that the negative side of the bridge supply
must be returned to analog ground.