I/O Wiring

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Input Source Module The figure on the right depicts an input source module. Note that one terminal of the module is connected to the +VDC. Now note the input device. One side of the input device is wired to VDC common. According to the definition, this input device is connected type sink, (one connection of a sink device or module is connected to VDC common.) These connections define another fact, source modules are wired with sink devices.

A source module supplies the I/O power supply +VDC to the I/O device. The I/O device supplies the return path to the VDC common.

The polarity of a module can always be determined by looking at how the field devices are wired to the module. In the figure on the right, since one side of the field device is wired the VDC common, as stated above the device is sinking. Since the field device is sink, then by definition the module must be source.

Ouptut Source Module The figure on the right depicts an output source module. Note that one terminal of the module is connected to the +VDC. Now note the output device. One side of the output device is wired to VDC common. According to the definition, this output device is connected type sink, (one connection of a sink device or module is connected to VDC common.) These connections define another fact, source modules are wired with sink devices.

A source module supplies the I/O power supply +VDC to the I/O device. The I/O device supplies the return path to the VDC common.

The polarity of a module can always be determined by looking at how the field devices are wired to the module. In the figure on the right, since one side of the field device is wired the VDC common, as stated above the device is sinking. Since the field device is sink, then by definition the module must be source.

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John G. (Skip) Todora   ⇔   Late updated: November 11, 2009