On Mon, 1 Feb 2021 15:46:51 -0800 (PST), in
gmane.comp.hardware.beagleboard.user Dwayne Zimmerman
<[email protected]> wrote:
>So the pull down is to keep the voltage under 1.8 correct? My confusion is
>I have one screw per input, 4-20mA is two wire where is the other half of
>the circut?
>
I suspect the pull-down is only ensuring that the floating voltage is
tied to 0V; feeding anything with a voltage over 1.8V will still fry the
input. And since 0V likely also means 0mA, it indicates a fault condition
in the loop.
https://www.fluke.com/en-us/learn/best-practices/test-tools-basics/process-tools/what-is-a-4-20-ma-current-loop
https://www.predig.com/indicatorpage/back-basics-fundamentals-4-20-ma-current-loops
{Many others|
The input to the BBB likely needs to consist of a current->voltage
tranform, so the ADC can measure the voltage corresponding to the current.
Which might be built-into the cape (I've not looked at it).
--
Dennis L Bieber
--
For more options, visit http://beagleboard.org/discuss
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