izentrop wrote:You need what you need to make precise measurements at low power with a dual-channel oscilloscope: https://www.chauvin-arnoux.com/sites/de ... ce_ed1.pdf
Very well thank you. The Metrix OX7104 has an insulated box, it is a spectrum analyzer but 3500 euros! (In truth, it is not so expensive considering the possibilities).
The signal must be purely sinusoidal otherwise the measurements are erroneous, but my oscilloscope shows a signal that is rather triangular and very rich in "parasites" which are added to its own harmonics. As a result, power factor measurements are necessarily very approximate.
In short, even if the savings made over 25 years is only €2000 instead of the calculated €4000, I did well to unplug or cut!