[sdiy] A little OT, Begging a hand

[Ian Fritz]

At 12:47 PM 2/8/2011, Jerry Gray-Eskue wrote:
>Apparently there are 5 independent variables, R1,R2,R3,R4 and R5.  R6=R1 
>and R7 = R2.

Maybe I misunderstand, but I believe R3 = const - R1 - R2.

Ian


>----- Original Message ----- From: "Ian Fritz" <ijfritz at comcast.net>
>To: "Veronica Merryfield" <veronica.merryfield at shaw.ca>; "synth DIY" 
><synth-diy at dropmix.xs4all.nl>
>Sent: Tuesday, February 08, 2011 1:16 PM
>Subject: Re: [sdiy] A little OT, Begging a hand
>
>
>>Hi --
>>
>>I'm pretty sure your problem is underdetermined. Here's my reasoning:
>>
>>The problem has four independent variables, if I understand it correctly. 
>>Take the delta in the circuit and convert it into a wye (pictorially). 
>>You now have a wye with series resistors in each arm.  You may add the 
>>series resistors together. Now you have a wye with three unknown 
>>resistors connected to V1, V2 and V0, plus a known resistor connected 
>>from V0 to V3.
>>
>>So now you see that your system is equivalent to a circuit with only 
>>three unknowns.  Thus whatever measurements you make the best you can do 
>>is to determine three combinations of your four unknown resistances.
>>
>>Ian
>>
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