Procedure
In the figure below we have the way to connect the oscilloscope to the circuits which generate signals whose lag must be measured.
After heating, the oscilloscope must be adjusted so that the signs of the figure below are observed.
The various angles of the Lissajous figures are used as parameters for the measurement of the discrepancy.
If the same figures cannot be obtained, or the signals do not have the same frequency, see the article about Lissajous Figures about how to proceed.