Three-Wire Transducers; 2-Wire Supply Voltage; 3-Wire With Datalogger Power - Campbell CURS100 Instruction Manual

CURS100 100 Ohm Current Shunt Terminal Input Module
4.2

Three-Wire Transducers

6
transducer and everything is fine. However, if the battery voltage drops to 11
volts, a 20 mA current will leave just 9 volts for the transducer. In this case,
when the battery drops below 11 volts, the output of the transducer may be in
error.
H
Signal
2 VDC ≥ 9 VDC
I
(Max)
L
Power
– +
11 VDC
(minimum)
Battery
FIGURE 4-3. 2-wire supply voltage
A three-wire current loop transducer has the power supply connected directly
to the transducer. The voltage of the power supply is the voltage applied to the
transducer. The current output returns to power ground. Datalogger ground is
connected to sensor ground and the current output by the sensor must pass
through the resistor before going to ground.
Datalogger
H
I
L
G
+12 V
FIGURE 4-4. 3-wire with datalogger power
Transducer
Transducer
Signal
Ground
Power