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37
Controller
Hardware and Accessories Setup and Utility
Sensors connection .7
All 4-20mA sensors have electronic adapters to convert the original value received from
the probe into the “I” value. Sensors may be categorized into three different types:
Passive sensors:
The sensor’s circuit receives its operational power from the controller,
using the value-transmitting core as the negative pole. (PT100, KTY, Electronic Humidity
sensor)
Semi-active sensors:
The sensor’s circuit receives its operational power from the
controller in both the positive and negative (common) cores. The third core is used only for
value transmitting. (Meteorology station, Mixer level sensor, etc.)
Active sensors:
The sensor’s circuit has its own power source. It transmits the value in
one core and uses the second core connected to controller’s common pole for reference.
(EC pH, CO
2
)
Sensor wiring
Inputs
1 2 3 4 5 6 7
+24V Common
Passive
sensor
Semi-Active
sensor
Active
sensor
External
power supply