Rockwell Automation Publication 1756-UM540E-EN-P - December 2017 43
1756-IF8I Isolated Analog Input Module Chapter 3
Power Calculations with the 1756-IF8I Module
The 24V backplane current requirements of the module increase when it operates
with a Current input type and Source Loop Current mode enabled.
The 1756-IF8I module uses the power provided across the ControlLogix® chassis
backplane as the source for loop power. The 1756-IF8I module consumes 10.6 W
of backplane power. Because of the demands that are placed on that supply, take
special care when calculating the power requirements for modules in the same
chassis as a 1756-IF8I module.
For example, when used with the 1756-L75 controller and operating in the
Sourcing Loop Current mode, you can place only six 1756-IF8I modules in the
chassis before exceeding the wattage capacity of the power supply.
Other Devices in the Wiring Loop
The voltage source on each channel can drive loop impedance of up to
approximately 1300 Ω. This lets you include other devices, such as chart
recorders and meters, in the current loop.
For more information on wiring the 1756-IF8I module, see page 84
.
Multiple Input Ranges
The 1756-IF8I module offers multiple input ranges that are dictated by channel
configuration choices. The input type selection determines the available ranges.
To see where to select the input range, see page 131
.
Notch Filter
The Notch Filter is a built-in feature of the Analog-to-Digital convertor (ADC)
that removes line noise in your application for each channel. The removal of line
noise is also known as noise immunity.
The Notch Filter attenuates the input signal at the specified frequency. That is,
the filter reduces the amplitude of the signal with minimal signal distortion.
Choose a Notch Filter based on what noise frequencies are present in the
operating environment for the module and any sampling requirements needed
for control. The default Notch Filter setting is 60 Hz.
Input Type Input Range
Current (mA) 0…20 mA
Voltage (V) Any of the following:
• -10…10V
• 0…5V
• 0…10V
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