you can use an current to voltage converter then an opamp to level shift it
On 2/2/2021 5:03 PM, Dwayne Zimmerman wrote:
Can anyone tell me how to connect a sensor to the 4-20mA input on the
comms board.I need temperature and all 4-20mA temperature sensors I'm
familiar with are 24 VDC not 1.8
On Monday, February 1, 2021 at 7:29:46 PM UTC-5 Dennis Bieber wrote:
On Mon, 1 Feb 2021 15:46:51 -0800 (PST), in
gmane.comp.hardware.beagleboard.user Dwayne Zimmerman
<dzimmermanpas-re5j...@public.gmane.org> 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.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
<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
<http://beagleboard.org/discuss>
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