The mathematics behind the non-invasive measurement was incorporated into the OMICRON Lab Bode 100 VNA software, sold by Picotest.com, starting in late 2011. The solution was included as a single cursor based measurement utilizing a piecewise linear approximated solution. The approximate solution is most accurate below 40 degrees, while the method is capable of accurately determining phase margins up to nearly 70 degrees.
Thanks to the completion of a license agreement with OMICRON Lab, the Bode Analyzer Suite V2.43 now includes the exact solution, improving the accuracy for measurements at higher phase margin values. While there are small measurement errors due to interpolation, measurement noise, and even the accuracy of the Bode plot measurement, the Bode and non-invasive results are generally within 1 degree accuracy.