how to calculate phase difference in radians?
Continuing the example, 360 * -0.001 / 0.01 gives a phase shift of -36 degrees. Because the result is a negative number, the phase shift is also negative; the second wave lags behind the first by 36 degrees. For a phase difference in radians, use 2 * pi * td / p; in our example, this would be 6.28 * -. 001 / .