Rigol VS5000 Series User Manual page 125

RIGOL
Sinθ = A/B or C/D, where θ = phase shift (in degrees) between the two signals.
From the formula above:
θ must be in the range of (0~π/2) or (3π/2~2π) if the main axis of the ellipse is
between I and III quadrant, . If the main axis is at II and IV quadrant, θ must be in
the range of (π/2~π) or (π~3π/2).
© 2008 RIGOL Technologies, Inc.
Signal must be
centered in X
D
C
Figure 3-6
Instruction of the Ellipse Method
θ = ±arcsine (A/B) or ±arcsine (C/D)
User's Guide for VS5000 Series
B
A
3-7