Analog Inputs; Differential Current Inputs (Ain 1 & 2 Only); Figure 18 - Differential Current Inputs - Elpro Technologies 915U-2 User Manual

915U-2 Wireless I/O

2.5.6 Analog Inputs

The 915U-2 provides two floating differential analog inputs and two grounded single-
ended analog inputs.
Analog Input 1 & 2 will automatically measures Current (0-20 mA) or Voltage (0-25V)
depending on what is connected to the input.
Analog input 3 & 4 must be configured to measure Current (0-20mA) or Voltage (0-5V)
via the DIP switches under the Side Access Configuration Panel (See Section 2.5.2 ).
An internal 24V Analog Loop Supply (ALS) provides power for any current loops with a
maximum current limit of 100mA.
The LEDs have an analog diagnostic function and will indicate the status of the input.
If the current is less than 3.5 mA the LED will be off and if greater than 20.5mA the LED
will be on.
The LED will flicker with the duty cycle relative to the analog reading in this range. (Note
by default there is a 5 second delay on the input because of the Filter) Filter times can
be changed by accessing the Analog Input on the I/O configuration web page or using
the E-Series Configuration software.
The LEDs beside AI1+, AI2+ flash according to current the on these inputs. LEDs
beside AI1- and AI2- flash according to the voltage on the Analog inputs.
Differential Current Inputs (AIN 1 & 2 only)
Differential mode current inputs should be used when measuring a current loop, which
cannot be connected to earth or ground. This allows the input to be connected
anywhere in the current loop. Common mode voltage can be up to 27VDC.
The diagram below indicates how to connect Loop powered or externally powered
devices to the 915U-2 Differential Analog Inputs.
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Externally powered
ALS +24V
sensor
AIN1+
_
AIN1-
AIN2+
AIN2-
+
Loop
powered
mA
sensor
-
Figure 18 – Differential Current Inputs
915U-2
GND
V-
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User Manual