Building my own noninductive 8R 150W load using wire wound resistors

[nigel pearson]

If the inductance with the cheap Bosch clone element is a real problem divide the loop in two and spread it out. It's very easy to do that.

 

[mchambin]

What is the inductance of the wirewound resistors used in the OP ?

The cancelling cap set up is a good way to measure it. L= Ccomp*R*R.

 

[Mark Johnson]

I've stuffed and soldered every resistor I bought, into these two PCBs. Fortunately they are in stock at Mouser and at DigiKey; feel free to order a few and measure them yourself. The measured value of the 4x7 array, with cancellation from mutual inductance but without the RC compensator installed, was approx 510 nanohenries. Schematic and 3D build guide are in post #6.

SQP10AJB-56R Yageo | Mouser

SQP10AJB-56R Yageo | Resistors | DigiKey

 

[SyncTronX]

That represents a square term, sE2 = s²
(where E = exponential).

Likewise, CE2 = C²
The text editor here seems not to support such characters as s²

Multiplying the ratio of the two quadratics by sC/sC
clears out all 1/s terms without changing the value
of the ratio of the quadratics, since sC/sC =1.
It makes the algebra a little easier.

Comparing like powers of s in the impedance determines
any constraints, since each term of the quadratics must
be the same for the quadratics to cancel out, leaving R.

Hi Ray,

Are you a physics guy? If I recall correctly, that is some of the stuff
we were doing in my University Physics...the one that transfers to any of
the engineering or way out universities, you know, MIT, Cal Tech,
Rensselaer (sp) Polytechnic Institute, Rice, AggieLand, Cal Poly, Stanford and the like.

You can imagine my surprise when MJ started quoting,
"Chig-gar-roo-gar-rem!
Chig-gar-roo-gar-rem!
Rough! Tough! Real Stuff! Texas A&M!"
It's out there somewhere, where exactly
I don't know.

I was going to hit up MJ for one of his boards, but I'm about
4 years too late.

And the answers that most of the class couldn't solve where the ones
that you solved by multiplying sC/sC. Only one guy in class got it
and he had a physics degree from an Iranian school but needed US
classes for proper accreditation.

It always looks so simple when someone who knows what they're doing
does it. But so challenging for us mortals.

Touche'

 

[Mark Johnson]

Aircraft maintenance logbook entry by pilot: "#3 engine missing"

Matching logbook entry by licensed repair technician: "engine found on right wing after brief search"

Similarly found after brief search: attached below. Google Advanced Search feature named "this exact word or phrase" was successful

_

 

[AllenB]

This is an old thread, wouldn't you prefer a shiny new one?

Thread closed.