I have put together a circuit that involves two logic-level N-channel MOSFETs that are turned on and off using GPIO pins to allow two different sources to power a single load at different times.
When one MOSFET is turned on by receiving a logic high input at its gate, the other MOSFET is turned off with a logic low input at its gate.
One of the power sources is a constant current source and the other is a programmable power supply. I hooked up a multimeter to replace the load to see if the load is receiving the right values and I observed that when the multimeter is in voltage mode the voltage reading indicates that the circuit is properly switching between the two sources.
However, when I switch the multimeter into current mode, the programmable supply starts to beep, and the current reading indicates that the currents from both sources are being combined even though the MOSFETs are switching between sources correctly. Does anyone know what could be going wrong? I have attached a schematic of the bread board circuit that I have built.
Please note that both the sources and their respective MOSFET have their grounds separated so they don't share a common ground or else the switching would not work properly.