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Thread: Bridge voltage calculation - conclusion!!!
www.piclist.com/techref/power.htm?key=voltage
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face BY : mikespamBeGone@EraseMEwhitewing.co.uk



Thanks for the input on this one. For your info, after some headscratching and a lot of paper, here's
the best answer I've got to, and verifed correct with Excel
<use fixed pitch font>

Given a bridge :  Vin
+----+
R1  R2
+----|--- Vout (differential)
|    +---
R3  Rx
+----+
GND


Calculate Rx given V, V=Vout/Vin

      R2
Rx = ------------------
     R1+R3
  -----------   -1
  R3-V(R1+R3)

For my case, where R1=R2, we can also say R2=R2=1 as R3 and Rx can be
scaled to compensate.

This then simplifies to  
     R3-V(1+R3)
Rx = -----------
    1+(V(1+R3))

And can be coded as
N=V*(1+R3)
Rx=(R3-N)/(1+N)

..which shouldn't take too much code, even in C! - any improvements
welcome, though!

Now to figure out where all the fixed points need to go...!

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<pmcn9tkest7nnk3umun1sudrv5k5ddeqpn@4ax.com> quoted-printable

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