piclist 2001\02\27\085558a >
Thread: Bridge voltage calculation - conclusion!!!
www.piclist.com/techref/power.htm?key=voltage
BY : mike@spam_OUTwhitewing.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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