
ZENO
®
-3200 USER MANUAL
Coastal Environmental Systems (206) 682-6048
Page 244
If the source “low” output is connected to ground (either directly or through a high resistance) then the
connection shown in the following figure will work.
Figure 13-3. Connecting a Differential Circuit.
However, in quite a few cases the output will be fully floating. In these cases you must provide a return
path by adding a resistor between the ZENO
®
-3200 analog ground and the sensor/source. This resistor
should be about 10
4
times greater than the source resistance. The simplest option is to connect a single
resistance between the source low and the ZENO
®
-3200 analog ground as shown below. This connection
will work well if the source resistance is low.
Figure 13-4. Providing a Return Path to a Differential Circuit.
In conclusion, although the ZENO
®
-3200 has differential inputs, there must be a return path for the
leakage currents. Using one of the connections shown in this section should allow you to make accurate
differential measurements.
®
-
LOW
ZENO
®
-3200
CH+
CH-
AGND
HIGH
Chassis
HIGH
LOW
CH+
CH-
AGND
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