Basic AC Ammeter for SCT-013 clamps — single, dual, or triple-channel current sensor on a clean I²C bus. Add cheap current channels to your bus when voltage is already measured by another module (rbAmp wattmeter on the same bus), or use for standalone current logging — protection logic, load-on detection, overload trip.
- Voltage is already measured by a UI-series wattmeter on the same I²C bus — add cheap current channels for sub-metering
- You only need current logging (protection, load-on detection, overload trip) — voltage / power not needed
- You have a fleet of SCT-013 clamps and want to deploy them as ammeters across branch circuits
- Your PZEM uses precious UART ports — switch to I²C and chain multiple ammeters on two pins
- Sub-meter installations where master-side software combines I from this module with U from the wattmeter
Choose your channel count
| Variant | Current channels (SCT-013) | What it measures | Energy (Wh) |
|---|---|---|---|
| I1 | 1 jack | I_rms, I_peak on one branch circuit | — |
| I2 | 2 jacks | I_rms, I_peak per channel on two circuits | — |
| I3 | 3 jacks | I_rms, I_peak per channel on three circuits | — |
No energy accumulator on the A-series. Without an on-board voltage sensor the module cannot compute power (P = mean(u·i)) — these are ammeter modules, not wattmeters. For Wh / tariff zones / energy accounting, pair the I-series with a UI-series wattmeter on the same bus, or buy the wattmeter variant directly.
Four lines of YAML — current channels in Home Assistant
rbamp:
- id: rbamp_branch
address: 0x61
data_ready_pin: GPIO5
sensor:
- platform: rbamp
rbamp_id: rbamp_branch
For a complete monitoring setup (current + voltage + power + Wh), pair this ammeter with a UI-series wattmeter on the same bus. Master-side software combines I from this module with U from the wattmeter — typical pattern for residential sub-metering across multiple branch circuits.
What you get
I²C bus architecture
Multiple modules share two ESP32 signal lines (SDA + SCL). Default address 0x50; reprovision each module to a unique 7-bit address in 0x08..0x77 before sharing the bus. Up to ~16 modules per I²C bus — Basic and Standard tiers coexist without distinction. Common topology: one UI-series wattmeter on main feed + several ammeters on branch circuits.
5 kHz hardware sampling
True-RMS calculation over 1000 samples per 200 ms window on-module via DMA. Your ESP32 reads pre-computed I_rms values, not raw ADC samples. Frees the host MCU for application logic.
Hardware DataReady interrupt
Open-drain pin pulses LOW for ~10 µs every 200 ms when fresh I_rms data is ready. The master catches the falling edge as an interrupt — no polling timers, no UART contention, no SoftwareSerial fragility.
Native ESPHome integration
Auto-discovery via the rbamp-esphome external_component. Roughly 4 lines of YAML for a single ammeter. Current readings surface as native Home Assistant entities — I_rms[ch], I_peak[ch] per channel.
What's in the box
- rbAmp Basic SCT-013 Ammeter module (PCB)
- 1 / 2 / 3 × 3.5 mm stereo jacks on the board for SCT-013 clamps (depends on variant: I1 / I2 / I3)
- Quick reference card with link to documentation
SCT-013 clamps are NOT included. Buy separately — we recommend YHDC SCT-013-030 (30 A, 1 V output) as the default for residential branch-circuit monitoring, or SCT-013-100 (100 A, 1 V output) for higher-current circuits.
Compatible clamps: any voltage-output SCT-013 (5 / 10 / 30 / 50 / 100 A — all with 1 V full-scale output). NOT compatible: SCT-013-000 (current output 50 mA — use the rbAmp Basic CT TA Wired variant for current-output sensors).
No voltage input on the A-series. The module has no screw terminals for voltage — current measurement only.
Real-time data (refreshed every 200 ms)
| Register | Description |
|---|---|
I_rms[ch] |
RMS current per channel (A) — 1, 2, or 3 channels depending on variant |
I_peak[ch] |
Peak current value per channel within the 200 ms window |
What this module does NOT measure: voltage (U_rms), active power (P_active), reactive power (Q_reactive), power factor (PF), line frequency, energy (Wh). For these — pair with a UI-series wattmeter on the same bus, or buy the wattmeter variant.
Compatibility
- ESPHome — native
external_componentwith auto-discovery (rbamp-esphome on GitHub) - Home Assistant — via ESPHome, current readings as native HA entities
- Arduino / PlatformIO — high-level library (rbamp-arduino on GitHub)
- Raspberry Pi — Python via I²C (rbamp-examples on GitHub)
- Tasmota — Berry driver
- Any I²C master — documented register map at /docs/modules-basic-standard-api-reference
Specifications
| Spec | Value |
|---|---|
| Supply voltage (VCC) | 5 V DC (on-board 3.3 V regulator) |
| I²C / DataReady logic level | 3.3 V (ESP32 / Raspberry Pi GPIO direct, no level shifter) |
| Current draw | <15 mA typical (less than wattmeter — no voltage front-end) |
| I²C address | 0x50 default, reprovisionable to 0x08..0x77 |
| DataReady pin | Open-drain, idle HIGH, ~10 µs LOW pulse every 200 ms — falling-edge interrupt |
| AC current range | 0.25–100 A (depends on SCT-013 model) |
| Accuracy (current) | module ~0.5% + sensor (SCT-013) 1–3% — total = module + sensor |
| Current noise floor | ~150–200 mA (SCT-013 clamp-limited) |
| Sampling rate | 5 kHz per channel (5,000 samples per second) |
| Real-time integration window | 200 ms |
| ADC resolution | 12-bit |
| AC mains isolation | Galvanic via SCT-013 clamp (clamp encircles the conductor — no direct contact with mains; no on-board voltage front-end) |
| Connector for SCT-013 | 3.5 mm stereo jack (TRS) per channel |
| Voltage input | None — current measurement only |
Installation safety
⚠️ SCT-013 clip-on install is non-invasive — clamp around a live conductor without powering down the wiring. Careful jaw alignment matters: poor seating adds 1–2% error. All work must follow local electrical codes. For panel-level work, a qualified electrician is strongly recommended.
⚠️ The module ships as a bare PCB. The Basic line does not include enclosures — for DIN-rail housings or panel boxes, use third-party project enclosures.
This module is not certified for revenue metering (utility-grade billing). For commercial accounting, use a certified meter alongside rbAmp for diagnostic / per-circuit detail.
Warranty and support
- 12-month warranty on electrical defects
- GitHub Discussions — public support channel at github.com/rb-amp
- Documentation — Quick Start · API Reference · Migration from PZEM-004T
Upgrade pointer
Need voltage / power / energy accounting? Get the UI-series wattmeter (same SCT-013 form factor, adds voltage front-end + atomic period latch for Wh accounting).
Need higher accuracy? rbAmp Standard tier delivers sub-0.5% real-world accuracy, sub-10 mA noise floor, signed power for solar bidirectional, diagnostic alarms, and traceable factory calibration. Drop-in upgrade on the same I²C bus (different address range).