These calculators are designed to help you determine the values of the components you'll need for the current transformer(s) used in the Open Energy Monitor project. Go check it out!

Please note these calculators do not take into account core permeability and core AL value. **Use at your own risk.**

**Update November 2017:** Fixed formulas displayed below each calculator to halve the system voltage as was originally intended.

Volts

For energy monitors based on 5V arduinos (mostly older ones), enter 5 above

### Burden Resistor

Calculates the value of the burden resistor to use across a current transformer

Amps

:1

Ohms

Formula:

### Max current

Calculates the maximum current you can reasonably expect to measure using a current transformer

Ohms

:1

Amps

Formula:

### Current Sensor Turns

Calculates an estimate of the number of turns a current transformer would need

Ohms

Amps

Formula:

For energy monitors based on 5V arduinos (mostly older ones), enter 5 above

Amps

:1

Ohms

Formula:

`burden_resistor = (system_voltage / 2.0) / ((I_RMS * 1.414) / ct_turns)`

Ohms

:1

Amps

Formula:

`I_RMS = (((system_voltage / 2.0) / burden_resistor) * Turns) * 0.707`

Ohms

Amps

Formula:

`turns = (I_RMS * 1.414) / ((system_voltage / 2.0) / burden_resistor)`