Chapter 3 Signal Connections 19
If the signal source has one side connected to a local ground, the
signal source ground and the PCM-3718H/3718HG ground will not
be at exactly the same voltage, as they are connected through the
ground return of the equipment and building wiring. The difference
between the ground voltages forms a common-mode voltage.
To avoid the ground loop noise effect caused by common-mode
voltages, connect the signal ground to the LOW input. Do not
connect the LOW input to the PCM-3718H/3718HG ground directly.
In some cases you may also need a wire connection between the
PCM-3718H/3718HG ground and the signal source ground for better
grounding. The following two diagrams show correct and incorrect
connections for a differential input with local ground:
Correct connection
Incorrect connection
A.GND
+
Vs
-
+
Vin
-
+
-
HIGH
LOW
GND
+
Vs
-
+
Vin
-
+
-
HIGH
LOW
Vin=Vs
Vcm
+
_
GND
+
Vs
-
+
Vin
-
+
-
HIGH
LOW
Vin=Vs+Vcm
Vcm
+
_
Summary of Contents for 3718HG
Page 1: ...PCM 3718H 3718HG PC 104 12 bit DAS Module with Programmable Gain User s manual ...
Page 2: ......
Page 5: ...1 General Information CHAPT ER ...
Page 13: ...2 Installation CHAPT ER ...
Page 21: ...3 Signal Connections CHAPT ER ...
Page 26: ...22 PCM 3718H 3718HG User s Manual ...
Page 27: ...4 Register Structure and Format CHAPT ER ...
Page 38: ...34 PCM 3718H 3718HG User s Manual ...
Page 39: ...5 A D Conversion CHAPT ER ...
Page 45: ...6 Digital Input Output CHAPT ER ...
Page 47: ...7 Programmable Pacer CHAPT ER ...
Page 57: ...8 Direct Memory Access Operation CHAPT ER ...
Page 60: ...56 PCM 3718H 3718HG User s Manual ...
Page 61: ...9 Calibration CHAPT ER ...
Page 64: ...60 PCM 3718H 3718HG User s Manual ...