Enter Divider Values
Model used: Vin feeds a source resistor, a fixed upper resistor, and the upper potentiometer segment. The output is taken at the wiper.
Lower path: The lower potentiometer segment plus any fixed lower resistor go to ground. The load is placed from output to ground.
Example Data Table
| Case | Vin (V) | Rtop (Ω) | Rp Total (Ω) | Wiper (%) | Rbottom (Ω) | RL (Ω) | Output (V) | Source Current (mA) |
|---|---|---|---|---|---|---|---|---|
| Bench supply trim | 12 | 1000 | 5000 | 40 | 220 | 10000 | 3.7159 | 2.0454 |
| Sensor bias adjust | 24 | 2200 | 10000 | 70 | 470 | 47000 | 13.2835 | 2.0609 |
| Logic threshold set | 5 | 330 | 1000 | 25 | 100 | 2200 | 1.0847 | 3.5921 |
These rows show how loading and wiper position change actual output compared with an ideal unloaded divider.
Formula Used
α = Wiper Position / 100
Rpot,lower = α × Rp
Rpot,upper = (1 - α) × Rp
Rupper = Rs + Rtop + Rpot,upper
Rlower = Rbottom + Rpot,lower
Reff = Rlower || RL when a load is connected.
Vout = Vin × Reff / (Rupper + Reff)
Isource = Vin / (Rupper + Reff)
Vth = Vin × Rlower / (Rupper + Rlower)
Rth = Rupper || Rlower
The tolerance window estimates minimum and maximum output using supply tolerance and resistor tolerance at worst-case resistor directions.
How to Use This Calculator
- Enter the source voltage and any source resistance.
- Enter the fixed upper resistor, potentiometer total value, and wiper position from ground.
- Add a fixed lower resistor or load resistance when your design needs them.
- Click Calculate Divider to view loaded output, currents, power dissipation, output range, and tolerance window above the form.
Frequently Asked Questions
1) What does the wiper position represent?
It shows the tap location on the potentiometer, measured from ground. Higher percentages place more resistance below the wiper and usually raise the output voltage.
2) Why is the loaded output lower than the open-circuit output?
A connected load draws current from the divider node. That load appears in parallel with the lower leg, reducing effective resistance and pulling the output voltage downward.
3) Why does output resistance matter?
Lower output resistance makes the divider less sensitive to attached loads. High output resistance means even a moderate load can change the voltage significantly.
4) Can this calculator help size resistor wattage?
Yes. It estimates power in each resistor section and suggests a minimum wattage using a simple safety margin. Real designs may still need extra headroom.
5) What happens when load resistance is set to zero?
This form treats zero as an open load entry field instruction. Enter a positive value for a real load. Leaving zero avoids load-induced voltage drop.
6) Why include source resistance?
Some sources are not ideal. Battery internal resistance, sensor outputs, and previous stages can add series resistance that affects final divider voltage and regulation.
7) What does the tolerance window show?
It estimates a likely worst-case minimum and maximum output using entered supply and resistor tolerances. It helps judge design robustness before hardware is built.
8) Is an adjustable divider suitable for powering heavy loads?
Usually no. Dividers are best for references, bias points, and sensing. Heavy loads waste power, create voltage sag, and reduce accuracy significantly.