# Burden Resistor calculation

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This is how burden resistors are calculated for a given CT and desired range.

## Burden Resistor Formulae

**R**: Burden resistor value in Ohm

**Vadc**: ADC reference voltage

- This is 3.3V for all RPICT3T1 RPICT3V1 and RPICT8/RPICT7V1/RPICT4V3 in version 3 and earlier.
- This is 4.096V for all RPICT8/RPICT7V1/RPICT4V3 in version 4 and 5.

**Nturns**: Number of CT sensor turns (see specs).

- SCT-013-000 is 2000 turns.
- SCT-019 is 6000 turns.
- SCT-006 is 800 turns.
- SCT-024 400A/100mA is 4000 turns.
- SCT-031 600A/100mA is 6000 turns.

Nturns can be deduced dividing primary current by secondary current. For example the SCT-013-000 is rated as 100A/50mA. Therefore we get 100/0.05 = 2000 turns.

**Irms**: Max current to be read in Ampere (rms)

## Current Coefficient Formulae

This will compute ICAL.

**ICAL**: Current Coefficient

**Nturns**: Number of CT sensor turns

**R**: Burden resistor value in Ohm

## Application

You will find tables of pre-calculated resistors values in the links below.

- For RPICT3T1 RPICT3V1 RPICT4T4v2.5 and also RPICT8/RPICT7V1/RPICT4V3 in version 3 and RPICT4T4 v2

- For RPICT7V1 RPICT8 and RPICT4V3 in version 4

- For RPICT7V1 RPICT8 RPICT4V3 in version 5 (also RPICT4W3T1 and RPICT4V3T2 and RPICT4T4 v5)