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How to compute voltage divider top resistor by ratio in Python using UliEngineering

You can easily compute the top resistor value for a voltage divider based on the desired voltage ratio using the UliEngineering Python library:

top_resistor_by_ratio.py
from UliEngineering.Electronics.VoltageDivider import top_resistor_by_ratio
from UliEngineering.EngineerIO import *

# Compute top resistor for 0.5 ratio (50% of input voltage) with 10k bottom
rtop = top_resistor_by_ratio(0.5, "10k")
print(f"Top resistor (ratio 0.5, 10k bottom): {format_value(rtop, 'Ω')}")

# Compute top resistor for 0.33 ratio with 10k bottom
rtop = top_resistor_by_ratio(0.33, "10k")
print(f"Top resistor (ratio 0.33, 10k bottom): {format_value(rtop, 'Ω')}")

# Compute top resistor for 0.75 ratio with 10k bottom
rtop = top_resistor_by_ratio(0.75, "10k")
print(f"Top resistor (ratio 0.75, 10k bottom): {format_value(rtop, 'Ω')}")

Example output

top_resistor_by_ratio_output.txt
Top resistor (ratio 0.5, 10k bottom): 10.0 kΩ
Top resistor (ratio 0.33, 10k bottom): 4.95 kΩ
Top resistor (ratio 0.75, 10k bottom): 30.0 kΩ

The voltage divider top resistor calculation determines the required top resistor value to achieve a specific voltage ratio given a known bottom resistor. This is essential for circuit design, sensor interfacing, and creating reference voltages. The voltage ratio is the fraction of the input voltage that appears at the output of the divider.

The top resistor is computed using the formula: $R_{top} = R_{bottom} \times \frac{1 - \text{ratio}}{\text{ratio}}$, where $\text{ratio} = \frac{V_{out}}{V_{in}}$ is the desired voltage ratio, and $R_{bottom}$ is the known bottom resistor value. This relationship ensures that the output voltage is the specified fraction of the input voltage.

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