User manual

Chapter 5: Installation and Wiring
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Hardware User Manual, 4th Edition, Rev. B
DC Input Wiring Methods
I/O modules with DC inputs can be wired as either sinking or sourcing
inputs. The dual diodes (shown in this diagram) allow current to flow
in either direction. Inputs grouped by a common point must be either
all sinking or all sourcing. DC inputs typically operate in the range of
+12-24 VDC.
Sinking Input Sensor (NPN Type) to PAC Sourcing Input
In the following example, a field device has an open-collector NPN transistor output. When
energized, it sinks current to ground from the DC input point. The PAC input current is
sourced from the common terminal connected to power supply (+).
Sourcing Input Sensor (PNP Type) to PAC Sinking Input
In the following example, a field device has an open-emitter PNP transistor output. When
energized, it sources current to the PAC input point, which sinks the current to ground. Since
the field device loop is sourcing current, no additional power supply is required for the module.
DC Output Wiring Methods
I/O modules with DC output circuits are wired as all current sinking only or current sourcing
only depending on which output module part number is used. DC outputs typically operate in
the range of +5-24 VDC.
PAC Sinking Output to Sourcing Load Device
Many applications require connecting a PAC output point to a DC input on a field device load.
This type of connection is made to carry a low-level DC signals.
In the following example, the PAC output point sinks current to ground (common) when
energized. The output is connected to a field device load with a sourcing input.
Field Device
PAC DC Input
Output (sourcing)
Ground Common
Input
(sinking)
PAC DC Input
Common
Input
DC PNP Sensor
(Sourcing)
PAC Input
(Sinking)
Field Device
+
–
PAC DC Input
Output
Ground Common
Supply
(sinking)
Input
(sourcing)
DC NPN Sensor
(Sinking)
PAC Input
(Sourcing)
Field DevicePAC DC Output
+DC Power
+
–
Power
20-28 VDC
Output
(sinking)
Common
Input
(sourcing)
Ground
DC Load
(Sourcing)
PAC Output
(Sinking)