Passive universal dummyload

The front

The front

After I made some dynamic loads I needed a dummyload with known parameters and usable for AC and DC. This is very handy for things like load am unkown transformer or adapter because they give a higher voltage unloaded. I used a bunch of old power resistors and added a capacitor and coil to get a mix of real and reactive power. The 10A meter is suitable for AC and DC and polarity does not matter. I allready measured the DC values. You see the stickers between the terminals. The AC parameter I have measured those with my VNA, but I keep that in my notebook for when I need it. I was a bit a suprised how well it behaved. The max deviation was  0.7 Ohm of the DC and I measured upto 1 MHz.

Inside

Inside

The resistors are NOS power resistors and by placing a bunch of the parallel you can get good powerratings. The green ones omn the right in vertical position I used to repair and adjust a 130W guitar tube amp. But putting them in series also increases the powerratings. Current stays the same in serie but Voltage will be half. So it can handle more current that way. I use combinations. For instance 4 parralel and that two times in series. Then I use 3 connectors so I get two choises.

 

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