I tried 24- to gnd 24+ to sensor and - return from the sensor to AI5 same way I would connect a typical loop powered 4-20mA circuit. With the circuit connected to AI5 I get a reading but after a few seconds I also get a reading on AI6 close to the reading on AI5. If I remove the wire from AI5, AI5 imeadiatly drops to zero AI6 will stay elevated for a minute or more. If I connect to AI6 I get 0 on AI5 and AI6. Any ideas
On Monday, February 1, 2021 at 6:58:44 PM UTC-5 [email protected] wrote: > I think you have to provide an external voltage source - the 4-20 mA > circuits are sort of like the Sink-A and Sink-B circuits, they are just one > end of something. > > I connect my 4-20 mA pressure gauges to the same 24V source that supplies > my power cape. Then the return path from the pressure gauge goes through > the shunt resistor across the analog input. However, I’m not using this > cape, I built my own shunt circuit on a protoboard. > > On Feb 1, 2021, at 6:46 PM, 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? > > On Monday, February 1, 2021 at 6:40:01 PM UTC-5 RobertCNelson wrote: > >> On Mon, Feb 1, 2021 at 5:24 PM Dwayne Zimmerman <[email protected]> >> wrote: >> > >> > Thanks I have that. It doesn't detail the 4-20mA circut, unless I'm >> missing something. I'm trying to understand where power comes from and at >> what voltage. >> >> Each of those two connectors are connected to an adc pin. >> >> They both have a pull-down.. >> >> The ADC's can only take 1.8V, any more and they will fry.. >> >> Regards, >> >> -- >> Robert Nelson >> https://rcn-ee.com/ >> > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/60ff116c-040f-47cd-a34f-58e726fb88d7n%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/60ff116c-040f-47cd-a34f-58e726fb88d7n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/fd933788-5207-4818-9bb1-50f0f93e06d2n%40googlegroups.com.
