voltage - Circuit Analysis

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I'm trying to figure out Vout. I need a formula that calculates Vout. Vout goes to an ADC. I have tried the voltage divider formula Vout=(Vs*R2)/(R1+R2), this doesn't give me the voltage that I measure. What steps do I need to complete to get the correct Vout? Thank you

Answer

First off, you've shorted ground. Secondly you are using the wrong voltage divider equation.

If the bottom leg of the voltage divider is not zero, then you end up with a different equation:

$$ \frac{V_1-V_{out}}{R_1} = \frac{V_{out}- V_2}{R_2} $$ or $$V_{out} = \frac{R_1V_2+R_2V_1}{R_1+R_2} $$

if you set \$ V_2 \$ to 0v (ground) you get the standard form:

$$V_{out} = \frac{R_1*0+R_2V_1}{R_1+R_2} = \frac{R_2V_1}{R_1+R_2} $$