Overview

The SCT-013-030 is a non-invasive split-core AC current transformer (CT) clamp manufactured by YHDC. Designed for home energy monitoring, heat pump telemetry, and sub-metering, it clamps around a single insulated AC conductor wire to measure alternating currents from 0 to 30 Amperes RMS0\text{ to }30\text{ Amperes RMS} without cutting live high-voltage wiring.

Equipped with an internal 62 Ω62\ \Omega burden resistor, the SCT-013-030 outputs a continuous 0 to 1.0 V0\text{ to }1.0\text{ V} AC RMS voltage across a standard 3.5 mm TRS audio plug. It is natively supported by OpenEnergyMonitor, ESPHome (ct_clamp), and Arduino ADC sampling circuits.

Quick reference

Max AC current input (IRMSI_{RMS})0 to 30 A0\text{ to }30\text{ A} AC RMS
Max AC voltage output (VRMSV_{RMS})0 to 1.0 V0\text{ to }1.0\text{ V} AC RMS (at rated 30A input)
Internal burden resistor62 Ω62\ \Omega built-in burden resistor
Operating frequency50 Hz / 60 Hz (Mains power frequency)
Opening aperture13 mm×13 mm13\text{ mm} \times 13\text{ mm} split-core window
Non-linearity±1%\pm 1\% across 10% to 120%10\%\text{ to }120\% rated current
Dielectric insulation6.0 kV6.0\text{ kV} AC / 1 min (high-voltage safety isolation)
Connector3.5 mm TRS stereo audio jack (Tip & Sleeve connected to coil)

Connector Wiring & 3.5mm Jack Pinout

text
             ┌────────────────────────────────┐
             │ Tip: AC Voltage Signal (+)     │
             │ Ring: No Connection            │
             │ Sleeve: AC Voltage Signal (-) │
             └────────────────────────────────┘
  • Tip: Secondary coil AC output (+)
  • Sleeve: Secondary coil AC output (-)
  • Ring: Unconnected

Specifications

ParameterSymbolMinTypMaxUnitConditions
Rated Input CurrentIratedI_{rated}0—30AAC RMS (50/60 Hz50/60\text{ Hz})
Output Voltage at 30AVoutV_{out}—1.0—VAC RMS voltage
Turn RatioRatioRatio—1800:1——Internal secondary winding turns
Burden ResistorRBR_B—62—ΩInternal voltage conversion resistor
Non-Linearity ErrorENLE_{NL}-1.0%±0.5%\pm 0.5\%+1.0%—Within 3A to 36A range
Max Aperture Wire DiameterDiawireDia_{wire}—13.0—mmInsulated wire diameter

Interfacing with Microcontroller ADCs (DC Bias Circuit)

Microcontroller ADCs (such as Arduino or ESP32) measure only positive DC voltages (0V0\text{V} to 3.3V3.3\text{V} or 5V5\text{V}). Because the SCT-013-030 outputs a bi-directional sine wave (±1.414V\pm 1.414\text{V} peak-to-peak at 30A RMS), a DC bias offset circuit (VCC/2V_{CC} / 2) must be added:

text
        3.3V Power Rail
           │
        [10kΩ]
           │
           ├─── Voltage Divider Center Point (1.65V DC Offset)
           │     │
        [10kΩ]  [10µF Cap] ─── GND
           │     │
          GND    ├─── SCT-013 Sleeve (Audio Jack (-) Lead)
                 │
                 ├─── SCT-013 Tip (Audio Jack (+) Lead) ─── Microcontroller ADC Pin

RMS Current Calculation Math

IRMS=Calibration Factor×1N∑i=1N(Vsample[i]−Voffset)2I_{RMS} = \text{Calibration Factor} \times \sqrt{ \frac{1}{N} \sum_{i=1}^{N} (V_{sample}[i] - V_{offset})^2 }

For the SCT-013-030 (1V output at 30A input), the ideal calibration multiplier is 30.0:

IRMS (A)=30.0×VRMS_ACI_{RMS}\text{ (A)} = 30.0 \times V_{RMS\_AC}

Wiring

SCT-013-030 3.5mm Plug→Bias Circuit & MCUNotes
TipMCU Analog Pin (A0 / ESP32 ADC)Reads AC sine wave centered at 1.65V
Sleeve1.65V DC Bias Node (VCC/2V_{CC}/2)Virtual AC ground reference
Warning

High Voltage & Clamping Rules:

  • Clamp the SCT-013 around a single conductor wire (either Live/Phase OR Neutral). Clamping around a two-conductor power cord (carrying both Live and Neutral together) causes magnetic fields to cancel out, resulting in zero current output.
  • Ensure the ferrite split-core latch snaps completely shut. Air gaps between ferrite pole faces decrease inductance and cause massive calibration errors.

Example (ESPHome Configuration)

yaml
sensor:
  - platform: ct_clamp
    sensor: adc_sensor
    name: "Main Circuit Current"
    update_interval: 2s
    filters:
      - calibrate_linear:
          - 0.0 -> 0.0
          - 1.0 -> 30.0

  - platform: esp32_adc
    id: adc_sensor
    pin: GPIO34
    attenuation: 11db

Common mistakes

  • Clamping both Live and Neutral together: Clamping over an intact power cord yields 0A0\text{A} because ILive+INeutral=0I_{Live} + I_{Neutral} = 0. Strip outer jacket and clamp over the Live wire alone.
  • Conflating SCT-013-030 and SCT-013-000: The SCT-013-030 has an internal 62 Ω62\ \Omega burden resistor outputting 0–1V0\text{--}1\text{V} voltage; the SCT-013-000 has NO internal burden resistor and outputs 0–50mA0\text{--}50\text{mA} current (requires an external burden resistor).

Notes

  • SCT-013 Current Rating Family: SCT-013-000 (50mA current output), SCT-013-005 (5A), SCT-013-015 (15A), SCT-013-030 (30A), SCT-013-050 (50A), SCT-013-100 (100A).

Assets & downloads