Intab PC-Logger 3100i How To Use Manual page 21

6.3.2 Current Loops
Current loops are usually process type signals (0 - 20mA).
The transmitters that output this type of signal are usually "floating" and don't
present any problem in so far as grounding is concerned. Problems can,
however, arise because other equipment that receives this signal may or may
not be grounded.
Care must also be taken so that other equipment don't introduce common
modes outside the permitted range. Least problems should arise if the "3100i"
is inserted as near the most negative end of the loop as possible.
1) "Grounded" current loops.
0-20mA
0-20mA
2) "Floating" current loops.
0-20mA
0-20mA
ANDRA INSTRUMENT
BASIC UNIT
+
-
+
-
DIFF GND
2
1
+
-
+
-
DIFF GND
2
1
Connect "3100i" signal
GND to system
ground.
Connect your loops
Place switch in
position "DIFF"
Leave signal GND
unconnected.
Connect your loops
Refer loops to signal
GND by placing
switch in position
"GND"
21