How are unused channels wired to eliminate AI fault indication in PLC?

[user1337]

How do I wire both 2 and 4 wire 4-20mA unused inputs to eliminate an AI fault indication on a BMX AMI 0810? Assume I cannot disable the channel via software or make PLC code modifications?

[Michael_Chan]

Try to simulate a minimum current signal to prevent the AI fault indication on the BMX AMI 0810 module:

For 2-Wire 4-20mA Inputs:

• Connect a 250Ω resistor: Place a 250Ω resistor across the input terminals of the unused channel. This will simulate a 4 mA signal, which is the minimum current for a 4-20 mA loop.

For 4-Wire 4-20mA Inputs:

• Connect a 250Ω resistor: Similar to the 2-wire method, place a 250Ω resistor across the input terminals of the unused channel.

Analog Input Open Channel Resistor 

[Bosswaffle]

@user1337 I like to disable unused inputs on my AMI modules, just by checking the "Used" checkbox in the configuration of the module. You can also uncheck overflow below to stop the IO fault that appears when an AI channel is open. I preferer the first approach because if you need the channel in the future, you just need to enable it; but in the second option you need to dive into to the channel parameters (if you remember that you disabled checking for overflows).