Connecting a 4-20mA loop powered sensor to USB-6255

[crossrulz]

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JoeKellyATI wrote:

Do I have the sensor wired up backwards to the diode?

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Yes you do.  The current needs to flow out of the power supply, into the sensor, out of the sensor and then through the diode to the power supply return.  With your diagram, to current flows counter clockwise.  So to have current flow through the diode, it needs to be in the same direction as the diode is pointing (look at the diode as an arrow).  Otherwise, it looks like that optocoupler will work.

[JoeKellyATI]

Thanks!

Here is an updated schematic for future people who stumble upon this thread:

I'll purchase that optocoupler and call it good.

Thanks everyone!

[JoeKellyATI]

Here's the final (working) schematic for the pressure switch:Thanks for all the help!

Joe