Calculating r1 from R1 + R2

[Mike Blair]

Confused my self calculating r1 or 21 from R1+R2 on a ring circuit did this a while back and compared calculations with measurements to see the differences. but tried the other day think i have muddled the equation! or maybe because its monday haha can someone show me an example

 

[Leesparkykent]

For example you have an R1+R2 of 0.33ohms

0.33x4=1.32

1.32/1.64=0.80 for r2

1.32-0.80=0.52 for r1

Edit: should of added this is for 2.5mm cable with 1.5mm CPC.

 

[The Ghost]

Where did you get 1.64 from?

 

[Deleted member 72666]

I think he meant 1.67.

 

[The Ghost]

Thats what I thought 1.67 it comes to the same anyway.

 

[Wilko]

My inner Sheldon just can't resist ... I got r1=0.495 and r2=0.825 ... Probably why I've got no mates. Or work.

 

[Mike Blair]

so for a r1 and r2 i got 1.12 in the real world

calcultion is
r2 2.74

r1 = 1.74

seems high

 

[Mike Blair]

shouldnt i be deviding by 4?

 

[Leesparkykent]

LOL, yes I meant 1.67.....It was well past my bed time when I posted that last night

 

[Wilko]

Hi Mike, is this R1+R2=1.12 ?

 

[Leesparkykent]

so for a r1 and r2 i got 1.12 in the real world

calcultion is
r2 2.74

r1 = 1.74

seems high

That would indicate a circuit length of 230-240 meters.

 

[The Ghost]

so for a r1 and r2 i got 1.12 in the real world

calcultion is
r2 2.74

r1 = 1.74

seems high

shouldnt i be deviding by 4?

Errm can you show your maths on that answer?

 

[Mike Blair]

sorry guys my zs was 1.12 i dont do as much testing as i should be tbh drives my nut in

 

[Mike Blair]

ok so say if my zs was 1.32

ze was 12

needed to find r1 and r2

theoretically what would it be isnt it devide by 4 to R1+R2?

 

[Leesparkykent]

R1+R2= (r1+r2)/4

Zs=1.32

Ze=0.12

1.32-0.12=1.2

1.2x4=4.8

4.8/1.67= 2.87

4.8-2.87= 1.93

r2=2.87 and r1=1.93

Now using r1 and r2 figures

2.87+1.93=4.8

4.8/4=1.2

This is where your getting confused with multiply and divide