Walchem WebMaster ONE Instruction Manual page 28

WebMaster 4-20 mA Input Wiring Guide
KEY:
A. (-) minus terminal is the signal input. The 4-20mA signal goes here.
B. (+) plus terminal is a +24VDC power supply for the transmitters.
C. GND terminal is the return for completing circuits, both signal and power.
D. +24 terminal at the top middle of the board is the same supply as the (+) plus terminal.
Use shielded cable, grounded only at the controller end, for all connections.
A. Two-Wire Loop-Powered Transmitter
Input 1 -
Input 1 +
Input 2 -
Input 2 +
Input 3 -
Input 3 +
Notes:
Input 4 -
The (-) signal wire is the actual 4-20mA
Input 4 +
signal and is also the GND return wire
to complete the circuit.
'Input -' is internally connected to GND
via 25 ohm resistor.
C. Three-Wire Transmitter
Input 1 -
Input 1 +
Input 2 -
Input 2 +
Input 3 -
Input 3 +
Input 4 -
Input 4 +
E. Non-Isolated Two-Wire Externally-Powered Transmitter
Input 1 -
Input 1 +
Input 2 -
Input 2 +
Input 3 -
Input 3 +
Input 4 -
Input 4 +
Notes:
The analog inputs share their negative terminals.
They are all isolated from earth ground but not isolated from each other.
One non-isolated device may be connected without problems.
If more than one non-isolated transmitter is connected, they must be installed with an isolator.
- SIGNAL
+ 24
GND +24
+24
-SIGNAL
+SIGNAL
GND +24
POWER+
Isolator
POWER-
OUT- IN- -SIGNAL
+SIGNAL
OUT+ IN+
B. Two-Wire Externally-Powered Transmitter
Input 1 -
Input 1 +
Input 2 -
Input 2 +
Input 3 -
Input 3 +
Input 4 -
Notes:
Input 4 +
This transmitter gets its power from its own
dedicated power supply.
* Connecting a powered transmitter to the
'Input +' terminal of the WebMaster will
permanently damage the input!
D. Four-WireTransmitter
Input 1 -
Input 1 +
Input 2 -
Input 2 +
Input 3 -
Input 3 +
Input 4 -
Input 4 +
F. Non-Isolated Four-Wire Externally-Powered Transmitter
Input 1 -
Input 1 +
Input 2 -
Input 2 +
Input 3 -
Input 3 +
Input 4 -
Input 4 +
24
C D
+24V
TB1
GN +24
A
B
+
+
+
+
GND +24
POWER+
POWER-
-SIGNAL
+SIGNAL
GND +24
+24
GND
-SIGNAL
+SIGNAL
GND +24
+24
GND
-SIGNAL
+SIGNAL
+
+
+
+
+24V
GND