Hi Guys,
we have a power supply 24VDC that powers 3 MFCs (Mas Flow controllers ( each MAX 250mA) ) and 2 pressure sensors (max each 20 mA), these sensors produce voltage signals 0-10V pressure sensors and setting signals on the MFCs is 0-5V ( voltage generated using lab jack DAC). all sensors are power by the 24VDC.
the voltage signals on those instruments are based on the instrument GND which is connected to the power supply COM, so I have to connect the labjack GND to the power supply GND. Do you think that will lead to noises?. I read somewhere that I need to connect resistance between the lab jack GND and the power supply GND, that's will prevent any noises, what do you think?
also, I have been advised to connect a resistance between the sensor GND (-) and the power supply GND so MFC GND/COM connects to the resistance which connects to power supply GND, sam apply to the pressure sensors. what do you thing ?
any advice what is the best approach to not have any noises on the sensors GNDs or the labjack GND
Thank you
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It is hard to say for certain if directly connecting the supply ground to the LabJack ground would cause noticeable noise, but we do recommend adding the resistor to avoid the possibility. The following page has our recommendations for interfacing with external supplies:
https://labjack.com/support/app-notes/externally-powered-signals
I do not think you should have resistors between sensor GND and supply GND. Ideally, the resistance from your sensor GND to supply GND should be 0 ohms; you want the sensor GND to be at the same potential as the supply GND. Adding a resistor would lift the sensor ground potential above the supply GND, creating a ground loop, which could cause noise.