JF-1A Conductivity Sensor
A440-009
Page 43 of 56
FEBRUARY 2009
3
2
1
4
3
2
1
3
2
1
GND
-
+24 VDC ISOLATED
POWER SUPPLY
+
PLC CURRENT DETECTOR
+
GND
-
-
+24 VDC ISOLATED
POWER SUPPLY
-
+
PLC CURRENT DETECTOR
+
GND
GND
Example 3
JF-1A Conductivity Current Device Loop, with a secondary
Temperature Current loop, and a connection for a serial data
link:
As in example 1, a 24 VDC isolated power supply supplies loop power and a 250
ohm sense resistor is used to sense the current in the conductivity loop (convert
the current to a voltage in the PLC). As in example 1 the JF-1A derives its
power for its operation from the loop current supply. Note both the supply and
loop current detector are normally isolated from ground.
As in example 2, a second fully isolated 24 VDC supply is needed for the
temperature current loop. This is required as the conductivity current loop has
established a “virtual” common voltage point. If the user is to establish another
