SCT-013 Burden Resistor Calculator
Choosing the correct burden resistor for a current transformer is critical for accurate AC measurement. This calculator goes beyond simple Ohm’s law: it considers RMS ↔ peak conversion, ADC headroom, custom bias midpoint, core saturation limits, and your real maximum current. Perfect for SCT‑013‑000, CT08‑1200, or any 50/100mA output CT.
① Current Transformer (CT)
⚡ Auto-calculated from turns ratio & primary current. Edit to override (breaks preset).
Limiting range improves resolution. E.g., 60A instead of 100A.
② ADC & Bias Configuration
AC signal centers here. Changing this affects available peak swing.
Default 20% (10% below bias, 10% above).
📐 Calculated Burden Resistor & Math
Why Burden Resistor Math Matters for SCT‑013
Current transformers output a current proportional to the primary current. The SCT‑013‑000 delivers 50mA at 100A (1:2000 turns). Using a burden resistor converts this current to a voltage your ADC can read. But because AC current swings both positive and negative, a simple V=I×R will cause clipping unless you bias the signal to mid‑supply. Many online tutorials blindly recommend 33Ω for 5V Arduinos — that works for 5V, but for 3.3V systems and limited current ranges the correct value changes significantly.
Our calculator respects: (1) Peak current = RMS × √2, (2) symmetrical headroom to avoid ADC saturation, (3) reduced max current to improve resolution, (4) custom bias midpoint, (5) core saturation warning when burden exceeds ~100Ω. Always verify the CT linearity region. For most home energy monitoring (≤60A), a 33–39Ω burden on 3.3V ADC gives excellent accuracy. Use standard E12 resistors or combine in series.
⚠️ Note: The manufacturer's “max sampling resistor 10Ω” applies when output is limited to 0-1V. With higher ADC ranges and proper biasing, larger resistors are safe, but exceeding ~100Ω risks core saturation at high currents — the calculator will warn you.