Measuring inductance with DC current does not require anything but AC-DC voltmeter. Connect a resistor in series with choke. Feed it rectified (but not smoothed) AC. Measure AC and DC voltages across choke and resistor. Calculate inductance.
Note that inductance will be strongly affected not only by DC current, but by AC voltage across the choke as well.
Note that inductance will be strongly affected not only by DC current, but by AC voltage across the choke as well.
https://www.qsl.net/wb4kdi/JunkBox/JunkBoxChokes.html
Simple but effective way to measure the choke inductance and saturation - without complicated measuring equipment. First found in Sound Practices.
Simple but effective way to measure the choke inductance and saturation - without complicated measuring equipment. First found in Sound Practices.
BarG01, yes Hubelhank's technique is effectively what is described in post #12 link. I can suggest that if aiming to use Hubelhank's technique then use a separate 5V heater supply transformer for the rectifier valve so that the 5V is not dependant on the variac setting. Also try and keep Vac across the choke as constant as practical - Hubelhank's example results show Vac varies between 48 and 60V which is not too wide a range, and suggests that the calculated inductance value relates to using the choke with a high incoming ripple voltage. Modern instrumentation may help as it is likely true-rms, compared to an averaging meter like a VTVM. If access is available to a multiple decade resistor box, with sufficient current capability, then that can be used in lieu of a rheostat and speed up such a measurement campaign, compared to having to turn off the supply to measure the rheostat resistance for each step change.
Link to original Hubelhank article:
http://www.vacuum-tube.eu/wp/wp-content/uploads/articles/Measuring_Unknown_Choke.pdf
Link to original Hubelhank article:
http://www.vacuum-tube.eu/wp/wp-content/uploads/articles/Measuring_Unknown_Choke.pdf
I've been using this method for many-many years, ordered a transformer with 1; 5; 10; 20; 30; 50; 100V independent windings, 1A capability. Instead of the tube rectifier I use solid state Graetz connected diodes and 3 individual multimeters. 1 for DC current, 1 for voltage measurement on the choke and the power potentiometers - 3,3k 3pcs 100W each!, 470ohm 100W in serial connection - and 1 for resistance measurement on the adjusted potentiometers. Sometime I forgot to switch off the circuit when I try to measure the resistance and then I need to replace the fuse of the multimeter 😕 . These may be the starting point of the measurements. Recently I needed to prepare some high current chokes - 5A max with extreme low resistance - and I have chosen a slightly different methodology - I changed the windings of a high current transformer and used a constant load such as 2-3ohms 100-200W from many parallel connected 10W resistors. This also worked well.