Measuring the inductance of a wirewound resistor

[Arouse1973]

Hey Chris
Had a go and got some good results. Changed my setup a bit. Wound 15 turns of 1mm wire around the resistor (0.33R) and a series connected 200nF. Connected 100nF across resistors and wound up frequency until the signal peaked across resistor. Peaked at 1.5Mhz, this works out to be 112nH. Did the same thing for a 470R but reduced the capacitance across the resistor to 470pF. Results again 22uH. I had the same thought as you last minute about removing the coupling issue.
@Steve .This has been fun, Thanks.
Cheers
Adam

 

[CDRIVE]

On a side note my collection of historic instruments includes a (portable) 100KHz - 30MHz RF Signal Generator, circa 1930's. It was manufactured by General Radio Corp. for the U.S. Navy. I think my first hernia can be traced back to the first time I attempted to lift it. Back in those days the U.S. armed forces classified anything with a handle on it as "portable", even if it took 6 men to lift it!

Anyway, this generator employed a unique step (dB) attenuator. Besides Zo being an oddball 10R, the resistors employed were wire-wound but not the classic round design we're familiar with. The form was a flat multilayer Mylar or Bakelite and the windings were non inductive Bifilar.

Chris

 

[Arouse1973]

I bet the weight was because it had bricks in it to make the price tag seem worth while.

 

[CDRIVE]

I bet the weight was because it had bricks in it to make the price tag seem worth while.

Actually no. Don't confuse the bad press about government $10,000 toilets and $500.00 hammers with Mil Spec. This thing was built like a Brinks safe! Every component (mechanically and electrically) was a work of art! The main variable cap (fo) was silver plated with 1/8" thick blades! The geared (zero backlash) tuning mechanism is a thing of beauty too. BTW, the power supply was a separate (heavy) unit with its own handle. The transformer barely got warm!

Mil Spec equipment is manufactured to withstand extremely harsh environments. Those of us that served in those harsh environments appreciated knowing our equipment could take the beating too!

Hold an old 5U4 in on hand and a 5R4 (the Mil Spec version) in the other. You'll get the big picture in a flash!

Chris