Voltage Divider |

Written by Bryce Ringwood | ||||

(Under construction - for comment) This program provides a means of determining the Voltage, at the junction of two resistors in an electrial circuit. There is assumed to be a load of some sort on the voltage divider ## UsesUsed to calculate the correct voltage at a resistor junction when measuring with a multimeter. For example a 20 000 Ohms/Volt meter on the 10 volt range will look like a load resistance of 20 000 X 10 = 200 K.
## Data Entry Section
Enter the values for supply voltage, R1, R2 and R If you know the supply Voltage, the voltage V and the load current through RL - enter these via boxes 1,5 and 6, leaving the other boxes as zero. The resistor values will be calculated, including the load resistor. (Entering a voltage here will over ride all other values.)
On ## Additional Results
## Example - Applying and Measuring Screen VoltageA pentode valve requres a screen voltage of 100 Volts. The HT+ voltage is 250 Volts, and the screen grid current at that voltage is 1.0 mA - What are values for R1 and R2 ? What will the voltage recorded on a 1000 Ohms/Volt meter on its 250 volt range.
Boxes 1,5 and 6-put zeroes in the rest) R1 will be 15k and R2 will be 11.1k. Note that the equivalent load resistance will be 100k.
Enter V as 0, re-enter R Many old radio manuals specified a meter with a resistance of 1000 Ohms/Volt, although the more modern ones usually specify a 20000 Ohms/Volt meter. From the above calculation, you can see that a simple inexpensive meter is often "good enough". ## Theory
R2 and the load resistance are resistors in parallel. Since the same current is flowing through R1 and the R2||R ## Formulae
\textstyle V=V_{supply} \times {\displaystyle{R2 \over {R1+R2||R_L}}}
{\displaystyle R2||R_L} ={\displaystyle {R2 \times R_L} \over {R2 + R_L}}
## References
Horowitz P, Hill W " |