If you use a Digilent Discovery instrument this extension board will let you measure the waveform of two monophasic power outlets with shared neutrals. To see more details, further versions and instructions about this project you can visit jubeormk1 at github.
This circuit is intended to be use to measure monophasic power mains up to 240Vrms. Such a voltage imply electric risk and only professionals with the right skills and safety protections should use it.
The neutral of the power outlet under test will be connected to the GND of the instruments in use. Before any use make sure that there is no connection from the GND of the instrument with the protective heart (PE) of your installation.
If the GND of your instrument is connected to PE you should isolate it using an appropriate method, which could be an isolation transformer.
Prior to the first use it is necessary to adjust the gain of both channels using resistor trims. See the tune procedure section in this document to understand the procedure.
If used without a plastic case, provide adequate means to prevent accidental contact with the AC voltage present by isolating the exposed metal points.
If unsure about above conditions are met please don't use this design.
Use under your responsibility
Any damage caused by the use of this design is responsibility of the licensed professional using it