VNA resolution
Posted: Sun Jan 21, 2024 11:47 am
Hello,
with the VNA program of Pavel I tested a coil on a ferrite rod. The wire is a RF strand with 50 windings. The impedance shows 200 ohms at 200 khz and about 500 ohms at 500 khz. But the realpart of Z (which should show the serial loss resistance) hangs at the value of 9,99 mohms. But in the narrow frequency of 220 khz it goes up to 277 mohms. But I doubt about this value too. In fact after calculations the DC value should go to about 100 mohms, and only with increased frequency it can increase too due to skin effect, maybe capacitve effects also could disturb these values.
I do know, that it can be a result of resolution limitations, because 100 mohms and 500 ohms is already about 12 bits apart.
In fact I wanted to determine quality (Q) of coils.
Thanks
Dieter
with the VNA program of Pavel I tested a coil on a ferrite rod. The wire is a RF strand with 50 windings. The impedance shows 200 ohms at 200 khz and about 500 ohms at 500 khz. But the realpart of Z (which should show the serial loss resistance) hangs at the value of 9,99 mohms. But in the narrow frequency of 220 khz it goes up to 277 mohms. But I doubt about this value too. In fact after calculations the DC value should go to about 100 mohms, and only with increased frequency it can increase too due to skin effect, maybe capacitve effects also could disturb these values.
I do know, that it can be a result of resolution limitations, because 100 mohms and 500 ohms is already about 12 bits apart.
In fact I wanted to determine quality (Q) of coils.
Thanks
Dieter