Hi there,
If I am interpreting your schematic correctly, and the two symbols for GND are actually a different GND, them the GND of your converter is floating (with the pressure sensor) and the GND of the MCU is at input GND reference. Try referencing everything but the sensor of course to input GND. Place the sensor (with the current sensor) in parallel. You only need to make sure that both your own circuit and the sensor together do not consume more than 4mA on 24V, as to not influence the current loop to the point where you enter the band of measurement.
Happy metering...
I updated the schematic to be clearer. I’ve read that loop powered things should always be in series of each other and drop the voltage down to not influence the current signal. They should never be in parallel since this would cause both electronics to add to one another and would result in an offset of the signal. I could be mistaken since I’m just a student
I kind of solved this...So the micro controller ground is grounded to the DC-DC ground with is floating, sorry for the confusion in the previous schematic. The op amp is still referenced to "main" ground because I’m not sure how ill ground it.
How I kind of solved it:I noticed that when powering up the system with nothing attached it worked fine and when adding my electronics to the already powered on system it worked (If I used a resistor in parallel with my electronics). However when turning them on at the same time nothing worked. I have no idea what is causing this but after testing it a few times this seems to be the case. I added a push button, resistor and a transistor
In the update schematic, the button has to be pressed during power on. However I want to replace the push button and make it do the switching automatically, I’m not sure how I’ll do this since I can’t use the micro controller to do the switching since it won’t be power on during this startup phase.
Because I’m using a resistor to drop the voltage I’m wasting a lot of energy and when the sensor puts out <4.7mA my electronics start to flicker and when the sensor outputs >16mA my electronics consume so much power that the sensor shuts down. I need a better DC-DC converter...
The remaining problems:Powering on the electronics after the sensor has powered on ~1s
Not suing a resistor to drop the voltage
I really appreciate all the help!